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Essential Neurosurgery - THIRD EDITION

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Essential Neurosurgery - THIRD EDITION Powered By Docstoc
					Essential
Neurosurgery
   THIRD EDITION


Essential
Neurosurgery
Andrew H. Kaye
MBBS,MD,FRACS
James Stewart Professor of Surgery and Head of Department of Surgery,
The University of Melbourne
Director of Neurosurgery and Director, The Melbourne Neuroscience Centre,
The Royal Melbourne Hospital, Melbourne, Australia
© 1991 Longman Group UK Limited
© 1997 Pearson Professional Limited
© 2005 Andrew Kaye
Published by Blackwell Publishing Ltd
Blackwell Publishing, Inc., 350 Main Street, Malden, Massachusetts 02148-
5020, USA
Blackwell Publishing Ltd, 9600 Garsington Road, Oxford OX4 2DQ, UK
Blackwell Publishing Asia Pty Ltd, 550 Swanston Street, Carlton, Victoria
3053, Australia
The right of the Author to be identified as the Author of this Work has been
asserted in accordance with the Copyright, Designs and Patents Act 1988.
All rights reserved. No part of this publication may be reproduced, stored in
a retrieval system, or transmitted, in any form or by any means, electronic,
mechanical, photocopying, recording or otherwise, except as permitted by
the UK Copyright, Designs and Patents Act 1988, without the prior
permission of the publisher.
First published 1991
Second edition 1997
Third edition 2005
Library of Congress Cataloging-in-Publication Data
Kaye, Andrew H., 1950–
  Essential neurosurgery / Andrew H. Kaye. — 3rd ed.
       p. ; cm.
  Includes bibliographical references and index.
  ISBN 1-4051-1641-2
  1. Nervous system — Surgery.
  [DNLM: 1. Neurosurgical Procedures. 2. Central Nervous System —
surgery. 3. Central Nervous System Diseases — diagnosis. WL 368
K23e 2005] I. Title.
RD593.K28 2005
617.4¢8 — dc22
                                                                 2004021462
ISBN-13: 978-1-405-1641-1
ISBN-10: 1-4051-1641-2
A catalogue record for this title is available from the British Library
Set in 9/12 Palatino by SNP Best-set Typesetter Ltd., Hong Kong
Printed and bound in India by Replika Press Pvt., Ltd.
Commissioning Editor: Vicki Noyes
Development Editor: Lorna Hind
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Contents


   Preface to the third edition, vii

   Preface to the first edition, ix

 1 Neurological assessment and examination, 1

 2 Neurosurgical investigations, 14

 3 Raised intracranial pressure and hydrocephalus, 27

 4 Head injuries, 40

 5 Traumatic intracranial haematomas, 56

 6 Brain tumours, 64

 7 Benign brain tumours, 93

 8 Pituitary tumours, 109

 9 Subarachnoid haemorrhage, 125

10 Stroke, 140
   Stephen M. Davis MD, FRACP

11 Developmental abnormalities, 158

12 Infections of the central nervous system, 170

13 Low back pain and leg pain, 185

14 Cervical disc disease and cervical spondylosis, 197

15 Spinal cord compression, 206

16 Spinal injuries, 225

17 Peripheral nerve entrapments, injuries and tumours, 234

18 Facial pain and hemifacial spasm, 248

19 Pain — neurosurgical management, 254

20 Movement disorders — neurosurgical aspects, 263

21 Epilepsy and its neurosurgical aspects, 269
   Christine Kilpatrick MD, FRACP

   Index, 281

                                                             v
                          Preface to the third edition



Neurosurgery has continued to benefit consider-       editions, but has incorporated many of the ad-
ably from a wide range of technological advances     vances described. Modern neurosurgical prac-
that have enabled better imaging of central ner-     tices still differ considerably in North America
vous system disease, understanding of disease        and Europe, and despite the ‘global village’ there
processes and the consequent development of          continues to be substantive differences in the
rational treatments.                                 philosophical approach to the management of
  Magnetic resonance imaging has now become          clinical problems. The author has described his
the standard radiological technique to investi-      own practice, which hopefully continues to uti-
gate central nervous system disease, and this has    lize the best of both systems, as well as incorpo-
further demystified the diagnostic process in         rating the unique advances and philosophies of
neurosurgery. However, it has entailed a new         the Asia–Pacific rim region.
learning process not only for students, but also        It is not possible to list and acknowledge all the
for practising clinicians. Magnetic resonance        many people who have helped in the preparation
spectroscopy has become a routine diagnostic         of this third edition. However, I particularly ac-
tool as has magnetic resonance angiography.          knowledge my neurological and neurosurgical
  Improved understanding of the biology of the       colleagues at The Royal Melbourne Hospital.
central nervous system and tumour biology, has       Stephen Davis and Christine Kilpatrick have
led to the introduction of more rational treatment   again provided chapters on their own areas of ex-
regimes, with improved outcomes. Molecular           pertise. I am very grateful to Nicholas Maartens
biology techniques, the introduction of biological   for his considerable help with chapters on Head
therapies including gene therapies, and the          Injury, Brain Tumours and Pituitary Tumours,
development of endovascular surgery have             John Laidlaw for his assistance with a chapter on
considerably broadened the horizon for the           Subarachnoid Haemorrhage and Bhadu Kavar
management of a wide range of neurological dis-      for his input into the rewriting of the Spinal
eases. Technological advances in the operating       Injuries chapter.
theatre have increased the surgical possibilities,      I would like to especially thank Kate
particularly combining stereotactic techniques       Lagerewskij for the many hours she spent
with microneurosurgery. Our patients have ben-       preparing the manuscript and to Helen Harvey
efited considerably from these advances, and          at Blackwell Publishing for making this edition
over the next two decades biological and techni-     possible.
cal advances will continue to provide consider-         As always I am especially grateful to the en-
able benefit for even more of our patients.           couragement and patience of my wife Judy and
  This third edition of Essential Neurosurgery       son Ben.
has essentially been based on the first and second                    Andrew H. Kaye, Melbourne, 2004




                                                                                                       vii
                           Preface to the first edition



Clinical neurosurgery requires an understanding        general described his own practice, which hope-
of the art of neurology and of the principles of the   fully utilises the best of both systems.
neurosciences, particularly neuropathology and            The references have been chosen for their gen-
neurophysiology. In the past the mystique of           eral coverage of the topics, ease of access, histori-
neurosurgery has inadvertently prevented both          cal interest and, in some cases, because they will
medical trainees and physicians from a proper          provide thought provoking alternatives that give
appreciation of even basic neurosurgery and con-       a different perspective to the subject.
sequently has created a rather nihilistic view of         It is not possible to list and acknowledge all the
neurosurgical illnesses. The improvements in           many people who have helped in the preparation
medical technology have markedly improved              of this book, both knowingly and as a result of
the accuracy of the diagnosis, the efficacy of neu-     their influence on my own neurosurgical prac-
rosurgical treatment and the range of diseases         tices. However, the late John Bryant Curtis was
that can be diagnosed and treated. In particular,      the major initial influence not only on my own
the exciting advances in neuroradiology have           neurosurgical education but on that of many
simplified the diagnostic process and made neu-         other Australian neurosurgeons. I particularly
rosurgery more accessible.                             acknowledge the help of my neurological and
   This book is intended as an introduction to         neurosurgical colleagues at the Royal Melbourne
neurosurgery. It is hoped that it will be useful for   Hospital in the preparation of this book. Stephen
physicians in training, neurosurgical trainees         Davis and Christine Kilpatrick have provided
and medical students. The book is not intended         chapters on their own areas of expertise. Profes-
to be an exhaustive coverage of neurosurgery but       sor Brian Tress, Director of Radiology at the
rather concentrates on the more common neuro-          Royal Melbourne Hospital, has always been ac-
surgical problems and only briefly mentions rare        cessible and helpful and I am indebted to him for
entities.                                              his expert teaching over many years and for as-
   The neurological principles, pathological basis     sistance with the details on magnetic resonance
and relevant investigations that form the basis of     imaging. His department supplied most of the X-
the diagnosis are emphasised. The neurosurgical        rays. Dr Meredith Weinstein, neuroradiologist at
management is outlined but the surgical tech-          the Cleveland Clinic, kindly provided magnetic
niques are only briefly mentioned, so that the          resonance scans (Figs 7.9, 12.7, 13.5). Professor
reader will understand the postoperative prob-         Colin Masters, Department of Pathology, Univer-
lems likely to be encountered in the management        sity of Melbourne and Dr Michael Gonzales, neu-
of the patient. Modern neurosurgery has evolved        ropathologist at the Royal Melbourne Hospital,
principally from North American and European           gave assistance with the pathology details and
practices and there are often significant differ-       illustrations. My residents and registrars at the
ences in the philosophical approach in the man-        Royal Melbourne Hospital have always pro-
agement of clinical problems. The author has in        vided stimulating advice and criticisms. I par-

                                                                                                          ix
 x                                                          PREFACE TO THE FIRST EDITION


ticularly acknowledge the assistance of Drs John     The book would not have been possible with-
Laidlaw and Michael Murphy, registrars in          out the guidance and stimulus from Peter
neurosurgery, who proof read the manuscript        Richardson at Churchill Livingstone.
and offered constructive criticism. I thank Sue      I am especially grateful to the encouragement
Dammery for the many hours spent preparing         and patience of my wife Judy and son Ben.
the manuscript and Richard Mahoney for the                       Andrew H. Kaye, Melbourne, 1990
illustrations.
                            CHAPTER 1


  1                         Neurological assessment
                            and examination


An accurate neurological assessment is funda-           meeting the patient and while taking the history.
mental for the correct management of the patient.       The way in which the patient walks into the ex-
The basic aim of the neurological examination is        amination room, sits on the chair, answers ques-
to solve the following four questions:                  tions and climbs on to the examination couch will
1 Is there a neurological problem?                      provide vital clues in the search for the diagnosis.
2 What is the site of the lesion (or lesions) in the    Initially it is important to allow the patient ade-
nervous system?                                         quate opportunity to explain their symptoms in
3 What are the pathological conditions that can         an unstructured and unprompted manner. Direct
cause the lesions?                                      questioning should then follow.
4 Having ascertained the neuroanatomical site              The questions concerning neurological symp-
and the pathological cause from the history, what       toms are in essence a verbal examination of the
is the most likely diagnosis?                           neurological system. It is not just the content of
   Answering these four questions in turn will in-      the answer that is important but the way in which
dicate the type of investigation necessary to con-      the patient responds to the questions. The follow-
firm the diagnosis.                                      ing is a general classification of neurological
   The neurological assessment involves:                symptoms.
• the history of the illness                            1 General neurological symptoms:
• clinical examination:                                    (a) headache
    (a) of the nervous system                              (b) drowsiness (decreased conscious state)
    (b) general examination.                               (c) vertigo
                                                           (d) seizures, blackouts.
                                                        2 Symptoms of meningismus:
The neurological history
                                                           (a) headache
As in general medicine and surgery the neuro-              (b) photophobia
logical history is the key to the diagnosis. The his-      (c) neck stiffness
tory involves not only questioning the patient             (d) vomiting.
but also careful observation. Many neurological         3 Symptoms related to the special senses:
illnesses can be diagnosed just by observing the           (a) vision
patient. The patient’s general manner, mood,               (b) hearing
posture, gait, facial expression and speech are all        (c) taste
vital clues to the final diagnosis. In addition, pa-        (d) smell.
tients who do not have an organic disease may           4 Symptoms related to speech and comprehen-
present in a characteristic manner, particularly        sion.
with an exaggeration of the complaint.                  5 Motor symptoms:
   The history and examination commences with              (a) power
observation, and this should begin when first               (b) coordination.

                                                                                                          1
 2                                                                                               CHAPTER 1


6 Sensory symptoms.                                           (a) posture
7 Cognitive symptoms, e.g. memory.                            (b) wasting
8 Symptoms of other systems which may relate                  (c) tone
to diseases of the nervous system.                            (d) power
   Careful questioning will ascertain the impor-              (e) reflexes
tant details concerning each symptom. These                   (f) sensation
include:                                                      (g) coordination and gait.
• The time, mode of onset, progression and
duration of the symptom. The mode of onset is a
                                                            Mental state
valuable clue in discerning the pathological
process. Sudden onset of a neurological distur-             Examination of the mental state involves an as-
bance is usually due to a vascular or epileptiform          sessment of:
cause; a sudden severe headache is characteristic           • conscious state
of subarachnoid haemorrhage whereas a slowly                • orientation in time, place and person
progressive headache is more in keeping with a              • memory
cerebral tumour. Similarly, the abrupt onset of a           • emotional state
hemiplegia may result from a vascular catastro-             • presence of delusions or hallucinations.
phe and slowly progressive weakness may be                  A correct assessment of the mental state is essen-
due to a compressive or infiltrative cause.                  tial prior to the evaluation of the other neurologi-
• What factors result in alleviation or exacerba-           cal signs. The remainder of the neurological
tion of the symptom? Headache from raised in-               examination will be undertaken within the con-
tracranial pressure is characteristically worse in          text of the patient’s mental state. The accurate
the morning and on coughing and straining.                  assessment of conscious state is especially
Patients find the hand pain associated with                  important in neurosurgical disorders and the
carpal tunnel syndrome is often worse at night              evaluation of the level of consciousness using the
and is alleviated by shaking the hand over the              Glasgow coma scale is described in the chapter
side of the bed.                                            on head injuries (Chapter 4). Imprecise terms
• Is there a past history of any similar event?             such as ‘stuporose’ should be avoided and the
   It is often helpful to obtain details of the histo-      examiner should objectively assess and des-
ry from the patient’s relatives or a witness; it is         cribe the patient’s response to specific stimuli.
vital to do this if the patient is a child or if there is   ‘Drowsiness’ — a depressed conscious state — is
impairment of conscious state or memory distur-             the most important neurological sign and indi-
bance. Details of the nature of epileptic seizures          cates major intracranial pathology. As with all
should always be obtained from a relative or                neurological symptoms and signs it is essential to
friend who has witnessed an event.                          obtain an assessment of the progression of the
   A thorough understanding of the nature of the            drowsiness by questioning the patient’s friends
illness and symptomatology should have been                 or relatives. A deteriorating conscious state is a
obtained before the examination is commenced.               neurosurgical emergency.
                                                               Memory disturbances should be tested for-
                                                            mally for both short-term and long-term preser-
Neurological examination
                                                            vation. Short-term memory should be tested by
The formal neurological examination should be               listing a name, address and type of flower and
undertaken in a systemic fashion in the following           asking the patient to recall it after 5 minutes. Loss
order.                                                      of short-term memory with relative preservation
1 Mental state.                                             of memory for long-past events is typical of de-
2 Speech.                                                   mentia, e.g. Alzheimer’s disease. In Korsakoff’s
3 Cranial nerves.                                           psychosis the disturbance of recent memory and
4 Examination of limbs and trunk:                           disorientation may be so severe that the patient
 NEUROLOGICAL ASSESSMENT AND EXAMINATION                                                                  3


will make up stories to provide a convincing               Dysarthria may result from lesions of the lower
answer to the questions. This is confabulation          motor neurones and the muscles, such as occur in
and is classically associated with alcoholism,          palatal palsies or paralysis of the tongue.
although it may rarely be seen as a result of              ‘Rigid dysarthria’. This is characteristic of
anterior hypothalamic lesions due to trauma             Parkinson’s disease. In severe cases the phenom-
or following subarachnoid haemorrhage and               enon of palilalia is seen, in which there is a con-
vasospasm.                                              stant repetition of a particular syllable.

                                                        Dysphasia
Speech disorders
                                                        Dysphasia may be either expressive or receptive.
There are four main speech disorders:                   Patients with expressive dysphasia can under-
1 Mutism.                                               stand speech but cannot formulate their own
2 Aphonia.                                              speech. Patients with receptive dysphasia cannot
3 Dysarthria.                                           understand spoken or written speech. Although
4 Dysphasia.                                            one type of dysphasia may predominate there is
                                                        frequently a mixture of the two patterns of dis-
Mutism                                                  ability. Dysphasia results from lesions of the
Mutism is characterized by the patient being alert      dominant hemisphere, which is the left hemi-
but making no attempt to speak. It may result           sphere in right-handed people as well as in a high
from lesions affecting the medial aspect of both        proportion of left-handed people.
frontal lobes, classically occurring as a result of        Expressive dysphasia. This is due to a lesion
vasospasm following subarachnoid haemor-                affecting either Broca’s area in the lower part of
rhage from a ruptured anterior communicating            the precentral gyrus (Fig. 1.1) or the left posterior
artery aneurysm.                                        temporoparietal region. If the latter region is af-
                                                        fected the patient may have a nominal dysphasia,
Aphonia                                                 in which the ability to name objects is lost but the
Aphonia is said to occur when the patient is able       ability to speak is retained.
to speak but is unable to produce any volume of            Receptive dysphasia. This results from lesions in
sound. It is due to a disturbance of the vocal cords    Wernicke’s area, which is the posterior part of the
or larynx. If the patient is able to cough normally     superior temporal gyrus and the adjacent pari-
then it is usually hysterical.                          etal lobe.

Dysarthria                                              Alexia
Dysarthria is due to impaired coordination of the       Alexia is the inability to understand written
lips, palate, tongue and larynx and may result          speech. Alexia with agraphia (inability to write)
from extrapyramidal, brainstem or cerebellar le-        is due to a lesion in the left angular gyrus. The pa-
sions. The volume and content of the speech will        tient is unable to read or write spontaneously and
be normal but the enunciation will be distorted.        the condition is often accompanied by nominal
   Spastic dysarthria. This is due to bilateral upper   dysphasia, acalculia, hemianopia and visual
motor neurone disease due to pseudobulbar               agnosia. Gerstmann’s syndrome consists of fin-
palsy, motor neurone disease or brainstem               ger agnosia for both the patient’s own finger and
tumours.                                                the examiner’s finger, acalculia, right/left disori-
   Ataxic dysarthria. This is due to incoordination     entation and agraphia without alexia. It is found
of the muscles of speech; the words are often stac-     in lesions of the dominant hemisphere in the re-
cato or scanning and the rhythm is jerky. This          gion of the angular gyrus.
type of dysarthria is seen in cerebellopontine
angle tumours, cerebellar lesions, multiple scle-
rosis and phenytoin toxicity.
 4                                                                                                    CHAPTER 1


                Motor activity                       Sensory activity
                                    Cortex

                              Trunk Hip   Hip Trunk
                       Shoulder                   Shoulder
                   Elbow                                   Elbow
                                  Knee    Knee                 Wrist
               Wrist
                                                                Hand
            Fingers                                              Fingers
                                    Leg    Leg
        Thumb
                                                                     Thumb
       Neck
                                  Ankle   Ankle                        Neck
     Brow
                                                                       Brow
     Eyelid                      Toes     Toes                           Eyelid
  Nose                                                                     Nose
 Lips                                                                       Lips
 Tongue                                                                     Jaw
 Larynx



                                         Primary
                                        motor area

Supplementary motor area                                                Central sulcus

 Precentral gyrus                                          Primary somatosensory
                                                           area

                                                            Secondary visual area        Fig. 1.1 Major areas of
                                                                                         somatotopic organization of
Broca's motor speech area                                      Primary visual area       the cerebrum.




                                                             Visual acuity
Examination of the cranial nerves
                                                             The visual acuity should be tested using the stan-
Olfactory nerve                                              dard Snellen type charts placed at 6 m. The acuity
The sense of smell should be tested by the patient           is recorded as a fraction, e.g. 6/6 or 6/12, in
sniffing through each nostril as the other is com-            which the numerator indicates the distance in
pressed. The common causes of anosmia are ol-                metres from the chart and the denominator the
factory nerve lesions resulting from head injury,            line on the chart that can be read. 6/6 is normal
and tumours involving the floor of the anterior               vision. Refractive errors should be corrected by
cranial fossa, especially olfactory groove menin-            testing with the patient’s glasses or by asking the
giomas. It is important to use non-irritant sub-             patient to view the chart through a pinhole.
stances when testing olfaction, as irritating
compounds (e.g. ammonia) will cause irritation               Visual fields
of the nasal mucosa. The stimulus is then per-               The visual fields can be charted by confrontation,
ceived by the general sensory fibres of the trigem-           with the patient facing the examiner and objects
inal nerve.                                                  of varying size being moved slowly into the visu-
                                                             al field (Fig. 1.2). Formal testing using perimetry
Optic nerve                                                  should be undertaken in all cases of visual
The optic nerve should be tested by:                         failure, pituitary tumour, parasellar tumour,
• measuring the visual acuity and colour                     other tumours possibly involving the visual
vision                                                       pathways and demyelinating disease, or if there
• charting the visual fields                                  are any doubts after confrontation that the fields
• fundal examination with an ophthalmoscope                  may be restricted.
• the pupillary light reflex.                                    Perimetry can be performed using either a tan-
                                                             gent screen, such as a Bjerrum screen (Fig. 1.3), or
 NEUROLOGICAL ASSESSMENT AND EXAMINATION                                                                     5


                                                            • total visual loss — optic nerve lesion
                                                            • altitudinous hemianopia — partial lesion of the
Examiner
                                                            optic nerve due to trauma or vascular accident
                                                            • homonymous hemianopia — lesions of the
                                                            optic tract, radiation or calcarine cortex
                                                            • bitemporal hemianopia — optic chiasm lesions
                                                            such as pituitary tumour, craniopharyngioma or
                                                            suprasellar meningioma.

                                             Test object    Fundal examination
                                                            The fundus should be examined using the oph-
                                                            thalmoscope with particular attention to the:
Patient
                                                            • optic disc
                                                            • vessels
                                                            • retina.
Fig. 1.2 Visual field testing by confrontation.
                                                            A pale optic disc is due to optic atrophy which
                                                            may be either primary, as a result of an optic
                                                            nerve lesion caused by compression or demyeli-
                   BJERRUM SCREEN
                                                            nation, or consecutive, which follows severe
                           30∞                              swelling of the disc. Papilloedema is due to
                                                            raised intracranial pressure and is evident by:
                           20∞                              • blurring of the disc margins
                           10∞                              • filling in of the optic cup
                                                            • swelling and engorgement of retinal veins,
                                                            with loss of normal pulsation of the veins
                                                 Fixation
                                                 point      • haemorrhages around the disc margin (if
                                                            severe).

                                                            Third, fourth and sixth cranial nerves
                                                            As these cranial nerves are all involved in inner-
Record target colour and
diameter/distance of eye                                    vation of the extraocular muscles they are usually
from fixation point, e.g. 10/2000                           examined together. This examination involves
Fig. 1.3 The Bjerrum screen.                                assessment of:
                                                            • the position of the eyelids
                                                            • the pupils
a Goldmann perimeter. The Bjerrum screen                    • extraocular movements.
records the central field of vision. By enlarging
the central area out to 30° it is easier to detect sco-     Position of the eyelids
tomas and to measure the blind spot and, provid-            Ptosis is due to paralysis of the levator palpebrae
ed a small enough target is used, the tangent               superioris as a result of a 3rd cranial nerve lesion
screen provides an accurate representation of the           or due to weakness of the tarsal muscle due to a
peripheral fields. An automated perimetry ma-                sympathetic lesion (Horner’s syndrome).
chine will enable an accurate and reproducible
field test that is particularly useful in cooperative        The pupils
patients.                                                   An assessment should be made of the pupil size,
  The pattern of visual field loss will depend on            shape and equality. The pupils’ reaction to light
the anatomical site of the lesion in the visual             should be tested by shining a beam into the eye
pathways (Fig. 1.4):                                        and noting the reaction in that eye, as well as the
 6                                                                                             CHAPTER 1


            Temporal            Nasal
              field             field




     Left                               Right    Left             Right
     eye                                eye

                                                                             A
                                        Optic
                           B            nerve
              A
                                        Optic                                B
                                        chiasm
                       C

                                        Optic
                                                                             C
                                        tract



                                                                             D




                                                   Lateral geniculate body

     D
                                                   Geniculocalcarine tract

                                                                                 Fig. 1.4 Diagrammatic
                                                                                 representation of visual
                                                                                 pathways, the common sites
                                                                                 of lesions and the resulting
                  Occipital cortex                                               field defects.



consensual response in the opposite eye. The reac-        pressure on these fibres in the 3rd cranial nerve
tion to convergence and accommodation for near            (Chapter 9) and tentorial herniation resulting
vision should be tested by asking the patient to fix       from intracranial pressure with the herniated
on a distant object and then placing a pen approx-        uncus of the temporal lobe compressing the 3rd
imately 12 cm in front of the bridge of the nose.         nerve (Chapter 5).
   A unilateral constricted pupil (miosis) often             The Argyll–Robertson pupil is a small, irregu-
indicates a lesion in the sympathetic supply to           lar pupil not reacting to light, reacting to accom-
the pupillary dilator muscle.                             modation but responding poorly to mydriatics; it
   Horner’s syndrome, in its complete state, con-         is usually caused by syphilis.
sists of miosis, ptosis, enophthalmos and dryness            The myotonic pupil (Holmes–Adie) usually
and warmth of half of the face. It is due to a lesion     occurs in young women and presents as a unilat-
of the sympathetic supply such as results from an         eral dilatation of one pupil with failure to react to
intracavernous carotid artery aneurysm, or a              light. The pupil shows a slow constriction occur-
Pancoast’s tumour of the apex of the lung.                ring on maintaining convergence for a prolonged
   A dilated pupil (mydriasis) results from paral-        period. In the complete syndrome the knee and
ysis of the parasympathetic fibres originating             ankle jerks are absent.
from the nucleus of Edinger–Westphal in the
midbrain, and is therefore seen in a 3rd nerve            Ocular movement
palsy. The possible causes are an enlarging poste-        The following are the general actions of the ex-
rior communicating artery aneurysm causing                traocular muscles.
 NEUROLOGICAL ASSESSMENT AND EXAMINATION                                                                    7


• Lateral rectus (6th nerve) moves the eye hori-        peripherally in the labyrinth, centrally at the nu-
zontally outwards.                                      clei, in the brainstem or in the cerebellum. In pe-
• Medial rectus (3rd nerve) moves the eye hori-         ripheral lesions the quick phase is away from the
zontally inwards.                                       lesion and the amplitude is greater in the direc-
• Superior rectus (3rd nerve) elevates the eye          tion of the quick phase. In cerebellar lesions the
when it is turned outwards.                             quick phase is in the direction of gaze at that mo-
• Inferior oblique (3rd nerve) elevates the eye         ment but the amplitude is greater to the side of
when it is turned inwards.                              the lesion. By convention the quick phase is taken
• Inferior rectus (3rd nerve) depresses the eye         to indicate the direction of the nystagmus, so that
when it is turned outwards.                             if the slow phase is to the right and the quick
• Superior oblique (4th nerve) depresses the eye        phase to the left the patient is described as having
when it is turned inwards.                              nystagmus to the left.
   The patient should be tested for diplopia,              Vertical nystagmus is due to intrinsic brain-
which will indicate ocular muscle weakness be-          stem lesions such as multiple sclerosis, brainstem
fore it is evident on examination. The following        tumours or phenytoin toxicity. The so-called
rules help determine which muscle and cranial           ‘downbeat’ nystagmus, which is characterized
nerve are involved.                                     by a vertical nystagmus exaggerated by down-
• The displacement of the false image may be            gaze, is particularly evident in low brainstem
horizontal, vertical or both.                           lesions as caused by Chiari syndrome, where
• The separation of images is greatest in the di-       the lower brainstem has been compressed by
rection in which the weak muscle has its purest         the descending cerebellar tonsils (Chapter 11).
action.
• The false image is displaced furthest in the di-      Trigeminal nerve
rection in which the weak muscle should move            The 5th cranial nerve (trigeminal nerve) is tested
the eye.                                                by assessing facial sensation over the three divi-
   Disorders of eye movement may be due to im-          sions of the cranial nerve; corneal sensation
paired conjugate ocular movement. The centre            should be tested using a fine piece of cotton wool.
for the control of conjugate lateral gaze is situated   The motor function of the 5th nerve can be tested
in the posterior part of the frontal lobe, with input   by palpating the muscles while the patient
from the occipital region. The final common              clenches their jaw, testing the power of jaw open-
pathway for controlling conjugate movement is           ing and lateral deviation of the jaw (Fig. 1.5).
in the brainstem, particularly the median longi-
tudinal bundle. A lesion of the frontal lobe causes     Facial nerve
contralateral paralysis of conjugate gaze (i.e. eyes    The facial nerve is tested by assessing facial
deviated towards the side of the lesion) and a le-      movement. In an upper motor neurone facial
sion of the brainstem causes ipsilateral paralysis      weakness the weakness of the lower part of the
of conjugate gaze (i.e. eyes deviated to side oppo-
site to the lesion).
   Nystagmus should be tested by asking the pa-
                                                        Greater occipital
tient to watch the tip of a pointer. This should be                                            Ophthalmic
                                                        C. 2, 3
                                                                                               (V1)
held first in the midline and then moved slowly          Lesser occipital
                                                        C. 2                                   Maxillary
to the right, to the left and then vertically up-       Greater auricular                      (V2)
wards and downwards.                                    C. 2, 3
                                                                                               Mandibular
                                                        Dorsal rami of
   Jerk nystagmus is the common type, consist-          C. 3,4,5
                                                                                               (V3)
ing of slow drift in one direction and fast correct-    Supraclavicular                    Transverse cutaneous
                                                        C. 3,4                             nerves of neck C. 2,3
ing movement in the other.
   Horizontal jerk nystagmus is produced by le-         Fig. 1.5 Cutaneous nerve supply of the face, scalp and
sions in the vestibular system which may occur          neck.
 8                                                                                             CHAPTER 1


face is very much greater than the upper, with the         Glossopharyngeal and vagus nerves
strength of the orbicularis oculis being relatively        The glossopharyngeal and vagus nerves can be
preserved. This is due to a lesion between the cor-        most easily assessed by testing palatal movement
tex and the facial nucleus in the pons. Lower              and sensation from the pharynx and soft palate.
motor neurone weakness is evident by equal in-             If necessary the vocal cords (vagus nerve) can be
volvement of the upper and lower parts of the              examined and taste from the posterior one-third
face and is due to a lesion in, or distal to, the facial   of the tongue (glossopharyngeal nerve) can be
nerve nucleus in the pons.                                 tested.
   The chorda tympani carries taste sensation
from the anterior two-thirds of the tongue and             Accessory nerve
this should be examined using test flavours                 The accessory nerve supplies the motor power to
placed carefully on the anterior tongue.                   the upper part of the trapezius and sternocleido-
                                                           mastoid. The latter muscle can be tested by turn-
Vestibulocochlear nerve                                    ing the patient’s head against resistance and
The 8th cranial nerve consists of:                         watching and palpating the opposite sternomas-
• the cochlear nerve — hearing                             toid muscle. The trapezius muscle is best tested
• the vestibular nerve.                                    by asking the patient to shrug the shoulders and
                                                           attempting to depress the shoulders forcibly.
The cochlear nerve
Hearing can be examined at the bedside by mov-             Hypoglossal nerve
ing a finger in the meatus on one side, to produce          The hypoglossal nerve is responsible for move-
a masking noise, and repeating words at a stan-            ments of the tongue. The tongue should be in-
dard volume and from a set distance in the other           spected to detect wasting and movements from
ear. Differentiation between conduction and sen-           side to side should be observed to detect weak-
sorineural deafness can be aided using tests with          ness. The tip of the protruded tongue will deviate
a tuning fork.                                             toward the side of weakness.
   The Rinne’s test involves holding a vibrating
tuning fork in front of the external meatus and
                                                           Examination of the periphery
then on the mastoid process. In nerve deafness
both air and bone conduction are reduced, but air          Posture and general inspection
conduction remains the better. In conductive               The patient’s posture may indicate an underlying
deafness bone conduction will be better than air           neurological disability, or an abnormal posture
conduction.                                                may result from pain. A patient with sciatica will
   In Weber’s test the vibrating tuning fork is            often lie on the opposite side with the affected leg
placed on the centre of the forehead. In nerve             flexed at the hip and knee. The decerebrate pos-
deafness the sound appears to be heard better in           ture is discussed in Chapter 4.
the normal ear, but in conductive deafness the                The limbs should be inspected to compare
sound is conducted to the abnormal ear.                    size and shape and to detect deformity; long-
   Formal audiometry should be performed if                standing neurological lesions may result in
there are symptoms of impaired hearing.                    impaired growth or wasting. Lesions of lower
                                                           motor neurone in infancy, such as a brachial
The vestibular nerve                                       plexus palsy or poliomyelitis, will cause marked
The simplest test of vestibular function is the            retardation in limb growth. Upper motor neu-
caloric test, which is usually performed in pa-            rone lesions of long standing, such as acute infan-
tients suspected of having a cerebellopontine              tile hemiplegia and cerebral birth trauma, will
angle tumour or as a test of brainstem function in         also cause retardation in growth, but of a lesser
patients with severe brain injury. The test is de-         degree, with a hemiplegic posture and exaggera-
scribed in Chapter 4, p. 44.                               ted reflexes.
 NEUROLOGICAL ASSESSMENT AND EXAMINATION                                                                   9


Wasting                                                  legs; the muscles have a pseudohypertrophic
The limbs and shoulder girdles should be in-             appearance.
spected to detect wasting and fasciculation. As
well as palpating for specific muscle wasting in          Tone
each limb the circumference of the limbs should          The tone in the upper limbs should be tested
be measured at clearly identifiable positions,            using a flexion–extension movement of the wrist,
such as 8 cm above or below the olecranon, 10 cm         by holding the patient’s terminal phalanges and
above the patella and 8 cm below the tibial              by pronation–supination of the forearm. The tone
tuberosity.                                              in the lower limbs should be tested by flexion of
  The pattern of wasting will be an important            the hip, knee and ankle.
clue as to the underlying neurological disease.
                                                         Decreased tone
Wasting of the forearm and small muscles of the hand.    This is due to:
This results from lower motor neurone lesions af-        • a lower motor neurone lesion involving the
fecting particularly the C7, C8 and T1 levels and        spinal roots or anterior horn cell of the spinal
may be due to lesions of the:                            cord
• spinal cord — motor neurone disease, syr-              • lesions of the sensory roots of the reflex arc, e.g.
ingomyelia, cervical cord tumours                        tabes dorsalis
• cervical nerve root — cervical disc prolapse           • cerebellar lesions, which cause ipsilateral
• brachial plexus — trauma, cervical rib, axillary       hypotonia
tumour                                                   • myopathies
• peripheral nerve — ulnar nerve compression at          • spinal shock (the acute phase of a severe spinal
the elbow, carpal tunnel syndrome (median                lesion usually due to trauma).
nerve).
                                                         Increased tone
Wasting of the muscles of the lower leg. This will re-   This will be produced by any upper motor neu-
sult from compression of the cauda equina or             rone lesion involving the corticospinal tracts
lumbosacral nerve roots caused by a lumbar disc          above the level of the anterior horn cell in the
prolapse or tumour.                                      spinal cord.
                                                            There are three major types of hypertonicity.
Muscular dystrophies. These are genetically deter-       1 ‘Clasp knife’ spasticity, in which the resistance
mined inherited degenerative myopathies and              is most pronounced when the movement is first
cause particular patterns of muscle wasting.             made. It is usually more marked in the flexor
• Facioscapulohumeral dystrophy involves the             muscles of the upper limbs and extensor muscles
face and shoulder girdle.                                of the lower limbs and is a sign of an upper motor
• Proximal limb girdle dystrophy involves both           neurone lesion.
shoulder and hip girdles.                                2 ‘Lead pipe’ rigidity, in which there is equal re-
• Dystrophia myotonica involves the face, ster-          sistance to all movements. This is a characteristic
nomastoids and quadriceps femoris. Myotonia              feature of a lesion of the extrapyramidal system
(the failure of muscle to relax after contraction) is    but is also seen in severe spasticity from an upper
present, particularly in the peripheral muscles          motor neurone lesion.
and tongue.                                              3 ‘Cog wheel’ rigidity, in which there is an alter-
• Peroneal muscular atrophy, with predominant            nating jerky resistance to movement and which
involvement of the lower limbs, causes the ‘in-          occurs in degenerative lesions of the extrapyra-
verted bottle appearance’ with similar but less          midal system, particularly Parkinson’s disease.
striking changes in the upper limbs.                        ‘Clonus’ is best demonstrated by firm rapid
• Duchenne’s muscular dystrophy occurs                   dorsiflexion of the foot and is indicative of
mainly in young boys and affects the arms and            marked increased tone.
 10                                                                                           CHAPTER 1


Power                                                     Increased deep tendon reflexes
The power should be tested in all limbs, compar-          Due to lesions of the pyramidal system, increased
ing each side. A systematic evaluation will enable        deep tendon reflexes may be excessively pro-
the recognition of a particular pattern of weak-          longed, with a larger amplitude in a cerebellar le-
ness that will be in keeping with either a cerebral,      sion. In myxoedema the relaxation phase of the
spinal cord, plexus or peripheral nerve weak-             reflex is retarded.
ness. The major nerve and main root supply of                Each deep tendon reflex is associated with a
the muscles are shown in Table 1.1.                       particular segmental innervation and peripheral
   The Medical Research Council classifies the de-         nerve as listed in Table 1.3.
gree of weakness by recording power, ranging                 The superficial abdominal reflex has a segmen-
from 0 to 5 (Table 1.2). It is apparent that there is a   tal innervation extending from T9 in the upper
considerable range of power between grades 4              abdominal region to T12 in the lower area. The re-
and 5 and some clinicians make their own further          flex may be absent in pyramidal lesions above the
subclassification in this region.                          level of segmental innervation, particularly in
   Weakness due to a corticospinal tract lesion is        spinal lesions. However, the reflex may also be
most marked in the abductors and extensors of             difficult to elicit when the abdominal muscles
the upper limbs and the flexors of the lower               have been stretched or damaged by surgical oper-
limbs. It is normally associated with increased           ations, or in a large, pendulous, obese abdomen.
tone and exaggerated reflexes.
   Weakness due to lower motor neurone lesions            Plantar reflex
is usually more severe than when the upper                This should result in the great toe flexing the
motor neurone is involved and is seen in the dis-         metatarsophalangeal joint. The Babinski re-
tribution of the nerve affected. It is associated         sponse consists of extension of the great toe at the
with wasting, hypotonia and diminished                    metatarsophalangeal joint, and usually at the in-
reflexes.                                                  terphalangeal joint, and indicates disturbance of
   Fasciculation is an irregular, non-rhythmical          the pyramidal tract.
contraction of muscle fascicles which is most eas-
ily seen in the deltoid or calf muscles. It occurs        Sensation
classically in motor neurone disease but may also         The modalities of sensation which should be
occur in lower motor neurone lesions, e.g. in the         tested are:
lower limbs following long-standing lumbar root           • light touch
compression.                                              • pinprick (pain)
                                                          • temperature
Reflexes                                                   • position (proprioception)
The deep tendon reflex requires the stimulus,              • vibration.
sensory pathway, motor neurone, contracting                  Sensory testing involves an accurate under-
muscle and the synapses between the neurones              standing of the anatomical pathways of sensa-
in order to elicit a response.                            tion. All modalities of sensation travel by the
                                                          peripheral nerve and sensory root to the spinal
Reduced or absent tendon reflex                            cord, or via the cranial nerves to the brainstem.
This may occur due to any breach in the reflex             The fibres for pain and temperature sensation
arc:                                                      enter the posterolateral aspect of the spinal cord,
• sensory nerve — polyneuritis                            travel cranially for a few segments and then cross
• sensory root — tabes dorsalis                           to the opposite anterolateral spinothalamic tract.
• anterior horn cell — poliomyelitis                      This tract ascends to the brainstem and is joined
• anterior root — compression                             by the quintothalamic (trigeminothalamic) tract
• peripheral motor nerve — trauma                         in the pons. The fibres end mostly in the ventro-
• muscle — myopathy.                                      lateral nucleus of the thalamus and from here the
NEUROLOGICAL ASSESSMENT AND EXAMINATION                                                                   11



Table 1.1 Nerve and major root supply of muscles.

                                        Spinal roots                                             Spinal roots

Upper limb                                             Ulnar nerve
Spinal accessory nerve                                   Flexor carpi ulnaris                    C7, C8, T1
  Trapezius                             C3, C4           Flexor digitorum profundus III          C7, C8
                                                           and IV
Brachial plexus
                                                         Hypothenar muscles                      C8, T1
  Rhomboids                             C4, C5
                                                         Adductor pollicis                       C8, T1
  Serratus anterior                     C5, C6, C7
                                                         Flexis pollicis brevis                  C8, T1
  Pectoralis major
                                                         Palmar interossei                       C8, T1
    Clavicular                          C5, C6
                                                         Dorsal interossei                       C8, T1
    Sternal                             C6, C7, C8
                                                         Lumbricals III and IV                   C8, T1
  Supraspinatus                         C5, C6
  Infraspinatus                         C5, C6
  Latissimus dorsi                      C6, C7, C8
                                                       Lower limb
  Teres major                           C5, C6, C7
                                                       Femoral nerve
Axillary nerve




                                                                                }
                                                         Iliopsoas                               L1, L2, L3
  Deltoid                               C5, C6
                                                         Rectus femoris
Musculocutaneous nerve                                   Vastus lateralis           Quadriceps   L2, L3, L4
 Biceps                                 C5, C6           Vastus intermedius         femoris
 Brachialis                             C5, C6           Vastus medialis

Radial nerve                                           Obturator nerve
  Triceps
    Long head
                                                        Adductor longus
                                                        Adductor magnus             }            L2, L3, L4

    Lateral head                        C6, C7, C8
                                                       Superior gluteal nerve
    Medial head
  Brachioradialis
  Extensor carpi radialis longus
                                        C5, C6
                                        C5, C6
                                                         Gluteus medius and minimus
                                                         Tensor fasciae latae               }    L4, L5, S1

                                                       Inferior gluteal nerve
Posterior interosseous nerve
                                                         Gluteus maximus                         L5, S1, S2
  Supinator                             C6, C7
  Extensor carpi ulnaris                C7, C8         Sciatic and tibial nerves
  Extensor digitorum                    C7, C8           Semitendinosus                          L5, S1, S2
  Abductor pollicis longus              C7, C8           Biceps                                  L5, S1, S2
  Extensor pollicis longus              C7, C8           Semimembranosus                         L5, S1, S2
  Extensor pollicis brevis              C7, C8           Gastrocnemius and soleus                S1, S2
  Extensor indicis                      C7, C8           Tibialis posterior                      L4, L5
                                                         Flexor digitorum longus                 L5, S1, S2
Median nerve
                                                         Flexor hallucis longus                  L5, S1, S2
 Pronator teres                         C6, C7
                                                         Small muscles of foot                   S1, S2
 Flexor carpi radialis                  C6, C7
 Flexor digitorum superficialis          C7, C8, T1     Sciatic and common peroneal nerves
 Abductor pollicis brevis               C8, T1           Tibialis anterior                       L4, L5
 Flexor pollicis brevis*                C8, T1           Extensor digitorum longus               L5, S1
 Opponens pollicis                      C8, T1           Extensor hallucis longus                L5, S1
 Lumbricals I and II                    C8, T1           Extensor digitorum brevis               L5, S1
                                                         Peroneus longus                         L5, S1
Anterior interosseous nerve
                                                         Peroneus brevis                         L5, S1
  Flexor digitorum profundus I and II   C7, C8
  Flexor pollicis longus                C7, C8
                                                       * Flexor pollicis brevis is often supplied wholly or
                                                       partially by the ulnar nerve.
 12                                                                                          CHAPTER 1


sensory impulses pass through the posterior limb       • loss of pain and temperature on one side of the
of the internal capsule to the postcentral sensory     face and the opposite side of the body — lesion of
cortex (see Chapter 19, Fig. 19.1). Fibres carrying    the medulla affecting the descending root of the
light touch, proprioception and vibration sensa-       5th nerve and the ascending spinothalamic tract
tion ascend mainly in the ipsilateral posterior        from the remainder of the body.
columns of the spinal cord on the same side to the
nuclei gracilis and cuneatus. The fibres cross the      Coordination
midline to ascend through the brainstem in             Coordination should be tested in the upper and
the medial lemniscus, to synapse in the thalamus       lower limbs. In the upper limb it is best assessed
and then on to the sensory cortex.                     using the ‘finger–nose’ test and in the lower limb
   The sensory loss involving nocioceptive stim-       using the ‘heel–knee’ test. It is important to deter-
uli (pain and temperature) should conform to a         mine whether abnormalities of coordination are
particular pattern:                                    due to defects in:
• peripheral nerve                                     • cerebellar function
• dermatome (nerve root)                               • proprioception
• spinal cord — resulting in a sensory level           • muscular weakness.
• ‘glove and stocking’ due to peripheral neu-
ropathy                                                Gait
• hemianalgesia — thalamic or upper brainstem          An essential part of the examination is to observe
                                                       the patient’s gait. This is best done not only as a
                                                       formal part of the examination but also when the
                                                       patient is not aware of observation. The type of
  Table 1.2 Medical Research Council classification     gait is characteristic of the underlying neurologi-
  of power.                                            cal disturbance.
                                                          A hemiparesis will cause the patient to drag the
  0 Total paralysis                                    leg and, if severe, the leg will be thrown out from
  1 Flicker of contraction but no movement of limb     the hip, producing the movement called circum-
  2 Muscle only able to make normal movement           duction.
    when limb is positioned so that gravity is            A high stepping gait occurs with a foot drop
    eliminated                                         (e.g. L5 root lesion due to disc prolapse, lateral
  3 Normal movement against gravity but not
                                                       popliteal nerve palsy, peroneal muscular
    against additional resistance
                                                       atrophy). The patient raises the foot too high to
  4 Full movement but overcome by resistance
                                                       overcome the foot drop and the toe hits the
  5 Normal power
                                                       ground first. In tabes dorsalis the high stepping
                                                       gait is due to a profound loss of position sense but



  Table 1.3 Deep tendon reflexes, peripheral nerve and segmental innervation.

  Tendon reflex                     Major segmental innervation                 Peripheral nerve

  Biceps jerk                      C5(6)                                       Musculocutaneous
  Supinator jerk                   C5/C6                                       Radial
  Triceps jerk                     C7(8)                                       Radial
  Flexor finger jerk                C6–T1                                       Median and ulnar
  Knee jerk                        L3/L4                                       Femoral
  Ankle jerk                       S1(2)                                       Medial popliteal and sciatic
 NEUROLOGICAL ASSESSMENT AND EXAMINATION                                                                       13


a similar gait, of lesser severity, will result from    The preconditions are that all reversible causes of
involvement of the posterior column of the spinal       brainstem depression have been excluded. These
cord or severe sensory neuropathy which inter-          include:
feres with position sense. The gait is worse in the     • depressant drugs
dark and the heel usually strikes the ground first.      • hypothermia (temperature must be greater
   In Parkinson’s disease or other extrapyrami-         than 35°C)
dal diseases the patient walks with a stooped,          • neuromuscular blocking drugs
shuffling gait. The patient may have difficulty in        • metabolic or endocrine disturbance as a cause
starting walking and stopping. A slight push for-       of the patient’s condition.
ward will cause rapid forward movement (pro-            Brain death testing must be delayed until these
topulsion).                                             preconditions are absolutely satisfied.
   In the ataxic gait, the patient is unstable due to      The tests for brainstem function are:
cerebellar disturbance. A midline vermis tumour         • lack of pupil response to light
will result in the patient reeling in any direction.    • lack of corneal reflex to stimulation
If the cerebellar hemisphere is involved then the       • lack of oculocephalic reflex
patient will tend to fall to the ipsilateral side.      • failure of vestibulo-ocular reflex (caloric testing)
   A waddling gait is associated with congenital        • failure of a gag or cough reflex on bronchial
dislocation of the hips and muscular dystrophy.         stimulation
   The hysterical gait is often bizarre and is di-      • no motor response in the face or muscles sup-
minished when the patient is unaware of any ob-         plied by the cranial nerves in response to painful
servation.                                              stimulus
   Following the clinical assessment, a presump-        • failure of respiratory movements when the pa-
tive diagnosis is made and further investigations       tient is disconnected from a ventilator and the
can be performed to confirm the diagnosis. These         PaCO2 is allowed to rise to 50 mmHg.
laboratory investigations and radiological proce-          The tests should be repeated after an interval of
dures are described in the following chapter.           30 minutes and it is essential that they should be
                                                        carried out by two doctors of adequate seniority
                                                        and with expertise in the field.
Brain death
The use of donor organs for transplantation and
                                                        Further reading
the advent of improved intensive care facilities
have resulted in the necessity of medically and         Conference of Medical Royal Colleges and Their Facul-
legally accepted criteria of brain death.                 ties in the UK (1979) Diagnosis of death. British Jour-
   If there is irrecoverable brainstem damage and         nal of Medicine 1, 322.
the tests described below show no evidence of           Harrington D (1974) The Visual Fields, 4th edn. C V
                                                          Mosby, St Louis.
brainstem function, then the patient is medically
                                                        Jennett B (1981) Brain death. British Journal of Anaesthe-
and legally dead. If artificial ventilation is contin-
                                                          sia 53, 1111–1119.
ued the other organs may continue to function for       Medical Research Council (1976) Aids to the examination
some time. However, continued prolonged venti-            of the peripheral nervous system. Her Majesty’s Sta-
lation of the patient after the diagnosis of brain        tionery Office, London.
death is not only undignified for the dead patient       Plum F (1980) Brain death. Lancet ii, 379.
and distressing to the relatives, but is also waste-    Plum F, Posner JB (1980) Diagnosis of Stupor and Coma,
ful of expensive medical resources that are often         3rd edn. F A Davis, Philadelphia.
in short supply.                                        Walton J, ed. (1977) Brain. In: Diseases of the Nervous Sys-
   The diagnosis of brain death relies on:                tem. Oxford University Press, Oxford.
• preconditions before testing can be performed
• brain death tests.
                            CHAPTER 2


  2                         Neurosurgical investigations



Investigations to determine the exact diagnosis         subarachnoid space 30 ml and the remainder of
are nearly always necessary following the clinical      the fluid is found in the basal cisterns. Table 2.1
examination. The following is a list of the more        shows the normal constituents of CSF.
common investigations that may need to be                 The CSF glucose content is approximately 65%
undertaken:                                             of the blood plasma level in the fasting state.
• cerebrospinal fluid (CSF) studies                      There is a gradient for many of the constituents of
• radiological investigations                           CSF along the cerebrospinal axis (Table 2.2).
• electroencephalography                                  The fluid is normally clear and colourless; it
• nerve conduction studies                              will appear turbid if it contains more than 400
• evoked potential studies                              white blood cells or 200 red blood cells per mm3.
• nuclear medicine investigations.                      Yellow discolouration, xanthochromia, is due to
   Some of these investigations will be described       the breakdown products of red blood cells; these
in this chapter. The others will be dealt with in the   follow haemorrhage into the CSF.
chapters dealing with the relevant neurosurgical          CSF can be obtained by:
problems.                                               • lumbar puncture
                                                        • cisternal puncture
                                                        • cannulation of the lateral ventricle.
Cerebrospinal fluid investigation
                                                        The fluid is usually obtained by lumbar punc-
The CSF is produced by the choroid plexus at            ture. Cisternal puncture is performed if the
a rate of approximately 0.4 ml per minute.              lumbar puncture has failed due to technical
The fluid circulates from the lateral ventricles         difficulties, if there is local skin sepsis or, in some
through the interventricular foramen (of Monro)         radiology investigations, where it is the preferred
into the 3rd ventricle, through the cerebral aque-      route of contrast administration for myelogra-
duct of Sylvius into the 4th ventricle, and into the    phy. Ventricular puncture is usually only per-
subarachnoid space via the two laterally placed         formed as an intraoperative procedure or for
foramina of Luschka and a medial aperture in            temporary reduction of intracranial pressure in
the roof of the 4th ventricle — the foramen of          an emergency.
Magendie. The fluid circulates caudally into the
spinal subarachnoid space, throughout the basal
                                                        Lumbar puncture
cisterns, up through the tentorial hiatus and then
over the cerebral hemispheres. It is absorbed by        The most common indications for CSF examina-
the arachnoid villi of the dural sinuses, and espe-     tion by lumbar puncture are:
cially by the superior sagittal sinus. Approxi-         • meningitis
mately 500 ml of CSF is produced each day. The          • subarachnoid haemorrhage
total CSF volume is 140 ml; the lateral ventricles      • neurological diseases such as multiple
contain approximately 25 ml, the spinal cord            sclerosis

14
 NEUROSURGICAL INVESTIGATIONS                                                                          15


                                                       this lies at the L3/4 level. The lumbar puncture
  Table 2.1 CSF statistics (lumbar).
                                                       can be carried out at this space or at the spaces
                                                       immediately above or below. The area is pre-
  Volume                     140 ml
                                                       pared with antiseptic solution and draped. The
  Rate of production         0.4 ml/min
  Pressure (recumbent)       10–15 cm of CSF
                                                       procedure must be performed under completely
  Cells                      Less than 3–4 white       sterile conditions. The interspinous area is pal-
                               cells/mm3               pated and the skin injected with 1–2 ml of 1% lig-
  Protein                    0.15–0.45 g/l             nocaine local anaesthetic. The lumbar puncture
                               (15–45 mg/100 ml)       needle is inserted between the two spinous
  Glucose                    2.8–4.2 mmol/l            processes, pointing in a slightly cranial direction.
                               (50–75 mg/100 ml)       If performed carefully it is usually possible to feel
  IgG                        10–12% of total protein   the needle pass through the interspinous liga-
  Chloride                   120–130 mmol/l            ment and then through the dura. The stilette of
                                                       the lumbar puncture needle is withdrawn and a
  The values are expressed in SI (Système
                                                       manometer attached to measure the pressure.
  Internationale) units and the corresponding
                                                       The fluid is drained into sterile containers and
  traditional units are in parentheses.
                                                       sent for examination.

                                                       Complications of lumbar puncture
                                                       If performed properly, with the appropriate indi-
  Table 2.2 CSF gradients along the cerebrospinal
  axis.
                                                       cations, lumbar puncture is well tolerated and
                                                       complications should be minimal. However,
                      Ventricle   Cisternal   Lumbar   there are several potential hazards and complica-
                                                       tions; these include:
  Protein (g/l)       0.1         0.2         0.4
                                                       • progression of brain herniation
  Glucose (mmol/l)    4.5         4.0         3.4
                                                       • progression of spinal cord compression
                                                       • injury to the neural structures
                                                       • headache
                                                       • backache
• cytological examination for neoplastic disease       • infection — local and meningitis
• radiological imaging (e.g. myelography) or           • implantation of epidermoid tumour (rare).
radio-isotope investigations                              The potential risk of lumbar puncture worsen-
• measurement of intracranial pressure.                ing brain herniation can be avoided if the proce-
   The most important contraindication to lum-         dure is not undertaken in patients with raised
bar puncture is clinical evidence of raised in-        intracranial pressure. Neurological deterioration
tracranial pressure. Papilloedema is an absolute       may follow lumbar puncture and myelography
contraindication and a lumbar puncture should          in patients with spinal tumours where there is se-
never be performed in a patient in whom an in-         vere cord compression. Although the procedure
tracranial space-occupying lesion is suspected. If     may occasionally be necessary to make the diag-
there is any doubt a CT scan or MRI must be per-       nosis, myelography should be avoided as mag-
formed prior to lumbar puncture. A lumbar              netic resonance imaging is the investigation of
puncture should not be performed if there is local     choice for spinal tumours. Neurological deterio-
infection.                                             ration requires prompt surgery; this is discussed
                                                       in Chapter 15. Infection should be avoided by the
Technique of lumbar puncture                           use of scrupulous sterile techniques. If the proce-
The patient should be positioned on the side, the      dure is performed at a level that is too high there
back vertical on the edge of the bed and the knees     is a risk of neural damage, particularly to the
flexed up to the chest. The iliac crest is palpated;    conus medullaris. Rarely, a nerve root may be in-
 16                                                                                        CHAPTER 2


jured by the improper placement of the needle.         hours of the release of blood into the subarach-
Injury to a spinal radicular artery may occasion-      noid space. It reaches a maximum in the first 36
ally give rise to a spinal subdural or epidural        hours and gradually disappears over the next
haematoma; this risk is increased if the patient is    7–10 days.
taking anticoagulation therapy.                           Bilirubin is yellow and is the iron-free deriva-
   The traumatic effects of the lumbar puncture        tive of haemoglobin produced in vivo following
are responsible for minor, transient low back dis-     the haemolysis of red cells. Bilirubin formation
comfort. Very rarely, frank disc herniation has        in the CSF probably depends on the ability
been reported due to damage of the annulus             of macrophages and other cells in the lep-
fibrosus of the disc.                                   tomeninges to degrade haemoglobin. It is first
                                                       detected about 10 hours after the onset of
Headache                                               subarachnoid bleeding and reaches a maximum
The most common complication of lumbar punc-           at 48 hours. It may persist for 2–4 weeks after
ture is headache. In most cases this is due to low     extensive haemorrhage.
CSF pressure that results from persistent leakage         Methaemoglobin is a reduction product of
of the fluid through a hole in the arachnoid and        haemoglobin. It is a brown pigment that is dark
dura. It is generally recommended that patients        yellow in dilution and it is characteristically
should remain flat for 12 hours following a lum-        found in encapsulated subdural haematomas.
bar puncture to minimize the risk of this com-         Although it may be detected by spectrophotome-
plication. The use of a narrow-gauge needle            try of the spinal fluid in patients with large
(20 gauge or less) and avoiding multiple punc-         encapsulations of this sort, the pigment is not
ture holes in the meninges also decreases the          usually observed in other xanthochromic spinal
chance of troublesome postlumbar puncture              fluids.
headache.                                                 Xanthochromic spinal fluid may also occur in
   If the headache develops following mobiliza-        jaundice, such as jaundice secondary to liver
tion the patient should be instructed to lie flat for   disease or in haemolytic disease of the newborn.
a further 24 hours and encouraged to drink large          The fluid should be sent for microbiological
volumes of non-alcoholic fluids. Some clinicians        and biochemical examination and, if clinically in-
advocate the use of ‘blood patch’ for the treat-       dicated, cytological examination for malignant
ment of persistent postspinal headache. This           cells.
technique uses the epidural injection of autolo-          The common abnormalities are shown in
gous blood at the site of dural puncture to form a     Table 2.3. Normal CSF contains no more than
thrombotic tamponade which seals the dural             four lymphocytes or mononuclear cells per mm3.
opening, but this is usually unnecessary.              Polymorphonuclear cells are never found in nor-
                                                       mal CSF but an isolated granulocyte, presumably
                                                       derived from blood at the time of lumbar punc-
CSF examination
                                                       ture, may be seen if the CSF has been cytocen-
The CSF should be examined immediately. If the         trifuged. A granulocyte pleocytosis is the
fluid is blood-stained it should be spun down in a      hallmark of bacterial infection; a granulocytic
centrifuge and examined for evidence of xan-           phase also occurs at the onset of a viral meningi-
thochromia, this being indicative of haemor-           tis, prior to the development of a purely mononu-
rhage into the CSF.                                    clear reaction.
  Three major pigments derived from red cells             Eosinophils are not seen in normal CSF. The
may be detected in CSF: oxyhaemoglobin, biliru-        most common causes of prominent eosinophilic
bin and methaemoglobin.                                reaction are parasitic diseases, but eosinophilia
  Oxyhaemoglobin is red, but after dilution it         may also occur in inflammatory diseases and in a
appears pink or orange. It is released by lysis of     range of other diseases, as shown in Table 2.3.
red cells and may be detected in the CSF within 2         Examination of the CSF using the polymerase
 NEUROSURGICAL INVESTIGATIONS                                                                          17



  Table 2.3 CSF abnormalities.

  CSF abnormality                                      Disease suspected

  Polymorphonuclear pleocytosis                        Bacterial meningitis

  Mononuclear pleocytosis                              Viral meningitis
                                                       Tuberculous meningitis
                                                       Acute demyelination

  Eosinophils                                          Parasitic infections
                                                         Trichinella and Ascaris
                                                         Toxoplasma
                                                         Cysticercosis
                                                       Inflammatory diseases
                                                         Tuberculosis
                                                         Syphilis
                                                         Subacute sclerosing panencephalitis
                                                         Fungal infections
                                                       Other diseases
                                                         Lymphoma
                                                         Hodgkin’s disease
                                                         Multiple sclerosis

  Raised protein                                       CNS infection
                                                       Spinal block (very high levels — Froin’s syndrome)
                                                       Carcinomatosis of the meninges
                                                       Spinal neurofibromas
                                                       Acoustic neuromas
                                                       Guillain–Barré syndrome

  Low sugar                                            Bacterial meningitis
  Low chloride (<110 mmol/l)                           Tuberculous meningitis




chain reaction (PCR) technique is useful in           gamma globulins have been demonstrated
confirming the diagnosis of herpes simplex             in concentrated CSF with agarose gel elec-
encephalitis (Chapter 12).                            trophoresis and other gels. This technique
                                                      demonstrates discrete bands in the gamma
CSF electrophoresis                                   globulin pattern which have been called oligo-
Electrophoresis of the spinal fluid is useful in the   clonal bands. The term describes a population of
diagnosis of patients suspected of having de-         proteins, having identical electrophoretic charac-
myelination. An IgG of over 15% of the total pro-     teristics derived from the same population of
tein is suggestive of disseminated sclerosis but it   immunocompetent cells. A single antigen is
may also be raised in autoimmune states, such as      presumed to give rise to a single band. Oligo-
Guillain–Barré syndrome and carcinomatosis.           clonal bands are reported in about 90% of pa-
Electrophoresis of the CSF may also demonstrate       tients with multiple sclerosis and are frequently
myeloma protein.                                      observed whenever CSF gamma globulin
   In addition to the absolute increase noted in      is increased due to a variety of inflammatory
gamma globulins in inflammatory diseases of the        disorders of the nervous system. In patients with
nervous system, qualitative changes in CSF            multiple sclerosis the band pattern seems to be
 18                                                                                       CHAPTER 2


unique for each patient, and it remains stable        • evidence of metastatic tumour with erosion or
over time.                                            sclerosis of the vertebral body, pedicles or lamina
  Serological investigations for neurosyphilis        • enlargement of a neural foramen indicating a
should be performed on the CSF if suspected.          spinal schwannoma
                                                      • congenital abnormalities such as spina bifida.

Radiological investigations
                                                      Computerized tomography scanning
The major radiological investigations are:
• plain X-rays                                        Computerized tomography (CT) scanning was
• CT scan                                             introduced in the 1970s and at that time revolu-
• cerebral angiography                                tionized the radiological investigation of neuro-
• myelography                                         logical disease. Since then considerable technical
• MRI.                                                advances have greatly improved the quality of
                                                      scanning which can now be performed in both
                                                      the axial (horizontal) and coronal planes. Sagittal
Skull X-ray
                                                      reconstruction pictures can be obtained by com-
The usefulness of the plain skull X-ray has been      puter manipulation of the data.
largely superseded by CT scanning. However, it           The CT scan is the initial investigation of
is still a helpful preliminary investigation in       choice in the investigation of nearly all intracra-
patients with head injuries. The details of the use   nial diseases. Figure 2.1 shows the normal struc-
of this investigation in trauma are discussed in      tures seen in axial CT scans at various positions
Chapter 4.                                            through the cranium.
   The major abnormalities to look for on a skull        Intracranial calcification may be seen on the
X-ray are:                                            plain CT scan. Intracranial lesions that show cal-
• fractures                                           cification on the plain CT scan include:
• hyperostosis, e.g. meningioma                       • meningioma — will also show hyperostosis of
• bone erosion due to skull vault tumours             cranial vault
• midline shift of the pineal gland — from space-     • most oligodendrogliomas
occupying lesion                                      • astrocytoma — 30% of low-grade tumours but
• abnormal calcification, e.g. tumours such as         infrequently in high-grade tumours
meningioma, oligodendroglioma, craniopharyn-          • ependymoma and subependymoma
gioma or calcified wall of an aneurysm                 • craniopharyngioma
• signs of long-standing raised intracranial pres-    • wall of giant aneurysm, arteriovenous
sure — erosion of the dorsum sellae                   malformations.
• ‘copper beating’ of the skull vault. Enhanced          The pineal gland is usually calcified and calci-
digital markings are not uncommon under the           fication of the choroid plexus, basal ganglia and
age of 30 but may indicate long-standing raised       falx may occur in normal scans.
intracranial pressure if present over the whole          Following a plain CT scan iodine-based con-
vault.                                                trast medium is administered intravenously; this
                                                      will enhance areas with increased vascularity or
                                                      with impairment of the blood–brain barrier. The
Plain X-rays of the spine
                                                      non-ionic iodine agents have reduced the very
These are useful preliminary investigations for       small risk following intravenous administration
patients presenting with spinal pain. Particular      of contrast, the most serious side-effect being an
note should be taken of:                              anaphylactic reaction. Intracranial lesions that
• vertebral alignment                                 enhance following contrast administration
• presence of degenerative disease with narrow-       include:
ing of the neural foramina and spinal canal           • high-grade cerebral gliomas
    NEUROSURGICAL INVESTIGATIONS                                                                                      19


                                                                                         Corpus
                                                          Frontal lobe                   callosum   Sulci

                                                         Lateral ventricle
                                                                                              Falx cerebri
                                  Frontal horn           Parietal lobe
                                  of lateral             Occipital lobe
                                  ventricle
                                                         Septum
                                                         pellucidum




                                                         Pineal
                                                         gland
                                  Occipital horn
                                  of lateral ventricle

                                  Sylvian fissure



                                                            3rd ventricle
                                                                                       Frontal   Temporal
                                                                                       sinus     lobe
                                                                                       Orbital
                                                            Chiasmatic                 roof
                                                                                                 Pons
                                                            cistern
                                  Quadrigeminal cistern
                                                                                                 Mastoid
Fig. 2.1 Normal intracerebral                       Temporal lobe                                air cells
and cranial structures on CT
scan at various levels through                              Midbrain
                                                                                                 4th ventricle
the cranium.                                                          Quadrigeminal cistern                      Cerebellum




•  meningiomas                                                    • spinal trauma
•  acoustic neuromas                                              • spinal dysraphism.
•  large pituitary tumours                                          CT scanning, when combined with intrathecal
•  metastatic tumours                                             iodine contrast, has been utilized as a useful
•  arteriovenous malformations.                                   imaging technique for cervical disc prolapse but
   Cerebral abscesses usually enhance with a pe-                  has been superceded by MRI. This is discussed in
ripheral ring. Low-grade gliomas often have                       Chapter 14.
scanty, if any, enhancement.
   An intracranial mass will cause distortion of
                                                                  Cerebral angiography
the lateral ventricles either as a result of the lesion
itself or because of the associated cerebral                      Angiography of the intra- and extracranial ves-
oedema, which appears as an area of decreased                     sels is now usually performed using com-
density around the lesion.                                        puterized digital subtraction angiographic
   CT scanning of the spine is valuable in the                    techniques. The procedure is usually done under
management of:                                                    local anaesthesia in the adult patient. The
• lumbar disc prolapse                                            catheter is inserted into the femoral artery and
• degenerative disease of the lumbar spine                        threaded up into the carotid or vertebral artery
• lumbar canal stenosis                                           origin with the aid of an image intensifier.
• cervical disc prolapse                                            Digital subtraction angiography has consi-
• cervical canal stenosis                                         derably reduced the complications of standard
  20                                                                                                             CHAPTER 2


angiography, although there is still a very small                     investigation of spinal disease causing com-
risk of cerebral embolus from a clot or an athero-                    pression of the adjacent neural structures. The
sclerotic plaque broken off by the catheter tip.                      use of water-soluble contrast agents has made the
   The major indications for angiography are:                         technique safer and produces higher quality
• investigation of cerebral ischaemia due to                          imaging than was achieved with the previously
carotid artery disease and intracranial atheroma                      used oil-based media. In particular, the dreaded
• investigation of subarachnoid haemorrhage,                          complication of postmyelography arachnoiditis
e.g. cerebral aneurysm, arteriovenous malfor-                         does not occur with water-based media. Compli-
mation                                                                cations, which are now very uncommon, include
• investigation of venous sinus thrombosis                            epileptic seizures, systemic reactions to the
• preoperative embolization of meningioma.                            contrast medium and the risks of the lumbar
   Cerebral angiography is now only infrequen-                        puncture itself. The major indications for
tly used in the investigation of intracranial                         myelography were:
tumours. The major intracranial vessels are                           • cervical disc prolapse
shown in Fig. 2.2.                                                    • lumbar disc prolapse
                                                                      • spinal tumour
                                                                      • cervical canal stenosis causing cervical
Myelography
                                                                      myelopathy
Myelography has been used in the past in the                          • lumbar canal stenosis.


      Posterior cerebral                         Callosomarginal                  Pericallosal


                                   Frontopolar




                                  Anterior
                                  cerebral

                                   Ophthalmic
                                Middle cerebral
                           Posterior communicating
Anterior cerebral      Internal carotid             Middle cerebral artery Anterior choroidal
(a)

  Towne's view                                             Lateral view




                               Posterior cerebral
                               arteries


                                   Posterior
                                   cerebral
                                   artery


                              Basilar artery
                              Superior cerebellar artery


                       Anterior inferior                                                          Fig. 2.2 The major intracranial
Vertebral arteries     cerebellar artery                   Posterior inferior cerebellar artery   vessels seen on cerebral
(b)                                                                                               angiography.
 NEUROSURGICAL INVESTIGATIONS                                                                          21


   However, the advent of high-quality CT scan-        a radio signal, which progressively dies away.
ning and MRI have considerably reduced the in-         Although faint, the decaying signal can be detec-
dications for myelography. Myelography (often          ted by sensitive antennae (receiver coils) placed
combined with CT) is now used occasionally for         strategically in relation to the part of the body
patients with clinical features of cervical or lum-    being scanned. Initially, the strength of the signal
bar nerve root compression, such as due to disc        is proportional to the distribution of the protons
prolapse (often recurrent) or perineural fibrosis       within the tissue. The rate of decay, or ‘relaxa-
(that can follow previous surgery) and in whom         tion’, is dependent upon three factors.
the MRI findings are equivocal and not                     The first is the efficiency with which energy is
diagnostic.                                            transferred from the protons to their imme-
                                                       diately adjacent molecular lattice, or framework,
                                                       which is described by an exponential curve with
Magnetic resonance imaging
                                                       time constant T1. Although this is commonly
Magnetic resonance imaging (MRI) is a diagnos-         named ‘T1 relaxation time’, other eponyms used
tic radiological technique which utilizes the mag-     include ‘longitudinal relaxation time’, ‘spin lat-
netic properties of the body’s hydrogen nuclei to      tice relaxation time’ and ‘thermal relaxation
produce cross-sectional images in any plane. A         time’. The second factor contributing to signal
moving charged particle creates a small magnetic       decay is the destructive interference of the pro-
field. At equilibrium the multiple tiny magnetic        tons’ spins with each other. Because the protons
fields created by the randomly spinning hydro-          are exposed to minute differences in local mag-
gen nuclei (protons) within the body cancel each       netic field, their spins become out of phase, re-
other out. If the body is placed within a strong ex-   sulting in loss of synchronization, or resonance.
ternal magnetic field, the protons tend to align        The rate of signal decay due to this factor is de-
themselves within that field. If energy, in the         scribed by another exponential curve with time
form of pulses of electromagnetic waves of             constant T2, which is commonly called ‘T2 relaxa-
precisely the right frequency and band width           tion time’. It is also known as ‘horizontal relaxa-
(usually in the FM radio range), is introduced         tion time’ and ‘spin–spin relaxation time’.
into the body, the protons can be induced to spin         The third factor is ‘magnetic susceptibility’ of a
in unison, or resonantly (Fig. 2.3). When the          tissue. This refers to the ease with which tissue
external energy source is removed, the energy          becomes magnetized when placed in a strong
from the excited protons is emitted in the form of     magnetic field. The induction of relatively strong
                                                       local magnetic fields induces marked phase
                                                       dispersal and signal loss. This phenomenon is
                                                       commonly exhibited by haematoma degrada-
                                                       tion products such as deoxyhaemoglobin and
  N                                N                   haemosiderin. Magnetic susceptibility is directly
                                                       proportional to the square of the magnetic field,
                                                       so that a 1.5-tesla magnet is 25 times more sensi-
                                                       tive to magnetic susceptibility than a 0.3-tesla
                                                       magnet. The phenomenon is best exhibited at all
                                                       field strengths when gradient echo sequences are
                                                       used.
                                                          Contrast between different tissues in MRI
                                                       images is due to differences in proton concentra-
  S                                S                   tion, T1 and T2, magnetic susceptibility and flow.
Fig. 2.3 The spinning protons are aligned in a         These differences can be maximized by varying
magnetic field (left). An electromagnetic pulse         the rate of the pulses of electromagnetic energy
displaces the protons (right).                         (TR, or pulse repetition time) and the time interval
 22                                                                                           CHAPTER 2


following the pulses at which the signal is record-    by measuring a single voxel, but using spatially
ed (TE, or echo time).                                 encoding gradients as is done with standard
   In MRI studies of the CNS the T1-weighted           MRI, multiple voxels can be simultaneously
scans show the anatomical structures in detail         examined. Individual peaks can be selected and
(Fig. 2.4) ; the CSF is black. The T2-weighted scans   their distribution shown as a coloured overlay on
show intracranial pathological processes, all of       standard MRI images. This technique is known
which are associated with abnormal accumula-           as chemical shift spectroscopy.
tions of water: the CSF is white, and fast-moving         MRI, or nuclear magnetic resonance, has con-
blood in arteries and venous sinuses is black. A       siderable potential advantages over CT scanning
significant exception to the rule that T2-weighted      including:
sequences depict the CSF as white is the sequence      • no ionizing radiation
known as fluid-attenuated inversion recovery            • no bone artefact so that lesions around the
(FLAIR) which is a heavily T2-weighted se-             skull base are clearly identified
quence, but has pulse timing such that normal          • high resolution.
CSF signal is dulled so that it appears black.            Intravenous contrast medium using gadoli-
Pathological accumulations of fluid still appear        nium compounds considerably enhances the
white against a predominantly grey background.         value of MRI. These media are water-soluble and
The differential signal of moving blood is utilized    cross the abnormal blood–brain barrier in a man-
by subtracting out the static background to de-        ner similar to the iodine-based, water-soluble
pict only blood vessels in a technique known as        contrast media used in CT scanning. The para-
magnetic resonance angiography (MRA). The              magnetic compounds function by changing the
images of the blood vessels are retained in the        local magnetic environment. The signal intensity
computer as a three-dimensional data stack,            of those hydrogen nuclei that are in direct contact
which allows viewing from any angle. The reso-         with the paramagnetic compounds is altered.
lution of MRA is still inferior to that of digital     The consequent shortening of the T1 relaxation
subtraction angiography (DSA), but intravenous         time results in an enhancement or brightening of
contrast-enhanced MRA has partially bridged            the area.
that gap.                                                 Ultrafast image acquisition with echoplanar
   Magnetic resonance spectroscopy (MRS) ex-           imaging (EPI) allows accurate measurement of
ploits the empirical fact that the frequency with      blood flow. The technique either utilizes a bolus
which protons spin (process) in space is directly      of gadolinium contrast medium or detects
proportional to the magnetic field to which they        changes in the ratio of oxyhaemoglobin to deoxy-
are exposed. Electrons have 800–1000 times the         haemoglobin in stimulated portions of the brain
magnetic strength of protons. Thus protons in          (blood oxygen level-dependent imaging, or
different molecules and even in different parts of     BOLD). BOLD allows accurate localization of a
the same molecule are exposed to very slightly         range of motor or sensory functions. Of particu-
different net magnetic fields and therefore spin at     lar use in neurosurgery is the accurate de-
very slightly different frequencies. MRS mea-          lineation of the functional motor strip, which is
sures those differences in spin frequency and
depicts them as a spectrum of peaks, with
separation of the peaks measured in parts per          Fig. 2.4 Normal MRI. T1, T2 and magnetic resonance
                                                       spectroscopy. (a) Axial T1 MRI through midpons
million. The resultant proton spectra show lac-
                                                       showing upper 4th ventricle. (b) Axial T1 MRI through
tate peaks in areas of ischaemia or anaerobic
                                                       lower midbrain. (c) Axial T1 MRI showing cerebral
metabolism, as seen in infarcts and malignant          peduncles. (d) Axial T1 MRI showing symmetrical
tumours. Decreased N-acetyl aspartate (NAA)            midline lateral ventricles. (e) Axial T1 MRI showing
levels indicate neuronal loss, and increased           hyperdense CSF in lateral ventricles and subarachnoid
choline is seen in areas of increased membrane         space. (f) Midline sagittal T1 MRI. Arrow points to 4th
tumour. The most sensitive results are obtained        ventricle. Arrowhead shows genu of corpus callosum.
NEUROSURGICAL INVESTIGATIONS         23




     (a)                       (b)




     (c)                       (d)




                               (f)


     (e)
 24                                                                                         CHAPTER 2


simply obtained by performing BOLD sequences          radionecrosis, as the thallium will be taken up
during repetitive hand movements. This form of        into the tumour region. Radio-isotope cisternog-
imaging is sometimes named ‘functional MRI’           raphy is sometimes useful in the detection of the
(fMRI).                                               site of CSF leakage following a fracture of the
   EPI obtains individual images in as little as 30   skull base. The technique is also sometimes used
milliseconds. Diffusion-weighted sequences            to assess CSF flow in patients with communicat-
are able to image actual water diffusion rate         ing hydrocephalus; reflux into the ventricular
differences at the molecular level. Cytotoxic or      system, followed by slow clearance, suggests
cellular oedema results in restricted diffusion,      communicating or normal-pressure hydro-
which appears white in diffusion-weighted se-         cephalus. However, the technique has been
quences. Standard diffusion-weighted sequences        largely superseded by intracranial pressure
measure diffusion in all directions (isotropic        monitoring.
diffusion). By applying gradients in at least six        Other highly sophisticated techniques using
different directions, directionally restricted or     radioisotopes, such as single photon emission
anisotropic diffusion can be measured. Because        computerized tomography (SPECT) or positron
diffusion in axons is largely restricted to their     emission tomography (PET), are used to mea-
longitudinal axes, white matter maps can be con-      sure cerebral blood flow or cerebral metabolism.
structed and superimposed on standard images.         They are particularly useful in the evaluation of
   The main disadvantage of MRI at present is its     patients for epilepsy surgery (Chapter 21).
relative unavailability due to insufficient availa-    SPECT utilizes single photon emitting radio-
bility of equipment. It is a valuable investigation   pharmaceuticals which distribute in the brain
in the following neurosurgical conditions.            according to regional blood flow. Imaging is
• Intracranial tumours — especially menin-            performed using a gamma camera and computer
gioma, acoustic neuromas, pituitary tumours,          analysis. PET utilizes positron-emitting isotopes
skull base tumours, metastases, lymphoma,             which depend on a cyclotron for their production
meningeal infiltration (with gadolinium con-           and, in general, their short half-life dictates that a
trast), glioma.                                       cyclotron should be readily available. The scan-
• CNS infection — cerebral abscess, herpes sim-       ning is of particular use in studying the relation-
plex encephalitis.                                    ship between cerebral blood flow, oxygen
• Arteriovenous malformations.                        utilization and extraction in focal ischaemia or
• Venous sinus thrombosis.                            infarction. Both techniques have been used for
• Craniospinal abnormalities such as the Chiari       the investigation of epilepsy and to study the
malformation.                                         biological activity of brain tumours, especially
• Syringomyelia.                                      gliomas, in order to differentiate low-grade
• Hippocampal or mesial sclerosis.                    tumours from high-grade and post-radiation
• Spinal tumours.                                     necrosis from recurrent tumour.
• Lumbar disc prolapse, lumbar canal stenosis.
• Cervical cord compression — cervical myelo-
                                                      Electroencephalography
pathy, cervical central disc prolapse.
• Cervical disc prolapse.                             Electroencephalography (EEG) records the spon-
• Thoracic disc prolapse.                             taneous electrical activity of the brain. The details
                                                      are described in the chapter on epilepsy (Chapter
                                                      21). The major indications for EEG recordings in
Radio-isotope studies
                                                      neurological practice are:
Isotope brain scanning for the initial diagnosis of   • suspicion of epilepsy in a new patient
a cerebral tumour is now obsolete. However iso-       • assessment of epilepsy in a patient with recur-
tope scanning using the thallium isotope may be       rent seizures
helpful in distinguishing a recurrent glioma from     • assessment of the risk of epilepsy in a patient
 NEUROSURGICAL INVESTIGATIONS                                                                         25


who has undergone intracranial surgery or fol-        •   peripheral nerve injuries (Chapter 17)
lowing a severe head injury                           •   peripheral nerve entrapment (Chapter 17)
• as an aid in the diagnosis of herpes simplex en-    •   brachial plexus injury (Chapter 17)
cephalitis and Creutzfeldt–Jakob disease.             •   neuropathy
                                                      •   myopathy (studies are normal)
                                                      •   muscular dystrophy (studies are normal).
Nerve conduction
studies/electromyography
                                                      Evoked potentials
The electrical activity within a particular
muscle is recorded by needle electromyography.        Visual, auditory and somatosensory evoked po-
Nerve conduction studies measure the electrical       tential monitoring may be of value in the detec-
activity occurring within a particular nerve.         tion of neurological and neurosurgical diseases
   In electromyography a needle is inserted into      as well as providing useful intraoperative moni-
muscle and the electrical activity assessed; nor-     toring. Stimulation of the sensory receptor will
mal muscle is electrically ‘silent’ at rest. As the   evoke a signal in the appropriate region of the
muscle contracts motor unit potentials appear.        cerebral cortex.
This activity, which is seen on voluntary contrac-
tion of the muscle, is known as the interference      Visual evoked potential
pattern. Neuropathy or myopathy will produce          This involves retinal stimulation using either a
characteristic abnormalities.                         stroboscopic flash or an alternating checkerboard
                                                      pattern. The evoked visual signal is recorded
Spontaneous activity at rest                          over the occipital cortex. It is particularly useful
• Fibrillation potentials are due to single muscle    in the diagnosis of multiple sclerosis. Intraopera-
fibre contraction and indicate active denervation,     tive visual evoked potential monitoring has been
e.g. neuropathy, motor neurone disease, some          used by some neurosurgeons during pituitary
myopathies.                                           surgery to detect subtle interference with the
• Fasciculation — spontaneous contraction of a        optic nerves and chiasm but the technique is not
bundle of muscle fibres.                               sufficiently developed for general use at this
• Slow negative waves preceded by sharp posi-         time.
tive spikes — known as ‘positive sharp waves’ —
in chronically denervated muscle.                     Brainstem auditory evoked potential
                                                      This stimulates the auditory pathways in the
Motor unit potentials                                 vestibulocochlear cranial nerve and records the
• In neuropathy. Where there is significant dener-     electrical activity in the auditory cortex. The tech-
vation the surviving motor unit potentials are        nique has been used in the detection of small
polyphasic with large amplitude and long duration.    acoustic neuromas but has been largely super-
• In myopathy the potentials are polyphasic           seded by high-quality MRI. Intraoperative
with small amplitude and short duration.              recording has been performed during acoustic
                                                      tumour surgery and microvascular decompres-
Interference pattern                                  sion operations but its use is limited.
• Neuropathy — reduced interference due to
diminished motor units.                               Somatosensory evoked potential
• Myopathy — interference pattern normal.             This involves sensory evoked potential recording
Nerve conduction studies measure the latency          over the cortex in response to stimulation of a pe-
from the stimulus to the recording electrodes         ripheral nerve and has been used in the detection
(distal latency), amplitude of the evoked re-         of lesions within the sensory pathways, particu-
sponse and conduction velocity. The studies are       larly the brachial plexus, spinal cord or
useful in assessing:                                  brainstem. The technique is used in some
 26                                                                                              CHAPTER 2


neurosurgical units during complicated spinal             Edelman RR, Warach S (1993) Magnetic resonance
and vascular surgery as an additional intraopera-           imaging (Review II). New England Journal of Medicine
tive monitoring technique.                                  328, 785–791.
                                                          Fishman RA (1980) Cerebrospinal Fluid in Diseases of the
                                                            Nervous System. W B Saunders, Philadelphia.
Further reading                                           McComb JG (1983) Recent research into the nature of
                                                            cerebrospinal fluid formation and absorption. Journal
Chien D, Edelman RR (1992) Basic principles and clini-
                                                            of Neurosurgery 59, 369–383.
  cal applications of magnetic resonance angiography
                                                          Stevens JM, Valentine AR (1987) Magnetic resonance
  (Review). Seminars in Roentgenology 27, 53–62.
                                                            imaging in neurosurgery. British Journal of
DuBoulay GH (1965) Principles of X-Ray Diagnosis of the
                                                            Neurosurgery 1, 405–426.
  Skull. Butterworth, London.
                                                          Taveras JM, Wood EH (1986) Diagnostic Neuroradiology,
Edelman RR, Warach S (1993) Magnetic resonance
                                                            2nd edn. Williams & Wilkins, Baltimore.
  imaging (Review I). New England Journal of Medicine
  328, 708–716.
                           CHAPTER 3


  3                        Raised intracranial pressure
                           and hydrocephalus


                                                          The intracranial contents are:
Raised intracranial pressure
                                                       • brain
Raised intracranial pressure is a major clinical       • CSF
feature of many neurological illnesses. It is a most   • blood.
important neurological condition, requiring               The relative volumes of the contents are shown
prompt diagnosis and often needing urgent              in Fig. 3.1. Raised intracranial pressure may be
treatment.                                             due to:
                                                       • increased volume of normal intracranial
                                                       constituents
Pathophysiology
                                                       • a space-occupying lesion.
The mechanisms of raised intracranial pressure            The increase in volume of normal intracranial
are best understood by considering the normal          contents may be due to:
physiology of pressure within the intracranial         • brain
cavity. The normal supine intracranial pressure is        • cerebral oedema
10–15 mmHg, measured at a position equal to the           • benign intracranial hypertension
level of the foramen of Monro. The intracranial        • CSF
pressure is directly related to the volume of the         • hydrocephalus
intracranial contents within the skull. The basis      • blood volume
of the Monro–Kellie doctrine is that the cranial          • vasodilatation due to hypercapnia.
cavity is a rigid sphere filled to capacity with non-      The increase in volume of intracranial contents
compressible contents and that an increase in the      will determine the rise of intracranial pressure.
volume of one of the constituents will lead to a       Figure 3.2 shows the intracranial pressure–
rise in intracranial pressure. In 1783, Alexander      volume relationship. Initially, a small increase in
Monro (the third Monro to become Professor of          the volume of the intracranial contents causes no
Anatomy in Edinburgh and the son of the man            rise in pressure; a small amount of CSF can move
who described the connection between the               into the spinal subarachnoid space, which is very
lateral and 3rd ventricles) published his observa-     slightly distensible. However, the skull being a
tions on the intracranial contents. Forty years        relatively closed container, a critical volume is
later, Kellie made observations that appeared to       soon reached when a small rise in intracranial
support Monro’s hypothesis, although at that           volume will result in an exponential rise in pres-
time neither was aware of CSF. Subsequently,           sure. The relationship of the volume to pressure
the Monro–Kellie doctrine has been generally           is described in terms of compliance or elastance
accepted but with the qualification that the            of the intracranial space. Compliance is ex-
craniospinal intradural space is nearly constant       pressed as dV/dP and is the amount of ‘give’
in volume and its contents are nearly                  available within the intracranial space. Elastance
incompressible.                                        is the inverse of compliance and is the resistance

                                                                                                       27
 28                                                                                              CHAPTER 3


                           Glia 700-900ml


Blood 100-150ml

   ECF 100-150ml

       CSF 100-150ml                                                                        1
                                    Neurones 500-700ml
Fig. 3.1 The volume of the intracranial contents.
                                                                                        3


                                                                                                2


Intracranial                                                                        4
pressure




                             Volume
Fig. 3.2 Intracranial pressure changes related to the    Fig. 3.3 Brain herniations. A lateral supratentorial
volume of the intracranial contents.                     mass will cause displacement of the lateral ventricles
                                                         with: (1) subfalcine herniation of the cingulate gyrus
                                                         below the falx cerebri; (2) herniation of the uncus into
offered to expansion of a mass or of the brain it-       the tentorial hiatus; (3) caudal displacement of the
self (Fig. 3.3). A brain that has a small degree of      brainstem. Raised pressure within the posterior fossa
compliance, i.e. very little ‘give’ within the in-       may cause herniation of the cerebellar tonsils into the
tracranial space, would be reflected by a small           foramen magnum (4). (Adapted from Jennett &
change in volume producing a large change in in-         Teasdale (1981). Reproduced with permission.)
tracranial pressure. This is the situation on the
vertical portion of the volume/pressure curve,           insult such as subarachnoid haemorrhage, this
where the compliance is said to be low and the           ability is compromised and the cerebral perfu-
elastance is high.                                       sion pressure (CPP) becomes virtually depen-
   Experiments using Rhesus monkeys, and in-             dent on the mean arterial pressure. Normal
volving the gradual expansion of an extradural           cerebral blood flow is about 800 ml/min or 20%
balloon, showed that the vertical section of the         of the cardiac output. The cerebral blood flow is a
curve could be shifted to the left with either more      function of the CPP and the cerebral vascular re-
rapid inflation of the balloon or pathological            sistance (CVR):
changes, such as experimentally produced brain
swelling, that reduced the amount of displace-           CBF = CPP/CVR
able CSF before the balloon was expanded.
                                                         The cerebral perfusion pressure is a function of
                                                         the systemic mean arterial pressure (MAP) and
Cerebral blood flow
                                                         the intracranial pressure (ICP):
Between physiological ranges in blood pressure,
the brain is able to maintain a constant cerebral        CPP = MAP - ICP
blood flow. This is achieved by a process called
autoregulation whereby the brain adjusts the in-         Thus in order to maintain cerebral perfusion in
tracranial vascular resistance by altering vessel        the presence of raised ICP, the systemic blood
diameter and tone. Following a severe cerebral           pressure needs to be elevated.
 RAISED INTRACRANIAL PRESSURE AND HYDROCEPHALUS                                                       29


                                                       will result in herniation of the cerebellar tonsils
Cerebral herniation
                                                       into the foramen magnum and compression of
Depending on the cause of the raised intracranial      the medulla. If this is slowly progressive the pa-
pressure or the position of the intracranial mass,     tient may develop an abnormal neck posture and
brain herniae may occur as shown in Fig. 3.3. The      a child with a posterior fossa tumour may have a
three major herniations of the brain are described     head tilt. Neck stiffness results from irritation of
as:                                                    the dura around the foramen magnum. Com-
1 Transtentorial.                                      pression of the medulla may cause rapid respira-
2 Foramen magnum.                                      tory failure, which is manifest as apnoea or
3 Subfalcine.                                          abnormalities of respiratory rate and rhythm,
   Transtentorial herniation involves displace-        such as Cheyne–Stokes breathing. These may
ment of the brain and herniation of the uncus of       occur without significant impairment of con-
the temporal lobe through the tentorial hiatus,        scious state. The pressure from the herniated ton-
causing compression of the 3rd cranial nerve and       sils may cause abrupt limb paresis and sensory
midbrain. The 3rd cranial nerve is affected, ini-      disturbance.
tially on the ipsilateral side, and in most cases         Progressive raised intracranial pressure causes
compression of the pyramidal tracts in the crus        further downward herniation of the brainstem
cerebri causes contralateral hemiparesis. How-         into the foramen magnum or ‘coning’. This re-
ever, lateral displacement of the brainstem may        sults in shearing of the perforators supplying the
result in the opposite crus cerebri being com-         brainstem and haemorrhage within (Duret
pressed against the sharp rigid tentorial edge, in-    haemorrhages). The descent of the intracranial
denting the crus (Kernohan’s notch), and causing       contents with raised intracranial pressure causes
an ipsilateral hemiparesis. Similarly, the posteri-    traction damage to the pituitary stalk, resulting
or cerebral artery may be kinked, causing              in diabetes insipidus. With progressive hernia-
cerebral ischaemia resulting in a hemianopia.          tion and destruction in the brainstem the pupils
Compression of the brainstem and the reticular         change from dilated and fixed to midsize and un-
activating system will result in a deterioration of    reactive. These are invariably irreversible events
conscious state leading to coma, hypertension          leading to brainstem death.
and bradycardia (the Cushing response) and res-
piratory failure, often being initially manifest by
                                                       Clinical symptoms and signs of raised
Cheyne–Stokes periodic breathing (Table 3.1).
                                                       intracranial pressure
   Increased pressure within the posterior fossa
                                                       The common causes of raised intracranial pres-
                                                       sure are:
                                                       • space-occupying lesion — cerebral tumour
  Table 3.1 Transtentorial herniation.                 (and oedema), abscess, intracranial haematoma
                                                       • hydrocephalus
  Compression of 3rd cranial nerve — causing initial   • benign intracranial hypertension.
    dilatation of the ipsilateral pupil                The clinical features will be determined in large
                                                       part by the underlying cause of the raised pres-
  Compression of the midbrain
                                                       sure. However, some of the clinical symptoms
    Hemiparesis, usually contralateral
    Occasional compression of opposite crus            and signs will be the same, no matter what the
      cerebri causes ipsilateral hemiparesis           cause of the raised pressure. The major features
    Hypertension, bradycardia — Cushing response       are:
    Respiratory failure                                • headache
                                                       • nausea and vomiting
  Compression of posterior cerebral artery
                                                       • drowsiness
                                                       • papilloedema.
 30                                                                                         CHAPTER 3


Headache. The headache associated with in-              honour of the eminent neurosurgeon Harvey
creased intracranial pressure is usually worse on       Cushing who first described it.
waking in the morning and is relieved by vomit-
ing. Intracranial pressure increases during sleep,      Sixth nerve palsy, causing diplopia, may occur in
probably from vascular dilatation due to carbon         raised intracranial pressure due to stretching of
dioxide retention. The cause of the headache in         the 6th nerve by caudal displacement of the
raised intracranial pressure is probably traction       brainstem. This is a so called ‘false localizing’
on the pain-sensitive blood vessels and compres-        sign, as it need not occur on the side of the
sion of the pain-sensitive dura at the base of the      primary lesion.
cranium.                                                   In an infant, raised intracranial pressure will
                                                        cause a tense, bulging fontanelle.
Nausea and vomiting. The nausea and vomiting is            Other clinical manifestations of raised in-
usually worse in the morning.                           tracranial pressure may result from brain hernia-
                                                        tion, as described above, and from the mass
Drowsiness. As is often repeated in this book,          lesion that has caused the rise in pressure.
drowsiness is the most important clinical feature
of raised intracranial pressure. It is the portent of   Measurement of intracranial pressure
rapid neurological deterioration and must never         Monitoring and recording the intracranial pres-
be brushed aside as simply ‘sleepiness’, or disas-      sure was first described in the early 1960s by
ter will almost certainly occur.                        Lundberg and Langfitt and within a decade was
                                                        being extensively used in clinical practice. The in-
Papilloedema. The definitive sign of raised in-          dications for monitoring the intracranial pres-
tracranial pressure, papilloedema is due to trans-      sure vary considerably in neurosurgical practice.
mission of the raised pressure along the                The most common indications are:
subarachnoid sheath of the optic nerve. The             • Head injury (Chapter 4).
oedema of the nerve head, which may also be             • Following major intracranial surgery, when
due to obstruction of axoplasmic flow, results           measurement of the intracranial pressure may
initially in ‘filling in’ of the optic cup and dilata-   help in the management of patients. In particular,
tion of the retinal veins. The experienced obser-       after posterior fossa surgery early detection of a
ver will be able to note that there is failure of the   prolonged rise in intracranial pressure will indi-
normal pulsations of the retinal veins and venous       cate evolving hydrocephalus and the possible
congestion. As the pressure rises the nerve head        need for a CSF shunt or ventricular drain.
becomes more swollen and the disc margins will          • In the assessment of dementia and benign in-
become blurred on fundoscopic examination.              tracranial hypertension, described later in the
Flame-shaped haemorrhages develop, particu-             chapter.
larly around the disc margins and alongside the            The major abnormalities in the pressure are:
vessels. In severe papilloedema ‘blob’ haemor-          • elevation of the baseline intracranial pressure
rhages and exudates appear. Long-standing pa-           • the development of pressure waves.
pilloedema from prolonged raised intracranial              Normal intracranial pressure has a baseline be-
pressure will subsequently develop into                 tween 10 and 15 mmHg, with small pulsations
secondary optic atrophy.                                due to respiration and the cardiac pulse. The nor-
                                                        mal amplitude of the combined cardiac and res-
Cushing reflex. As intracranial pressure rises, in       piratory variation is approximately 3–5 mmHg.
order to maintain a constant CPP, there has to be       As the intracranial pressure increases the pulse
a compensatory rise in the systemic blood               pressure will increase. When the pressure is
pressure. A hypertensive response is therefore          raised abnormal pressure waves may occur.
elicited which is classically associated with a         ‘Plateau’ waves, described by Lundberg as ‘A’
bradycardia. This is termed the Cushing reflex in        waves, are pressure waves above 50 mmHg and
  RAISED INTRACRANIAL PRESSURE AND HYDROCEPHALUS                                                            31


                                                          involve resection of a space-occupying lesion, or
                                                          in the case of hydrocephalus, a CSF shunt.
                                                              In an emergency situation, when the patient
                                                          has become comatose and has failing respiration,
                                                          it is essential that the patient’s ventilatory state is
                                                          urgently maintained and this will necessitate the
                                                          passage of an endotracheal tube and ventilatory
(a)                                                       support. While the patient is being transferred for
                                                          definitive treatment of the raised pressure it may
                                                          be possible to temporarily lower the intracranial
                                                          pressure by hyperventilation which will reduce
                                                          arterial CO2 and diminish vasodilatation, and by
                                                          the administration of a diuretic such as mannitol
                                                          or frusemide (furosemide) (Chapter 4).


(b)                                                       Hydrocephalus
Fig. 3.4 Intracranial pressure waves. (a) ‘A’ waves, or   Hydrocephalus is an abnormal enlargement of
plateau waves, are elevations of intracranial pressure    the ventricles due to an excessive accumulation
above 50 mmHg lasting 5–20 minutes. (b) ‘B’ waves
                                                          of CSF resulting from a disturbance of its flow,
have a smaller amplitude and short duration.
                                                          absorption or, uncommonly, secretion. The nor-
                                                          mal volume of CSF is 140 ml. CSF is produced by
last at least 5 minutes, but often up to 20 minutes.      the choroid plexus in the ventricles at a rate of
They are always pathological and are probably             0.4 ml per minute (or about 500 ml in 24 hours).
due to increased cerebral blood flow and blood             The CSF flows from the lateral ventricles through
volume. ‘B’ waves are smaller in height and have          the foramen of Monro into the 3rd ventricle, via
a short duration (1–2 minutes) (Fig. 3.4). If they        the aqueduct of Sylvius into the 4th ventricle and
are infrequent and of low amplitude they may be           then through the foramina of Magendie and
a normal finding.                                          Luschka into the subarachnoid space and basal
   The intracranial pressure may be recorded              cisterns. The CSF circulates throughout the
from the ventricle, brain substance, subdural or          spinal subarachnoid space and the basal cisterns
extradural space. The intracranial catheters are          up through the tentorial hiatus. It flows over the
attached by a transducer to a continuous                  cerebral hemispheres and is largely absorbed by
recorder. There are now numerous monitoring               the arachnoid villi of the dural sinuses. There are
devices with various degrees of technical sophis-         a number of ways of classifying hydrocephalus
tication. Every method has its own particular             but the most useful classification system is:
advantages and complications and the type of              • obstructive hydrocephalus — when there is an
monitoring performed will depend on the clini-            obstruction to the flow of CSF through the ven-
cal situation (e.g. size of the ventricles) and the       tricular system
neurosurgeon’s preference. The major complica-            • communicating hydrocephalus — when there
tion from intracranial pressure monitoring is in-         is no obstruction to the flow of CSF within the
fection and the risk is directly proportional to the      ventricular system but the hydrocephalus is due
duration of the monitoring.                               either to obstruction to CSF flow outside the ven-
                                                          tricular system or to failure of absorption of CSF
Management of raised intracranial pressure                by the arachnoid granulations.
The treatment of raised intracranial pressure will           The most common causes of hydrocephalus
depend on the underlying cause. The definitive             are:
treatment involves removing the cause. This may           1 Obstructive hydrocephalus:
 32                                                                                             CHAPTER 3


   (a) lateral ventricle obstruction by tumours,          survival of very low birth weight premature in-
   e.g. basal ganglia glioma, thalamic glioma             fants has resulted in an increase in infants with
   (b) 3rd ventricular obstruction, due to colloid cyst   hydrocephalus resulting from perinatal intracra-
   of the 3rd ventricle or glioma of the 3rd ventricle    nial haemorrhage.
   (c) occlusion of the aqueduct of Sylvius (either          Hydrocephalus can present as acute raised in-
   primary stenosis or secondary to a tumour)             tracranial pressure but because of the relative dis-
   (d) 4th ventricular obstruction due to posterior       tensibility of the infant skull the presentation can
   fossa tumour, e.g. medulloblastoma, ependy-            be more subtle.
   moma, acoustic neuroma.                                   The major clinical features in infants are:
2 Communicating hydrocephalus:                            • failure to thrive
   (a) obstruction to flow of CSF through the basal        • failure to achieve milestones
   cisterns                                               • increased skull circumference (compared with
   (b) failure of absorption of CSF through the           normal growth curves)
   arachnoid granulations over the cerebral               • tense anterior fontanelle
   hemispheres.                                           • ‘cracked pot’ sound on skull percussion
   The most common causes of communicating                • transillumination of cranial cavity with strong
hydrocephalus are infection (especially bacterial         light
and tuberculous) and subarachnoid haemor-                 • when severe, impaired conscious level and
rhage (either spontaneous, traumatic or                   vomiting
postoperative). Other uncommon causes are car-            • ‘setting sun’ appearance due to lid retraction
cinomatous meningitis, increased CSF viscosity            and impaired upward gaze from 3rd ventricular
from a high protein content and excessive secre-          pressure on the midbrain tectum
tion of CSF due to a choroid plexus papilloma.            • thin scalp with dilated veins.

                                                          Adult hydrocephalus (Fig. 3.5)
Presenting features
                                                          Adult patients with hydrocephalus may present
Hydrocephalus in infants                                  with either:
The incidence of infantile hydrocephalus is ap-
proximately 3–4 per 1000 births and most cases
are due to congenital abnormalities. The inci-
dence of hydrocephalus occurring as a single
congenital disorder is 1–1.5 per 1000 births. Hy-
drocephalus occurring with spina bifida and
myelomeningocele varies from 1.5 to 2.9 per 1000
births, but with prenatal screening and folate
supplementation the incidence of spina bifida is
decreasing (Chapter 11).
  The most common congenital cause is stenosis
of the aqueduct of Sylvius. This is a major cause
of hydrocephalus in children with spina bifida
and myelomeningocele who also have a Chiari
type II malformation (Chapter 11). Congenital
atresia of the foramen of Luschka and Magendie
(Dandy–Walker cyst) is a rare cause. The ac-
quired forms of hydrocephalus occur most fre-
quently after intracranial bleeding, particularly
in premature infants, in meningitis and because           Fig. 3.5 Hydrocephalus of the lateral and 3rd
of tumours. The marked improvements in the                ventricles due to aqueduct stenosis.
 RAISED INTRACRANIAL PRESSURE AND HYDROCEPHALUS                                                         33


• acute onset and deterioration or
                                                     Radiological investigation
• gradual onset and slowly            progressive
deterioration.                                       The most important investigation is either a CT
                                                     scan (Fig. 3.5) or MRI of the brain (Fig. 3.6) which
Acute-onset adult hydrocephalus                      will show which ventricles are dilated. If the
This type of presentation occurs particularly in     lateral ventricles and 3rd ventricle are all very di-
patients with tumours causing obstructive hy-        lated, and the 4th ventricle is small, it is likely that
drocephalus, although it may occur with any          the obstruction is at the level of the aqueduct of
of the causes of hydrocephalus and an acute          Sylvius. An enhanced CT scan or MRI will help
rapid neurological deterioration may occur in pa-    determine the cause, as it will better define the
tients who have had long-standing chronic            presence of an obstructing tumour. In a communi-
hydrocephalus.                                       cating hydrocephalus all the ventricles are dilated.
   The major presenting features are due to the         Magnetic resonance imaging. In the sagittal plane
signs and symptoms of raised intracranial pres-      MRI is particularly helpful in showing aqueduct
sure as described earlier:                           stenosis and lesions around the 3rd ventricle
• headache                                           causing obstructive hydrocephalus.
• vomiting                                              Ultrasonography. Ultrasonography through the
• papilloedema                                       open anterior fontanelle is useful in assessing
• deterioration of conscious state.                  ventricular size in infants and may obviate the
Upgaze will often be impaired due to pressure of     need for repeated CT scans.
the dilated 3rd ventricle on the superior collicu-      Plain skull X-ray. May demonstrate splayed
lus of the tectum.                                   sutures, erosion of the bony buttresses around
                                                     the tuberculum sellae or a ‘copper beaten’
Gradual-onset adult hydrocephalus                    appearance to the inside of the calvarium.
This type of onset occurs less frequently than the      Records of the head circumference and its com-
previous type in patients with obstructive hydro-    parison with body weight and length centile
cephalus due to a tumour. The symptoms of            charts are an integral part of postnatal follow-up
raised intracranial pressure are only very gradu-    of any child.
ally progressive and late diagnosis is common.
Early features in the adolescent involve deter-
                                                     Treatment
iorating school performance as a result of
headaches, failing mental function, memory loss      In general, the treatment of hydrocephalus is a
and behavioural disturbances. Endocrine abnor-       CSF shunt or a 3rd ventriculostomy. If there has
malities such as infantilism and precocious          been rapid neurological deterioration this will
puberty can occur in association with chronic        need to be performed as an emergency.
hydrocephalus in older children and adolescents         If the hydrocephalus is due to an obstructing
due to disturbance of the hypothalamus and pos-      tumour that is surgically accessible, resection of
sible compression of the pituitary gland. If the     the mass may lead to resolution of the hydro-
condition is unrecognized progressive visual         cephalus and a shunt might not be necessary.
failure will occur, secondary to papilloedema and       Arrested hydrocephalus. This is a state of chronic
optic atrophy. As mentioned earlier, acute de-       hydrocephalus in which the CSF pressure has
compensation may occur and the patient may           returned to normal and there is no pressure
suddenly develop a rapid deterioration of con-       gradient between the cerebral ventricles and
scious state.                                        brain parenchyma. It is uncommon and is most
   In elderly patients a chronic form of hydro-      likely to occur in communicating hydrocephalus.
cephalus is called ‘normal-pressure hydro-           The patients, often children and adolescents,
cephalus’; this is described later in the chapter.   should be followed carefully with neurological
                                                     examinations, IQ tests and careful assessment of
34                                                CHAPTER 3


           their development. If there is any deterioration of
           those parameters a shunt will be necessary.

           It is interesting to briefly review the history of
           surgical treatment of hydrocephalus, as this com-
           mon neurosurgical problem has only relatively
           recently been solved. Until early this century nu-
           merous remedies had been employed, including
           blood-letting, head-wrapping and repeated ven-
           tricular taps. In 1918 Walter Dandy introduced
           the technique of excising the choroid plexus to
           decrease the formation of CSF in patients with
           progressive hydrocephalus. In 1922 he described
           an operation of 3rd ventriculostomy, in which a
           hole was made in the thinned floor of the 3rd
     (a)   ventricle creating a fistula into the chiasmatic
           cisterns. Subsequently, the procedure was
           performed through the lamina terminalis. In 1939
           Torkildsen introduced the ventriculocisternos-
           tomy to treat hydrocephalus caused by lesions
           obstructing the outflow from the 3rd ventricle. A
           thin rubber tube was inserted into the lateral ven-
           tricle through an occipital burr hole and passed
           subcutaneously into the cisterna magna.
              All these procedures had significant limita-
           tions, risk of morbidity and substantial failure
           rates. The extracranial shunting procedures re-
           lied on the development of flow-directed valves,
           allowing CSF to flow in one direction without re-
           flux through the catheter. This type of valve was
           invented by an engineer, Holter, and was first
     (b)   used in 1952. Subsequently, numerous improve-
           ments and modifications have been made and at
           present there are a large variety of reliable shunt
           devices.

           Operative procedure
           The usual method of CSF diversion is a ventricu-
           loperitoneal shunt, in which a catheter is placed
           into the lateral ventricle and is connected to a
           subcutaneous unidirectional pressure-regulated



           Fig. 3.6 MRI demonstrating obstructive
           hydrocephalus. (a) Axial T1 MRI showing dilated
           lateral ventricles. (b) Axial T2 MRI showing
           hyperdense CSF in lateral ventricles. (c) Coronal T1
     (c)   MRI with arrow pointing to dilated 3rd ventricle.
 RAISED INTRACRANIAL PRESSURE AND HYDROCEPHALUS                                                       35


 Valve located                                           lateral ventricle, anterior to the choroid plexus.
 in burr hole
                                                         Insertion of the catheter in this way minimizes
          Ventricular catheter
                                                         the other major complication, shunt obstruction.
          in lateral ventricle                           As one of the major causes of obstruction of the
                                                         ventricular catheter is blockage by the choroid
        Subcutaneous
        catheter
                                                         plexus it is wise to place the perforations of the
                                                         catheter into the frontal horn. The peritoneal
                                                         catheter can be threaded subcutaneously be-
                                                         tween the abdominal and cranial wounds using
                                                         one of many devices. Each catheter is joined to
                                                         the valve, which is then sutured in place. After
        Catheter in the
        peritoneal cavity
                                                         checking that the system is functioning properly,
                                                         the peritoneal catheter is placed within the peri-
                                                         toneal cavity.
                                                            There are numerous shunt systems and the
                                                         type of shunt used, the particular clinical situa-
Fig. 3.7 Diagram of ventriculoperitoneal shunt.          tion and the neurosurgeon’s own preference re-
                                                         sult in many modifications of this basic system of
                                                         implanting a ventriculoperitoneal shunt.
valve which is attached to a catheter threaded
subcutaneously down to the abdomen and in-               Postoperative care
serted into the peritoneal cavity. Alternative           The postoperative management is similar for any
drainage sites such as the atrium, pleural cavity        intracranial procedure. Initially the patient is
and ureter have now been largely abandoned,              nursed flat, to avoid rapid decompression of the
except in exceptional circumstances. Modern              ventricular system. Deterioration of neurological
valves can have their draining pressures adjusted        state or failure to improve will require an urgent
percutaneously and shunts are being developed            CT scan to confirm that the catheter has been
allowing intracranial pressure to be monitored           placed accurately into the ventricular system and
percutaneously.                                          to exclude the possibility of intracranial compli-
   Technique of ventriculoperitoneal shunt (Fig. 3.7).   cations such as intracerebral haematoma.
The operation is performed under general anaes-
thesia and the shunt is usually inserted on the          Complications of ventriculoperitoneal shunt
right side, so as to avoid interference with the         The major possible complications are:
dominant hemisphere. The head is turned to               • infection of the shunt
the left on the neurosurgical headrest. The head,        • obstruction of the shunt
neck, chest and abdomen are shaved, prepared             • intracranial haemorrhage.
with antiseptic solution and draped. It is                 Shunt infection is a dreaded complication with
absolutely essential to maintain the most strict         possible disastrous consequences, particularly in
sterile techniques to avoid the serious complica-        patients who are shunt dependent. Avoidance of
tion of infection of the shunt. A small curvilinear      this complication is aided by:
incision is made in the parieto-occipital area and       • meticulous sterile technique, including the use
a small skin flap elevated. The peritoneal cavity is      of a ‘no touch’ technique of the shunt and total
opened, either through a transverse rectus split-        avoidance of skin contact with the shunt
ting incision in the right hypochondrium or              • intraoperative       prophylactic    antibiotic
through a midline incision. A burr hole is per-          medication.
formed, the lateral ventricle cannulated and the
ventricular catheter inserted into the lateral ven-      Infection
tricle so that its tip lies in the frontal horn of the   The use of intraoperative prophylactic antibiotics
 36                                                                                           CHAPTER 3


during shunt placement is relatively well sub-            initially be nursed lying flat and should be ele-
stantiated. Although the continuation of the anti-        vated gradually. Some neurosurgeons use shunts
biotics for 24–36 hours postoperatively has not           that incorporate an antisiphon device to decrease
been proven to be effective, it is a reasonable pre-      the possibility of a ‘siphoning’ effect causing fur-
caution. An infected shunt almost invariably              ther reduction of intracranial pressure.
needs to be removed and replaced by a new
shunt, preferably in a different position and             Other CSF shunts
under appropriate antibiotic cover.                       Also used sometimes are:
                                                          • ventriculoatrial shunts
Obstruction                                               • ventriculopleural shunts
The shunt may fail to perform satisfactorily due          • lumboperitoneal shunts.
to blockage of the ventricular catheter, malfunc-            The ventriculoatrial shunt, in which the distal
tion or blockage of the valve or obstruction of the       end is placed through the internal jugular vein
peritoneal catheter. The patient will usually pre-        into the right atrium, is occasionally necessary
sent with recurrent symptoms of raised intracra-          when there has been marked intraperitoneal sep-
nial pressure and in some cases there may be an           sis or multiple abdominal operations. It will occa-
alarmingly rapid deterioration of neurological            sionally be necessary to place the shunt into the
state. A useful clinical sign in the less acute case of   pleural cavity.
shunt malfunction is failure of upgaze due to                The lumboperitoneal shunt involves drainage
pressure of the distended 3rd ventricle on the su-        of the CSF from the lumbar theca rather than
perior colliculus. The diagnosis will usually be          the ventricle. This type of shunt can only be con-
confirmed by CT scan. Compression of the valve             sidered in patients with communicating hydro-
is often helpful in determining the position of the       cephalus. A catheter is threaded percutaneously
obstruction. If the ventricular catheter is blocked       into the lumbar theca and then tunnelled subcu-
the contents of the pump can be expressed but the         taneously to the anterior abdominal wall and
valve will refill slowly. If the block lies in the         placed into the peritoneal cavity. The technique
valve or the peritoneal catheter the valve is             has the theoretical advantage that the brain is not
usually not compressible.                                 manipulated, but the disadvantage is that the
   The treatment of a malfunctioning shunt is ex-         shunts are not as reliable and are more difficult to
ploration and revision of the component that is           assess if the patient develops symptoms resem-
not functioning adequately.                               bling malfunction of the shunt.

Intracranial haemorrhage                                  Third ventriculostomy
Intracranial haematomas may occur following               In recent years this old technique, originally
the insertion of a ventriculoperitoneal shunt and         performed by Walter Dandy in 1922, has been
may be either:                                            reintroduced for treatment of obstructive
• intracerebral or                                        hydrocephalus using an endoscopic technique. A
• subdural.                                               ventriculoscope is introduced into the lateral
   The intracerebral haematoma will be due to the         ventricle via a frontal burr hole and advanced
trauma of the passage of the ventricular catheter.        through the foramen of Monro. The floor of the
Subdural haematomas are particularly likely to            3rd ventricle just anterior to the mamillary bodies
occur in patients with long-standing severe hy-           is then fenestrated, allowing CSF to bypass any
drocephalus. If there is a sudden decompression           obstruction in the CSF pathway and be reab-
of the ventricular system the cortical mantle will        sorbed by the arachnoid villi.
fall away from the cranial vault; this may cause
rupture of a bridging vein and the development
                                                          Normal-pressure hydrocephalus
of a subdural haematoma. Consequently, pa-
tients thought to be particularly at risk should          Normal-pressure hydrocephalus was first de-
 RAISED INTRACRANIAL PRESSURE AND HYDROCEPHALUS                                                     37


scribed as a clinical entity by Hakim and Adams in      Other investigations, including isotope cis-
1965. They described a group of patients with        ternography, neuropsychological assessment
symptoms of dementia, ataxia and incontinence,       and CSF infusion studies, have been used. These
where the radiological studies showed hydro-         investigations have a high failure rate in predict-
cephalus but the lumbar CSF pressure was normal.     ing which patients will benefit from a CSF shunt.
                                                     Abnormal isotope cisternography, with pro-
                                                     longed ventricular retention of isotope and slight
Aetiology
                                                     or delayed flow over the cerebral convexity, is as-
The exact cause of the ventricular dilatation can-   sociated with improvement following shunting
not be defined in every case. However, in a large     in only a half to two-thirds of cases of normal-
percentage the communicating hydrocephalus           pressure hydrocephalus. Improvement in symp-
may have resulted from obliteration of the           toms after lumbar puncture and removal of CSF
subarachnoid pathways in the basal cisterns fol-     fluid may be a good prognostic sign but failure to
lowing an episode of meningitis or subarachnoid      improve does not exclude the diagnosis.
haemorrhage, from either rupture of an                  Continuous intracranial pressure monitoring
aneurysm, arteriovenous malformation or fol-         is a useful technique as it will exclude patients
lowing trauma.                                       with low intracranial pressure and make a defi-
  Although lumbar puncture pressure is, by           nite diagnosis in those patients with intermittent
definition, within the normal range, continuous       waves of raised intracranial pressure, which
monitoring of the intracranial pressure in these     occur particularly at night. However, some pa-
patients will frequently reveal abnormal wave        tients with intracranial pressure in the high
formation, especially at night.                      normal range will also benefit from a CSF shunt.


Clinical presentation                                Treatment
The classic clinical ‘triad’ consists of:            The major difficulty in the treatment of normal-
1 Dementia.                                          pressure hydrocephalus is in deciding which
2 Ataxia.                                            patient should be shunted. Dementia is a
3 Incontinence.                                      devastating disease with disastrous effects for
  The syndrome is progressive and the distur-        the patient and profound social consequences for
bance of gait, which may be the first and most        the patient’s family and the general community.
prominent symptom, is more of an apraxia than a      It is not surprising that the neurosurgeon is fre-
true gait ataxia. Urinary incontinence is common     quently asked to consider patients for a shunt
but not universal. The dementia is similar to that   where the diagnosis is far from certain. The slim
seen in Alzheimer’s disease, with profound loss      chance that an operative procedure might be of
of short-term memory. The patient does not           some benefit is often considered worthwhile by
usually complain of headaches.                       the patient and their relatives. The following cri-
                                                     teria can be used to assess those patients with the
                                                     greatest chance of improvement following a
Investigations
                                                     shunt.
The CT scan or MRI will show dilated ventricles      • A clinical presentation of the classic triad, par-
without significant cortical atrophy. The diffi-       ticularly if the features of gait disturbance
culty arises that normal-pressure hydrocephalus      predominate.
may occur in patients with a scan appearance of      • The CT scan or MRI showing marked hydro-
cortical atrophy, but in these patients the degree   cephalus with minimal cortical atrophy.
of ventricular dilation should be more than          • A clearly defined cause for the hydrocephalus,
would be expected just to compensate for the         such as a past episode of subarachnoid hae-
degree of atrophic change.                           morrhage, trauma or meningitis.
 38                                                                                         CHAPTER 3


• Abnormal pressure waves on continuous in-             thrombosis. Prior to antibiotic therapy chronic
tracranial pressure monitoring.                         mastoiditis was a cause of pseudotumour cerebri
   Naturally, a patient who has all these positive      as a consequence of spread of inflammation to
criteria deserves a shunt and should make a good        the sigmoid and lateral sinuses. This is now a
recovery following the operation. However, the          relatively rare occurrence but recent studies have
usual situation is a patient who presents with          shown that an ‘occult’ venous sinus thrombosis
only a few of these criteria and the neurosurgeon       may play a role in the development of benign
needs to make a careful assessment of whether a         intracranial hypertension.
shunt is truly appropriate.

                                                        Presenting features
Operative procedure
The usual operation is a ventriculoperitoneal           Most patients are obese females who present with:
shunt preferably with a programmable valve.             • headaches
  If the diagnosis has been correct and the shunt       • visual disturbance.
works satisfactorily, the patient can make a strik-        The headaches have the features of raised in-
ing recovery with almost complete resolution of         tracranial pressure in that they are worse in the
symptoms.                                               morning and exacerbated by straining, stooping
                                                        and coughing.
                                                           The visual problems result from:
Benign intracranial hypertension
                                                        • papilloedema
Benign intracranial hypertension, also known as         • secondary optic atrophy
pseudotumour cerebri, is, as its name implies,          • diplopia due to 6th cranial nerve palsy.
a disease of raised intracranial pressure which            The papilloedema may be severe and the
usually runs a self-limiting course. Although           visual fields will show enlargement of the blind
termed ‘benign’, this condition can cause blind-        spot. Obscurations of vision may occur, particu-
ness due to severe papilloedema. The pathogene-         larly on standing or stooping, and the swelling of
sis is poorly understood. The condition usually         the optic discs may be so severe as to lead to visu-
occurs in obese females.                                al failure and associated secondary optic atrophy.
                                                           An unusual but well-recognized complication
                                                        of benign intracranial hypertension is sponta-
Aetiology
                                                        neous CSF rhinorrhoea, usually associated with
The aetiology is generally poorly understood and        the empty sella syndrome (Chapter 8).
the exact mechanisms of the raised pressure are
not known. The condition is found typically
                                                        Investigations
in young, obese women, often with menstrual
irregularities or taking an oral contraceptive pill,    The CT and/or MRI scan will show no cause for
and an endocrine disturbance has been sugges-           the papilloedema and the ventricles will often be
ted. However, careful endocrine studies have            smaller than usual.
failed to show significant endocrine abnormali-            Digital subtraction cerebral angiography or
ties. In a minority of patients a definite precipitat-   magnetic resonance venography may be per-
ing cause is found; these include:                      formed to exclude thrombosis of a venous sinus
• hypoparathyroidism                                    as the cause.
• vitamin A excess (used to treat acne)                   If the CT scan or MRI shows no mass or lesion
• pernicious anaemia                                    a lumbar puncture is usually performed; the
• drug reaction — tetracycline, nalidixic acid,         pressure will be raised. CSF examination is nor-
sulfamethoxazole, indomethacin, danazole,               mal in benign intracranial hypertension but bio-
lithium carbonate, oral contraceptive steroids.         chemistry and cytological investigations should
   A similar condition results from venous sinus        be performed to exclude underlying pathology.
 RAISED INTRACRANIAL PRESSURE AND HYDROCEPHALUS                                                              39


  If there is doubt as to the diagnosis continuous     ing the papilloedema. Recently endovascular
intracranial pressure monitoring is occasionally       stenting of the narrow regions of the transverse
performed in order to assess the level of intracra-    sinus has been suggested as a treatment, but its
nial pressure.                                         safety and efficacy are as yet unproven in large
                                                       clinical trials.

Treatment
                                                       Further reading
Benign intracranial hypertension is usually a
self-limiting disease and most cases respond to        Adams RD et al. (1965) Symptomatic occult hydro-
simple conservative treatment. The usual mea-             cephalus with normal cerebrospinal fluid pressure: a
sures undertaken are:                                     treatable syndrome. New England Journal of Medicine
• weight loss (the patients are usually obese)            273, 117–126.
                                                       Beks JWF, Bosch DA, Brock M (1976) Intracranial
• stopping any medication that may have led to
                                                          Pressure III. Springer Verlag, Berlin.
the disease, e.g. oral contraceptives, tetracycline
                                                       Black P McL (1980) Idiopathic normal pressure hydro-
• diuretic therapy                                        cephalus. Journal of Neurosurgery 52, 371–377.
• acetazolamide (reduces CSF production).              Corbett JJ et al. (1982) Visual loss in pseudotumour
   Visual acuity, visual field examination (espe-          cerebri. Archives of Neurology 39, 461–474.
cially size of the blind spot) and fundal photogra-    Greer M (1968) Management of benign intracranial
phy are essential to evaluate the progress of the         hypertension (pseudotumour cerebri). Clinical
disease. If there is no improvement with the              Neurosurgery 15, 161–174.
above measures, treatment with glycerol or             Hakim S, Adams RD (1965) The special clinical problem
steroids may be tried. However, both of these             of symptomatic hydrocephalus with normal cere-
medications will tend to increase obesity. Some           brospinal fluid pressure: Observations on
                                                          cerebrospinal fluid hydrodynamics. Journal of
clinicians recommend serial lumbar punctures
                                                          Neurological Science 2, 307–372.
but this is of limited value as the formation of CSF
                                                       Jefferson A, Clark J (1976) Treatment of benign intracra-
quickly replaces any that is withdrawn.                   nial hypertension by dehydrating agents with partic-
   The major indications for surgical treatment           ular reference to measurement of the blind spot as a
are:                                                      means for recording improvement. Journal of
• persistent severe papilloedema despite con-             Neurology, Neurosurgery and Psychiatry 39, 627–639.
servative measures                                     Jennett B, Teasdale G (1981) Management of Head
• failing vision                                          Injuries. Contemporary Neurology Series. F A Davis,
• intractable headaches despite conservative              Philadelphia.
measures.                                              Kaye AH, Black P McL (2000) Operative Neurosurgery.
   The surgical procedures that can be performed          Churchill Livingstone, London, New York,
                                                          Edinburgh.
are:
                                                       Langfitt TW et al. (1964) Transmission of intracranial
• optic nerve sheath decompression
                                                          pressure. I. Within the cranio-spinal axis. Journal of
• lumboperitoneal shunt.                                  Neurosurgery 21, 989–997.
   If the symptoms are primarily visual and            Langfitt TW et al. (1964) Transmission of intracranial
headache is not a problem then optic nerve                pressure. II. Within the supratentorial space. Journal
sheath decompression may be useful. In this pro-          of Neurosurgery 21, 998–1005.
cedure a small window of dura is excised from          Nulsen FE, Spitz EB (1952) Treatment of hydrocephalus
the optic nerve sheath to decompress the optic            by direct shunt from ventricle to jugular vein.
nerve head. If this procedure is not successful in        Surgical Forum 2, 339–343.
improving papilloedema or reversing the failing        Shulman K et al. (1980) Intracranial Pressure. IV. Springer
vision, or if headaches are a major component of          Verlag, Berlin.
                                                       Torkildsen A (1939) A new palliative operation in cases
the disease, then a lumboperitoneal shunt can be
                                                          of inoperable occlusion of the sylvian aqueduct. Acta
performed. This operation is usually highly ef-
                                                          Chirurgica Scandinavica 82, 117–119.
fective in reversing the symptoms and in improv-
                           CHAPTER 4


     4                     Head injuries



Head injuries are a major cause of morbidity and      events associated with what was considered irre-
mortality in the community. Trauma is the third       versible brain injury are potentially preventable,
most common cause of death in the United              or even reversible if treatment is instituted early
States, exceeded only by cardiocerebral vascular      enough. The distinction between primary and
disease and cancer. Trauma is the leading cause       secondary injury has become blurred, and the
of death in youth and early middle age and the        terms, whilst useful concepts, are now becoming
death is often associated with major head trau-       obsolete.
ma. Head injury contributes significantly to the          Most head injuries result from blunt trauma, as
outcome in over half of trauma-related deaths.        distinct from a penetrating wound of the skull
There are approximately 2.5 deaths from head          and brain caused by missiles or sharp objects.
injury per 10 000 population in Australia and         The pathological processes involved in a head
neurotrauma causes approximately 3.5% of all          injury are:
deaths. Road traffic accidents are responsible for     • direct trauma
about 65% of all fatal head injuries in Australia.    • cerebral contusion
   There is a wide spectrum of head injury from       • intracerebral shearing
mild concussion to severe brain injury resulting      • cerebral swelling (oedema)
in death. The management of the patient follow-       • intracranial haemorrhage
ing a head injury requires the identification of the   • hydrocephalus.
pathological processes that have occurred.
                                                      Direct trauma. Although penetrating injuries pro-
                                                      duce most of their damage by direct trauma to
Pathophysiology of head injury
                                                      the brain this is not the case with blunt injuries, in
The management of head injury has been based          which the energy from the impact has a more
on the concept of primary and secondary brain         widespread effect.
injury. The primary brain injury was defined as
the irreversible pathology sustained at the time      Cerebral contusion. This may occur locally under
of the trauma, whereas the secondary brain in-        the position of the impact although it usually oc-
jury has been considered the subsequent or pro-       curs more severely at a distance from the area of
gressive brain damage that occurs due to an           impact as a result of a ‘contre-coup’ injury. As the
evolving pathology following the injury. It has       brain is mobile within the cranial cavity the sud-
been the general contention that the primary          den acceleration/deceleration force will result in
injury is irreversible, and management should         the opposite ‘poles’ of the brain being jammed
be directed at preventing or treating secondary       against the cranial vault. A sudden blow to the
pathology (such as cerebral swelling, hydroceph-      back of the head will cause the temporal lobes
alus and intracerebral haematoma). However,           to slide across the floor of the middle cranial
it is now clear that some of the biochemical          fossa and the frontal lobes across the floor of the

40
 HEAD INJURIES                                                                                       41


anterior cranial fossa, causing contusion on the
undersurface of those lobes and to the temporal                                             Frontal lobe
and frontal poles of the brain as they strike the
sphenoid ridge and frontal bones, respectively.                                             3rd nerve
Cerebral contusion consists of lacerated haemor-                                            deformed
                                                     Midbrain                               Temporal lobe
rhagic brain, and a ‘burst temporal lobe’ may re-    distorted                              Haematoma
sult when the temporal pole has been severely        Posterior                              Transtentorial
injured.                                             cerebral                               herniation of
                                                     artery                                 uncus of
                                                                                            temporal lobe
Shearing forces. Intracerebral shearing forces
occur as a result of the differential brain move-    Fig. 4.1 Herniation of the uncus and hippocampal
ment following blunt trauma, frequently in con-      gyrus of the temporal lobe into the tentorial notch
junction with a contre-coup type of injury. The      causing pressure on the 3rd nerve and midbrain.
rotational acceleration following injury will        (Adapted from Jennett & Teasdale, 1981. Reproduced
                                                     with permission.)
cause shear forces that result in petechial haem-
orrhages (particularly in the upper brainstem,
cerebrum and corpus callosum), and tearing of
axons and myelin sheaths. The early pathological     placement of the brainstem and/or cerebellum,
changes consist of retraction balls or microglial    herniating into the foramen magnum.
scars, and if the patient lives for a number of
months before death then widespread degenera-        Hydrocephalus. This occurs infrequently in the
tion of myelin will be apparent at postmortem.       early stages after a head injury. It may be due
                                                     to obstruction of the 4th ventricle by blood,
Cerebral swelling. This occurs following trauma,     swelling in the posterior fossa, or the result of a
either in a focal pattern around an intracerebral    traumatic subarachnoid haemorrhage causing
haematoma or diffusely throughout the cere-          obstruction to the absorption of CSF and result-
brum and/or cerebellum. The nature of the            ing in a communicating hydrocephalus. This lat-
pathological processes are not clearly under-        ter type of hydrocephalus is an uncommon, but
stood but involve a disturbance of vasomotor         important, cause of delayed neurological deterio-
tone causing vasodilatation and cerebral             ration either in the weeks following the head
oedema. In addition, cerebral contusion and          injury or some years later (see ‘Normal-pressure
petechial haemorrhages will contribute to the        hydrocephalus’, Chapter 3).
brain swelling.
                                                     Concussion
Intracranial haemorrhage. Intracranial haemor-
rhage following trauma is discussed in more          Concussion involves an instantaneous loss of
detail in Chapter 5 and may be:                      consciousness as a result of trauma. The term
• intracerebral                                      ‘concussion’ was introduced by Pare and is de-
• subdural                                           rived from the Latin ‘concutere’ which means to
• extradural.                                        shake. In 1941 Denny-Brown and Russell showed
   The intracranial haematoma or cerebral            that concussion was produced by a blow on the
swelling may cause the types of cerebral hernia-     cranium when it was free to move and subse-
tion described in Chapter 3. The medial surface of   quent studies showed that the acceleration/de-
the hemisphere may be pushed under the falx          celeration of the head resulted in shear strains,
(subfalcine), the uncus and hippocampal gyrus        contre-coup injury, petechial and punctate haem-
of the temporal lobe may herniate through the        orrhages throughout the brainstem, cerebral
tentorium causing pressure on the 3rd nerve and      hemispheres and corpus callosum, and neuronal
midbrain (Fig. 4.1), or there may be a caudal dis-   injury, the extent depending on the force of the
 42                                                                                         CHAPTER 4


impact. The term concussion is not strictly de-         the nerve is easily damaged by torsion or hernia-
fined with respect to the severity of the injury.        tion of the brain.
However, a minimum criterion is that the patient
will have had a period of amnesia. The retro-           The 3rd nerve. This may also be damaged by direct
grade amnesia of most cerebral concussion is            trauma or by brain herniation, the herniated
usually short term, lasting less than 1 day. The        uncus of the temporal lobe either impinging on
initial retrograde amnesia may extend over a            the midbrain or directly stretching the nerve.
much longer period but it gradually shrinks
down. A more reliable assessment of the severity        The optic nerve. This is infrequently injured by
of the head injury is the post-traumatic amnesia.       direct trauma.
If the amnesia following the head injury lasts
more than 1 day then the concussion is regarded         Skull fractures
as being severe.                                        Trauma may result in skull fractures which are
                                                        classified as:
                                                        • simple — a linear fracture of the vault
Associated injuries
                                                        • depressed — when the bone fragments are
Cranial nerves                                          depressed beneath the vault
The cranial nerves may be injured as a result of        • compound — when there is a direct communi-
either direct trauma by the skull fracture,             cation with the external environment. This may
movement of the brain, or cerebral swelling.            result from either a laceration over the fracture or
                                                        a fracture of the base of the skull which will be
The olfactory nerves. These are the most commonly       compound because there will be a direct connec-
affected and this may be as a result of either a        tion outside the vault, usually via the air sinuses.
fracture through the anterior cranial fossa, directly
affecting the tracts, or tearing of the delicate        Scalp lacerations
nerve rootlets passing through the cribriform           The extent of the scalp laceration does not neces-
plate caused by the sudden brain movement,              sarily indicate the degree of trauma to the under-
particularly from a blow to the back of the head.       lying brain.

The 8th nerve. Damage to this nerve is often asso-      Other injuries
ciated with a fracture of the petrous temporal          The most common associated injuries are to the
bone. Deafness may be conductive, due to a              chest, skeletal and cardiovascular systems.
haemotympanum, or sensorineural as a result
of injury to the inner ear or to the nerve itself.
                                                        Initial management of head injury
Vertigo and nystagmus are due to vestibular
nerve or end-organ damage and usually resolve           The key aspects in the management of patients
within a few months of the injury.                      following head injury involve:
                                                        • accurate clinical assessment of the neurologi-
Facial paralysis. This is usually associated with a     cal and other injuries
fracture through the petrous temporal bone,             • determination of the pathological process
although this may only be evident on a high-            involved
resolution CT scan using the bone ‘window’. It          • the concept that a change in the neurological
may be either immediate, as a result of direct          signs indicates a progression or change in the
compression of the nerve, or delayed, due to            pathological processes.
bleeding and/or swelling around the nerve.                 Immediate treatment at the site of the injury
                                                        involves a rapid restoration and maintenance of
The 6th cranial nerve. This has a long course from      an adequate airway, ventilation, essential circu-
the brainstem to its entry into Dorello’s canal and     latory resuscitation, first aid treatment of other
 HEAD INJURIES                                                                                       43


injuries and the urgent transfer of the patient      different meanings to different observers. The
to hospital. It is essential to avoid hypoxia and    assessment is more accurate and reproducible
hypotension as these will cause further brain        if either the exact nature of the response is
injury.                                              described or, more simply, the Glasgow coma
                                                     scale is used.
                                                        The Glasgow coma scale (Table 4.1) gives a nu-
Clinical assessment
                                                     merical value to the three most important para-
It is fundamental to the management of the           meters of the level of consciousness — opening of
patient to know of changes in the neurological       the eyes, best verbal response and best motor
condition as soon as possible. It is essential to    response. The exact response can be represented
ascertain the type of accident that caused the       on a chart (Fig. 4.2) or the level of conscious-
head injury and the time injury occurred. An         ness given as a numerical score — the sum of the
accurate assessment of the patient’s initial         three parameters of the Glasgow coma scale. A
neurological condition, albeit in non-medical        score of 8 or less indicates a severe injury.
terms, can be obtained from bystanders at the site
of the accident or from the ambulance officers.       Pupillary size and reaction
                                                     Careful evaluation of the pupil size and response
Neurological examination                             to light is essential at the initial clinical assess-
An accurate neurological examination will help       ment and during further observation. Raised
to determine the type and position of the patho-     intracranial pressure causing temporal lobe her-
logical process and provide a baseline for           niation will cause compression of the 3rd nerve,
comparison with subsequent examinations.             resulting in pupillary dilatation, which nearly
Although a full neurological examination should      always occurs initially on the side of the raised
be undertaken, special emphasis should be given      pressure. The pupil will at first remain reactive to
to the:                                              light but subsequently will become sluggish and
• conscious state                                    then fail to respond to light at all. As the intra-
• pupillary size and reaction                        cranial pressure increases this same process com-
• focal neurological signs in the limbs.             mences on the contralateral side. A traumatic
                                                     mydriasis will also result from direct trauma
The conscious state                                  to the eye, and the dilated pupil should not be
If the patient will respond verbally an assessment   confused with that due to a 3rd cranial nerve
should be made of the retrograde amnesia and         palsy.
post-traumatic amnesia.                                 Disorders of ocular movement occur following
   There is a continuum of altered consciousness     head injury as a result of injury to an extraocular
between those patients who are alert and             muscle or its nerve supply, or due to disturbance
respond appropriately to verbal command and          of the conjugate gaze centres and pathways. A
those who are deeply unconscious. The first sign      destructive lesion of either a frontal or pontine
of a depressed conscious state is drowsiness, at     gaze centre results in tonic overaction of the
which time the patient may be easily arousable       opposite frontal–pontine pathway for horizontal
and orientated in time, place and person. As the     eye movement, causing ipsilateral deviation of
level of consciousness deteriorates the patient      the eyes with a frontal lobe lesion and contralat-
will become confused and more drowsy. The            eral gaze deviation with pontine lesions. The
term ‘coma’ is generally restricted to patients      oculocephalic manoeuvre and caloric stimula-
who show no response to external stimuli, do not     tion are important tests of functional activity of
obey commands, are unable to utter comprehen-        the brainstem reticular formation.
sible words, and do not open their eyes. How-           The oculocephalic response should only be
ever, the use of the words ‘coma’, ‘semicoma’ or     performed after a cervical spine fracture has been
‘stuporose’ should be avoided, as they convey        excluded. The head is raised 30° and rotated from
 44                                                                                            CHAPTER 4



  Table 4.1 The Glasgow coma scale.

  Parameter                                        Response                                Numerical value

  Eye opening                                      Spontaneous                             4
                                                   To speech                               3
                                                   To pain                                 2
                                                   None                                    1

  Best verbal response                             Orientated                              5
                                                   Confused                                4
                                                   Inappropriate                           3
                                                   Incomprehensible sounds                 2
                                                   None                                    1

  Best motor response to painful stimulus          Obeys commands                          6
                                                   Localize to pain                        5
                                                   Flexion to pain — withdrawal            4
                                                   Flexion — abnormal                      3
                                                   Extension to pain                       2
                                                   None                                    1

  TOTAL                                                                                    3–15




side to side in the horizontal plane. In the normal    against the trunk, extended at the elbow and
response the eyes maintain their position in space     flexed at the wrist and fingers, with the lower
by moving opposite to the rotation of the head.        limbs adducted, extended at the hip and knee
The afferent impulses are from the cervical nerve      with the feet plantar flexed. There is a continuum
roots and the semicircular canals.                     of severity of brain injury with the decerebrate
   Caloric testing should also be performed with       posturing response being partial and unilateral
the head elevated 30° so that the horizontal           and occurring only as a result of a painful stimu-
canals are positioned in the vertical plane. Irriga-   lus to severe continuing bilateral decerebrate
tion with ice-cold water causes ipsilateral tonic      rigidity. The posture probably results from an
gaze deviation.                                        upper brainstem injury. Less frequently, the
   Skew deviation involves divergence of the           upper limbs may be flexed, probably due to the
eyes in the vertical plane and is a sign of a lesion   injury predominantly involving the cerebral
within the brainstem.                                  white matter and basal ganglia — corresponding
   Ocular bobbing occurs only after a very severe      to a posture of decortication.
head injury resulting in pontine damage.                  Particular attention must be given to the pa-
                                                       tient’s ventilation, blood pressure and pulse. At
Focal neurological signs in the limbs                  all times it is essential that care is taken to ensure
Neurological examination of the limbs will as-         the patient’s ventilation is adequate. Respiratory
sess the tone, power and sensation. A hemipare-        problems may result either as a direct manifesta-
sis will result from an injury of the corticospinal    tion of the severity of the head injury or due to an
tract at any point from the motor cortex to the        associated chest injury. Cheyne–Stokes breathing
spinal cord. Following a severe brain injury the       is due to either intrinsic brainstem damage or
limbs may adopt an abnormal ‘posturing’ atti-          raised intracranial pressure causing pressure and
tude. The decerebrate posture consists of the          distortion of the brainstem. Bradycardia and
upper limbs adducted and internally rotated            hypertension, the Cushing response, are also
 HEAD INJURIES                                                                                          45




Fig. 4.2 The standard observation chart used at the Royal Melbourne Hospital and at many major trauma
centres. The chart incorporates the Glasgow coma scale.
 46                                                                                       CHAPTER 4


both indicative of brainstem compression due             Cerebral angiography is indicated if a carotico-
to raised intracranial pressure (Chapter 3).          cavernous fistula is suspected by the presence
   Pyrexia frequently occurs following a head         of a bruit over the orbit or by pulsating prop-
injury. A temperature lasting for more than 2         tosis. Carotid or vertebral angiography will be
days is usually due to traumatic subarachnoid         necessary if arterial dissection is considered a
haemorrhage or may occur in patients with a           possibility.
severe brainstem injury.                                 NB Full radiological assessment of the cervi-
                                                      cal spine utilizing plain X-ray and CT scan is
General examination                                   essential in patients who have sustained a
Careful assessment must be made of any other          significant head injury, particularly if there are
injuries. Chest, skeletal, cardiovascular or intra-   associated facial injuries.
abdominal injury must be diagnosed and the ap-
propriate management instituted. Hypotension
                                                      Further management of head injury
or hypoxia may aggravate the brain injury, and, if
severe, will themselves cause brain damage.           Following the clinical and radiological assess-
                                                      ment the subsequent management will depend
                                                      on the intracranial pathology and the extent of
Radiological assessment
                                                      any neurological injury.
Following the clinical evaluation radiological
assessment will be essential unless the injury
                                                      Minor head injury
has been minor. The CT scan will show the
macroscopic intracranial injury and should be         The patient would be assessed as described
performed where:                                      above. Any patient who has suffered a head
• there is loss of consciousness (post-traumatic      injury must be observed for at least 4 hours. The
amnesia) of greater than 10 minutes                   following are the minimal criteria for obligatory
• the patient is persistently drowsy or has a         CT scan and admission to hospital:
more seriously depressed conscious state              • loss of consciousness (post-traumatic amne-
• there is persisting nausea or vomiting              sia) of greater than 10 minutes
• there are lateralizing neurological signs           • persistent drowsiness
• there is neurological or focal deterioration        • focal neurological deficits
• there is skull fracture                             • skull fracture
• there is CSF rhinorrhoea                            • persisting nausea or vomiting after 4 hours’
• there are associated injuries which will entail     observation
prolonged ventilation so that ongoing neurologi-      • intracranial pathology noted on a CT scan
cal assessment is difficult.                           • if the patient does not have adequate care at
   The CT scan will clearly show the presence of      home.
intracerebral or extracerebral haematoma, as well        The further management of these patients will
as cerebral contusion, oedema and infarction.         be careful observation; the neurological observa-
Small ‘slit’ ventricles and absence of the basal      tions should be recorded on a chart displaying
cisterns will indicate generalized brain swelling.    the features of the Glasgow coma scale. If there
   The indications for a skull X-ray have dimin-      has been a period of significant loss of conscious-
ished since the introduction of the CT scan, espe-    ness, or if the patient is drowsy, then the follow-
cially as the bony vault can be assessed by the CT    ing measures should be instituted to minimize
scan using the bone ‘windows’. If a CT scan has       the development of cerebral swelling:
not been performed, a skull X-ray is obligatory if    • elevation of the head of the bed 20°
there has been any loss of consciousness or if the    • mild fluid restriction to 2–2.5 l/day in an adult.
mechanism of injury is suggestive of an underly-         Should the patient’s neurological state deterio-
ing fracture.                                         rate an immediate CT scan is essential to re-
 HEAD INJURIES                                                                                     47


evaluate the intracranial pathology; further           as a result of suppression of aldosterone
treatment will depend on the outcome.                  secretion occurring as a response to overhy-
                                                       dration and expansion of the circulating vol-
                                                       ume. The term ‘cerebral salt wasting’, which
Severe head injury
                                                       has been applied to this syndrome, is usually
The management of a patient following a severe         inappropriate.
head injury depends on the patient’s neurologi-           Serum sodium of less than 125 mmol/l may
cal state and the intracranial pathology resulting     produce neurological impairment with de-
from the trauma. In general, the following apply.      pression of conscious state. If due to SIADH
1 The patient has a clinical assessment and CT         the usual treatment is to restrict fluid intake to
scan as described previously.                          800 ml per day or less.
2 If the CT scan shows an intracranial                    Hypernatraemia is usually associated with
haematoma causing shift of the underlying              hyperosmolality and often results from inade-
brain structures then this should be evacuated         quate fluid intake. Other causes are diabetes
immediately.                                           insipidus, as a result of hypothalamic injury
3 If there is no surgical lesion, or following the     and excessive use of osmotic agents for control
operation, the management consists of:                 of intracranial pressure. Excessive administra-
   (a) Careful observation using a chart with the      tion of some feeding mixtures may lead to
   Glasgow coma scale.                                 electrolyte abnormalities, particularly when
   (b) Measures to decrease brain swelling; these      complicated by diarrhoea.
   include:                                            (c) Temperature control — pyrexia may be due
      (i) careful management of the airway to en-      to hypothalamic damage or traumatic sub-
      sure adequate oxygenation and ventilation.       arachnoid haemorrhage. However, infection as
      Hypercapnia will cause cerebral vasodilata-      a cause of the fever must be excluded. The most
      tion and so exacerbate brain swelling            common sites of infection after a head injury
      (ii) elevation of the head of the bed 20°        are the respiratory and urinary tracts, particu-
      (iii) fluid and electrolyte balance.              larly if a urinary catheter has been inserted. If
      Maintenance of isotonic fluid requirements,       the injury is compound, and especially if there
   avoiding dextrose solutions and following           has been a CSF leak, intracranial infection
   resuscitation should be administered until the      should be suspected. The temperature can
   patient is able to commence nasogastric feed-       usually be controlled using tepid sponges, and
   ing. Blood loss from other injuries should be       rectal paracetamol or aspirin. Chlorpromazine,
   replaced with colloid or blood and not with         to abolish the shivering response, should be
   crystalloid solutions. Care should be taken to      administered if a cooling blanket is required.
   avoid overhydration, as this will increase cere-    Every attempt should be made to control the
   bral oedema.                                        temperature because hyperthermia can elevate
      Following general injury there is retention of   the intracranial pressure, will increase brain
   salt and water and excretion of potassium. The      and body metabolism and will predispose to
   retention of water is usually greater than the      seizure activity. Although hypothermia has
   retention of sodium, resulting in mild hypo-        been advocated in the management of a severe
   natraemia. Following a severe head injury           head injury no clear-cut benefit has been
   fluid and electrolyte abnormalities may occur        demonstrated.
   for a variety of reasons. Severe hyponatraemia      (d) Nutrition — during the initial 2–3 days the
   (sodium less than 130 mmol/l) may be due to         fluid therapy will include 1.5–2 l of 4–5%
   excessive fluid intake or, occasionally, because     dextrose, providing 250–400 calories per day.
   of inappropriate excessive secretion of antidi-     Proper nutritional support should be com-
   uretic hormone (SIADH). The urine is usually        menced after 3–4 days. Feeding at this stage
   hypertonic with a high sodium level, probably       is best done by intragastric administration,
 48                                                                                       CHAPTER 4


   usually by a nasogastric tube, unless this is      pressure monitor the patient will be transferred
   precluded by other injuries. The nasogastric       to the intensive care department. The techniques
   feeding should supply 2500–3000 calories per       used to control intracranial pressure are as
   day with a calorie : nitrogen ratio of 180 : 1.    follows.
   The feeding should commence slowly, with           • Controlled ventilation, maintaining PaCO2 at
   dilute mixtures, and the stomach should be         30–35 mmHg. Reduction of the PaCO2 will reduce
   aspirated regularly to prevent regurgitation       cerebral vasodilatation and consequently de-
   and pulmonary aspiration.                          crease the intracranial pressure.
   (e) Routine care of the unconscious patient        • If the pressure remains elevated despite hyper-
   including bowel, bladder and pressure care.        ventilation CSF can be drained from a ventricular
   More aggressive methods to control intra-          catheter if this has been inserted.
cranial pressure are advisable if:                    • Diuretic therapy utilizing intermittent admin-
• the patient’s neurological state continues to       istration of mannitol or frusemide (furosemide)
deteriorate and the CT scan shows evidence of         can be used if the preceding techniques have
cerebral swelling without an intracranial             failed to control the intracranial pressure. Manni-
haematoma                                             tol is an osmotic diuretic and may also exert its
• there is a posturing (decerebrate) response to      effect by increasing serum osmolality and draw-
stimuli                                               ing water out of the brain. The usual dose is
• the Glasgow coma score is less than 8.              0.5–1.0 g/kg. The serum osmolality should not
   In these patients an intracranial pressure         exceed 320 mosmol/kg.
monitor should be inserted to assess the intracra-    • Barbiturate therapy can be considered if the in-
nial pressure as accurately as possible. A trans-     tracranial pressure is resistant to treatment with
ducer can be placed intraparenchymally via a          the above techniques. Pentobarbitone (thiopen-
twist drill craniostomy. A catheter placed into the   tone) when given as a bolus dose (3–5 mg/kg) is
ventricle will give an accurate reading of the        frequently effective in temporarily reducing the
intracranial pressure and CSF can be drained to       intracranial pressure. There is probably little
help in the control of the pressure. However, the     value in using barbiturate infusion at a dose to
disadvantages of an intraventricular catheter in-     control burst suppression on EEG, although it
clude difficulty of placement if the ventricles are    has been postulated that this provides brain
small, possible injury to the brain during place-     protection by reducing cerebral metabolism.
ment and infection resulting in ventriculitis         • Steroids. Although steroids dramatically re-
following prolonged monitoring. A subdural            duce the oedema around cerebral tumours they
catheter will also give an adequate measurement       have little effect in controlling the brain swelling
of the intracranial pressure but may be difficult      following a head injury. Steroid medication is no
to insert satisfactorily if the brain is swollen,     longer considered advisable as there is no proven
and will tend to block. Extradural monitors are       benefit for the patient and possible complica-
less accurate, although satisfactory recordings       tions, such as gastrointestinal bleeding, poor
are obtainable with meticulous placement              wound healing and infection, may result from
technique.                                            their administration.
   An intracranial pressure monitor will also be      • Hypothermia. In some centres hypothermia
useful in patients requiring prolonged sedation       (to reduce cerebral metabolism and intracranial
and ventilation as a result of other injuries.        pressure) has been advocated, with cooling the
Measurement of the intracranial pressure will         patient to 34°C. However there is no clear evi-
provide another useful monitoring parameter           dence it is beneficial.
and any sustained rise in the pressure will be an     • Hyperbaric oxygen has been used in the past,
indication for careful reassessment and, if neces-    but without proven benefit.
sary, CT scan.                                           Decompressive craniotomy involving re-
   Following the insertion of the intracranial        moval of a large area of cranial vault from the
 HEAD INJURIES                                                                                          49


frontal and temporal regions bilaterally has been
                                                       Management of associated conditions
advocated as a means of controlling raised
intracranial pressure due to severe cerebral           Scalp injury
swelling following a head injury. The technique        Scalp injuries may include:
is controversial, but it needs to be performed         • abrasion
early following the injury if it is to have a chance   • confusion
of being of benefit to the patient. At present there    • laceration
are no clinical trials proving its efficacy in head     • subgaleal haematoma.
injury.                                                   A large scalp laceration may result in consider-
   There is some controversy concerning the            able blood loss. When the patient arrives in
effectiveness of the more aggressive techniques        the emergency department ‘spurting’ arteries
to treat patients with severe head injuries. If a      should be controlled with haemostatic clips prior
patient has suffered a profound brain injury and       to the application of a sterile bandage to the head.
the neurological examination shows little or no        The extent of the soft tissue scalp injury may not
remaining brainstem function then it is obvious        reflect the severity of the underlying brain injury.
that the aggressive techniques will provide no         The principles of management are similar to
benefit and only delay the inevitable. Similarly,       those of soft tissue injury at other sites of the body
there are some patients who have suffered a se-        and the wound should be closed without delay.
vere head injury and whose intracranial pressure          The hair should be shaved widely around the
continues to rise despite all the above techniques.    wound, which should be meticulously cleaned
Other patients will have a fatal brain injury with-    and debrided. The closure should be performed
out any substantial rise in intracranial pressure,     in two layers if possible, with careful apposition
usually when the brainstem has been the primary        of the galea prior to closing the skin. The skin
site of injury. However, about 30% of patients         sutures should approximate the cut edges of the
who have suffered a severe brain injury will           skin and care should be taken to avoid excessive
obtain substantial benefit from control of the          tension which would cause skin necrosis and
intracranial pressure. Clinical studies have not       wound breakdown.
yet conclusively proven the value of intracranial         Straightforward, clean scalp lacerations can
pressure control in reducing morbidity following       nearly always be closed with local anaesthetic
a brain injury as it is thought that the patients in   infiltration. However, if the scalp wound has
the studies that were performed were overventi-        resulted in loss of soft tissue the wound may
lated and the cerebral blood flow might have            need to be extended to provide an extra ‘flap’
been compromised. There is now consensus that          of healthy tissue so that the skin edges can be
a reduction in raised intracranial pressure will       approximated without tension.
not only decrease the mortality but will improve
the quality of the patient’s outcome after a severe    Skull fractures
head injury.                                           Simple linear fracture. There is no specific manage-
   Cerebral perfusion pressure is a vital physio-      ment for a simple skull fracture that is
logical parameter in the management of severely        undisplaced without an overlying skin injury.
head injured patients. The cerebral perfusion          However, the presence of a fracture is an indica-
pressure — mean arterial BP minus mean in-             tion that the trauma was not trivial and it should
tracranial pressure — should be maintained             provide a warning that a haematoma may
above 70 mmHg. Consequently head injury man-           develop beneath the fracture. The patient
agement involves ensuring that the arterial blood      should be admitted for observation and CT scan
pressure is maintained whilst the intracranial         performed.
pressure is reduced. This often involves close
cooperation between the neurosurgeon and the           Compound fracture. A skull fracture may be
intensive care physician.                              compound either because of an overlying scalp
 50                                                                                         CHAPTER 4




                                                      Fig. 4.4 Depressed skull fracture with underlying
                                                      brain contusion.
Fig. 4.3 Depressed skull fracture.

                                                      quiring a general anaesthetic, should be per-
laceration or if it involves an air sinus. The        formed as soon as possible. A preoperative CT
scalp wound should be debrided and closed as          scan will show not only the position of the de-
described above. A short course of prophylactic       pressed skull fragments but also the presence of
antibiotics should be administered to reduce the      any underlying intracranial pathology (Figs 4.4
risk of infection.                                    and 4.5). At operation the scalp wound should be
                                                      cleaned and debrided, as described previously,
Depressed skull fracture (Fig. 4.3). A skull vault    and the bone fragments elevated. If the dura has
fracture is considered to be significantly de-         been penetrated, or if bone fragments and exter-
pressed if the inner table fragments are depressed    nal foreign material have been driven down into
by at least the thickness of the skull. About half    the brain, this must be meticulously debrided
the injuries are due to road trauma and most of       and haemostasis obtained. It is desirable that the
the remainder are due either to objects falling on    dura should be closed and this may require the
the head at work or to assault with a heavy, blunt    use of a patch of pericranium or fascia lata from
instrument. A depressed fracture caused by a          the thigh. If the wound and bone fragments are
non-missile injury usually causes only focal brain    heavily contaminated, and particularly if there
damage, so that many patients never lose con-         has been some delay in surgery, the bone should
sciousness. If the underlying injured brain is an     not be replaced and a reconstructive cranioplasty
eloquent area the patient will exhibit focal neuro-   may be necessary later.
logical signs. Haemorrhage from the bony edges,          If the depressed fracture is closed there is
the dura or underlying brain trauma may result        no urgency in elevating the bone fragments,
in an intracranial haematoma which will cause         provided there is no underlying intracranial
progressive neurological deterioration. If the de-    complication. There is controversy over whether
pressed fracture is compound and the dura has         a depressed fragment might lead to epilepsy due
been lacerated there is a significantly increased      to continued pressure on the brain. In general, the
risk of intracranial infection.                       depressed fragments should be elevated if:
   If the depressed skull fracture is compound,       • careful studies using the bone ‘windows’ on
prophylactic antibiotics and tetanus prophylaxis      the CT scan show that the dura might have been
should be administered and surgery, usually re-       penetrated
 HEAD INJURIES                                                                                                   51




                                                                      Sphenoid sinus    Ethmoid sinus    Frontal sinus

                                                            Fig. 4.6 Relationship of base of skull to air sinuses.
    (a)


                                                            Cerebrospinal fluid rhinorrhoea
                                                            A fracture involving the base of the anterior
                                                            cranial fossa may cause tearing of the basal dura
                                                            resulting in a fistula into the frontal, ethmoid or
                                                            sphenoid sinuses (Fig. 4.6). This type of fistulous
                                                            connection should also be suspected if the patient
                                                            suffers from an episode of meningitis or if the ra-
                                                            diological investigations show a fracture in the
                                                            appropriate site. An intracranial aerocele (Fig.
                                                            4.7) is proof of a fistulous connection. CSF rhinor-
                                                            rhoea may also occur as a result of a fistula
                                                            through the tegmen tympani into the cavity of the
                                                            middle ear, and may leak via the eustachian tube.
    (b)                                                        Base of skull fractures are relatively frequent as
Fig. 4.5 (a,b) CT showing severe trauma resulting in        skull fractures are often directed into the skull
multiple fractures, disruption of the orbit, intracranial   base by its bony buttresses. They are often occult
contusions involving the right temporal lobe and            radiologically but diagnosed clinically. Anterior
intracranial air.                                           fossa fractures may open into the frontal, sphe-
                                                            noid or ethmoid sinuses, often running across the
• there is significant brain compression                     cribriform plate. They present with:
• the fracture is compound                                  • subconjunctival haemorrhages extending to
• there are cosmetic considerations such as a               the posterior limits of the sclera. Periorbital
frontal fracture in a young child.                          haematomas or ‘racoon eyes’ indicate subgaleal
   The risk of epilepsy following a depressed frac-         haemorrhage and not necessarily a base of skull
ture is 15% for the whole group, but the risk               fracture
ranges from 3 to 70% depending upon other asso-             • anosmia
ciated intracranial pathology resulting from the            • nasal tip paraesthesiae due to anterior eth-
injury. Prophylactic anticonvulsant medication              moidal nerve injury.
should be continued for 1 year if the dura has                 Middle fossa fractures involving the petrous
been penetrated.                                            temporal bone present with:
 52                                                                                         CHAPTER 4


                                                        unplugged. Alternatively, CSF leakage may cease
                                                        due to a brain hernia ‘plugging’ the hole in the
                                                        dura and bone. Although the brain hernia might
                                                        stop the CSF escaping it will not provide protec-
                                                        tion against future intracranial infection, as the
                                                        dural defect will remain.
                                                           There is controversy concerning the indica-
                                                        tions for an anterior cranial fossa exploration and
                                                        dural repair, but there is general agreement that
                                                        surgery should be performed if:
                                                        • CSF leakage continues for more than 5 days,
                                                        indicating the fistula is not trivial
                                                        • there is an intracranial aerocele
                                                        • there has been an episode of meningitis in a pa-
                                                        tient with a fracture of the anterior cranial fossa.
                                                           Patients with a possible dural fistula should be
                                                        placed on prophylactic antibiotic medication. In
                                                        general, penicillin is recommended as Pneumo-
Fig. 4.7 CT scan showing intracranial air in a          coccus is the most common organism; amoxy-
subarachnoid space and within the lateral ventricles.   cillin is appropriate in children due to the risk of
                                                        Haemophilus infection. Broad-spectrum anti-
                                                        biotics may lead to the development of resistant
• CSF otorrhoea (or rhinorrhoea) via the eu-            organisms and should be avoided. Nasal swabs
stachian tube                                           may indicate the need for more individualized
• deafness due to 8th nerve injury or ossicular         antibiotic prophylaxis.
disruption                                                 It is best to delay surgery for about 2 weeks,
• haemotympanum                                         until the initial brain swelling has resolved. Early
• Battle’s sign — bruising over mastoid bone            surgery, using a craniofacial type of exposure,
• 7th nerve palsy — often delayed.                      has been advocated by some neurosurgeons if
   The diagnosis of CSF rhinorrhoea may be diffi-        there are associated major facial and anterior
cult. In the early stages following a head injury       vault fractures. However, early surgery may re-
involving fractures to the facial bones, CSF needs      sult in further damage to an already swollen
to be differentiated from a bloody nasal dis-           frontal lobe during the retraction necessary to ob-
charge. Allergic rhinitis is the major differential     tain adequate exposure of the dural tear.
diagnosis in patients presenting weeks or                  The operative procedure involves a frontal
months after a head injury. Testing for sugar or        craniotomy with repair of the dural defect using
B2-transferrin in the nasal discharge may help to       either pericranium or fascia lata taken from the
identify the fluid as being CSF. CSF isotope scans       thigh.
using technetium-99 injected through the lumbar
theca are only likely to be positive if there is a      Cerebrospinal fluid otorrhoea
large leak. High-resolution CT scanning follow-         CSF otorrhoea may occur as a result of a base of
ing the administration of intracisternal contrast       skull fracture involving the petrous temporal
may help to identify the position of the hole.          bone. Unlike fractures of the anterior cranial
   The major concern of a dural fistula is the risk      fossa the leakage nearly always settles and the
of intracranial infection, particularly bacterial       fistula does not usually provide a route of infec-
meningitis. A CSF leak may not become apparent          tion, unless there is evidence of chronic middle
for a few days after the head injury, but as the        ear infection. Occasionally, a persistent leak may
brain swelling decreases the dural tear becomes         require surgical exploration and repair.
 HEAD INJURIES                                                                                           53


Cranial nerve injuries                                   The missile causes cerebral damage via three
Injuries to the cranial nerves occurring directly as     mechanisms:
a result of the trauma are not helped by surgery.        • mechanical laceration of brain tissue during
Steroid medication is appropriate for patients           transit
with a delayed facial nerve palsy following frac-        • the shock wave promulgated ahead of the
ture of the petrous temporal bone. Some otolo-           missile
gists recommend surgical decompression of the            • cavitation in the wake of the missile.
facial nerve when the palsy is delayed but, as the          The pathological processes involve scalp
facial function nearly always recovers, operative        injury, depressed skull fracture, intracranial
intervention is usually not justified.                    haemorrhage and the intracranial pathological
                                                         sequelae resulting from a ‘closed’ head injury,
Post-traumatic epilepsy                                  including cerebral contusion, haemorrhage,
The indications for prophylactic medication              swelling and raised intracranial pressure. The
following head injury are discussed in Chapter           pattern of injury will depend on the velocity of
21.                                                      the weapon and the trajectory of the missile
                                                         through the bone and brain. A high-velocity
                                                         wound may result in a rapid increase of intracra-
Missile injuries
                                                         nial pressure of more than 3000 mmHg due to
Although most literature on missile injuries is re-      the temporary cavity about the missile, which
lated to warfare, these injuries are unfortunately       might be 50 times as large as the missile itself.
becoming more common in civilian conflict, par-           The high intracranial pressure resulting from
ticularly as a result of the increased availability of   the cavitation may result in death from failure
firearms. In general the cranial injury is directly       of the respiratory and cardiac centres in the
proportional to the velocity of the missile. The         brainstem.
‘high-velocity’ injury is defined as resulting from
a missile travelling faster than the speed of sound
                                                         Management
(1050 ft/s), and modern rifle bullets have a
muzzle velocity greater than 3000 ft/s. There are        Rapid transport of the patient to hospital and ur-
three categories of missile injury:                      gent treatment is of paramount importance. The
• tangential — the missile does not enter the            early definitive treatment resulting from prompt
cranium but causes a depressed skull fracture,           transport and the introduction of antibiotics were
lacerating the scalp with an underlying cortical         the major factors in lowering mortality from head
contusion, laceration or haematomas                      wounds in the Korean and Vietnam wars.
• penetrating — the missile enters the cranium              The management of the patient after transfer to
resulting in the deposition of metal, bone frag-         hospital is essentially the same as described for
ments and debris within the brain                        severe head injuries previously. Antibiotics
• through-and-through — the missile enters and           should be administered immediately, in large in-
exits the cranium, frequently creating more than         travenous doses because of the risk of infection;
one tract due to fragmentation                           penicillin and chloramphenicol were the most
   The cranial injury is directly related to the ve-     commonly used during the Vietnam conflict. Op-
locity of the missile. The energy dissipated by the      timal antibiotic administration should provide
missile equals MV2 where M is the mass and               a broad cover of Gram-positive, Gram-negative
V the velocity of the missile. Modern ballistics         and anaerobic organisms. After neurological
has designed missiles to have maximal velocity           assessment, a CT scan should be performed to
and stability in flight with maximal dissipation of       ascertain the position of the intracranial
energy upon impact. The primary missile fre-             haematomas, depressed bone fragments and
quently fragments and can cause further sec-             metal fragments.
ondary missiles from fragments of bone or metal.            Surgery is not appropriate if the patient is brain
 54                                                                                           CHAPTER 4


dead with no evidence of brainstem reflexes.               and social services. MRI now plays an important
Patients with less severe injuries should have            role in determining the chronicity of cerebral
urgent surgical intervention, particularly as             injuries in infants. Collections of different
early exploration reduces the risk of subsequent          chronicity, or in unusual locations, should alert
infection.                                                the physician to the possibility of non-accidental
   The operation is performed under general               injury.
anaesthesia and intravenous diuretic therapy is
administered to reduce intracranial pressure. A
                                                          Rehabilitation
large scalp flap is designed, with excision and de-
bridement of the entry and exit wounds. Meticu-           Some form of rehabilitation is essential following
lous care is taken to remove any accessible bone          any significant head injury. If the injury has been
or metallic fragments. Haematoma and necrotic             relatively minor then the necessary rehabilitation
brain debris are excised. A watertight dural clo-         may involve only advice and reassurance to the
sure should be performed and the scalp should             patient and family. However, rehabilitation
be closed in two layers (galea and skin). Follow-         following a severe head injury will usually
ing surgery, a repeat CT scan will identify any           involve a team of paramedical personnel, includ-
further retained bone or metallic fragments.              ing physiotherapists, occupational therapists,
Accessible fragments should be removed, but               speech therapists and social workers.
isolated deep or inaccessible bone or metallic               The major groups of disabilities resulting from
fragments are probably best left as further neuro-        a head injury are:
logical damage may occur during an attempt at             • impairment of motor function — hemiparesis,
excision of these particles. In civilian practice,        quadriparesis, ataxia, poor coordination
infection is unlikely if exploration has taken            • speech disturbances — dysphasia, dysarthria
place within 2 hours of the injury. In general it         • impairment of special senses — vision, hearing
is thought that retained metallic fragments have          • cognitive disturbance — memory impairment,
less potential for infection than other debris.           intellectual disability, personality change.
   Postoperative management is similar to that               The general aims of the rehabilitation process
described for severe head injury, with particular         are:
attention to controlling intracranial pressure.           • in the initial period, to prevent complications
Prophylactic antibiotics and anticonvulsant               such as contractures of the limbs and to provide
medication are administered.                              counselling for the family
                                                          • to maximize the neurological recovery by
                                                          restoring old skills and teaching new skills — this
Non-accidental head injury
                                                          is usually undertaken in a rehabilitation unit
The infantile chronic subdural haematoma or ef-           • retraining for future employment, if necessary
fusion is a distinct clinical entity. Birth trauma is a   and if possible.
frequent cause but in many cases a past history is           The rehabilitation process should commence
inadequate to establish the nature of the injury          as soon as possible after the head injury and
with certainty. Chronic subdural haematomas               should initially concentrate on preventing com-
occur in approximately 20% of battered children.          plications. Limb contractures and pressure sores
The violent shaking of the immature brain might           are avoided by frequent patient turning, physio-
be sufficient to rupture bridging veins or cause           therapy and the use of splints. As the neurologi-
shearing at the grey/white interface without evi-         cal state improves the patient’s rehabilitation will
dence of external trauma. If an inadequate histo-         normally be undertaken in a rehabilitation unit.
ry is provided in such a setting, it is important to      Orthotic devices will assist hemiplegic patients
screen for a coagulopathy, examine the fundi for          to walk and, if they can follow simple instruc-
retinal haemorrhages, arrange a skeletal survey           tions, most are able to relearn the activities of
and when appropriate involve a paediatrician              daily living.
 HEAD INJURIES                                                                                                  55


  The speech therapist may provide valuable                     anterior cranial fossa. The selection of patients for
assistance for patients with dysarthria and                     dural repair. British Journal of Surgery 59, 585–592.
swallowing difficulties. Formal speech therapy                 Jennett B, Miller JD (1972) Infection after depressed
probably does little to improve global aphasia                  fracture of the skull. Implications for management of
                                                                non-missile injuries. Journal of Neurosurgery 36,
but it does offer important psychological support
                                                                333–339.
for the patient with a severe communication
                                                              Jennett B, Miller J D, Braakman R (1974) Epilepsy after
disorder.                                                       non-missile depressed skull fracture. Journal of
  Damage to the non-dominant hemisphere                         Neurosurgery 41, 208–216.
results in perceptual disturbances, particularly              Jennett B, Teasdale G (1981) Management of Head In-
relating to visual spatial tasks. Although the                  juries. Contemporary Neurology Series. F A Davis,
perceptual problems may resolve with time and                   Philadelphia.
rehabilitation, the problems associated with cog-             Johnston IH, Johnston JA, Jennett B (1970) Intracranial
nitive disturbances and alteration of personality               pressure changes following head injury. Lancet ii,
may persist. Family counselling and support is                  433–436.
essential to help the relatives understand and                Kaye AH, Black P McL (2000) Operative Neurosurgery.
                                                                Churchill Livingstone, London, New York,
cope with these long-term disabilities.
                                                                Edinburgh.
                                                              Langfitt TW (1978) Measuring the outcome from head
Further reading                                                 injuries. Journal of Neurosurgery 48, 673–678.
                                                              Levy ML, Masri LS, Lavine S, Apuzzo M (1994) Out-
Becker DP, Miller JD, Ward JD, Greenberg RP, Young              come prediction after penetrating craniocerebral
   HF, Sakalas R (1977) The outcome from severe head            injury. Neurosurgery 35, 77–85.
   injury with early diagnosis and intensive manage-          Plum F, Posner JB (1972) The Diagnosis of Stupor and
   ment. Journal of Neurosurgery 47, 491–502.                   Coma, 2nd edn. F A Davis, Philadelphia.
Blackwood W, Corsellis JAN, eds (1976) Greenfield’s            Rosner MJ, Rosner SD, Johnson AH (1995) Cerebral per-
   Neuropathology. Edward Arnold, London.                       fusion pressure: Management protocol and clinical
Cushing H (1908) Surgery of the head. In: Kean WW, ed.          results. Journal of Neurosurgery 83, 949–962.
   Surgery — Principles and Practice. W B Saunders,           Russell WR, Schiller F (1949) Crushing injuries of
   Philadelphia, Vol 3, 217–276.                                the skull: Clinical and experimental observations.
Cushing H (1918) Notes on penetrating wounds of the             Journal of Neurology, Neurosurgery and Psychiatry 12,
   brain. British Medical Journal 1, 22–26.                     52–60.
Gurdjian ES, Thomas RS (1964) Surgical management             Stone JL, Lichtor T, Fitzgerald LF (1995) Gunshot
   of a patient with head injury. Clinical Neurosurgery 12,     wounds to the head in civilian neurosurgery.
   56–74.                                                       Neurosurgery 37, 1104–1112.
Holbourn AHS (1943) Mechanisms of brain injuries.             Teasdale G, Jennett B (1974) Assessment of coma
   Lancet ii, 438–441.                                          impaired consciousness. Lancet ii, 81–84.
Jamieson KG, Yelland JD (1975) Surgical repair of             Walsh FB, Hoyt WF (1969) Clinical Neuro-ophthalmology,
   anterior fossa because of rhinorrhoea, aerocele or           Vol 3. Williams & Wilkins, Baltimore.
   meningitis. Journal of Neurosurgery 39, 328–331.
Jefferson A, Reilly G (1972) Fractures of the floor of the
                           CHAPTER 5


  5                        Traumatic intracranial
                           haematomas


Intracranial haematoma formation following            may occur in the presence of a severe head
head injury is the major cause of fatal injuries in   injury and coexist with a severe primary brain
which death may have been potentially avoid-          injury, the important feature of an extradural
able and in which many survivors are unneces-         haematoma is that it may occur when the
sarily disabled following head injury due to a        injury to the underlying brain is either trivial or
delay in the evacuation of the haematoma. The         negligible.
incidence of intracranial haematomas and the
type of haematoma varies widely depending on
                                                      Distribution of extradural haematomas
the different admission policies. In general hospi-
tals that receive an unselected series of patients,   The most common sites for extradural
the incidence varies between 1 and 5% of all head     haematoma are the temporal region followed by
injuries, while the incidence will be much higher     the frontal area. Posterior fossa and parasagittal
in specialist neurosurgical centres.                  extradural haematomas are relatively uncom-
                                                      mon. The relative proportions in a consecutive
                                                      series of 200 cases from The Royal Melbourne
Classification of traumatic
                                                      Hospital are shown in Fig. 5.1. In most cases the
intracranial haematomas
                                                      haemorrhage is from a torn middle meningeal
The general classification depends on the rela-        artery or its branches but haematomas may also
tionship of the haematoma to the dura and brain.      develop from haemorrhage from extradural
Haematomas can be:                                    veins, the superior sagittal sinus, transverse
• extradural                                          sinus or posterior meningeal artery, the last
• subdural                                            two being responsible for the posterior fossa
• intracerebral.                                      extradural haematomas. A fracture overlies the
However, many haematomas occupy more than             haematoma in nearly all (95%) adults and most
one of the intracranial sites (Table 5.1).            (75%) children.


Extradural haematoma                                  Clinical presentation
Extradural haematomas are more likely to occur        As previously mentioned, an extradural
in the younger age group as the dura is able          haematoma may occur as a result of a severe head
to strip more readily off the underlying bone.        injury and the haematoma will then become
In patients under 20 years of age, extradural         manifest as a further deterioration of the neuro-
haematomas account for about two-thirds of all        logical state, particularly with lateralizing fea-
traumatic intracranial haematomas, but repre-         tures involving a 3rd nerve palsy (dilatation of
sent less than 5% of haematomas in patients over      the pupil) and progressive hemiparesis.
the age of 50. Although an extradural haematoma          More frequently the extradural haematoma

56
 TRAUMATIC INTRACRANIAL HAEMATOMAS                                                                            57



  Table 5.1 Position of traumatic intracerebral haematomas.

                                      Extradural   Extradural and   Subdural   Subdural and        Intracerebral
  Series                              only (%)     intradural (%)   only (%)   intracerebral (%)   only (%)

  International Collaborative Study   16            7               22         34                  20
    (Glasgow, Rotterdam,
    Groningen, Los Angeles)
  Brisbane (Jamieson & Yelland)       13           11               34         36                   6
  Melbourne (The Royal                13            9               29         31                  18
    Melbourne Hospital)




                                                         Deteriorating conscious state. This is the most
                         7                               important neurological sign, particularly when it
                                                         develops after a ‘lucid’ interval. It is essential that
                                                         the drowsiness that occurs in a patient following
                                            11           a head injury is not misinterpreted just as the
                                                         patient wishing to sleep. It is well to remember
  8
                                                         the nursery rhyme:
                                                              It’s raining, it’s pouring,
                         66                                   The old man is snoring,
           9                                                  He bumped his head and went to bed,
                                                              And couldn’t get up in the morning.
                                                         This is a classic description of an extradural
                                                         haematoma leading to drowsiness and death.

Fig. 5.1 Frequency of sites of extradural haematomas     Focal neurological signs. These will depend upon
in The Royal Melbourne Hospital series of 200            the position of the haematoma. In general, a
consecutive cases.
                                                         temporal haematoma will produce a progressive
                                                         contralateral spastic hemiparesis and an ipsilat-
occurs following a head injury that has resulted         eral dilated pupil. Further progression will result
in only a transient loss of consciousness and in         in bilateral spastic limbs, a decerebrate posture
approximately one-quarter of cases there has             and bilaterally dilated pupils (see Chapter 4, Fig.
been no initial loss of consciousness. In these          4.1). Occasionally the hemiparesis may initially
patients the most important symptoms are:                be ipsilateral, due to compression of the con-
• headache                                               tralateral crus cerebri of the tentorial edge, but it
• deteriorating conscious state                          is rare for the opposite pupil to be involved first.
• focal neurological signs (dilating pupil, hemi-
paresis)                                                 Change in vital signs. The change in vital signs
• change in vital signs (hypertension, brady-            shows the classic Cushing response to a rise in
cardia).                                                 intracranial pressure — bradycardia accompanied
                                                         by an increase in blood pressure. Disturbances in
Headache. This is the outstanding initial symptom        respiration will develop into a Cheyne–Stokes
in patients who have not lost consciousness or           pattern of breathing.
who have regained consciousness. The headache
increases in severity and is followed by vomiting.       Extradural haematomas occurring at other than
 58                                                                                        CHAPTER 5


                                                      deterioration may be so rapid that there is not
                                                      sufficient time for a CT scan and the patient
                                                      should be transferred immediately to the operat-
                                                      ing theatre. Infusion of mannitol (20% solution,
                                                      1 g/kg) or frusemide (20 mg intravenously) may
                                                      temporarily reduce the intracranial pressure
                                                      during the transfer to the operating theatre. If
                                                      unconscious, the patient must be intubated and
                                                      hyperventilated during the transfer. It is essen-
                                                      tial that there should be no delay in evacuating
                                                      the haematoma. An extradural haematoma is a
                                                      surgical emergency which will result in death if
                                                      not removed promptly.

                                                      Operation for extradural haematoma
                                                      The type of operation performed will depend on
                                                      the circumstances in which the patient is being
Fig. 5.2 Extradural haematoma with the typical
                                                      treated.
hyperdense biconvex appearance.
                                                      1 If a CT scan has been performed and the posi-
                                                      tion of the haematoma is known, the skin flap
the temporal position show modifications of this       will be lifted directly over the haematoma.
clinical presentation. Frontal haematomas show        2 If the patient’s neurological state is stable or
evidence of lateralizing signs late in their evolu-   only slowly progressive and if the surgeon is
tion, the predominant features being a deteriora-     trained in neurosurgical operations, a formal
tion of consciousness and pupil abnormalities. In     craniotomy can be performed over the site of the
the posterior fossa the vital signs tend to be af-    haematoma.
fected early, followed by a change in conscious       3 A craniectomy, rather than a craniotomy,
state. The pupils and limbs may not be affected       should be performed:
until the patient becomes deeply unconscious.            (a) if the surgeon is inexperienced
Haematomas in the posterior fossa may cause              (b) if craniotomy instruments are not available
sudden respiratory failure.                              (c) if the rate of neurological deterioration has
                                                         been so rapid that time has not permitted a CT
Radiological investigations                              scan to be performed.
The CT scan is the radiological investigation of            Exploratory burr holes should be inserted
choice and must be performed urgently if an ex-          first in the temporal region and then in the
tradural haematoma is considered a possibility.          frontal and parietal areas (Fig. 5.3). When the
The CT scan will show the typical hyperdense             haematoma is identified the burr hole incision
(white) biconvex haematoma (Fig. 5.2) with com-          should be extended and the bone over the
pression of the underlying brain and distortion of       region of the haematoma should be rapidly
the lateral ventricle.                                   removed. If the haematoma is not found on the
                                                         first side that is explored burr holes should be
                                                         performed in the same order on the other side.
Treatment
                                                            The following are guidelines for the position
The treatment of extradural haematoma is urgent          of the haematoma if a CT scan has not been
craniotomy with evacuation of the clot.                  performed:
   The patient should have an urgent CT scan as             (i) it underlies the fracture (that may have
soon as an extradural haematoma is suspected                been seen on the skull X-ray)
clinically. In some cases the rate of neurological          (ii) it underlies a boggy swelling on the skull
 TRAUMATIC INTRACRANIAL HAEMATOMAS                                                                          59




                   (a)                        (b)                         (c)
Fig. 5.3 Emergency surgery for suspected extradural haematoma. (a) Position of exploratory burr holes. (b) If
haematoma found in the temporal position the skin wound is extended. (c) Further bone removed to enable
complete evacuation of haematoma and haemostasis.




      (iii) it is on the same side as the pupil that      potentially reversible, provided the haematoma
      dilated first                                        is evacuated before pressure from the blood clot
      (iv) in 85% of cases it is on the contralateral     has caused secondary intracranial pathological
      side to the hemiparesis.                            effects.
   Following removal of the bone of the vault by
craniotomy or craniectomy it is easy to evacuate
                                                          Subdural haematoma
the haematoma. The original source of the
haematoma, usually the bleeding middle                    Subdural haematomas have been classified into
meningeal artery in the temporal haematoma, is            acute, subacute and chronic, depending on the
controlled by diathermy or with a haemostatic             time they become clinically evident following
clip. The haematoma will have stripped away the           injury:
dura from the inner table of the vault, often             • acute subdural haematoma — less than 3 days
resulting in considerable oozing from the dural           • subacute subdural haematoma — 4–21 days
surface. The dura should be opened, if a CT scan          • chronic subdural haematoma — more than 21
has not previously been performed, to exclude             days.
the coexistence of a subdural haematoma. It                  The CT scan enables a further classification de-
should then be closed in a watertight fashion. It is      pending on the density of the haematoma rela-
usually advisable to insert a closed-system, low-         tive to the adjacent brain. An acute subdural
pressure extradural drain to evacuate any blood           haematoma is hyperdense (white) and a chronic
that may continue to ooze.                                subdural haematoma is hypodense. Between
   The postoperative care is similar to that for any      the end of the 1st week and the 3rd week the
other intracranial procedure. If the neurological         subdural haematoma will be isodense with the
state fails to improve following the evacuation of        adjacent brain.
the haematoma, or if there is further deteriora-
tion, another CT scan should be performed to
                                                          Acute subdural haematoma
exclude recurrence of the haematoma formation.
                                                          The acute subdural haematoma frequently
Prognosis. If the initial head injury has resulted in     results from severe trauma to the head and com-
only a transient loss of consciousness, the patient       monly arises from cortical lacerations. However,
should make a full recovery following removal             an acute subdural haematoma can result from a
of the extradural haematoma, provided the                 less severe trauma caused by rupture of a bridg-
haematoma has been evacuated early enough to              ing vein or focal tear of a cortical artery, especially
prevent permanent neurological disability. The            if the patient has been anticoagulated for other
damage caused by an extradural haematoma is               medical reasons (e.g. for atrial fibrillation). Cases
 60                                                                                        CHAPTER 5


of spontaneous acute subdural haematoma have           washed out with gentle irrigation through burr
been reported and in these patients it is essential    holes. However if bleeding persists a craniotomy
to exclude a ruptured aneurysm or bleeding             will be required for haemostasis.
diathesis as a cause. Acute subdural haematomas
are bilateral in approximately one-third of cases,
                                                       Chronic subdural haematoma in the adult
in comparison with less than 3% of extradural
haematomas.                                            In 1863, Virchow first proposed chronic inflam-
   An acute subdural haematoma often presents          mation of the meninges as being the cause of a
in the context of a patient with a severe head in-     chronic subdural haematoma. In 1914, Trotter
jury whose neurological state is either failing to     suggested trauma as the aetiological factor and in
improve or deteriorating. The features of deterio-     1932 Gardner, and later Zollinger and Gross, pro-
rating neurological state — decrease in conscious      posed that an osmotic gradient occurred from the
state and/or increase in lateralizing signs —          breakdown of haemoglobin. However, it was
should raise the possibility of a subdural             subsequently shown that the osmolarity of the
haematoma.                                             haematoma did not change with time and so this
   The CT scan will show the characteristic hy-        theory was abandoned.
perdense haematoma, which is concave towards              Chronic subdural haematoma can be divided
the brain, with compression of the underlying          into two major groups. The first involves patients
brain and distortion of the lateral ventricles (Fig.   having suffered a significant, and often severe
5.4). Over 80% of patients with acute subdural         head injury. However, in approximately one-
haematomas have a fracture of either the cranial       third of patients there is no definite history of
vault or the base of the skull, which may be           preceding head trauma. The aetiology of the
evident on the bone ‘windows’ of the CT scan.          subdural haematoma in this non-traumatic
   A craniotomy is nearly always necessary to          group is probably related to rupture of a fragile
evacuate an acute subdural haematoma. If the           bridging vein in a relatively atrophic ‘mobile’
haematoma is liquid the blood can sometimes be         brain. In this group the majority of patients are
                                                       over 50 years of age. Shrinkage of the brain re-
                                                       sulting from atrophy allows the brain to become
                                                       more mobile and increases the space traversed by
                                                       the veins bridging between the cortex and the
                                                       vault. A relatively trivial injury may result in
                                                       movement of the brain, like a walnut inside its
                                                       shell, with tearing of the bridging vein. Patients
                                                       who are anticoagulated are especially prone to
                                                       develop a subdural haematoma following rela-
                                                       tively minor trauma.

                                                       Clinical presentation
                                                       The presence of a chronic subdural haematoma
                                                       should be considered if the neurological state of a
                                                       patient being treated in hospital for a significant
                                                       head injury begins to deteriorate. Alternatively,
                                                       the patient may present without the history of a
                                                       significant head injury in one of three characteris-
                                                       tic ways.
                                                       1 Raised intracranial pressure without signifi-
Fig. 5.4 Acute subdural haematoma causing marked       cant localizing signs. The patient presents with
shift of the lateral ventricle.                        headache, vomiting and drowsiness and the
 TRAUMATIC INTRACRANIAL HAEMATOMAS                                                                      61


absence of focal neurological signs, raising the     excise all the membrane of the haematoma. As
differential diagnosis of a cerebral neoplasm        these haematomas may be multiloculated it is
or chronic subdural haematoma.                       advisable to insert more than one burr hole and
2 Fluctuating drowsiness. The predominant            to visualize the underlying brain at each site.
characteristic is a decline in the level of con-
sciousness and the patient may abruptly become
deeply unconscious.
3 A progressive dementia, which may be misdi-
agnosed as Alzheimer’s disease. However, the
course of the dementia is usually more rapid
and progressive. Focal neurological signs may
develop, particularly a hemiparesis with an ex-
tensor plantar response. In up to 20% of cases the
hemiparesis may be ipsilateral to the side of the
haematoma due to shift of the brain causing
the contralateral crus cerebri to be compressed by
the tentorial edge.
  A chronic subdural haematoma will be diag-
nosed on the CT scan as a hypodense, extra-
cerebral collection causing compression of the
underlying, brain (Fig. 5.5). In 25% of cases the
haematoma is bilateral (Figs 5.6 and 5.7).

Operation
                                                     Fig. 5.6 Bilateral chronic subdural haematoma. The
The chronic subdural haematoma can be drained
                                                     collection on the left is not as hypodense, indicating
through burr holes or a craniotomy located over
                                                     that it is more recent than the haematoma fluid on the
the haematoma. No attempt should be made to          right. It also has a hyperdense area, indicating more
                                                     recent haemorrhage.




Fig. 5.5 Chronic subdural haematoma. The fluid is     Fig. 5.7 T1 MRI showing bilateral chronic subdural
hypodense compared with the adjacent brain.          haematoma.
 62                                                                                          CHAPTER 5


The haematoma fluid should be washed out
                                                        Intracerebral haematoma
completely and after the operation it is usually
advisable to place a subdural catheter for further      Traumatic intracerebral haematomas occur as a
drainage in a closed drainage system.                   result of a penetrating injury (such as a missile in-
   Following the operation the patient is nursed        jury) or a depressed skull fracture, or following a
flat, or even with the head down initially, to en-       severe head injury. Intracerebral haematoma is
courage the brain to expand into the haematoma          frequently associated with subdural haematoma.
space. Careful attention should be given to the            The size of the haematoma varies considerably
fluid intake and serum electrolytes. The normal          and multiple haematomas are frequently seen on
daily fluid requirements are given (3 l/day in           the CT scan following a severe head injury. The
adults) provided there is no clinical or radiologi-     contre-coup injury described in Chapter 4 may be
cal evidence of brain swelling. The patient should      responsible for a ‘burst’ temporal lobe which re-
be slightly more hydrated after this type of oper-      sults in a large temporal haematoma associated
ation than other intracranial procedures, in an         with subdural blood.
attempt to encourage the brain to swell into the           An intracerebral haematoma should be sus-
previous haematoma space. However, hypona-              pected in any patient with a severe head injury
traemia is a common occurrence, both prior to           or in a patient whose neurological state is
and following surgery, and if the serum sodium          deteriorating.
decreases to less than 130 mmol/l the fluid intake          The CT scan will show the size and position of
should be reduced.                                      the haematomas (Fig. 5.8). It should be noted that
                                                        traumatic intracerebral haematomas not infre-
                                                        quently evolve more than 24 hours after the
Subdural haematomas in infancy
                                                        trauma. Consequently if is essential to repeat
The infantile chronic subdural haematoma, or            a CT scan if the initial scan performed after the
effusion, is a distinct clinical entity. Birth trauma   injury was negative but the patient’s neurologi-
is a frequent cause but in many cases a past his-       cal state deteriorates.
tory is inadequate to establish the nature of the
injury with certainty. Chronic subdural haema-
tomas occur in 10% of ‘battered children’ and the
violent shaking of an infant may be sufficient to
lacerate bridging cerebral veins without evi-
dence of external trauma. Subdural bleeding in
infants occurs bilaterally in 85% of cases and is
usually over the dorsolateral surfaces of the
frontal and parietal lobes.
   The earliest finding in infants with chronic
subdural haematomas is excessive cranial
enlargement as the sutures are unfused. The
symptoms are non-specific and usually involve
listlessness, irritability and failure to thrive.
   The diagnosis will be confirmed by CT scan.
Treatment initially involves aspiration of the
fluid but if, after 2 or 3 weeks, repeated taps have
failed to reduce the volume significantly, a shunt
may be inserted to drain the fluid from the sub-
dural space to the peritoneal cavity.
                                                        Fig. 5.8 Traumatic frontal intracerebral haematomas
                                                        resulting from contre-coup injury.
 TRAUMATIC INTRACRANIAL HAEMATOMAS                                                                               63


   A large intracerebral haematoma should be                  Management Study. British Medical Journal 2,
evacuated, unless the patient’s neurological state            955–958.
is improving. Small intracerebral haematomas,               Jennett B, Teasdale G (1981) Intracranial haematoma.
particularly if multiple, are not removed but the             In: Jennett B, Teasdale G, eds. Management of Head
                                                              Injuries. Contemporary Neurology Series. F A Davis,
clinician must be aware that they may expand
                                                              Philadelphia.
and require subsequent evacuation.
                                                            Kaye AH, Black P McL (2000) Operative Neurosurgery.
                                                              Churchill Livingstone, London, New York,
Further reading                                               Edinburgh.
                                                            Reilly PJ, Adams JH, Graham DI et al. (1975) Patients
Gardner WJ (1932) Traumatic subdural haematoma                with head injury who talk and die. Lancet ii, 375–381.
  with particular reference to the latent interval.         Teasdale G, Galbraith S (1981) Acute traumatic intra-
  Archives of Neurology and Psychiatry 27, 847–855.           cranial haematomas. In: Teasdale G, Galbraith S, eds.
Hooper RS (1959) Observations on extradural haemor-           Progress in Neurological Surgery 10. Karger, Basel.
  rhage. British Journal of Surgery 47, 71–87.              Trotter W (1914–1915) Chronic subdural haemorrhage
Jamieson KG, Yelland JD (1968) Extradural haema-              of traumatic origin and its relation to pachymeningi-
  toma. Report of 167 cases. Journal of Neurosurgery          tis haemorrhagica interna. British Journal of Surgery 2,
  29, 13–23.                                                  271–291.
Jamieson KG, Yelland JD (1972) Traumatic intracerebral      Weir BKA (1971) The osmolarity of subdural
  haematoma. Report of 63 surgically treated cases.           haematoma fluids. Journal of Neurosurgery 34,
  Journal of Neurosurgery 37, 528–532.                        528–533.
Jennett B, Murray A, Carlin J et al. (1979) Head injuries
  in three neurosurgical units, Scottish Head Injury
                            CHAPTER 6


  6                         Brain tumours



Brain tumours are responsible for approximately         position but chromosome abnormalities have
2% of all cancer deaths. Central nervous system         been noted in many CNS tumours (Table 6.3).
tumours comprise the most common group of               Neurofibromatosis type 1 (NF1), previously
solid tumours in young patients, accounting for         known as von Recklinghausen’s disease, occurs
20% of all paediatric neoplasms. The overall inci-      with an approximate frequency of 1 in 4000 live
dence of brain tumours is 8–10 per 100 000 popu-        births. It is inherited as an autosomal dominant
lation per year. A study by the United States           pattern and there is a high spontaneous mutation
Department of Health in 1966 showed the inci-           rate. NF1 is associated with a variety of central
dence to be 21 per 100 000 per year at 2 years old      and peripheral nervous system tumours. An
and 1 per 100 000 during the teenage years. The         optic nerve glioma is the most common CNS tu-
incidence increases after the 4th decade of life to     mour associated with NF1, occurring in about
reach a maximum of 16 per 100 000 per year in the       15% of those affected. Less commonly low-grade
7th decade. There has been an intense debate con-       glioma of the hypothalamus, cerebellum, brain-
cerning the increased incidence of brain tumours,       stem or spinal cord may occur. Peripheral neu-
especially in the elderly, but this possible increase   rofibromas are the hallmark of NF1 (Chapter 17).
could be explained due to the advent of CT and          Neurofibromas of the spinal roots are a common
MRI leading to better detection of tumours.             feature of NF1 (Chapter 15). The gene causing
                                                        NF1 is located on the long arm of chromosome 17
                                                        (17q 11.2).
Classification
                                                           Neurofibromatosis type 2 (NF2), previously
The general brain tumour classification is related       known as central neurofibromatosis, is an auto-
to the cell of origin, and is shown in Table 6.1.       somal dominant disorder which, beyond a few
   Table 6.2 shows the approximate distribution         superficial similarities, is phenotypically and
of the more common brain tumours.                       genetically distinct from NF1. It has an incidence
   This chapter will discuss the tumours derived        of approximately 1 in 100 000 live births. The hall-
from the neuroectoderm and metastatic tumours.          mark of NF2 is bilateral acoustic (vestibular)
The following chapters will describe the benign         schwannomas, but patients with NF2 have an in-
brain tumours and pituitary tumours.                    creased risk of other intracranial schwannomas,
                                                        multiple meningiomas (both cranial and spinal)
                                                        and gliomas. The NF2 gene locus is sited on
Aetiology
                                                        the long arm of chromosome 22 (22q 11.2) (Table
Epidemiology studies have not indicated any             6.4).
particular factor (viral, chemical or traumatic)           There is no specific evidence linking CNS tu-
that causes brain tumours in humans, although a         mours to environmental carcinogens, although
range of cerebral tumours can be induced in ani-        many chemicals, especially ethyl and methyl
mals experimentally. There is no genetic predis-        nitrosourea and anthracene derivatives, show

64
 BRAIN TUMOURS                                                                                          65



  Table 6.1 General classification of brain tumours.     Table 6.2 Incidence of common cerebral tumours
                                                        (%).
  Neuroepithelial tumours
  Gliomas                                               Neuroepithelial                                 52
    Astrocytoma (including glioblastoma)                Astrocytoma (all grades including               44
    Oligodendrocytoma                                     glioblastoma)
    Ependymoma                                          Ependymoma                                       3
    Choroid plexus tumour                               Oligodendroglioma                                2
  Pineal tumours                                        Medulloblastoma                                  3
  Neuronal tumours
                                                        Metastatic                                      15
    Ganglioglioma
    Gangliocytoma                                       Meningioma                                      15
    Neuroblastoma                                       Pituitary                                        8
  Medulloblastoma
                                                        Acoustic neuroma                                 8
  Nerve sheath tumour — acoustic neuroma

  Meningeal tumours
  Meningioma

  Pituitary tumours
                                                        Table 6.3 Chromosomal deletions and loci of loss
  Germ cell tumours                                     of heterozygosity (LOH) in CNS tumours.
  Germinoma
  Teratoma                                                                          Chromosomal
  Lymphomas                                             Tumour                      deletions/loci of LOH

  Tumour-like malformations                             Astrocytoma                 #10, #13, 17p, 17q,
  Craniopharyngioma                                                                    19q, #22
  Epidermoid tumour                                     Glioblastoma multiforme     9, #10, 17p, 19q, 22q
  Dermoid tumour                                        Oligodendroglioma           1p, 4, 6, 11p, 19q, 22q
  Colloid cyst                                          Medulloblastoma             17p, 10, 11, 19
                                                        Retinoblastoma              13q 1.4
  Metastatic tumours                                    Meningioma                  1p, 14, #22, 22q
  Local extensions from regional tumours                                               12.3-qter
  e.g. glomus jugular (i.e. jugulare), carcinoma of     Haemangioblastoma           3p
    ethmoid                                               (von Hippel–Lindau)
                                                        Pituitary adenoma           11q
                                                          (MEN1)
                                                        Acoustic nerve tumours      22q
                                                          (NF2)
carcinogenic activity in animals and produce            Neurofibromas (NF1)          17q
CNS tumours.
   Viral induction of brain tumours has been used
in animal models but there is no firm evidence for
viral aetiology in humans. A human polyoma JC
virus injected into primates produces tumours         of the brain, particularly in transplant recipients,
similar to human astrocytomas after an 18-month       there is not the corresponding increased inci-
incubation period. This type of ‘slow virus’ effect   dence of gliomas.
may account for some of the problems of isolat-          At present there is considerable conjecture re-
ing viruses from human tumours.                       garding the role of other possible aetiological
   Although immunosuppression is known to in-         agents, including trauma, electromagnetic radia-
crease markedly the risk of primary lymphoma          tion and organic solvents but, as yet, there is no
 66                                                                                        CHAPTER 6


                                                       the identification of a variety of alterations in the
  Table 6.4 Diagnostic criteria for
                                                       genome of the tumour cell, including those of
  neurofibromatosis.
                                                       brain tumours. The present concept of oncogene-
                                                       sis involves both the addition of oncogenes to the
  NF1: Two or more of the following
  1 Six or more café au lait macules, each greater
                                                       genome and the loss of the normally occurring
  than 5 mm in diameter in prepubertal persons         tumour suppressor genes. Transformation (spon-
  and over 15 mm in diameter in postpubertal           taneous or induced) is a multistep process requir-
  persons                                              ing both initiation and promotion. Oncogenes
  2 Two or more neurofibromas or any type of one        encode proteins that participate in the signal
  plexiform neurofibroma                                transduction and second messenger systems that
  3 Freckling in the axillary or inguinal regions      modulate cell metabolism and proliferation.
  4 Optic glioma                                       These proteins include both growth factors and
  5 Two or more Lisch nodules (iris hamartomas)        growth factor receptors such as epidermal
  6 A distinctive osseous abnormality such as
                                                       growth factor receptor, platelet-derived growth
  sphenoid dysplasia or thinning of long bone
                                                       factor, tryosine-specific protein kinases and
  cortex with or without pseudoarthrosis
  7 A first-degree relative (parent, sibling or
                                                       guanine-binding proteins.
  offspring) with NF1 by the above criteria               Tumour suppressor genes are normally pre-
                                                       sent in the genome and act as a ‘brake’ on cell
  NF2: One of the following
                                                       transformation. Mutations in the p53 tumour
  1 Bilateral 8th nerve tumours seen with magnetic
                                                       suppressor gene on chromosome 17 are the most
  resonance imaging or computerized tomography
  2 A first-degree relative with NF2 and either a
                                                       common gene alteration found to date in tu-
  unilateral 8th nerve tumour or two of the            mours and have been shown to occur in both as-
  following:                                           trocytomas and meningiomas. The Li–Fraumeni
    • neurofibroma                                      syndrome is due to a germ line mutation in the
    • meningioma                                       p53 gene with the development of numerous
    • glioma                                           cancers including gliomas, ependymomas and
    • schwannoma                                       medulloblastomas.
    • juvenile posterior subcapsular lenticular
    opacity
                                                       Glioma
                                                       Neuroectodermal tumours arise from cells de-
                                                       rived from neuroectodermal origin. Gliomas
convincing evidence to implicate these as being        comprise the majority of cerebral tumours and
involved with the development of brain tumours         arise from the neuroglial cells. There are four
in humans.                                             distinct types of glial cells: astrocytes, oligo-
   The four hallmarks of the development of a          dendroglia, ependymal cells and neuroglial
cancer cell are the ability to proliferate, with the   precursors. Each of these gives rise to tumours
intracellular growth pathways constituitively ac-      with different biological and anatomical charac-
tivated, the evasion of apoptosis, with the cancer     teristics. The neuroepithelial origin of microglia
cells having escaped from cell death pathways,         is in question.
the attraction and induction of new blood vessels
(angiogenesis) to supply increased metabolic ac-
                                                       Astrocytoma
tivity of tumour cells, and tissue invasion. Each
of these are dependent on ligand–receptor inter-       The most common gliomas arise from the astro-
actions on the cell surface leading to a cascade of    cyte cells which comprise the vast majority of
cytoplasmic events that eventually result in dif-      intraparenchymal cells of the brain. Their main
ferential gene expression.                             function appears to be as a supporting tissue for
   Molecular biology techniques have enabled           the neurones. The tumours arising from astro-
 BRAIN TUMOURS                                                                                                    67


cytes range from the relatively benign to the                  A valuable prognostic system of subclassifica-
highly malignant. The term ‘malignant’ for brain            tion of astrocytoma was described by Kernohan
tumours differs from its usage for systemic                 in 1949. Astrocytomas were graded from I to IV,
tumours. Intrinsic brain tumours very rarely                with Grade IV being the most malignant and
metastasize (except for medulloblastoma and                 Grade I cytologically, but not necessarily biologi-
ependymoma), and ‘malignant’ refers to aggres-              cally, benign. Ringertz simplified the four-grade
sive biological characteristics and a poor                  classification of Kernohan into a three-tiered sys-
prognosis.                                                  tem; the comparison between the two is shown in
                                                            Fig. 6.1. The glioblastoma multiforme, equivalent
                                                            to the Kernohan Grade III and IV tumours, is the
Classification
                                                            most common adult cerebral tumour, accounting
There are many classification systems of brain tu-           for approximately half of all gliomas. The
mours in general and gliomas in particular. The             low-grade gliomas — the astrocytoma, or Grade
period of systematic classification of tumours               I or II Kernohan astrocytoma — account for only
began in 1846, when Virchow described the neu-              10–15% of astrocytomas.
roglia and related it to brain tumours. Although               The World Health Organization (WHO) classi-
Virchow created the term ‘glioma’, these tu-                fication recognizes four grades of astrocytoma.
mours had already been described under other                Grade I is assigned to the pilocytic astrocytoma
names. In 1926, Bailey and Cushing described a              which is biologically distinct from the diffuse as-
histogenetic classification system which com-                trocytomas, which are classified as astrocytoma
pared the predominant cell in the tumours with              (WHO Grade II), anaplastic astrocytoma (WHO
the embryonal development of the neuroglia.                 Grade III) and glioblastoma multiforme (WHO
The comparison with stages of cytogenesis was               Grade IV).
probably more of a working hypothesis than an                  A grading system proposed by Daumas-
oncological theory for the origin of the tumours’           Duport and also known as the St Anne–Mayo
cells. The theory that gliomas originate from pro-          System assessed the tumours according to the
liferation of cells of varying degrees of maturity          presence or absence of four morphological fea-
lying dormant in the brain is not generally ac-             tures — nuclear atypia, mitosis, endothelial pro-
cepted except in the case of medulloblastoma,               liferation, and necrosis — and they are graded
which may arise from a primitive layer in the               according to the cumulative features score.
cerebellar cortex.                                          Grade I tumours have none of the features, Grade


Ringertz                   Grade I                      Grade II                         Grade III
                    (Well differentiated)       (Anaplastic astrocytoma)        (Glioblastoma multiforme)


Kernohan                   Grade I
                                                        Grade II
                                                                                       Grades III and IV


WHO                       Grade I                 Grade II                Grade III                    Grade IV
                     Juvenile pilocytic     Astrocytoma variants         Anaplastic             Glioblastoma variants
                       astrocytoma                • Fibrillary          astrocytoma                  • Giant cell
                                                  • Protoplasmic                                     • Gliosarcoma
                                                  • Gemistocytic


St Anne-Mayo              Grade I                Grade II                  Grade III                Grade IV
                          Score: 0               Score: 1                  Score: 2               Score: 3 or 4
Fig. 6.1 Relationship of the Kernohan system, the ‘three-tiered’ classification system, the WHO system and the St
Anne/Mayo (Dumas-Deport) grading system for astrocytomas.
 68                                                                                        CHAPTER 6


II tumours have one feature, Grade III tumours       with the tumour’s grade. The low-grade astrocy-
have two features and Grade IV tumours have          toma is characterized by an increased cellularity,
three or four features.                              composed entirely of astrocytes (Fig. 6.2).
                                                     Intermediate-grade tumours show nuclear
                                                     pleomorphism, mitotic figures are frequent, and
Pathology
                                                     there is increased vascularity, as evidenced by en-
Macroscopic changes                                  dothelial and adventitial cell proliferation. In the
An astrocytoma may arise in any part of the          high-grade astrocytoma very few astrocytes ap-
brain, although it usually occurs in the cerebrum    pear normal. There is marked cellular pleomor-
in adults and the cerebellum in children.            phism, extensive endothelial and adventitial cell
   A low-grade tumour in the cerebral hemi-          proliferation and numerous mitotic figures with
spheres invades diffusely into the brain. The tu-    extensive necrosis (Fig. 6.3).
mour does not have a capsule and there is no           The major histological features of glioblastoma
distinct tumour margin. The low-grade gliomas        multiforme are endothelial proliferation and
are usually relatively avascular with a firm fi-       necrosis. The anaplastic astrocytoma is char-
brous or rubbery consistency. Fine deposits of       acterized by nuclear pleomorphism and mitoses,
calcium are present in 15% of astrocytomas. Oc-      which are absent in the astrocytoma.
casionally, a low-grade astrocytoma may invade
diffusely throughout the cerebral hemisphere. In
                                                     Clinical presentation
contrast, the macroscopic appearance of a high-
grade tumour, the glioblastoma multiforme, is        The presenting features can be classified under:
characterized by a highly vascular tumour mar-       • raised intracranial pressure
gin with necrosis in the centre of the tumour. Al-   • focal neurological signs
though in certain areas the margin of the tumour     • epilepsy.
may seem to be macroscopically well defined              The duration of the symptoms and the pro-
from the surrounding brain, there are micro-         gression and evolution of the clinical presenta-
scopic nests of tumour cells extending well out      tion will depend on the grade of the
into the brain.                                      tumour — that is, its rate of growth. A patient pre-
                                                     senting with a low-grade astrocytoma (Grade I
Microscopic changes                                  or II) may have a history of seizures extending
The histological appearance of the tumour varies     over many years, antedating the development of




                                                                             Fig. 6.2 Low-grade
                                                                             astrocytoma. There is only a
                                                                             slight increase in the
                                                                             cellularity and mild nuclear
                                                                             atypia. There is a disturbed
                                                                             architecture with formation of
                                                                             triplets and quadruplets of
                                                                             astrocytes (haematoxylin and
                                                                             eosin, ¥40).
 BRAIN TUMOURS                                                                                              69




         (a)                                            (b)
Fig. 6.3 Glioblastoma multiforme. (a) There is a marked increase in cellularity and variation in nuclear size,
shape and staining density with frequent mitotic figures (haematoxylin and eosin, ¥40). (b) Low-power view of
the same tumour showing pallisaded necrosis typical of glioblastoma multiforme.


progressive neurological signs and raised in-            state, is the most important symptom and sign of
tracranial pressure. The tumours may evolve his-         raised intracranial pressure. The extent of im-
tologically into the more malignant anaplastic           pairment of conscious state will be related to the
astrocytoma or glioblastoma multiforme. Pa-              severity of raised intracranial pressure. An alert
tients with the higher-grade tumours present             patient with severely raised intracranial pressure
with a shorter history and glioblastoma multi-           may rapidly deteriorate and become deeply un-
forme is characterized by a short illness of weeks       conscious when there is only a very small further
or a few months.                                         rise in the pressure within the cranial cavity.

Raised intracranial pressure                             Focal neurological deficits
Raised intracranial pressure is due to the tumour        Focal neurological deficits are common in
mass, surrounding cerebral oedema and hydro-             patients presenting with cerebral gliomas; the
cephalus due to blockage of the CSF pathways.            nature of the deficit will depend on the position
The features of raised intracranial pressure are         of the tumour.
described in detail in Chapter 3. The major symp-           Patients presenting with tumours involving
toms are headache, nausea and vomiting, and              the frontal lobes frequently have pseudopsychi-
drowsiness.                                              atric problems, personality change and mood
   Headache is the most common symptom in                disturbance. These changes are particularly char-
patients with cerebral astrocytoma and occurs            acteristic of the ‘butterfly glioma’, so called be-
in nearly three-quarters of patients; vomiting           cause it involves both frontal lobes by spreading
occurs in about one-third. The headaches are             across the corpus callosum, giving it a character-
usually gradually progressive and although               istic macroscopic (Fig. 6.4) and CT or MRI ap-
frequently worse on the side of the tumours, they        pearance. This type of tumour may also occur
may be bitemporal and diffuse. Characteristi-            posteriorly, with spread across the splenium of
cally, the headache is worse on waking and im-           the corpus callosum into both parieto-occipital
proves during the day. Nausea and vomiting               lobes.
occur as the intracranial pressure increases, and           Limb paresis results from interference with
the patient frequently indicates that vomiting           the pyramidal tracts, at either a cortical or a sub-
may temporarily relieve the severe headache.             cortical level, and occurs in just under 50% of pa-
Drowsiness, that is, a deterioration of conscious        tients. Field defects associated with tumours of
 70                                                                                           CHAPTER 6




                                                        Fig. 6.5 Low-grade astrocytoma. CT scan shows
                                                        non-enhancing low-density lesion with little or no
                                                        mass effect.

Fig. 6.4 ‘Butterfly glioma’. Glioblastoma multiforme
of corpus callosum spreading into both frontal lobes.   Investigations
                                                        Computerized tomography
                                                        CT scan or MRI of the brain are the essential radi-
the temporal, occipital and parietal lobes are          ological investigations (Figs 6.5 and 6.6); an accu-
common, but may be evident only on careful test-        rate diagnosis can be made in nearly all tumours.
ing. Dysphasia, either expressive or receptive, is      Low-grade gliomas show decreased density on
a particularly distressing symptom occurring in         the CT scan; this does not enhance with contrast
patients with tumours involving the relevant            and there is little or no surrounding oedema. Cal-
areas of the dominant hemisphere.                       cification may be present. High-grade gliomas
  The particular characteristics of posterior fossa     are usually large and enhance vividly following
and brainstem gliomas will be discussed in the          intravenous injection of contrast material (Fig.
following section on paediatric tumours.                6.7). The enhancement is often patchy and non-
                                                        uniform and frequently occurs in a broad, irregu-
Epileptic seizures                                      lar rim around a central area of lower density.
Seizures are the most frequent initial symptom in       Although tumour cysts may occur in the high-
patients with cerebral astrocytoma and occur in         grade tumours, the central area of low density
50–75% of all patients. Tumours adjacent to the         surrounded by the contrast enhancement is usu-
cortex are more likely to be associated with            ally due to tumour necrosis. High-grade tumours
epilepsy than those deep to the cortex and tu-          are surrounded by marked cerebral oedema and
mours involving the occipital lobe are less likely      there is frequently considerable distortion of the
to cause epilepsy than those which are more             lateral ventricles. Compression of the lateral ven-
anteriorly placed. Astrocytomas may produce             tricle in one hemisphere, with pressure extending
either generalized or focal seizures; the focal         across the midline, may result in an obstructive
characteristics will depend on the position within      hydrocephalus involving the opposite lateral
the brain and the cortical structures involved.         ventricle.
 BRAIN TUMOURS                                                                                           71




        (a)                                                (b)
Fig. 6.6 MRI showing low-grade glioma in posterior frontal region. (a) T1 scan, (b) T2 scan.




Fig. 6.7 Glioblastoma multiforme. CT shows a large         Fig. 6.8 Glioblastoma multiforme. MRI shows large
tumour with contrast enhancement particularly at           enhancing tumour invading into corpus callosum and
the margins surrounding a necrotic centre. There is        ventricle.
marked surrounding oedema with compression
of the ventricles.
                                                           sensitive than CT scan, enabling the detection
Magnetic resonance imaging                                 of small tumours and particularly low-grade
When used with gadolinium contrast enhance-                gliomas that might be missed by CT scan. MRI
ment, MRI improves the visualization and                   provides better anatomical detail and is more
anatomical localization of the tumours (Figs 6.8           useful in visualizing skull base, posterior fossa
and 6.9). MRI has the advantage of being more              and brainstem tumours.
 72                                                                                       CHAPTER 6




        (a)                                           (b)
Fig. 6.9 Cystic anaplastic astrocytoma.


   Low-grade astrocytomas may show up on MRI          performed as a routine. The most common
as abnormal areas of increased T2 signal and de-      abnormality is erosion of the sella turcica due
creased T1 signal, even if the CT scan was normal.    to long-standing raised intracranial pressure.
High-grade astrocytomas characteristically have       Radiologically visible calcification is present in
low signal intensity on T1-weighted images and        about 8% of patients with astrocyte-derived
high signal intensity on T2-weighted images.          gliomas.
Gadolinium enhancement is more likely to occur
in the higher-grade tumour.
                                                      Management
   Perfusion-weighted MRI is used to determine
the regional cerebral blood volume, which is          Following the presumptive diagnosis of a glioma
increased in high-grade glioma and may be of          the management involves:
value in differentiating recurrent tumour from        • surgery
radiation necrosis. Magnetic resonance spec-          • radiotherapy
troscopy (MRS) is a non-invasive technique that       • other adjuvant treatments.
provides information on the composition and
spatial distribution of cellular metabolites. On      Surgery
proton MRS, tumours have an increased lactate         Surgery is performed with three principal aims.
production, loss of N-acetyl aspartate (due to loss   • To make a definite diagnosis.
of neurones in the tumour area) and increased         • Tumour reduction to alleviate the symptoms
choline levels (due to active membrane                of raised intracranial pressure.
biosynthesis).                                        • Reduction of tumour mass as a precursor to
                                                      adjuvant treatments.
Cerebral angiography                                     The patient is started on glucocorticoid steroid
This was the standard study in most patients          therapy (e.g. dexamethasone) when presenting
with astrocytomas prior to the introduction of        with clinical features of raised intracranial
CT. It provides helpful information on the            pressure with the aim of decreasing the cerebral
vascular supply of the tumours but is now only        oedema prior to surgery.
rarely indicated.                                        The type of operation performed will largely
                                                      be determined by the position of the tumour and
Plain X-rays                                          by the patient’s clinical presentation. In general,
Plain X-rays of the skull do not need to be           the tumour is excised as radically as possible,
 BRAIN TUMOURS                                                                                           73


provided the surgery will not result in any dis-
abling neurological deficit. Craniotomy is per-
formed in the position that provides the best
access to the tumour and usually with the aid of a
frameless stereotactic system to aid accuracy of
localization. If the tumour has not grown to in-
volve the cortical surface, a small incision is made
in a non-eloquent gyrus or sulcus and the subcor-
tical brain is divided down to the tumour mass.
The tumour is excised, often with the aid of an
ultrasonic aspirator. Occasionally, the tumour
may involve one of the ‘poles’ of the hemisphere
and the excision may entail a partial lobectomy.
Although a craniotomy with radical tumour
excision will alleviate the symptoms of raised
intracranial pressure, there has been controversy
as to whether a radical resection improves sur-
vival. Most high-grade gliomas weigh approxi-
mately 100 g at the time of diagnosis and consist
of 1011 cells. A radical tumour excision is able to    Fig. 6.10 Schematic diagram of stereotactic biopsy of
excise the macroscopic tumour but cannot re-           cerebral tumour using the Cosman–Roberts–Wells
move the tumour cells that are infiltrating deep        (CRW) system.
into the adjacent, often vital, areas of normal or
oedematous brain. Consequently, a radical exci-
sion is unlikely to achieve more than a 90–95%           Stereotactic biopsy involves localization of the
reduction in tumour cell numbers, resulting in         tumour with a stereotactic frame applied to the
1010 cells remaining. Whether the 1–2 logs of          head of the patient using the CT scan or MRI.
tumour cell reduction are a significant reduction       The three-dimensional coordinates of the tumour
in tumour burden prior to adjuvant therapy             are ascertained. The surgeon chooses the point of
and whether it improves the effectiveness of           entry and the desired path through the brain and
subsequent treatment is still not completely           a computer program determines the necessary
resolved, although recent clinical studies do          angles for the biopsy probe and the depth to the
seem to show a survival benefit following tu-           tumour (Fig. 6.10).
mour resection and this is favoured by most
neurosurgeons provided the tumour excision             Postoperative care
can be performed without causing significant            The postoperative management of astrocytoma
neurological mortality.                                involves the routine care of a patient following a
   Alternatively, a biopsy, which can be per-          craniotomy. Careful neurological observations
formed most accurately using stereotactic meth-        are performed, as prompt intervention is essen-
ods, may be undertaken to obtain the definite           tial if the patient’s neurological state deteriorates
histological diagnosis, without macroscopic tu-        as a result of either increasing cerebral oedema or
mour excision, if:                                     postoperative haemorrhage. A postoperative
• the tumour is small and deep seated                  haematoma may occur in the region of the tu-
• the tumour is diffuse, without major features        mour excision or it may be extracerebral, either
of raised intracranial pressure, and macroscopic       subdural or extradural. A CT scan should be
resection is not feasible                              performed urgently if there is neurological
• the tumour involves highly eloquent areas            deterioration, to determine the exact pathology.
(e.g. speech centre) without pronounced features       Occasionally, postoperative deterioration may
of raised intracranial pressure.                       be so rapid as to require urgent re-exploration
 74                                                                                          CHAPTER 6


of the craniotomy without prior radiological             median survival following surgery is approxi-
assessment.                                              mately 17 weeks and when radiation therapy is
   In the initial postoperative period it is essential   used as an adjuvant the median survival is ap-
to avoid overhydration of the patient so as not to       proximately 37 weeks. Chemotherapy for high-
precipitate cerebral oedema. The patient is              grade gliomas has been disappointing and the
nursed with the head of the bed elevated 20°, so         best results with surgery, radiation therapy and
as to promote venous return and reduce intra-            chemotherapy consistently show a median sur-
cranial venous pressure. Steroid medication is           vival time of less than 1 year. The median normal
usually required in the initial postoperative            for the low-grade glioma (fibrillary astrocytoma;
period and is gradually decreased over the               WHO Grade II, Daumus–Duport Grades I and II)
following days. The steroids may need to be              is approximately 8 years, with most tumours pro-
re-instituted during the course of radiotherapy.         gressing to a higher grade.
   The patient is usually mobilized as soon as              The role of surgery, radiation therapy and
possible, if necessary with the help of a                other adjuvant therapies in low-grade gliomas is
physiotherapist.                                         even less certain than for the high-grade glioma.
                                                         The low-grade tumour may remain relatively
Radiation therapy                                        quiescent for some years before it either con-
Postoperative radiation therapy is generally an          tinues to grow slowly or changes to a more
effective adjunct to surgery in the treatment of         anaplastic tumour with resulting debilitating
higher-grade gliomas. It has been shown to               neurological deterioration. In general, the same
double the median survival for high-grade                principles for surgical excision apply for low-
gliomas to 37 weeks.                                     grade gliomas as for high-grade gliomas. How-
   Radiation treatment is planned to optimize the        ever, a number of clinical studies have shown
homogeneity of the radiation dose throughout             that patients having a radical excision of a tu-
the tumour volume selected and to minimize               mour have a longer 5-year survival than those
high dose regions in normal brain transited by           with a subtotal excision. Radiation therapy has
the radiation beam. The size of the daily radiation      not been shown to improve the survival in pa-
fraction is related to the incidence of complica-        tients with low-grade tumours. In general, other
tions and a maximal daily dose is usually be-            adjuvant therapies are not used for the treatment
tween 1.8 and 2.0 gray. The total radiation dose         of low-grade astrocytoma, but may be of benefit
varies depending on the tumour type, location            for oligodendrogliomas.
and size of field, but for gliomas it is usually be-
tween 45 and 60 gray. Opinion varies regarding           Other adjuvant therapies
the tissue volume that should be treated for ma-         Many different adjuvant therapies have been in-
lignant glioma but radiation to the tumour area          vestigated for the treatment of glioma. These in-
and a ‘generous volume’ of surrounding brain is          clude the use of new chemotherapeutic agents,
now advocated, rather than radiation to the              new methods of administering cytotoxic chemi-
whole brain. The selection of the proper radiation       cals, immunotherapy, hyperthermia, new tech-
dose for gliomas is as controversial. Although in-       niques of radiotherapy, photodynamic therapy,
creasing the radiation dosage from 50 to 65 gray         and gene therapy.
does slightly improve survival, the higher dose            The lack of effectiveness of the present treat-
of radiation therapy, especially over 65 gray, sig-      ment of gliomas is related to the biology of the tu-
nificantly increases the risk of brain necrosis.          mour. The most common position for tumour
                                                         recurrence following conventional treatment is
Prognosis                                                locally, in the tumour bed, indicating that treat-
At present there is no satisfactory treatment for        ment has failed in local control. Although light
the malignant cerebral glioma — the anaplastic           microscopy shows high-grade gliomas to have a
astrocytoma and glioblastoma multiforme. The             relatively well-defined border with the adjacent
 BRAIN TUMOURS                                                                                           75


brain, special staining techniques, including             studies have shown it to be effective in about 40%
monoclonal antibodies, show malignant cells ex-           of patients. It is now the initial chemotherapy
tending well out into the surrounding brain. It is        agent of choice, but it is usually used at the time
the failure to control the growth of these cells that     of tumour recurrence, rather than as an adjuvant
is largely responsible for the local tumour recur-        to surgery.
rence. As indicated previously, a good surgical              It has been postulated that a reason for the lack
resection with 90% of the tumour excised would            of effectiveness of chemotherapy is the inability
still result in 1010 cells being present. Effective ra-   of the cytotoxic compound to reach the tumour
diotherapy will result in 1 log (90%) or at the most      cells which are invading the normal adjacent
2 logs (99%) of cell kill and it is unlikely that sub-    brain. This has resulted in new techniques
sequent chemotherapy would reduce remaining               of delivering the cytotoxic agent. High-dose
tumour cells by more than 90%. Consequently,              chemotherapy with bone marrow rescue has
the effect of cytoreductive surgery, radiotherapy         largely been abandoned because of its high
and chemotherapy would result in approxi-                 morbidity and lack of effectiveness. Techniques
mately 108 cells remaining; the immune system             of disrupting the blood–brain barrier have been
is unlikely to be able to cope with a tumour              used before chemotherapy infusion to improve
burden of more than 105 cells. It follows that, for       the delivery of chemotherapeutic agents to tu-
any extra treatment to be effective, whether              mour cells within the environment of a normal
surgery or adjuvant therapy, it must provide at           blood–brain barrier. This has resulted in substan-
least 1 log of cell kill.                                 tially increased neurotoxicity to the normal brain
                                                          without significantly improving survival. Intra-
Chemotherapy                                              carotid chemotherapy suffers from serious limi-
Conventional chemotherapy has been disap-                 tations — the perfusion of the tumour mass is less
pointing. Many of the chemotherapy agents that            than expected because most tumours are not
are active in vitro, or in other systemic tumours,        supplied entirely by one carotid artery and
have reduced activity in malignant brain tu-              ‘streaming’ of the cytotoxic agent results in
mours, either by exerting an inherently limited           very high doses of chemotherapy to small areas,
cytotoxic potential on brain tumour cells or by           with relative hypoperfusion in other regions.
the inability of the chemotherapeutic agent to            Complications such as serious retinal damage
reach the cells that are responsible for the tumour       and neurotoxicity have further reduced the
recurrence. A study of brain tumour cell kinetics         attractiveness of this technique.
of high-grade gliomas shows only a small pro-
portion of the cells (5–10%) in an active growth          Radiotherapy
phase; this has serious consequences for any cell         Attempts to enhance the effect of radiotherapy
cycle-specific cytotoxic agent. Until recently the         have included the use of radiosensitizers, such as
most commonly used single agent cytotoxic                 metronidazole and misonidazole, which increase
regime involves administration of nitrosourea             the radiosensitivity of hypoxic tumour cells with-
compounds. The high lipid solubility and low              out a corresponding increase in the sensitivity of
ionization of these agents ensures a relatively ef-       euoxic cells. However, the clinical trials have
fective penetration of the cytotoxic compound             shown only a marginal advantage. The use of in-
into the tumour. Combination therapy, utilizing           terstitial brachytherapy, involving stereotacti-
many different cytotoxic compounds, has been              cally implanted radioactive sources into the
used in various trials but none of the combina-           tumour, has the advantage of applying a high
tions has been shown to be more beneficial than            dose of radiotherapy to the tumour while sparing
the use of the single nitrosourea.                        the surrounding brain. However, the clinical
   Temozolomide is an alkylating agent that can           trials performed so far have resulted in a high in-
be taken orally, penetrates the CNS and is well           cidence of radionecrosis to the surrounding brain
tolerated with predictable myelotoxicity. Clinical        and improvements in the technique will need to
 76                                                                                         CHAPTER 6


be devised before this method would become             being investigated involve the use of retrovirus,
acceptable. Similarly, stereotactic radiosurgery,      adenoviruses or adeno-associated viruses to
that involves radiation to a very highly focused       carry a variety of gene therapies to the cancer cell.
area, is of limited use as it does not target the      It is hoped that as these treatments are refined
infiltrative tumour cells that are responsible for      over the next decade they will be useful in the
tumour recurrence.                                     treatment of cerebral glioma.

Hyperthermia
                                                       Oligodendroglioma
This has inherent basic limitations as, although
cell death occurs at approximately 42°C, damage        Oligodendrogliomas are responsible for
to the surrounding brain occurs at 45°C, so there is   approximately 5% of all gliomas and occur
a very narrow therapeutic index. In addition, there    throughout the adult age group with a maximal
is a marked tolerance of tumour cells to hyperther-    incidence in the 5th decade. The tumour is rare in
mia and the treatment has not been effective.          children.

Immunotherapy
                                                       Pathology
The possibilities for immunotherapy as an
adjuvant treatment have been investigated for          Nearly all oligodendrogliomas occur above the
many years. Investigations have included the           tentorium; most are located in the cerebral
use of active immunotherapy techniques and,            hemispheres and about half of these are in the
more recently, the application of adoptive             frontal lobes. Oligodendrogliomas may project
immunotherapy. This technique involves stimu-          into either the 3rd or lateral ventricles.
lating peripheral blood lymphocytes in vitro with         Oligodendrogliomas have the same spectrum
human recombinant interleukin-2 to produce             of histological appearance as astrocytomas, rang-
lymphokine activated killer cells (LAK cells)          ing from very slow growing, benign tumours to a
which can be administered in conjunction with          more rapidly growing, malignant variety with
interleukin-2. However, the LAK cells do not           abundant mitotic figures, endothelial prolifera-
cross the blood–brain barrier and so need to be        tion and foci of necrosis. Calcium deposits are
injected in close proximity to the tumour cells.       found by histological examination in up to 90% of
Recent studies using this technique have been          oligodendrogliomas. Unlike the astrocyte group,
disappointing.                                         most oligodendrogliomas are well differentiated.
                                                       Not infrequently tumours have mixed histology,
Photodynamic therapy                                   with both oligodendroglial and astroglial
This is a technique that offers special advantages     features.
as an adjuvant therapy of malignant brain tu-
mours since it has been shown to be an effective
                                                       Clinical presentation
method of controlling local tumours. The tech-
nique involves the selective uptake of sensitizer      The presenting features are essentially the same
into the brain tumour, followed by open or intra-      as for the astrocyte group but, as these tumours
operative irradiation of the sensitized tumour         are more likely to be slow growing, epilepsy is
cells with light of an appropriate wavelength to       common, occurring in 80% of patients and seen
activate the sensitizer and selectively destroy the    as an initial symptom in 50%. The features of
tumour cells. Clinical studies using this method       raised intracranial pressure and focal neurologi-
have shown a favourable trend, although formal         cal deficits are each present in approximately
phase III studies have not been undertaken.            one-third of patients.
                                                         As for astrocyte tumours, MRI with contrast
Gene therapy                                           may be beneficial but other investigations are
Experimental therapies of glioma at present            usually unnecessary.
 BRAIN TUMOURS                                                                                        77




       (a)
                                                       (b)
Fig. 6.11 Oligodendrogliomas. (a) Non-enhancing low-grade calcified tumour. (b) Contrast-enhancing
high-grade oligodendroglioma.


                                                       of histological malignancy. Five-year survival
Radiological investigation
                                                       rates are between 30 and 50% with a small num-
CT scanning and MRI are the fundamental inves-         ber of patients living for many years (up to 5% for
tigations. They will confirm the diagnosis of an        20 years). However, many tumours with histo-
intracranial tumour and in many cases the diag-        logical features of oligodendroglioma also have a
nosis of oligodendroglioma will be highly proba-       component of astrocyte-derived cells, usually
ble. Calcification will be present in 90% of cases      anaplastic astrocytoma, and the tumour behaves
and over half show contrast enhancement (Fig.          biologically and clinically as an anaplastic astro-
6.11).                                                 cytoma rather than an oligodendroglioma.


Treatment and results                                  Recurrent cerebral glioma
Treatment involves:                                    As discussed earlier, most high-grade cerebral
• surgical resection                                   gliomas will recur within 1 year of the initial
• radiotherapy                                         treatment with surgery and radiotherapy. Low-
• other adjuvant treatments.                           grade tumours may either recur as a continuing
   The standard treatment for oligodendroglioma        progression of the slow growth or, alternatively,
has been an aggressive resection of the tumour         the histological characteristics may alter and
followed by radiation therapy, although radio-         the tumour may become more anaplastic and
therapy would now not be given to low-grade tu-        rapidly growing.
mours, and utilized only for the intermediate- or         The clinical presentation of a recurrent tumour
high-grade oligodendroglial tumours. Oligoden-         will be evidenced by either a progression of the
drogliomas have been shown to be more sensi-           focal neurological signs or the signs of an increase
tive to chemotherapy than the astrocytoma              in the intracranial pressure. The diagnosis will be
tumours, especially if the oligodendrogliomas          confirmed by CT scan or MRI in most cases. The
belong to the group with loss of heterozygosity        major differential diagnosis is postradiotherapy
OF chromosome 1p or 19q.                               radiation necrosis, which may develop as early as
   The survival of patients depends on the degree      4 months or as late as 9 years after radiotherapy.
 78                                                                                        CHAPTER 6


The radiological features of necrosis are an avas-   tricle and, although predominantly intraventric-
cular mass, and the diagnosis may be suspected       ular, the tumour often invades into the adjacent
from the dose of radiotherapy that has been          cerebellum, brainstem or cerebral hemisphere.
administered. However, there may be consider-        Fourth ventricular tumours usually arise from
able difficulty in differentiating necrosis from      the floor or lateral recess of the 4th ventricle and
recurrent glioma, and sometimes an operation         they may extend into the subarachnoid space to
is required both for definitive diagnosis and to      encase the medulla or upper cervical spinal cord.
remove the mass.                                     Alternatively, the tumour may grow laterally
   The initial deterioration following a diagnosis   through the foramen of Luschka and into the
of recurrent glioma can usually be temporarily       cerebellopontine angle.
halted by the use of steroid medication. The            The tumours are well demarcated, nodular,
major decision is whether further surgery and        soft and pale. Calcification is common, especially
other adjuvant therapy should be undertaken. In      in supratentorial ependymomas.
general, a further operation involving debulking        There are numerous histological classification
of the tumour would be considered if:                systems of ependymomas, and the World Health
• the patient is less than 65 years old              Organization classification divides these tu-
• there has been a symptom-free interval of          mours into cellular, papillary and clear cell types
1 year or more since the first operation              of non-anaplastic ependymoma and anaplastic
• debilitating irreversible neurological signs are   ependymoma.
absent                                                  The myxopapillary variety is a slow-growing
• the tumour is in an accessible position and        distinct variant of ependymoma that occurs in
repeat surgery would not result in additional        the cauda equina and is discussed in the chapter
morbidity.                                           on spinal cord tumours (Chapter 15).
                                                        In an adult the subependymoma variant may
                                                     be encountered as an incidental autopsy
Adjuvant therapies
                                                     finding — a discrete nodular mass based in the
Adjuvant therapies have limited benefit for pa-       brain’s ventricular surface, particularly the floor
tients with recurrent tumour and, considering        or lateral recess of the 4th ventricle or the septum
the morbidity involved, may not be indicated.        pellucidum — or it may be large enough to pre-
Chemotherapy, utilizing temozolomide adminis-        sent clinically. It is usually heavily calcified and is
tered orally, has shown to have a temporary ben-     composed of cells with astrocytic as well as
efit in up to 40% of patients. Other chemotherapy     ependymal features.
agents, especially the nitrosourea compounds,           The papillary and anaplastic varieties of
have much greater toxicity.                          ependymoma are responsible for the majority of
                                                     clinically symptomatic ependymomas. The cellu-
                                                     larity and architecture of the ependymomas vary
Ependymoma
                                                     but a diagnostic feature is the presence of rosettes,
Ependymomas are glial neoplasms arising from         and most ependymomas contain areas in which
the ependyma and constitute approximately            perivascular pseudorosettes are conspicuously
5% of all gliomas. Approximately two-thirds of       developed. In these formations the blood vessel is
ependymomas occur in the infratentorial com-         surrounded by an eosinophilic halo composed of
partment and most of these present in children,      the radiating tapering processes of the cells. Ble-
adolescents and young adults. The supraten-          pharoplasts frequently occur in ependymomas
torial ependymomas occur mostly in adults.           but may be difficult to visualize. These are tiny
                                                     intracytoplasmic spherical or rod-shaped struc-
                                                     tures which represent the basal bodies of cilia,
Pathology
                                                     and are most frequently encountered in the apical
The tumour arises from the ependyma of the ven-      portion of cells that form ependymal rosettes.
 BRAIN TUMOURS                                                                                     79



Clinical presentation
Posterior fossa ependymomas
Details will be discussed in the section on paedi-
atric tumours (p. 91). Patients present with fea-
tures of raised intracranial pressure due to
hydrocephalus as a result of obstruction of the
4th ventricle, ataxia due to cerebellar involve-
ment, and occasionally features of brainstem
pressure or infiltration.

Supratentorial tumours
Virtually all patients with supratentorial ependy-
momas present with features of raised intracra-
nial pressure, often due to hydrocephalus as a
result of obstruction of the CSF pathways. Ataxia
is common and focal neurological deficits may
occur due to involvement of the underlying cere-
bral hemisphere.
                                                      Fig. 6.12 Calcified contrast-enhancing ependymoma
                                                      involving lateral ventricles.
Radiological investigation
The CT scan and MRI will show a tumour that
arises in the ventricle and enhances after admin-     pathways, sometimes whole neuraxis radiation
istration of intravenous contrast. Calcification is    is recommended.
common in tumours arising from the lateral ven-          The prognosis is related to the degree of
tricles (Fig. 6.12). There is frequently associated   anaplasia of the tumour and for intratentorial tu-
hydrocephalus. In the posterior fossa differentia-    mours varies from 20% to 50% 5-year survival.
tion from a medulloblastoma may be difficult.          The prognosis for the supratentorial tumours is
                                                      better, particularly in adults.

Treatment
                                                      Pineal tumours
The treatment of ependymomas is initially surgi-
cal, with an attempt to perform a radical macro-      Tumours arising in the region of the pineal gland
scopic resection of the tumour. Supratentorial        are mostly not of pineal origin, but are generally
tumours are often very large and may extend           called ‘pineal’, as they have a similar clinical
throughout the lateral and 3rd ventricles, but the    presentation.
associated hydrocephalus makes the excision of          The tumours are relatively uncommon, ac-
the intraventricular portion feasible. However,       counting for 0.5% of all intracranial tumours.
the tumour may arise from the ventricular wall in     However, they occur more frequently in Japan
the region of the basal ganglia and blend imper-      and China, where the incidence is up to 5%. Most
ceptibly with the underlying cerebral structures      tumours make their clinical appearance between
so that a complete excision is not possible. Fourth   10 and 30 years of age.
ventricular tumours can be excised from the ven-
tricle but microscopic infiltration into the under-
                                                      Classification
lying brainstem cannot be removed surgically.
Postoperative radiation therapy is advisable and,     Pineal region tumours are classified in decreas-
as these tumours may spread through the CSF           ing frequency as:
    80                                                                                 CHAPTER 6


•  germinoma                                        Radiological investigations
•  teratoma                                         CT scan and MRI will show a pineal region
•  pineocytoma                                      tumour and will often suggest the correct pathol-
•  pineoblastoma                                    ogical diagnosis (Fig. 6.13). On CT scan, before
•  miscellaneous:                                   contrast, a germinoma will be a hyperdense le-
   • glioma                                         sion in the region of the pineal gland infiltrating
   • cyst.                                          into the surrounding tissue and there will be uni-
   Germinoma is the most common pineal region       form vivid enhancement following intravenous
tumour and is similar in histological appearance    contrast. Calcification is uncommon. On MRI
to germinoma of the gonads and mediastinum; it      germinomas are relatively isointense to normal
occurs predominantly in males. These tumours        white matter on T1-weighted images and slightly
may also arise in the suprasellar region, and       hyperintense on T2-weighted scans. Gadolinium
synchronous tumours in both the pineal and          contrast defines the tumour well as germinomas
suprasellar region occur occasionally. Teratoma     enhance markedly and homogeneously.
is like germinoma; it also arises from displaced
embryonic tissue. The other tumour types occur
                                                    Management
less commonly.
                                                    This consists of surgery and radiotherapy.
                                                       A ventriculoperitoneal shunt or drainage of
Clinical presentation
                                                    CSF by a 3rd ventriculostomy may be required if
Patients with pineal tumours present with:          the hydrocephalus is severe.
• raised intracranial pressure                         There is controversy over whether the defini-
• neurological signs due to focal compression       tive treatment should be an attempt at surgical
• endocrine disturbance.                            excision or radiotherapy. As most of the tumours
                                                    are germinomas, and these tumours are very
Raised intracranial pressure. The features of       radiosensitive, a course of radiotherapy can be
raised intracranial pressure, such as headaches,    given as the initial treatment if the radiological
drowsiness and papilloedema, are due to             appearance is typical for germinoma. If serial CT
hydrocephalus, which is a result of the tumour      scans show the tumour has failed to respond to
occluding the aqueduct of Sylvius.                  radiotherapy then surgery may be necessary.
                                                    Alternatively, if the features on the initial CT
Focal compression. Compression of the efferent      and MRI scans are atypical, and the lesion does
cerebellar pathways in the superior cerebellar      not resemble a germinoma, exploration of the tu-
peduncle results in limb ataxia and distortion of   mour and surgical excision may be appropriate
the quadrigeminal plate, produces limitation of     as the initial procedure.
upgaze, convergence paresis with impairment            The preferred surgical approach is usually by a
of reaction of pupils to light and accommodation    posterior fossa craniotomy, above the cerebellum
(Parinaud’s syndrome), and may result in            and below the tentorium cerebelli. Alternative
convergence-retraction nystagmus on upgaze          supratentorial surgical exposures include ap-
(Koerber–Salius–Elschnig syndrome).                 proaching the tumour through the corpus callo-
                                                    sum or by retracting the occipital lobe.
Endocrine disturbance. Endocrine disturbances are
uncommon but include precocious puberty in
                                                    Metastatic tumours
10% of patients, almost invariably male, and
diabetes insipidus in 10%. The endocrine effects    Metastatic tumours are responsible for approxi-
can either be due to direct tumour involvement of   mately 15% of brain tumours in clinical series but
the hypothalamus or result from the secondary       up to 30% of brain tumours reported by patholo-
effects of hydrocephalus.                           gists. Approximately 30% of deaths are due to
 BRAIN TUMOURS                                                                                            81


                                                           cancer and 1 in 5 of these have intracranial
                                                           metastatic deposits at autopsy. The metastatic
                                                           tumours most commonly originate from:
                                                           • carcinoma of the lung
                                                           • carcinoma of the breast
                                                           • metastatic melanoma
                                                           • carcinoma of the kidney
                                                           • gastrointestinal carcinoma.
                                                              In 15% a primary origin is never found.
                                                              Most metastatic tumours are multiple and one-
                                                           third are solitary. In about half of these systemic
                                                           spread is not apparent. The incidence of tumours
                                                           in the cerebrum relative to the cerebellum is 8 : 1,
                                                           and most occur in the distribution of the middle
                                                           cerebral artery. The size of the tumours may
    (a)                                                    vary considerably if the deposits are multiple.
                                                           Metastatic tumours are often surrounded by
                                                           intense cerebral oedema.


                                                           Clinical presentation
                                                           The interval between diagnosis of the primary
                                                           cancer and cerebral metastases varies consider-
                                                           ably. In general, secondary tumours from carci-
                                                           noma of the lung present relatively soon after
                                                           the initial diagnosis, with a median interval of 5
                                                           months. Although cerebral metastases may pre-
                                                           sent within a few months of the initial diagnosis
                                                           of malignant melanoma or carcinoma of the
                                                           breast, some patients may live many years (up to
    (b)                                                    15 years) before an intracranial tumour appears.
                                                              The presenting features are similar to those
                                                           described for other intracranial tumours:
                                                           • raised intracranial pressure
                                                           • focal neurological signs
                                                           • epileptic seizures.
                                                              Headache and vomiting, indicative of raised
                                                           intracranial pressure, occur in most patients and
                                                           the presenting history is usually short, often only
                                                           a few weeks or months. The increased intracra-
                                                           nial pressure will be caused by either the tumour
                                                           mass and surrounding oedema or, in posterior
                                                           fossa tumours, obstructive hydrocephalus.
                                                              The pattern of focal neurological signs will de-
                                                           pend on the position of the tumour deposits and
                                                           the patient may present with a progressive hemi-
    (c)                                                    paresis or speech disturbance with supratentorial
Fig. 6.13 MRI in coronal (a), sagittal (b) and axial (c)   tumours or gait ataxia with cerebellar tumours.
plane showing pineal region germinoma causing
obstructive hydrocephalus.
 82                                                                                         CHAPTER 6


  Epileptic seizures occur in approximately
                                                        Treatment
25% of patients and may be either focal or
generalized.                                            Steroid medication (e.g. dexamethasone) will
  Occasionally, metastases, especially melanoma         control cerebral oedema and should be com-
or choriocarcinoma, present following an intra-         menced immediately if there is raised intracra-
cerebral haemorrhage.                                   nial pressure.
                                                           Surgery to remove the metastasis is indicated if:
                                                        • there is a solitary metastasis in a surgically
Radiological investigations
                                                        accessible position
CT scan or MRI will diagnose the metastatic tu-         • there is no systemic spread.
mour and will show whether the deposits are                Removal of a solitary secondary is preferable
solitary or multiple (Fig. 6.14). Most metastatic       only if the primary site of origin has been, or will
tumours are relatively isodense on the unen-            be, controlled. However, excision of a single
hanced CT scan and they enhance vividly after           metastasis will provide excellent symptomatic
intravenous contrast injection. Tumours that may        relief and consequently may be indicated even if
be hyperdense prior to contrast are melanoma,           the primary site cannot be treated satisfactorily.
choriocarcinoma, mucoid adenocarcinoma (e.g.            Surgery is, of course, mandatory if the diagnosis
from the gastrointestinal tract) and 50% of             is uncertain.
lymphomas. There is usually considerable sur-              Radiotherapy, together with steroid medica-
rounding cerebral oedema with distortion of             tion to control cerebral oedema, is used to treat
the ventricular system.                                 patients with multiple cerebral metastases and
   MRI following gadolinium contrast will               may be advisable following the excision of a
demonstrate small metastatic tumours often not          single metastasis. The treatment, up to 45 gray,
visible on the CT scan (Fig. 6.15).                     is usually given in a 2-week course.
                                                           Over the past decade stereotactic radiosurgery
                                                        utilizing a highly focused beam of radiation has
                                                        been used to treat single and multiple cerebral
                                                        metastases. The therapy does seem to be effective
                                                        in some cases and its role relative to surgery is
                                                        being evaluated.
                                                           Anticonvulsant medication is given both to
                                                        patients who have suffered epileptic seizures
                                                        and as a prophylactic measure.

                                                        Prognosis
                                                        About 30% of patients with solitary metastatic
                                                        deposits from carcinoma of the lung or
                                                        melanoma and 50% of patients with carcinoma of
                                                        the breast survive 1 year following surgical exci-
                                                        sion. In those patients where the source of the
                                                        metastatic tumours is undetermined, about 50%
                                                        survive 1 year.


                                                        Leptomeningeal metastases
                                                        Meningeal carcinomatosis is widespread, multi-
Fig. 6.14 Multiple contrast-enhancing tumours typical   focal seeding of the leptomeninges by systemic
of metastatic melanoma.                                 cancer. The clinical presentation includes:
BRAIN TUMOURS                                                  83


                • hydrocephalus, causing headaches and
                vomiting
                • cranial nerve abnormalities due to direct
                invasion by the tumours
                • spinal root involvement due to local infiltration.
                   The CT scan or MRI findings may be subtle but
                frequently show excessive enhancement of the
                meninges. Lumbar puncture can be performed
                if there is no evidence of raised intracranial
                pressure. Malignant cells may be seen in the
                CSF, the protein concentration is increased and
                the glucose reduced.


                Cerebral lymphoma
                The term cerebral lymphoma encompasses a
                number of distinct pathological and clinical
                entities. Current nomenclature divides cerebral
 (a)
                lymphoma into: non-Hodgkin’s lymphoma or
                Hodgkin’s disease; primary or secondary dis-
                ease; and patients who are immunocompetent or
                immunosuppressed.
                   Historically, lymphoma involving the CNS
                was considered to be rare, being less than 3% of
                all CNS tumours, with about half of these lym-
                phomas being primary cerebral lymphoma, that
                is, the tumour being confined entirely to the CNS.
                Over the past decade there has been an unprece-
                dented increase in the incidence of cerebral lym-
                phoma, which can be attributed to at least two
                known factors: the acquired immune deficiency
                syndrome (AIDS) epidemic and the use of im-
                munosuppressive therapy. However, there has
                also been an unexplained increase in the inci-
                dence of primary cerebral lymphoma in non-
                immunosuppressed patients.
 (b)
                   Cerebral lymphoma may be secondary to sys-
                temic lymphoma and in large studies of patients
                with systemic lymphoma, up to 30% of patients
                develop clinical or pathological evidence of cere-
                bral involvement. However, almost all cases are
                associated with either relapsed or progressive
                systemic disease and an isolated CNS relapse is
                very rare.



                Fig. 6.15 MRI following gadolinium shows multiple
                small metastatic tumours.

 (c)
 84                                                                                      CHAPTER 6


  Intracerebral Hodgkin’s disease is a very rare
                                                     Radiological investigations (Figs 6.16 and
entity.
                                                     6.17)

                                                     The CT scan characteristically shows a hypo-
Clinical presentation
                                                     dense or isodense or sometimes hyperdense
The most common site for primary cerebral            tumour, which enhances following contrast
lymphoma is in the frontal lobe, followed by the     injection with associated mild to moderate
temporal lobe, parietal lobe and deep nuclei.        oedema. Multifocal disease is observed in about
Tumours may also occur in the cerebellum and         40% of CT scans. Most primary cerebral lym-
brainstem. The tumours may be either solitary or     phomas arise in the periventricular region. MRI
multiple and primary leptomeningeal disease          is now the investigation of choice for primary
has been reported in up to 10% of primary cere-      cerebral lymphoma. The lesions are usually hy-
bral lymphoma.                                       pointense to isointense on T1-weighted images
   There are no pathognomonic presenting symp-       and isointense to hyperintense on T2-weighted
toms or signs in primary cerebral lymphoma and       images. The tumours enhance following intra-
the presenting features are similar to those de-     venous injection of gadolinium.
scribed for other intracranial tumours: raised in-      Although CSF examination may show a popu-
tracranial pressure, focal neurological signs and    lation of abnormal lymphocytes, concern regard-
epileptic seizures. The high frequency of frontal    ing raised intracranial pressure usually prevents
lobe involvement results in a common mode of         a lumbar puncture being performed in the major-
presentation as memory loss, forgetfulness and       ity of patients.
altered affect. Up to 10% of patients with primary
cerebral lymphoma present with a seizure. In
                                                     Management
view of the incidence of multiple lesions, it is
not surprising that many patients present with a     The principles concerning the management of
constellation of symptoms and signs. The pre-        primary cerebral lymphoma involve:
senting features in primary cerebral lymphoma        • histological diagnosis
arising in immunodeficient patients (including        • ensuring that the disease is confined to the brain
AIDS-related primary cerebral lymphoma)              • excluding an underlying, predisposing illness
do not appear to be different from those in im-      • instituting appropriate therapy.
munocompetent patients with primary cerebral           The usual sequence of events is a CT and MRI
lymphoma.                                            scan followed by a biopsy proving intracerebral
                                                     lymphoma. In general, it is thought appropriate




(a)                                                                            (b)
Fig. 6.16 (a) MRI and (b) CT of cerebral lymphoma.
 BRAIN TUMOURS                                                                                            85


                                                      the therapy of systemic non-Hodgkin’s lym-
                                                      phoma and include methotrexate, cortico-
                                                      steroids, anthracyclines, vinca alkaloids,
                                                      cytosine, arabinoside and alkylating agents. Me-
                                                      dian survival times of up to 44 months have been
                                                      reported. However, methotrexate given after
                                                      radiotherapy increases the risk of leukoen-
                                                      cephalopathy with consequent serious neuro-
                                                      psychological impairment. The need for
                                                      postchemotherapy radiation has been ques-
Fig. 6.17 Autopsy specimen of cerebral lymphoma.      tioned, in view of the effectiveness of chemother-
                                                      apy, especially in the elderly.

to exclude systemic disease, although concurrent
                                                      Paranasal sinus tumours
cerebral and systemic lymphoma is uncommon.
Patients usually undergo bone marrow aspirate         Tumours of the paranasal sinuses may spread di-
and trephine, chest X-ray, CT scan of the chest       rectly to involve the brain. These uncommon tu-
and abdomen and testing for evidence of HIV           mours most frequently arise from the ethmoid or
infection.                                            maxillary sinuses, less frequently from the sphe-
                                                      noid sinus and rarely from the frontal sinus. The
Surgical treatment                                    tumours invade through the floor of the anterior
There is no clear evidence that craniotomy with       cranial fossa in the region of the cribriform plate
excision of the lymphoma is superior to obtain-       and may extend through the dura into the frontal
ing an accurate tissue diagnosis using a stereotac-   lobe (Fig. 6.18). The tumours are usually squa-
tic biopsy. It must be noted that the early use of    mous cell carcinoma and less frequently adeno-
corticosteroids, to treat cerebral oedema, may        carcinoma or adenoid cystic adenocarcinoma.
make histological assessment difficult due to the      The aesthesioneuroblastoma is a rare nasal
exquisite sensitivity of primary cerebral lym-
phoma to steroids. The tumour may disappear
on the CT scan or MRI after the commencement
of corticosteroids and this has significant impli-
cations for obtaining a stereotactic biopsy.

Radiotherapy
Primary cerebral lymphoma is usually radiosen-
sitive with a clinical response rate of up to 80%.
However, cranial radiotherapy alone as a treat-
ment for primary cerebral lymphoma rarely
produces long-term survivors, despite the high
response rate and an improvement in median
survival time to 15 months.

Chemotherapy
Numerous chemotherapy regimes have been re-
ported, including the use of both intrathecal and
intravenous therapies which can be given prior        Fig. 6.18 Carcinoma of the ethmoid extending
to, synchronous with, or following radiotherapy.      through the cribriform plate into the anterior cranial
The most commonly used drugs are those used in        fossa.
 86                                                                                         CHAPTER 6


tumour arising from the olfactory epithelium           vacuolated and some will contain a single
that may invade through the cribriform plate.          large vacuole giving a ‘signet ring’ appearance.
    The patients usually present with a blood-         The characteristic histological appearance is
stained or purulent nasal discharge and pain in        physaliphorous (bubble-bearing) cells contain-
the involved region. CSF rhinorrhoea may occur         ing multiple vacuoles.
if the dura has been breached.
    Surgical excision using a craniofacial resection
                                                       Clinical presentation
may be the only method of controlling these tu-
mours and, if the tumour has spread into the           The majority of intracranial chordomas arise be-
orbit, an adequate resection may involve orbital       tween 20 and 60 years of age. The clinical features
exenteration.                                          result from the widespread tumour extension
                                                       and include:
                                                       • raised      intracranial    pressure,      causing
Chordomas
                                                       headaches and vomiting
Chordomas are rare tumours arising from noto-          • multiple cranial nerve palsies, often unilateral
chord cell nests. They may arise throughout the        • nasopharyngeal obstruction.
craniospinal axis but occur predominantly at the          The radiological appearances are of a destruc-
ends of the axial skeleton in:                         tive lesion at the base of the skull or in the verte-
• the basioccipital region                             bral bodies (Fig. 6.19).
• the sacrococcygeal region.
  The intracranial chordoma presents as a skull
                                                       Treatment
base tumour. It infiltrates and erodes the sphe-
noid and basiocciput and may spread into the           It is rarely possible to excise all the tumour. Post-
petrous bones, the paranasal sinuses, the sella        operative radiotherapy is usually administered
turcica and the cavernous sinuses. The tumour          but is of doubtful value.
will compress and distort the adjacent brain and
engulf the cranial nerves and arteries.
                                                       Paediatric tumours
  These tumours do not have histological fea-
tures of malignancy and only rarely metastasize.       Intracranial tumours are the most common form
However, it is not usually possible to excise the      of solid tumours in childhood, with 40% of the
cranial tumours completely; most patients die
within 10 years of initial presentation.
  Spinal chordomas occur predominantly in the
sacrococcygeal region, although they may also
arise in the cervical area. Like the cranial tu-
mours, spinal chordomas invade and destroy
bone and compress adjacent neural structures.
Remote metastases occasionally occur. Patients
with spinal chordomas present with back pain,
radicular pain and slowly progressive lum-
bosacral nerve root involvement resulting in
sphincter difficulties and sensory and motor dis-
turbances in the legs.


Histological appearance
The tumours consist of notochord cells and mu-         Fig. 6.19 Sacral chordoma. A destructive tumour
coid stroma. Many of the cells may be coarsely         extending into the vertebral canal.
 BRAIN TUMOURS                                                                                       87


tumours occurring above the tentorium cerebelli.      ‘false localizing sign’. Papilloedema is usually
The most common supratentorial tumours are            present at the time of diagnosis. In infants, an ex-
astrocytomas, followed by anaplastic astrocy-         panding head size is an additional sign of raised
tomas and glioblastoma multiforme. Cranio-            intracranial pressure.
pharyngioma occurs more commonly in children
than in adults and is situated in the suprasellar     Focal neurological signs
region; this tumour is described in Chapter 8.        These are due to the tumour invading or com-
Other, less common, supratentorial tumours            pressing the cerebellum (nuclei and tracts), the
include primitive neuroectodermal tumours             brainstem and cranial nerves. Truncal and gait
(PNETs), ependymomas, ganglioglioma and               ataxia result particularly from midline cerebellar
pineal region tumours.                                involvement. Horizontal gaze paretic nystagmus
                                                      often occurs with tumours around the 4th ventri-
                                                      cle. Upbeat vertical nystagmus is indicative of
Posterior fossa tumours
                                                      brainstem involvement.
Sixty per cent of paediatric brain tumours occur         Disturbances of bulbar function, such as diffi-
in the posterior fossa. The relative incidence of     culty in swallowing with nasal regurgitation of
the tumours is:                                       fluid, dysarthria and impaired palatal and
1 cerebellar astrocytoma 30%                          pharyngeal reflexes, result from brainstem in-
2 medulloblastoma (infratentorial primitive           volvement. In addition, compression or tumour
neuroectodermal tumour) 30%                           invasion of the pyramidal tracts may result in
3 ependymoma 20%                                      hemiparesis and, if the ascending sensory path-
4 brainstem glioma 10%                                ways are involved, sensory disturbance will
5 miscellaneous 10%:                                  occur in the trunk and limbs.
  (a) choroid plexus papilloma                           The tumour may directly envelop the lower
  (b) haemangioblastoma                               cranial nerves — glossopharyngeal, vagal, spinal
  (c) epidermoid, dermoid                             accessory and hypoglossal — as well as the 7th
  (d) chordoma.                                       cranial nerve.
                                                         Neck stiffness and head tilt may occur in chil-
Clinical presentation                                 dren with posterior fossa neoplasms, and may be
The presenting clinical features of posterior fossa   due to herniation of a cerebellar tonsil or tumour
neoplasms in children are related to:                 tissue resulting in dural irritation.
• raised intracranial pressure
• focal neurological signs.                           Investigations
                                                      CT scan and MRI have replaced the need for
Raised intracranial pressure                          the previous radiological investigations that
This is the most common presenting feature. It is     included radio-isotope brain scanning, air ven-
due to hydrocephalus caused by obstruction of         triculography and posterior fossa angiography.
the 4th ventricle and is manifest by headaches,       The CT scan and/or MRI will show the presence
vomiting, diplopia and papilloedema.                  of a posterior fossa tumour, its position and
   The headaches begin insidiously, gradually be-     whether it arises primarily in the brainstem, 4th
coming more severe and frequent; they are worst       ventricle or the cerebellum (Figs 6.20–6.24).
in the early morning. There is usually no specific
headache localization. Vomiting is frequently         Management
associated with the headaches and may tem-            The treatment of posterior fossa tumours
porarily relieve the headache. Raised intracranial    involves:
pressure may result in a strabismus causing           • surgery
diplopia due to stretching of one or both of the      • radiotherapy
6th (abducens) cranial nerves. This is a so-called    • chemotherapy.
88                                               CHAPTER 6




     (a)




           Fig. 6.21 Cystic cerebellar astrocytoma causing
           obstructive hydrocephalus. There is a contrast-
           enhancing nodule in a large cyst.



              A preliminary CSF shunt may need to be per-
           formed in a child with severely raised intracra-
           nial pressure due to hydrocephalus. The CSF
           diversion can be achieved by either an external
           drain or a ventriculoperitoneal shunt. An exter-
           nal drain is a temporary measure only, because of
           the risk of infection. A ventriculoperitoneal shunt
           provides immediate and controlled relief of
           intracranial hypertension and the subsequent
           posterior fossa operation can be performed
           as a planned elective procedure, rather than an
           urgent operation in suboptimal conditions. A
           criticism of a preoperative ventriculoperitoneal
           shunt is that it might promote the metastatic
           spread of tumour. A filtering chamber in the
           shunt system may lessen this risk but this predis-
           poses to shunt malfunction.



           Fig. 6.20 (a) CT scan. Contrast-enhancing
           medulloblastoma arising from the vermis causing
           obstructive hydrocephalus. (b) MRI scan.
           Medulloblastoma.

     (b)
 BRAIN TUMOURS                                                                                         89




                                                          (a)




Fig. 6.22 Contrast-enhancing ependymoma in the 4th
ventricle causing obstructive hydrocephalus.




   Steroid medication to control local oedema is
commenced preoperatively. The operation is per-
formed in either the sitting or prone position
through a vertical midline incision. A posterior
fossa craniotomy is performed, usually with exci-
sion of the bone down to and around the foramen
magnum. Tumour excision is aided by the use of
magnifying loupes and illumination with a fibre-
optic headlight, or by the use of an operating
microscope.
   Postoperative care involves careful monitoring
of the neurological signs. Postoperative haemor-
rhage or oedema may result in rapid deteriora-
tion of the neurological state, and in respiratory
arrest. An urgent CT scan may indicate the cause
and site of the problem but the deterioration may
be so rapid that the wound may need to be re-
opened without the benefit of prior scanning.
   If a ventriculoperitoneal shunt has not been in-
serted prior to tumour removal an exacerbation
of the obstructive hydrocephalus may occur if
the tumour excision has failed to relieve the CSF         (b)
obstruction. Disturbances of bulbar and lower         Fig. 6.23 MRI scan showing (a) pontine glioma,
cranial nerve function may cause difficulty in         (b) cystic brainstem glioma.
 90                                                                                             CHAPTER 6


                                                          swallowing. Nasogastric feeding may be neces-
                                                          sary until the protective mechanisms return, and
                                                          great care should be taken to avoid aspiration.


                                                          Medulloblastoma
                                                          Medulloblastoma, also referred to as an infraten-
                                                          torial PNET, is a malignant tumour usually aris-
                                                          ing in the midline from the cerebellar vermis,
                                                          although it may occur more laterally in a cerebel-
                                                          lar hemisphere in older patients. The tumour ex-
                                                          pands to invade the adjacent cerebellum and
                                                          large tumours completely fill the 4th ventricle
                                                          (see Fig. 6.19).
    (a)
                                                             The tumours arise from the external granular
                                                          layer of the fetal cerebellum (Obersteiner’s
                                                          layer). Histologically the medulloblastoma is
                                                          highly cellular, with numerous mitoses. True
                                                          rosettes do not occur but the cells are seen in con-
                                                          centric patterns around homogeneous material
                                                          or blood vessels (pseudorosettes).
                                                             Presenting features. The presenting features are
                                                          related to hydrocephalus and cerebellar dysfunc-
                                                          tion. Truncal ataxia is typically present in chil-
                                                          dren with medulloblastoma but cranial nerve
                                                          deficits, except for a 6th nerve palsy, are uncom-
                                                          mon in the early stages.
                                                             Surgery. At surgery the cerebellar vermis is
                                                          split in the midline and it is usually possible to ob-
                                                          tain a gross macroscopic excision of the tumour
    (b)
                                                          with complete removal from the 4th ventricle.
                                                             Radiation therapy. Medulloblastoma is rela-
                                                          tively radiosensitive and radiation therapy is
                                                          recommended to the entire neuraxis because of
                                                          the tendency of the tumours to seed along the
                                                          CSF pathways.
                                                             Chemotherapy. Adjuvant chemotherapy is
                                                          usually recommended and numerous protocols
                                                          using a variety of chemotherapeutic agents have
                                                          been investigated. There is no uniformity of
                                                          opinion as to which drugs or routes of adminis-
                                                          tration are the most effective and whether
                                                          chemotherapy should be administered as part of
                                                          the initial treatment plan or only used at the time
                                                          of recurrence of the tumour.
    (c)
                                                             Young children are exquisitely sensitive to the
Fig. 6.24 MRI scan showing glioblastoma invading          neurotoxicity due to radiation therapy, such that
through the brainstem of a 25-year-old man. Before
                                                          the possibility of utilizing chemotherapy alone
intravenous gadolinium contrast: (a) sagittal T1. After
intravenous gadolinium contrast: (b) axial and (c)
coronal.
 BRAIN TUMOURS                                                                                          91


and postponing the use of radiotherapy has been        ally due to hydrocephalus. Involvement of the
trialled.                                              dorsal brainstem results in unilateral or bilateral
   Prognosis. Although the combination of radical      facial weakness.
surgery and irradiation has improved the prog-            Surgery. The surgical excision of the ependy-
nosis, the 5-year survival rate is approximately       moma involves splitting the inferior vermis to
40%.                                                   obtain access to the 4th ventricle. It is usually pos-
                                                       sible to perform a gross macroscopic excision of
                                                       the tumour from the ventricle and adjacent cere-
Cerebellar astrocytoma
                                                       bellum but, as the tumour often originates from
The cerebellar astrocytoma is frequently a be-         the floor of the 4th ventricle, total excision is
nign, slowly growing cystic tumour which is the        rarely possible.
most favourable of all the intracranial paediatric        Radiation therapy. Postoperative radiation ther-
neoplasms. The tumours may arise in either the         apy is usually administered to the posterior fossa
hemisphere or vermis and frequently consist of a       and, as the tumour seeds along the CSF path-
large tumour cyst with a relatively small solid        ways, entire neural axis irradiation is often
component in the wall of the cyst (see Fig. 6.20).     recommended, particularly in the higher-grade
Less frequently the tumour may be entirely solid       ependymoma.
with little or no cystic component. Histologically,       There is no definite advantage from adjuvant
the solid portion of the tumour is usually a Grade     chemotherapy, although it may be used at the
1 or 2 astrocytoma.                                    time of tumour recurrence.
   Presenting features. The clinical presenting fea-
tures are similar to those of a medulloblastoma,
                                                       Brainstem glioma
but as the tumour may be located more laterally
the presenting features are accompanied by             The brainstem glioma arises predominantly in
ipsilateral cerebellar disturbance. The duration of    the pons, less frequently in the medulla but may
symptoms is variable but tends to be longer than       infiltrate extensively throughout the brainstem.
with medulloblastoma, averaging 6–12 months.           The tumour infiltrates between the normal
   Surgery. A complete surgical excision is usually    structures with a histological appearance vary-
possible and it is only necessary to excise the        ing from the relatively benign astrocytoma to
solid component from the cystic tumour.                anaplastic astrocytoma and glioblastoma multi-
   Radiation therapy. Postoperative radiation          forme. Over 50% of brainstem gliomas examined
therapy is not usually indicated if an excision        at autopsy will have microscopic features of
has been possible. The prognosis is the most           glioblastoma multiforme.
favourable of all intracranial childhood tumours          Clinical presentation. The clinical presentation
with a cure rate in excess of 75%.                     characteristically includes progressive multiple
                                                       bilateral cranial nerve palsies with involvement
                                                       of pyramidal tracts and ataxia. Facial weakness
Ependymoma
                                                       and 6th cranial nerve palsy are common and an
The ependymoma of the 4th ventricle arises from        internuclear ophthalmoplegia is indicative of an
the floor of the 4th ventricle and is attached to,      intrinsic brainstem lesion. The child’s personality
and may infiltrate, the underlying brainstem (see       often changes — they become apathetic. Raised
Fig. 6.21).                                            intracranial pressure is less common than with
   Pathological features. The pathological features    other paediatric posterior fossa neoplasms, as
and histology are described earlier in the chapter     obstruction of the 4th ventricle or aqueduct of
(see p. 78).                                           Sylvius occurs late in the illness.
   Presenting features. The presenting features are       The CT and MRI appearance is of an expanded
similar to those described for a medulloblastoma,      brainstem. MRI has considerably improved the
although the initial symptoms and signs are usu-       accuracy of the diagnosis (Fig. 6.22).
 92                                                                                                    CHAPTER 6


   Surgery. Surgical treatment is not usually indi-           Higginbotham NL, Phillips RJ, Farr HW (1979)
cated, although either an open or a stereotactic                Chordoma: thirty five year study at the Memorial
biopsy may be performed to confirm the                           Hospital. Cancer 29, 1841–1850.
diagnosis.                                                    Kaye AH, Black P McL (2000) Operative Neurosurgery.
                                                                Churchill Livingstone, London, New York,
   Radiation therapy. Palliative radiation therapy
                                                                Edinburgh.
is the only treatment. The tumour usually causes
                                                              Kaye AH, Laws EL (1995) Brain Tumours. Churchill
death within 24 months of diagnosis, although                   Livingstone, London.
some patients with low-grade tumours will live                Kaye AH, Morstyn G, Apuzzo MJ (1988) Photoradia-
longer.                                                         tion therapy and its potential in the management of
   Chemotherapy has limited benefit.                             neurological tumours. Journal of Neurosurgery 69,
                                                                1–14.
                                                              Kernohan JW, Maybon RF, Svein HJ, Adson AW (1949)
Further reading                                                 A simplified classification of gliomas. Mayo Clinic
Apuzzo MJ et al. (1984) Ionising and non-ionising               Proceedings 24, 71–75.
  radiation treatment of cerebral malignant gliomas:          Kornblith PL, Walker M (1988) Chemotherapy of
  specialised approaches. Clinical Neurosurgery 31,             gliomas. Journal of Neurosurgery 68, 1–17.
  470–496.                                                    Liebel SA, Sheline GE (1987) Radiation therapy for
Bailey P, Cushing H (1971) A Classification of Tumours           neoplasms of the brain. Review article. Journal of
  of the Glioma Group on a Histogenetic Basis with a Cor-       Neurosurgery 66, 1–22.
  related Study of Prognosis. J B Lippincott, Philadelphia,   Rich TA et al. (1985) Clinical and pathologic review of 48
  1926. Reprinted Argosy Antiquarian, New York.                 cases of chordoma. Cancer 56, 182–187.
Burger PC, Vogel FS (1982) Surgical Pathology of the          Ringertz N (1950) Grading of gliomas. Acta Pathologica
  Nervous System and its Coverings, 2nd edn. John               Microbiologica Scandinavica 27, 51–64.
  Wiley, New York.                                            Wold LF, Laws ER Jr (1983) Cranial chordomas in
Cairncross JG, Ueki K, Zlatescu MC et al. (1998) Specific        children and young adults. Journal of Neurosurgery
  genetic predictors of chemotherapeutic response               59, 1043–1047.
  and survival in patients with anaplastic oligoden-          Yung WK (2000 June) Temozolomide in malignant
  drogliomas. Journal of the National Cancer Institute 90       gliomas. Seminars in Oncology 27 (3 Suppl. 6), 27–34.
  (19), 1473–1479.                                            Zulch KJ (1986) Brain Tumours, Their Biology and
Dohrmann GJ, Farwell JR, Flannery JI (1976) Ependy-             Pathology, 3rd edn. Springer Verlag, Berlin.
  momas and ependymoblastomas in children. Journal
  of Neurosurgery 45, 273–283.
                           CHAPTER 7


  7                        Benign brain tumours



The benign brain tumours may be intimately as-        an aetiological factor, there have been cases
sociated with, and surrounded by, the adjacent        reporting the development of meningiomas at
brain, but the tumour cells do not invade the un-     the site of substantial meningeal trauma.
derlying brain. This is in contradistinction to the      Meningiomas are known to occur following
gliomas, which are intrinsic brain tumours ac-        low levels of irradiation as was given in the past
tively invading the adjacent brain. This chapter      for tinea capitis, and an analysis of the Nagasaki
will discuss the more common benign brain tu-         atomic bomb survivors found a high correlation
mours — meningioma and acoustic neuroma —             between the incidence of meningiomas and the
and give a brief description of the less common       distance from the epicentre of the explosion.
tumours: haemangioblastoma, epidermoid and               Meningiomas occur with a high frequency in
dermoid cysts and colloid cysts.                      patients with neurofibromatosis type 2 (NF2)
                                                      (often multiple). This association has prompted
                                                      cytogenetic studies, which have shown that
Meningioma
                                                      monosomy of chromosome 22 is the most
Meningiomas are the most common of the benign         common chromosomal abnormality noted in
brain tumours and constitute about 15% of all in-     meningiomas, occurring in 50–80% of sporadic
tracranial tumours, being about one-third of the      tumours. In addition, alterations of many other
number of gliomas. Although they may occur at         chromosomes (including chromosomes 1, 6, 9, 10,
any age, they reach their peak incidence in mid-      11, 13, 14, 18 and 19) have been noted to be
dle age, are very uncommon in children and            involved in the formation and progression of
occur more frequently in women than men.              meningioma.
   The term meningioma was introduced by                 The importance of sex hormones and their re-
Harvey Cushing in 1922, although the tumour           ceptors in meningioma is suggested by the 2–4
had been described in the late eighteenth century.    times incidence in females. Oestrogen binds in
The tumour arises from the arachnoid layer of the     less than 30% of meningiomas, with the majority
meninges, principally the arachnoid villi and         of those receptors being type II subtype, that
granulations.                                         have a lower affinity and specificity for oestrogen
                                                      than the classic type I receptor usually found in
                                                      breast cancer. Progesterone receptors are much
Aetiology
                                                      more commonly associated with meningiomas,
As for other brain tumours, no definite aetiologi-     occurring in 50–100% of tumours tested.
cal factor has been identified. However, the
possibility that head trauma predisposes to the
                                                      Position of meningiomas (Fig. 7.1)
development of meningioma has been the subject
of controversy for many years. Although epi-          Meningiomas arise from the arachnoid layer of
demiological studies do not support trauma as         the meninges, especially the arachnoid cap cells.

                                                                                                     93
 94                                                                                            CHAPTER 7


Basal

                                                          Olfactory groove

Sphenoidal wing
                                                         Tuberculum sellae
                                                                    Clivus
                                                         Foramen magnum
Posterior fossa
- cerebellopontine
angle




Parasagittal section

                                                        Parasagittal/falcine




Olfactory groove
Tuberculum sellae

                                                            Posterior fossa
                                                            (convexity)         Fig. 7.1 Typical positions of
                       Clivus                            Foramen magnum         intracranial meningiomas.



The most common location is in the parasagittal
                                                        Table 7.1 Position of intracranial meningiomas
region arising either from the wall of the superior
                                                        (%).
sagittal sinus (parasagittal) or from the falx
(falcine). Less frequently the tumours may arise
                                                        Parasagittal and falx                            25
from the convexity of the cranial vault, where          Convexity                                        20
they are particularly concentrated in the region of     Sphenoidal wing                                  20
the coronal suture. Sphenoidal ridge menin-             Olfactory groove                                 12
giomas are divided into those that arise from the       Suprasellar                                      12
inner part of the lesser wing of the sphenoid and       Posterior fossa                                   9
the adjacent anterior clinoid process, and those        Ventricle                                         1.5
arising from the outer sphenoidal ridge, compris-       Optic sheath                                      0.5
ing the greater wing of the sphenoid and the
adjacent pterion (the junction of the temporal,
parietal and frontal bones). Less frequently, the
tumours may arise from the olfactory groove, tu-      based on the histological appearance of the tu-
berculum sella (suprasellar), floor of the middle      mour, meningiomas are usually classified accord-
cranial fossa, cavernous sinus or posterior fossa     ing to their position of origin rather than their
(Table 7.1).                                          histology. The reason for this is that the biological
   Meningiomas usually occur as a single in-          activity of the tumour, the presenting features,
tracranial tumour but multiple intracranial           the treatment and prognosis are all related more
meningiomas may present in NF2 (see p. 64).           to the site of the tumour than to the histology.
                                                         The major histological types are listed below.
                                                      • Syncytial or meningotheliomatous — sheets of
Pathology
                                                      cells with varying amounts of stroma.
Unlike gliomas, where the classification system is     • The transitional type is characterized by
 BENIGN BRAIN TUMOURS                                                                                 95


whorls of cells which may undergo hyalin degen-
eration with subsequent deposition of calcium
salts. These calcified concentric psammoma
bodies form the characteristic feature of many
transitional meningiomas but they may also be
present in the syncytial or fibroblastic types.
• The fibroblastic type contains abundant
reticulin and collagen fibres.
• Angiomatous meningiomas are much less
common and their characteristic feature is the
predominance of vascular channels separated
by sheets of cells. Histologically, these tumours
resemble cerebellar haemangioblastomas.
• Malignant meningiomas occur infrequently.
The indications of malignancy include cellular
pleomorphism, necrosis, increased numbers of
                                                         (a)
mitotic figures and local invasion of brain. Atypi-
cal meningiomas are tumours that lack the
histological features of malignancy, but have a
biological behaviour intermediate between the
typical and malignant meningioma. These tu-
mours are most likely to recur.


Clinical presentation
Meningiomas present with features of:
• raised intracranial pressure
• focal neurological signs
• epilepsy.
  The position of the tumour will determine the
features of the clinical presentation. The tumours
grow slowly and there is frequently a long his-
tory, often of many years, of symptoms prior to
                                                         (b)
the diagnosis.
                                                     Fig. 7.2 Parasagittal meningioma. (a) CT scan.
                                                     (b) MRI.
Parasagittal tumours (Fig. 7.2)
These tumours most often arise in the middle
third of the vault and the patient may present       frontal tumour, especially if it is bilateral.
with focal epilepsy and paresis, usually affecting   Tumours arising from the posterior falx may
the opposite leg and foot as the motor cortex on     affect the parieto-occipital region and produce a
the medial aspect of the posterior frontal lobe is   homonymous hemianopia. If the tumour lies
affected. Tumours arising anteriorly are often       above the calcarine fissure the inferior quadrant
bilateral and patients present with features of      is more affected; when the tumour is below the
raised intracranial pressure. As these tumours       fissure the upper quadrant is predominantly
involve the frontal lobes, pseudopsychiatric         affected.
symptoms, as well as impairment of memory,
intelligence and personality, may occur. Urinary     Convexity tumours (Fig. 7.3)
incontinence is occasionally a symptom of a large    Convexity tumours may grow to a large size if
 96                                                                                          CHAPTER 7




                                                          (a)


    (a)




                                                          (b)
                                                       Fig. 7.4 (a) CT scan. Hyperostosis of the left
    (b)
                                                       sphenoidal ring causing unilateral proptosis due
Fig. 7.3 Convexity meningioma. (a) CT scan. (b) MRI.   to a sphenoidal ring meningioma. (b) MRI. Inner
                                                       sphenoidal wing meningioma.

situated in front of the coronal suture. They
present with raised intracranial pressure. More        The presenting features of primary optic atrophy
posterior tumours will cause focal neurological        in one eye and papilloedema in the other is
symptoms and focal epilepsy.                           known as the Foster Kennedy syndrome, and
                                                       was described in 1911. Inner sphenoidal ridge
Sphenoidal ridge tumours (Fig. 7.4)                    tumours may also cause compression of the
Tumours arising from the inner sphenoidal              olfactory tract, resulting in anosmia.
ridge cause compression of the adjacent optic            Patients with tumours involving the outer
nerve and patients may present with a history of       sphenoidal ridge present with features of raised
uniocular visual failure. If the tumour is large       intracranial pressure, often severe papilloedema
enough to cause raised intracranial pressure pa-       with relatively inconspicuous localizing symp-
pilloedema will develop in the contralateral eye.      toms or signs. Tumours in this region occur as a
 BENIGN BRAIN TUMOURS                                        97


thin sheet, and are known as ‘en plaque’. They
may cause an excessive bony reaction (hyperos-
tosis) resulting in proptosis (Fig. 7.4).

Olfactory groove tumours (Fig. 7.5)
Olfactory groove meningiomas cause anosmia,
initially unilateral and later bilateral. The pre-
senting features may include symptoms of raised
intracranial pressure, and failing vision either
from chronic papilloedema or from direct com-
pression of the optic nerve or chiasm causing
visual field defects. These tumours may also
present with the Foster Kennedy syndrome and
the intellectual and psychiatric problems caused
by frontal lobe compression described for inner
spheroidal ridge meningiomas.
                                                       (a)
Suprasellar tumours (Fig. 7.6)
Suprasellar meningiomas arising from the tuber-
culum sellae will cause visual failure and a
bitemporal hemianopia, but the lack of endocrine
disturbance will distinguish the clinical presenta-
tion of this tumour from that of a pituitary
tumour.

Ventricular tumours (Fig. 7.7)
Tumours arising in the lateral ventricle present
with symptoms of raised intracranial pressure
extending over several years and associated
with a mild global disturbance of function of
one hemisphere and frequently a homonymous
hemianopia.

Posterior fossa tumours (Fig. 7.8)
Posterior fossa tumours may arise from the cere-
bellar convexity or from the cerebellopontine
angle or clivus. The cerebellopontine angle tu-
mours simulate an acoustic neuroma with symp-
toms involving the acoustic nerve, trigeminal
nerve and facial nerve, ataxia due to cerebellar in-
volvement and raised intracranial pressure, often
due to hydrocephalus caused by obstruction of
the 4th ventricle. Meningiomas arising from the



Fig. 7.5 (a) CT scan. Olfactory groove meningioma.
(b) MRI. Olfactory groove meningioma extending on
to tuberculum sella and over pituitary fossa.

                                                       (b)
 98                                                                                           CHAPTER 7




    (a)                                               Fig. 7.7 Intraventricular meningioma.


                                                      the tumour attachment or, as seen with en plaque
                                                      meningioma, a more diffuse sclerosis. These
                                                      bone changes may also be seen on plain skull
                                                      X-ray.
                                                         Magnetic resonance imaging will demonstrate
                                                      meningiomas following the intravenous injec-
                                                      tion of gadolinium contrast (Figs 7.9–7.11).
                                                      Meningiomas are usually isointense on T1-
                                                      weighted images, but enhance intensely and usu-
                                                      ally homogeneously following administration of
                                                      gadolinium. Cerebral angiography is no longer
                                                      necessary as a diagnostic investigation but may
                                                      be useful preoperatively to ascertain the position
                                                      of the cerebral vessels. It will demonstrate exter-
                                                      nal carotid artery supply to the tumour with a
    (b)
                                                      characteristic tumour blush, differentiating it
Fig. 7.6 Tuberculum sellae meningioma. (a) CT scan.
                                                      from a glioma or metastatic tumour (Fig. 7.12).
(b) MRI.
                                                      Angiography also allows preoperative emboliza-
                                                      tion of the tumour, if necessary.
clivus or the foramen magnum region may com-
press the brainstem directly.
                                                      Preoperative management
                                                      Meningiomas are frequently surrounded by se-
Radiological investigations
                                                      vere cerebral oedema and patients should be
The CT scan appearance shows a tumour of              treated with high-dose steroids (dexamethasone)
slightly increased density prior to contrast; it      prior to surgery if possible. Preoperative
enhances vividly and uniformly following              embolization of the tumour vasculature may be
intravenous contrast. Hyperostosis of the             considered advisable in some anterior basal
cranial vault may be a focal process at the site of   and sphenoidal wing tumours where the major
 BENIGN BRAIN TUMOURS                                                                                   99




                                                           (a)




    (a)




                                                           (b)
                                                      Fig. 7.9 MRI of parasagittal meningioma. The
                                                      meningioma may be isodense on the plain T1 and T2
                                                      scans (a) but will enhance vividly after intravenous
                                                      gadolinium (b).

    (b)
                                                      vascular supply is not readily accessible in the
                                                      early stages of the operation.


                                                      Treatment
                                                      The treatment of meningiomas is total surgical
                                                      excision, including obliteration of the dural at-
                                                      tachment. Although this objective is usually pos-
                                                      sible there are some situations where complete
                                                      excision is not possible because of the position of
                                                      the tumour. Tumours arising from the clivus, in
                                                      front of the brainstem or those situated within
                                                      the cavernous sinus, are notoriously difficult to
                                                      excise without causing serious morbidity.
    (c)                                                  Radiation therapy may be used to treat
Fig. 7.8 (a) CT scan. Meningioma arising in the       residual tumours following subtotal resection,
cerebellopontine angle and from the tentorial edge.   in order to reduce the risk of recurrent growth.
(b) MRI. Clivus meningioma. (c) MRI. Foramen
magnum meningioma.
 100                                                                                          CHAPTER 7




                                                             (a)

    (a)




                                                             (b)
                                                         Fig. 7.11 MRI. Extensive parasagittal meningioma.
                                                         (a) Sagittal view. (b) Coronal view.
    (b)
Fig. 7.10 MRI. Falcine meningioma. (a) Before contrast
tumour is iso- or hypodense. (b) Tumour enhances
with intravenous contrast.




           (a)                            (b)                          (c)
Fig. 7.12 Cerebral angiogram of olfactory groove meningioma showing displacement of anterior cerebral arteries
(a,b) and the characteristic tumour blush, usually due to the external carotid artery supply (c).
 BENIGN BRAIN TUMOURS                                                                             101


   Stereotactic radiotherapy has been used to        and it is slightly more common in males than in
treat small meningiomas (less than 3 cm in diam-     females.
eter), particularly if the tumours are located in      The presenting features are dependent on the
portions not easily amenable to surgery, or in the   tumour location, with symptoms usually being
elderly or medically infirm patient.                  present for less than 1 year.
   Clinical studies have shown short-term control
rates of over 90%, but long-term studies will
                                                     Acoustic neuroma
be necessary to prove the efficacy and safety of
focused radiation treatment.                         Acoustic schwannomas arise from the 8th cranial
                                                     nerve and account for 8% of intracranial tu-
Postoperative management                             mours. Schwannomas occur less frequently on
The postoperative care of patients following exci-   the 5th cranial nerve and rarely involve other
sion of a meningioma involves the routine man-       cranial nerves. The acoustic schwannoma takes
agement of patients following a craniotomy but       origin from the vestibular component of the 8th
with particular attention to the minimization of     cranial nerve near the internal auditory meatus,
cerebral oedema. Steroid therapy is continued        at the transition zone where the Schwann cells
initially and gradually tapered. Care is taken to    replace the oligodendroglia. As such it should
avoid excessive hydration and the patient is         more correctly be called a vestibular schwan-
nursed with the head of the bed elevated to pro-     noma, although the term acoustic neuroma or
mote venous return. Neurological deterioration       schwannoma is more commonly used.
requires urgent assessment and a CT scan will           Macroscopically, the acoustic schwannoma is
determine the pathological cause, either post-       lobulated with a capsule that separates it from
operative haemorrhage or cerebral oedema.            the surrounding neural structures. Small tu-
                                                     mours usually arise from within the internal
                                                     auditory canal and occupy the porus of the inter-
Tumour recurrence
                                                     nal auditory canal and, as the tumour grows, the
The risk of tumour recurrence depends on the         8th nerve is destroyed and the adjacent cranial
extent of tumour excision. When the tumour           nerves become stretched around the tumour. The
and its dural origins are completely excised, the    7th nerve is typically displaced on the ventral
risk of recurrence is remote. The most common        and anterior surface of the tumour and the
source of recurrence is from a tumour that has       trigeminal nerve is carried upwards and for-
invaded a venous sinus and which was not re-         wards by the upper pole. The 6th nerve lies ven-
sected (e.g. superior sagittal sinus or cavernous    tral and usually medial to the major mass and the
sinus). Recurrence is more common if the tumour      lower cranial nerves are displaced around the in-
has histological features of malignancy.             ferior pole of the tumour. As the tumour grows
                                                     medially it compresses and displaces the cerebel-
                                                     lum and distorts the brainstem. Large tumours
Meningeal haemangiopericytoma
                                                     will result in obstruction of the 4th ventricle and
Meningeal haemangiopericytoma is a malignant         hydrocephalus.
neoplasm with sarcoma-like behaviour. It was            Bilateral acoustic neuromas are the hallmark of
originally classified by Cushing and Eisenhardt       neurofibromatosis type 2 (NF2), inherited as an
in 1938 as an angioblastic variant of meningioma.    autosomal dominant condition (see Chapter 6).
The tumour’s radiological and macroscopic ap-
pearance resembles a vascular meningioma, but
                                                     Clinical presentation
it arises from the meningeal capillary pericyte
and typically contains a subpopulation of cells      The presenting features will depend on the size
that express factor VIIIa.                           of the tumour at the time of diagnosis. The earlier
   The tumour incidence is 2–4% of meningioma        symptoms are associated with 8th nerve involve-
 102                                                                                          CHAPTER 7


ment. Tinnitus and unilateral partial or complete
sensorineural hearing loss are the earliest fea-
tures. Episodes of vertigo may occur but these
may be difficult to distinguish from Menière’s
disease. Although the tumour causes compres-
sion of the facial nerve, the growth of the tumour
is so slow that facial paresis is not evident until
the tumour is large. At that stage 5th nerve com-
pression may be evident, with diminished facial
sensation and a depressed corneal reflex. Cere-
bellar involvement will result in ataxia, and
compression of the pyramidal tracts from a very
large tumour causing brainstem compression
will cause a contralateral hemiparesis. If a large
tumour has caused obstructive hydrocephalus             Fig. 7.13 Acoustic neuroma. A contrast-enhancing
the patient will also present with features of          tumour in the cerebellopontine angle arising from the
raised intracranial pressure.                           8th cranial nerve in the internal auditory canal.



Radiological investigations
The CT scan or MRI will show an enhancing tu-
mour extending from the internal auditory canal
into the cerebellopontine angle (Fig. 7.13). The in-
ternal auditory meatus will be widened indicat-
ing that the tumour has arisen from the 8th
cranial nerve (Fig. 7.14). While there is no diffi-
culty in diagnosing a tumour large enough to be
evident on the CT scan, very small acoustic
neuromas, which are predominantly within the
internal auditory canal, may be more difficult to
diagnose. These tumours may be seen on high-
quality CT scan but are particularly evident            Fig. 7.14 Widened internal auditory meatus,
using MRI, especially following gadolinium con-         indicative of an acoustic neuroma.
trast (Fig. 7.15), which is now the investigation of
choice.
                                                        patients with acoustic neuroma. The Hallpike
                                                        caloric test is carried out with the patient supine
Other investigations
                                                        on a couch and the head raised to 30°C above
Pure tone audiometry, by both air and bone con-         horizontal, bringing the horizontal canals into
duction, is an essential part of the investigation of   the vertical plane with the position of maximum
a patient with an acoustic neuroma, the most            sensitivity to thermal stimuli. Warm and cool
common finding being high-frequency hearing              water is irrigated and the nystagmus reaction
loss. Other special auditory tests include the use      observed. The caloric response on the side of the
of brainstem auditory evoked responses which            acoustic nerve tumour is depressed or absent.
are particularly sensitive for changes in the retro-
cochlear auditory system; these are helpful in
                                                        Differential diagnosis
diagnosing a small intracanalicular tumour.
  Vestibular function is impaired early in              The major differential diagnoses for a cerebello-
 BENIGN BRAIN TUMOURS                                                                                 103


                                                        pontine angle tumour, in decreasing frequency,
                                                        are:
                                                        • meningioma
                                                        • metastatic tumour
                                                        • exophytic brainstem glioma
                                                        • epidermoid tumour.


                                                        Treatment
                                                        The total excision of a large acoustic neuroma
                                                        remains one of the major operative challenges
                                                        in what Cushing has described as ‘the gloomy
                                                        corner of neurologic surgery’.
                                                           The aim of the operation is complete resection
                                                        of the tumour while sparing the adjacent neural
                                                        structures. If the patient presents with a large tu-
                                                        mour causing severe hydrocephalus and raised
                                                        intracranial pressure, a preliminary ventricu-
                                                        loperitoneal shunt or ventricular drain may be
                                                        considered. Steroid administration prior to
                                                        surgery may be advisable if the tumour is large.
                                                           There are three basic approaches to the cerebel-
                                                        lopontine angle: by excision of the labyrinth
                                                        (translabyrinthine); through a posterior fossa
                                                        craniectomy (suboccipital/retrosigmoid); or via
                                                        the middle cranial fossa.
                                                           No clear consensus has emerged from the liter-
       (a)                                              ature as to which is the procedure of choice.
                                                        There are definite advantages and disadvantages
                                                        associated with each surgical approach. The
                                                        route chosen is governed by tumour size, the
                                                        degree of hearing loss, the hearing level in
                                                        the contralateral ear, and the surgical preference
                                                        and expertise of the operator.
                                                           The major advantage of the translabyrinthine
                                                        operation is that the facial nerve can be identified
                                                        lateral to the tumour at an early stage in the dis-
                                                        section, and access to the fundus of the internal
                                                        auditory meatus is excellent. Furthermore, re-
                                                        traction of the cerebellum is minimal and the risk
                                                        of postoperative oedema is consequently less.
                                                        The major disadvantage of this route is that
                                                        residual hearing is irrevocably destroyed. The
 (b)                                                    approach is unfamiliar to neurosurgeons, and
Fig. 7.15 (a) MRI showing small intracanalicular        requires the close cooperation of a neurotologist
meningioma. (b) MRI showing large acoustic neuroma      experienced in dissection of the temporal bone.
invading into temporal bone and extending into
                                                        Access is confined, but even the largest of tu-
cerebellopontine angle with severe compression of the
                                                        mours can be removed safely via this approach.
brainstem.
 104                                                                                       CHAPTER 7


   As a consequence of progressive improve-            bellopontine angle extension is preferred. The
ments in operative results, particularly in mortal-    middle fossa approach is preferred for intra-
ity and facial nerve outcome, attention has            canalicular tumours and for those with up to
turned more recently to the ability to preserve        1 cm cerebellopontine angle extension where tu-
useful hearing. The suboccipital operation pro-        mour completely fills the internal auditory canal.
vides good access to the cerebellopontine angle           Stereotactic radiosurgery using either a 60CO
but, if hearing is to be conserved, tumour at the      Gamma Knife or a highly focused linear accelera-
fundus of the internal auditory meatus may be          tor has been advocated for the treatment of
difficult to expose under direct vision. This is true   smaller tumours, less than 3 cm in diameter. The
particularly when the posterior semicircular           control rates are greater than 90% over a 5-year
canal is medially placed. Theoretically, this may      period, but post-radiation neurological compli-
increase the risk of subtotal tumour excision          cations have been reported including delayed
when compared with the translabyrinthine oper-         facial numbness and dysaesthesia, facial weak-
ation. Recently there has been renewed interest        ness and hearing loss. To minimize the complica-
in the middle fossa approach for removal of            tions of single-dose stereotactic radiosurgery
intracanalicular tumours or those with a small         many centres advocate fractionated stereotactic
cerebellopontine angle component, particularly         radiotherapy.
where the tumour in the internal auditory canal           There is continuing debate as to the relative
extends to the fundus. Higher rates of hearing         advantages of surgery and stereotactic radiation
preservation have been reported without any            treatment. Whilst some clinicians advocate radia-
compromise of facial nerve function, but this          tion treatment for smaller tumours, others would
route provides more limited access to the cerebel-     only recommend it for elderly or medically
lopontine angle, and is therefore restricted to the    infirm patients or if there is residual tumour or
treatment of small lesions.                            regrowth after subtotal resection.
   The question of hearing conservation deserves          The management plan for patients with bilat-
careful consideration when selecting the surgical      eral acoustic neuromas (NF2) is complex, and
approach. Anatomical preservation of the inner         must be tailored for each patient, with the aim of
ear and cochlear nerve does not guarantee func-        preserving useful hearing for as long as possible,
tion, and it is exceptional for hearing to be im-      whilst minimizing the possible serious neuro-
proved beyond its preoperative level. Whether          logical complications from enlarging tumours
such hearing is useful depends upon the level of       causing cranial nerve, cerebellar and brain-
hearing in the contralateral ear. Hearing loss         stem compression. Therapeutic options include
need not be profound before it is socially useless     surgery, radiosurgery and hearing preserva-
when the other ear is normal. For hearing to be        tions/restoration utilizing brainstem electrode
useful socially there must be both good speech         implants at the time of tumour resection.
discrimination, and a pure tone audiogram with-
in 20–40 dB of the contralateral ear. It is also       Postoperative care
essential that the attempt to preserve hearing         The postoperative management is similar to that
should not compromise the likelihood of com-           indicated for the posterior fossa tumours in the
plete tumour removal.                                  previous chapter. Any neurological deterioration
   At The Royal Melbourne Hospital the                 must be investigated urgently. A postoperative
translabyrinthine operation is favoured for large      haemorrhage in this region may be rapidly fatal.
tumours, regardless of hearing level, and for            Postoperative swallowing difficulties may
medium-sized lesions with poor hearing. It pro-        occur if there has been injury to the lower cranial
vides a more direct approach to the cerebellopon-      nerves or brainstem. Great care should be taken
tine angle, and retraction of the cerebellum is        to avoid aspiration and nasogastric feeding may
negligible. For hearing preservation the retrosig-     be necessary. Facial paralysis will occur if the 7th
moid approach for tumours with up to 2 cm cere-        nerve is not intact at the end of the operation and
 BENIGN BRAIN TUMOURS                                                                                105


may result even if the nerve is in continuity due
to neuropraxia of the nerve. A tarsorrhaphy may
be necessary to prevent corneal ulceration and
will be essential if there is a facial palsy and
corneal sensation is diminished due to 5th nerve
damage. Alternatively temporary closure of the
eye can be obtained by using botulinum toxin.
   The cosmetic appearance of a permanent
facial paralysis can be improved by a number of
procedures including:
• nerve anastomoses, such as a hypoglossal–
facial anastomosis
• cross-facial nerve grafts
• facial slings.
                                                         (a)

Haemangioblastoma
Haemangioblastomas are uncommon intracra-
nial tumours accounting for 1–2% of all brain
tumours and approximately 10% of posterior
fossa tumours.
   The haemangioblastoma arises from prolifera-
tion of endothelial cells. The tumour usually oc-
curs in young adults, although it may occur at
any age. It usually occurs in the posterior fossa
and often produces a large cyst. Although hae-
mangioblastoma may occur as a component of
von Hippel–Lindau’s disease, which includes              (b)
multiple haemangioblastomas, haemangioblas-         Fig. 7.16 Haemangioblastoma in the vermis of the
tomas of the retina (von Hippel tumour), renal      cerebellum. (a) A vividly enhancing tumour nodule
tumour, renal cyst, pancreatic cyst and tubular     in the wall of a cyst. (b) Vertebral angiogram shows
adenomata of the epididymis, the majority of        small tumour nidus (arrowhead).
patients with the cerebellar tumour do not have
von Hippel–Lindau’s disease. Incomplete forms
                                                    Radiological investigations
of the syndrome may occur and cerebellar hae-
mangioblastomas occur in about 20% of patients      CT scan or MRI show a cerebellar tumour which
with retinal haemangioblastoma.                     may involve the vermis and hemispheres and
                                                    which shows vivid enhancement following intra-
                                                    venous contrast (Fig. 7.16). There is usually a
Clinical presentation
                                                    low-density cyst surrounding the tumour nodule
The tumour presents as a slowly growing             (Fig. 7.17), although haemangioblastomas may
posterior fossa mass with features of raised        sometimes be solid. If considered necessary,
intracranial pressure and cerebellar involvement.   vertebral angiography will confirm the highly
Occasionally the patient may be polycythaemic       vascular mass.
due to increased circulating erythropoietin.           Total surgical excision through a posterior
                                                    fossa craniotomy is nearly always possible. Great
                                                    care must be taken not to enter the highly vascu-
                                                    lar tumour during the dissection and excision.
 106                                                                                      CHAPTER 7



                                                       Radiological investigations
                                                       The usual CT scan picture is a high-density,
                                                       rounded tumour in the anterior 3rd ventricle
                                                       which enhances following intravenous contrast
                                                       (Fig. 7.18), although isodense, hypodense and
                                                       non-enhancing tumours have been reported.
                                                       MRI helps to define the position of these tumours
                                                       (Fig. 7.18) and will be able to differentiate
                                                       between a colloid cyst and an aneurysm of
                                                       the basilar tip, which may occasionally be
                                                       indistinguishable on CT scan.


                                                       Treatment
                                                       Surgical excision is performed through a cran-
Fig. 7.17 MRI. Cystic haemangioblastoma.               iotomy with a small incision in the anterior
                                                       corpus callosum giving access to the lateral
                                                       ventricle. The tumour is seen expanding the fora-
                                                       men of Monro and, using the operating micro-
Colloid cyst of the 3rd ventricle
                                                       scope, a complete excision is usually possible.
The colloid cyst of the 3rd ventricle is situated in   Great care must be taken during the operation to
the anterior part of the ventricle and is attached     preserve the venous structures, including the
to the roof just behind the foramen of Monro.          septal veins, thalamostriate vein and internal
   Several possibilities as to the origin of the       cerebral veins. Damage to the columns of the
tumour have been proposed, including the para-         fornix will result in severe postoperative
physis, choroid plexus epithelium, ependyma            memory disturbance.
or a diverticulum of the diencephalon.
   The cyst consists of a thin, outer fibrous cap-
                                                       Epidermoid and dermoid cysts
sule lined by a layer of epithelium; the contents
consist of mucoid material, epithelial debris and      Epidermoid and dermoid cysts arise from
mucin. The cyst may be very small and asympto-         epithelial cells embryologically misplaced in-
matic, as was the case with Harvey Cushing,            tracranially, particularly into the meninges and
where a 1-cm colloid cyst was found at post-           ventricles and, less frequently, into the paren-
mortem. As the tumour grows it will cause              chyma of the brain. Rarely, the cells can be im-
bilateral obstruction to the foramina of Monro,        planted as a result of trauma such as a lumbar
leading to raised intracranial pressure from hy-       puncture, which can implant skin into the spinal
drocephalus. The headaches may fluctuate,               canal causing an epidermoid cyst.
being aggravated by stooping and relieved by              Epidermoid cysts make up about 1% of brain
standing upright. Episodes of abrupt, sudden           tumours, although their incidence is higher in
leg weakness causing the patient to fall may           Japan, where the incidence of dermoid cysts is
occur without a change in conscious state.             much less.
Alternatively, an abrupt loss of consciousness            Epidermoid tumours are found principally in
may occur and this, although usually transient,        the arachnoid spaces, the cisterns or the diploe
might be fatal.                                        of the bone. The most frequent localizations are
                                                       the cerebellopontine angle, the suprasellar and
                                                       parasellar regions, the lateral or 4th ventricles,
                                                       and the quadrigeminal cistern.
 BENIGN BRAIN TUMOURS                                            107




     (a)




                                                           (a)




     (b)




     (c)
Fig. 7.18 Colloid cyst of the 3rd ventricle. (a) CT scan
shows hyperdense tumour before contrast. (b) MRI.
Colloid cyst. (c) MRI. Colloid cyst sagittal view.


Fig. 7.19 (a) Dermoid cyst. A very low density lesion
on CT scan that does not enhance. (b) MRI.
Epidermoid cyst adjacent to brainstem.                     (b)
 108                                                                                        CHAPTER 7


  Dermoid tumours occur mostly in the
                                                     Treatment
posterior fossa as a midline lesion and a fistula
may connect the dermoid with the skin.               The treatment is operative, with resection of the
                                                     cyst. Complete excision may be prevented if the
                                                     cyst wall is densely adherent to major vessels and
Histology
                                                     important neural structures.
The epidermoid cyst contains desquamated
epithelium surrounded by keratin-producing
                                                     Further reading
squamous epithelium. The dermoid cyst in-
cludes dermal elements such as hair follicles,       Cushing H (1917) Tumours of the Nervus Acusticus and
sebaceous glands and sometimes sweat glands.           the Syndrome of the Cerebellopontine Angle. W B
                                                       Saunders, Philadelphia.
                                                     Cushing H, Eisenhardt L (1938) Meningiomas: their
Clinical presentation                                  Classification, Regional Behaviour, Life History and
                                                       Surgical End Results. Charles C Thomas, Springfield.
The cysts usually present following a long his-      Di Tullio MV, Rand RW (1978) The Rand–Kurze
tory of symptoms related to their position.            Suboccipital Transmeatal Operation. In: Rand RW,
Cranial nerve abnormalities such as trigeminal         eds. Microneurosurgery. C V Mosby, St Louis, 206–232.
neuralgia and hemifacial spasm may occur with        Kaye AH, Laws ER (2001) Brain Tumours. Churchill
cerebellopontine angle epidermoid tumours and          Livingstone, London.
the suprasellar cyst will produce visual impair-     Kaye AH, Black P McL (2000) Operative Neurosurgery.
ment with optic atrophy and often a bitemporal         Churchill Livingstone, London, New York,
hemianopia. Leakage of epidermoid cyst con-            Edinburgh.
                                                     Kennedy F (1911) Retrobulbar neuritis as an exact
tents may result in a chemical meningitis, and in
                                                       diagnostic sign of certain tumours and abscesses in
patients with posterior fossa dermoid cysts,
                                                       the frontal lobes. American Journal of Medical Science
bacterial meningitis may occur through the             142, 355–368.
dermal sinus connecting the cyst with the skin.      King TT (1982) The translabyrinthine operation for
                                                       removal of acoustic nerve tumours. In: Schmidek
                                                       HH, Sweet WH, eds. Operative Surgical Techniques:
Radiological investigations
                                                       Indications, Methods and Results. Grune & Stratton,
The CT scan of an epidermoid cyst is char-             New York, 609–636.
acterized by a low-density lesion that does not      Little JR, McCarty CS (1974) Colloid cysts of the third
enhance. The dermoid cyst will also have areas         ventricle. Journal of Neurosurgery 39, 230–235.
which are even less dense than CSF, indicating       Rand RW, Kurze T (1965) Facial nerve preservation by
                                                       posterior fossa transmeatal microdissection in total
the presence of fat (Fig. 7.19). MRI has sup-
                                                       removal of acoustic neuromas. Journal of Neurology,
erceded CT for accurate preoperative evaluation
                                                       Neurosurgery and Psychiatry 28, 311–316.
and planning. Epidermoid lesions are usually         Russell DS, Rubenstein LJ (1977) Pathology of Tumours
manifest as low signal on T1 and high signal on T2     of the Nervous System, 4th edn. Williams & Wilkins,
images, although depending on lipid content,           Baltimore.
variable signal intensities may be seen within the   Zulch KJ (1986) Brain Tumours, Their Biology and
same lesion.                                           Pathology, 3rd edn. Springer Verlag, Berlin.
                          CHAPTER 8


  8                       Pituitary tumours



Pituitary adenomas account for 8–10% of all in-      it is less than 10 mm in diameter it is known as a
tracranial tumours.                                  ‘microadenoma’. The tumour may grow locally
   In 1886 Pierre Marie first made the connection     within the sella and cause erosion and remodel-
between acromegaly and pituitary adenomas.           ling of the floor of the sella and posterior clinoid
Patients may present either with signs of en-        processes (macroadenoma). The tumour usually
docrine disturbance or with compression of the       spreads superiorly into the suprasellar cisterns,
adjacent neural structures, especially the optic     where it may cause compression of the optic
pathways.                                            pathways, particularly the optic chiasm. Further
                                                     growth superiorly causes compression of the hy-
                                                     pothalamus and, if large enough, obstruction of
Classification
                                                     the 3rd ventricle, resulting in hydrocephalus
Historically, three main types of pituitary adeno-   (Figs 8.2 and 8.3).
mas were defined by their cytoplasmic staining           The tumour may also grow laterally out of the
characteristics: chromophobic, acidophilic and       sella into the cavernous sinus. Occasionally the
basophilic — the implication being that these tu-    lateral extension may be sufficient to cause dis-
mours were either hormonally inactive, secreted      turbance of the cranial nerves in the cavernous
growth hormone, or produced adrenocorti-             sinus. Uncommonly the tumour penetrates fur-
cotrophic hormone (ACTH), respectively.              ther laterally, into the temporal lobe.
  The development of immunoperoxidase tech-             The tumour may infrequently extend inferior-
niques and electron microscopy has provided a        ly through the floor of the pituitary fossa into the
more refined classification of pituitary adenomas      sphenoid sinus, resulting in CSF rhinorrhoea.
based on the specific hormone that is produced.          The localization of microadenomas within the
This classification is shown in Table 8.1.            pituitary fossa corresponds somewhat with the
                                                     regional distribution of the normal adenohy-
                                                     pophyseal cells. Prolactin- and growth hormone-
Pathology
                                                     secreting microadenomas tend to occur laterally,
Pituitary adenomas arise from the anterior lobe      whereas most adenomas secreting ACTH occur
(adenohypophysis) of the pituitary gland which       in the central zone.
develops from Rathke’s pouch, an ectodermal             The pituitary hormones are synthesized in the
diverticulum arising from the roof of the            rough endoplasmic reticulum and are packaged
stomodeum, immediately in front of the               in the Golgi apparatus. After packaging they can
buccopharyngeal membrane. The posterior lobe         be visualized by either electron microscopy or
(neurohypophysis/pars nervosa) arises from the       immunoperoxidase staining as secretory gran-
infundibulum developing from the floor of the         ules within the cytoplasm. The hormone is re-
diencephalon (Fig. 8.1).                             leased from the cell by exocytosis, following
  The tumour arises within the pituitary fossa. If   fusion of the granule with the cell membrane

                                                                                                    109
  110                                                                                                   CHAPTER 8


                                                         which usually occurs at the vascular pole of the
  Table 8.1 Classification of pituitary adenomas.
                                                         cell. Adenomas may either be densely or sparsely
                                                         granulated and this will determine their staining
                                        Percentage
                                                         properties (Fig. 8.4).
  Hormone secreted                      of tumours
                                                           Multiple endocrine neoplasia type 1 (Werner’s
  Prolactin                             40               syndrome) is an autosomal dominant disorder
  Growth hormone                        20               representing the inherited occurrence of both be-
  Null cell (no hormone)                20
                                                         nign and malignant neoplasms involving the pi-
  ACTH                                  15
                                                         tuitary gland, parathyroid gland and pancreas.
  Prolactin and growth hormone          5
  FSH/LH                                1–2
  TSH                                   1                Functional types of pituitary adenoma
  Acidophil stem cell (no hormone)      1–2
                                                         Prolactin cell adenoma
  ACTH, adrenocorticotrophic hormone; FSH,
                                                         Prolactin is a 23 500-Da polypeptide hormone
  follicle-stimulating hormone; LH, luteinizing
                                                         produced by the prolactin-secreting cells (lac-
  hormone; TSH, thyroid-stimulating hormone.
                                                         totrophs) situated predominantly in the postero-




                                                                                                        3rd ventricle
                                                                                                        Optic chiasm

                                                                                                        Basal cisterns (CSF)

                                                                                                        Pituitary gland
                                                                                                        Oculomotor nerve
                                        Infundibulum                                                    Trochlear nerve
                                                                                                        Cavernous sinus
Arachnoid                               Basal cisterns                                                  Ophthalamic nerve
Dura                                    (CSF)                                                           (V1)
                                                                                                        Maxillary nerve
Sphenoid                                Posterior lobe                                                  (V2)
Anterior lobe
Pituitary fossa
                                        Clivus           Sphenoid   Internal carotid   Abducent nerve
                                                         sinus      artery

Fig. 8.1 Pituitary gland.                                Fig. 8.2 Anatomical relations of the pituitary gland.




                                                                                       Fig. 8.3 Large pituitary
                                                                                       tumour compressing the
                                                                                       hypothalamus and 3rd
                                                                                       ventricle.
 PITUITARY TUMOURS                                                                                  111


                                                      is primarily under the influence of an inhibitory
                                                      agent, ‘prolactin-inhibiting factor’, believed to be
                                                      dopamine.
                                                         Prolactinomas are the most frequently occur-
                                                      ring pituitary adenomas. The majority present
                                                      as microadenomas in young females with
                                                      symptoms of hypersecretion causing amenor-
                                                      rhoea and galactorrhoea; impotence may be the
                                                      only symptom in males. This explains the much
                                                      greater surgical frequency of prolactinomas in
                                                      women, and why these tumours may grow to a
                                                      large size in males and elderly females.
                                                         Three-quarters of prolactin-secreting tumours
                                                      are chromophobe by light microscopy, the rest
                                                      being either weakly acidophilic or composed of a
     (a)                                              mixture of cells. The serum levels of prolactin
                                                      will be elevated and levels exceeding 2000 ng/ml
                                                      are suggestive of an invasive prolactinoma. A
                                                      minor elevation of serum prolactin, up to a level
                                                      of twice normal, is not necessarily diagnostic of a
                                                      prolactin-secreting adenoma, as any lesion of the
                                                      hypothalamus, pituitary or pituitary stalk which
                                                      interferes with the production or release of
                                                      prolactin-inhibiting factor may cause some
                                                      increase in the serum prolactin.


                                                      Growth hormone cell adenoma
                                                      Growth hormone is a single chain 21 000-Da
                                                      polypeptide produced by cells situated princi-
                                                      pally in the lateral part of the gland. Growth
     (b)                                              hormone adenomas represent approximately
Fig. 8.4 Electron microscopy. (a) Membrane-bound      15–20% of pituitary adenomas. Under light mi-
electron-dense granules of growth hormone             croscopy the features are either acidophil or
synthesized in the endoplasmic reticulum and          chromophobe, depending on the extent of the
packaged by the Golgi apparatus (¥ 20 000).           cytoplasmic granules. The adenomas may be
(b) Immunogold labelling of granules with antiserum   composed of either densely or sparsely granu-
against growth hormone (¥ 75 000).                    lated cells, occurring with approximately equal
                                                      frequency; about 10% of tumours show a mixture
lateral hypophysis and constituting 15–20% of         of both cell types (Fig. 8.4).
adenohypophyseal cells. The best known physio-           Hyperprolactinaemia occurs quite frequently
logical functions of prolactin are stimulation of     in growth hormone-producing adenomas and
breast growth and promotion of lactation. Its role    may result either from an adenoma producing
in the male is poorly understood but it is impor-     both hormones or from a growth hormone-
tant in spermatogenesis.                              producing adenoma being of sufficient size to
   Unlike the secretion of other pituitary hor-       interfere with the release of prolactin-inhibiting
mones which is controlled primarily by a hypo-        factor, thereby elevating the serum prolactin
thalamic releasing hormone, prolactin secretion       secondarily.
 112                                                                                       CHAPTER 8


                                                      with extensive penetration of the pituitary cap-
ACTH (corticotrophic) adenomas
                                                      sule, dural sinuses and surrounding bone. Most
ACTH is a single chain polypeptide which stimu-       invasive pituitary adenomas are sparsely granu-
lates the adrenal cortex and promotes secretion of    lated or chromophobic and are either hormonally
cortisol and related steroids. Adenomas produc-       inactive or prolactin producing.
ing ACTH are the cause of Cushing’s disease.             Metastasizing pituitary carcinoma, either ex-
The adenomas are densely granulated with ba-          tracranially or throughout the CSF pathway, is
sophilic cytoplasm.                                   extremely rare.
   ACTH-producing tumours constitute approxi-
mately 15% of adenomas, over 80% of which are
                                                      Clinical presentation (Table 8.2)
microadenomas. About 15–20% of adenohy-
pophyseal cells are corticotrophs, located in the     The presenting features are due to:
central component of the anterior lobe of the pi-     • the size of the tumour
tuitary gland, and it is not surprising that most     • endocrine disturbance.
microadenomas are located centrally rather than         Headache occurs principally in patients with
laterally, as occurs with the other hormone-          acromegaly and is uncommon in other types of
producing microadenomas.                              pituitary tumour.


Gonadotroph cell adenoma                              Visual failure
Follicle-stimulating hormone (FSH) and luteiniz-      Careful assessment of the visual fields, the visual
ing (LH) cells represent approximately 10% of the     acuity and the optic fundi is essential.
normal pituitary cells and are scattered through-        Suprasellar extension of the pituitary tumour
out the adenohypophysis. Adenomas resulting           causes compression of the optic chiasm resulting
from these cells are very uncommon and most are       in a bitemporal hemianopia. The bitemporal
functionally silent.                                  hemianopia initially involves the upper quad-
                                                      rants, before extending to the lower quadrants of
                                                      the visual field. If the chiasm is prefixed, that is,
Thyrotroph cell adenoma
                                                      placed more anteriorly than usual, a homony-
Thyroid-stimulating hormone (TSH)-producing           mous hemianopia may occur due to compression
tumours are rare.                                     of the optic tract. Bilateral central scotomas result
                                                      from the tumour pressing on the posterior part of
                                                      the chiasm where the macular fibres decussate.
Null cell adenomas
                                                      Primary optic atrophy will be evident in patients
Twenty to thirty per cent of pituitary adenomas       with long-standing compression of the chiasm.
have no clinical or biological evidence of hyper-        Ocular palsies occur in about 10% of patients
function. Mild hyperprolactinaemia may occur          and are due to invasion of the cavernous sinus.
secondary to distortion of the pituitary stalk.       The 3rd nerve is the most frequently affected, fol-
Most (75% of) null cell adenomas are chromo-          lowed by the 6th and 4th cranial nerves. Facial
phobic, with few or no cytoplasmic granules.          pain results from compression of the trigeminal
Approximately 20% of null cell tumours show           nerve, usually the ophthalmic division, as a re-
marked accumulation of mitochondria and are           sult of cavernous sinus invasion.
called ‘oncocytomas’.
  Clinically, null cell adenomas are aggressive
                                                      Endocrine abnormalities
and, as they are hormonally silent, they may
grow to a large size, so that patients present with   Endocrine disturbance is due to either hypopi-
visual disturbance.                                   tuitarism or excess secretion of a particular
  About 10% of pituitary adenomas are invasive,       pituitary hormone.
 PITUITARY TUMOURS                                                                                     113


                                                        may be clinically evident in the larger tumours.
  Table 8.2 Clinical manifestations of pituitary
                                                        The endocrine secretions are not equally de-
  tumours.
                                                        pressed but there is a selective failure and the
                                                        order of susceptibility is as follows: growth hor-
  ‘Mass’ effects
  Headaches (especially acromegaly)
                                                        mone, gonadotrophin, corticotrophin, thyroid-
  Superior extension                                    stimulating hormone.
    Chiasmal syndrome (impaired visual acuity              Gonadotrophic deficiency prior to puberty re-
       and fields)                                       tards the development of secondary sex charac-
    Hypothalamic syndrome (disturbance in thirst,       teristics; adult men have poor beard growth,
       appetite, satiety, sleep and temperature         women suffer from amenorrhoea and both sexes
       regulation; diabetes insipidus — uncommon;       have loss of libido and deficient pubic and axil-
       inappropriate ADH syndrome — uncommon)           lary hair. The biochemical abnormality is mani-
    Obstructive hydrocephalus                           fest by a low oestrogen and androgen production
  Lateral extension
                                                        with reduced urinary 17-ketosteroids.
    Cranial 3rd, 4th, 6th, diplopia
                                                           Hypopituitarism initially results in vague
    Cranial 5th, facial pain
    Temporal lobe dysfunction
                                                        symptoms, including lack of energy, undue fa-
  Inferior extension                                    tiguability, muscle weakness and anorexia and,
    Nasopharyngeal mass                                 when prolonged and severe, it will cause low
    CSF rhinorrhoea                                     blood pressure. Clinical hypothyroidism is
                                                        manifest by physical and mental sluggishness
  ‘Endocrine’ effects
  Hyperpituitarism
                                                        and a preference for warmth. When the hypopi-
    GH — gigantism/acromegaly                           tuitarism is severe, episodic confusion occurs
    PRL — hyperprolactinaemic syndrome                  and the patient will become drowsy. It is essential
    ACTH — Cushing’s disease                            to recognize the features of severe pituitary insuf-
    TSH — thyrotoxicosis                                ficiency as an endocrine crisis can be precipitated
  Hypopituitarism                                       by minor stressful events occurring during hos-
    GH — child: shortness of stature,                   pital investigation or as a result of an intercurrent
      hypoglycaemia                                     infection.
    PRL — adult female: failure of postpartum              Pituitary apoplexy results from spontaneous
      lactation
                                                        haemorrhage into a pituitary tumour. It is charac-
    ACTH — hypocortisolism (Addison’s)
                                                        terized by sudden, severe headache followed by
    TSH — hypothyroidism
    LH/FSH — hypogonadism
                                                        transient or more prolonged loss of conscious-
                                                        ness with features of neck stiffness, vomiting and
  Acute deterioration                                   photophobia. The condition is similar to sub-
    Pituitary apoplexy
                                                        arachnoid haemorrhage resulting from a rup-
                                                        tured aneurysm, but is often associated with
  GH, growth hormone; PRL, prolactin; TSH,
                                                        paralysis of one or more of the ocular muscles
  thyroid-stimulating hormone; LH, luteinizing
  hormone; FSH, follicle-stimulating hormone;           (usually bilateral) and acute visual deterioration.
  ACTH, adrenocorticotrophic hormone.                   An acute endocrine crisis may be precipitated by
                                                        the apoplexy (Fig. 8.5).

                                                        Prolactinoma
Hypopituitarism                                         The prolactin-secreting tumour may be a mi-
Hypopituitarism results from failure of the hor-        croadenoma or macroadenoma within the pitu-
mones secreted by the adenohypophysis and it            itary fossa. The patients are usually women who
gives rise to the clinical features first described by   present with infertility associated with amenor-
Simmonds in 1914. Pituitary gland failure does          rhoea and galactorrhoea, although the tumour
not occur if the tumour is a microadenoma, but          may occasionally cause infertility in men. Large
 114                                                                                       CHAPTER 8


                                                       prolactinomas occur in the elderly and in males,
                                                       and these can cause endocrine disturbance asso-
                                                       ciated with hypopituitarism and visual failure.

                                                       Acromegaly
                                                       Acromegaly results from a growth hormone-
                                                       secreting pituitary adenoma which, as described
                                                       previously, consists of cells that stain either as
                                                       acidophils, chromophobes or both. The onset of
                                                       acromegaly is slow and insidious, usually during
                                                       the 3rd and 4th decades of life, with both sexes
                                                       being affected equally. The clinical features
                                                       (Table 8.3) include bone and soft tissue changes
                                                       that are evident as an enlarged supraciliary ridge,
                                                       enlarged frontal sinuses and increased mandibu-
                                                       lar size, which will cause the chin to project
Fig. 8.5 MRI showing pituitary tumour extending
                                                       (prognathism) (Fig. 8.6). The hands and feet en-
from expanded pituitary fossa into the suprasellar
cisterns with compression of optic chiasm.
                                                       large, and the skin becomes coarse and greasy



  Table 8.3 Clinical manifestations of growth hormone-producing pituitary tumours.

  Endocrine                                              Ophthalmological
  Effect of excess GH on tissue growth and               Related to tumour mass effects
    intermediary metabolism                              Related to GH hypersecretion
    Skin and subcutaneous tissue overgrowth                Glaucoma
    Skeletal overgrowth                                    Exophthalmos
    Visceromegaly
                                                         Laryngeal
    Increased BMR, heat intolerance, hyperhydrosis
                                                         Voice changes
    Carbohydrate intolerance
                                                         Cord fixation
    Diabetes mellitus
  Associated pituitary dysfunction                       Sleep disorders
    Owing to pituitary compression or destruction        Skeletal
    Hypopituitarism                                      Acral changes
  Associated thyroid dysfunction                         Arthropathy
    Goitre
    Thyrotoxicosis — toxic nodular goitre, Graves’       Cardiovascular
       disease                                           Hypertension
  Associated multiple endocrine neoplasia type 1         Cardiomegaly
    Primary hyperparathyroidism                          Congestive heart failure
    Tumours of the endocrine pancreas syndromes          Conduction defects and arrhythmias

  Neurological                                           Dermatological
  Related to tumour mass effects                         Acral changes
  Related to GH hypersecretion                           Hyperhydrosis
    Acroparaesthesias                                    Acne
    Entrapment neuropathies                              Hypertrichosis
    Peripheral neuropathy                                Hyperpigmentation
    Myopathy                                             Acanthosis nigricans
 PITUITARY TUMOURS                                                                                     115


                                                       patients complain of lack of energy, physical
                                                       weakness and lassitude.
                                                          Suprasellar extension of the tumour occurs in
                                                       about 15% of cases and may result in compres-
                                                       sion of the optic pathways.
                                                          A pituitary adenoma with excessive growth
                                                       hormone secretion occasionally presents in child-
                                                       hood and results in gigantism.

                                                       Cushing’s disease
                                                       Cushing’s disease is due to ACTH-producing
                                                       pituitary adenomas. Over 80% of the tumours
                                                       are microadenomas and the remainder are
                                                       macroadenomas involving the whole of the sella
                                                       or with extrasellar extension.
                                                          The onset is insidious and the disease may af-
                                                       fect children or adults. Severe obesity occurs, the
                                                       skin is tense and painful, and purple striae ap-
                                                       pear around the trunk. Fat is deposited, particu-
                                                       larly on the face (moon face), neck, cervicodorsal
                                                       junction (buffalo hump) and trunk. The skin be-
                                                       comes a purple colour due to vasodilatation
                                                       and stasis. Spontaneous bruising is common. The
                                                       skin is greasy, acne is common and facial hair ex-
                                                       cessive. Patients complain of excessive fatigue
                                                       and weakness. There is wasting and flaccidity of
                                                       the muscles. Osteoporosis predisposes to sponta-
                                                       neous fractures.
                                                          Glucose tolerance is impaired, the serum
                                                       potassium is low and vascular hypertension oc-
                                                       curs. If untreated, 50% of cases are fatal in 5 years.

                                                       Cushing’s syndrome
                                                       There is excessive cortisol production, due to an
                                                       ACTH-producing pituitary adenoma (Cushing’s
                                                       disease) in 90% of cases. Other causes of Cush-
                                                       ing’s syndrome are an adrenal adenoma or carci-
Fig. 8.6 A 58-year-old female with acromegaly. Above
is a photograph taken when she was 25 years old.
                                                       noma, or an ectopic source of ACTH production
                                                       such as from an oat cell carcinoma of the lung or
                                                       aberrant adrenocortical tissue occurring outside
                                                       the adrenal gland.
and sweats profusely. The voice becomes hoarse
and gruff and thoracic kyphosis occurs as a result     Nelson–Salassa syndrome
of osteoporosis.                                       This consists of an ACTH-producing pituitary
   Other problems associated with acromegaly           adenoma in a patient who has undergone bilater-
include hypertension, cardiac hypertrophy and          al or subtotal adrenalectomy. Before the develop-
diabetes. Headache is often severe in patients         ment of CT scanning and trans-sphenoidal
with pituitary tumours causing acromegaly and          microsurgery, patients with Cushing’s disease
 116                                                                                      CHAPTER 8


often underwent total adrenalectomy when              on imaging studies as the foremost diagnostic in-
pneumoencephalography had failed to reveal a          vestigation, a careful endocrinological assess-
pituitary tumour. However, accelerated growth         ment is critical in the diagnosis of Cushing’s
of an existing adenoma is induced by the loss         disease, especially as in nearly 50% a tumour is
of normal corticosteroid feedback. Unlike the         not evident on MRI.
adenomas of Cushing’s disease, about half of             There are three essential steps in the diagnosis
patients with Nelson–Salassa syndrome have            of Cushing’s disease due to pituitary pathology.
macroadenomas. Patients have marked cuta-             1 Confirm excess secretion of cortisol (normal
neous hyperpigmentation due to secretion of           120–650 nmol/l).
either beta melanocyte-stimulating hormone            2 Distinguish ACTH-dependent from ACTH-in-
and/or beta lipotrophin.                              dependent causes of hypercortisolaemia.
                                                      3 Distinguish pituitary-based Cushing’s disease
                                                      from ectopic states of ACTH production.
Laboratory investigations
                                                         A 24-hour urine specimen is the simplest initial
Radioimmunoassay will help to identify the hor-       means of establishing hypercortisolaemia.
mone being secreted.                                     The investigation of Cushing’s disease in-
   Serum prolactin level in patients with pro-        volves the measurement of ACTH by radioim-
lactinomas will vary from just above the upper        munoassay of samples of both peripheral blood
limit of normal to values greater than                and blood from the petrosal sinus. A differential
20 000 mIU/l (normal 70–550 mIU/l). The levels        level of ACTH in petrosal vein blood and periph-
may show considerable variation in a particular       eral blood will help confirm the presence of a pi-
patient and prolactin levels greater than             tuitary basis for the ACTH production, especially
2000 mIU/l are almost always indicative of a          after administration of corticotrophin-releasing
pituitary tumour. As mentioned previously, hy-        hormone (CRH). A dexamethasone suppression
perprolactinaemia may be associated with other        test will help diagnose Cushing’s syndrome and
pituitary tumours and has been noted in some          its cause. The urine- and plasma-free cortisol is
patients with acromegaly. Null cell tumours may       measured and is normally suppressed following
be associated with mild hyperprolactinaemia           administration of low-dose dexamethasone
due to distortion of the pituitary stalk or im-       (0.5 mg 6-hourly). The levels will be suppressed
pingement on the hypothalamus.                        following high-dose dexamethasone (2 mg 6-
   Serum growth hormone is measured by ra-            hourly) in pituitary-dependent Cushing’s dis-
dioimmunoassay, the normal values being less          ease. There will be a failure of suppression of the
than 5 mIU/l in males and less than 10 mIU/l in       levels with high-dose dexamethasone if the
females. Growth hormone exerts its effects on pe-     Cushing’s syndrome is due to other than pitu-
ripheral tissues indirectly via somatomedins —        itary causes.
polypeptides produced primarily by the liver
and fibroblasts. Serum somatomedin C (insulin-
                                                      Radiological investigations
like growth factor I, IGF-I) is a more accurate in-
dicator of growth hormone bioactivity than the        High-resolution CT scanning and magnetic reso-
serum growth hormone levels. Provocative              nance imaging using thin slices and intravenous
tests of growth hormone secretion are useful          contrast are the appropriate investigation. Pitu-
in confirming acromegaly. Most patients with           itary microadenomas are usually hypodense and
acromegaly do not show the normal suppression         may cause upward bulging and convexity of the
of growth hormone following glucose load.             upper border of the gland in adults, deviation of
Other provocative tests utilize thyrotrophin-         the pituitary stalk and thinning of the sellar floor
releasing hormone and growth hormone-                 on the side of the tumour (Fig. 8.7). High-quality
releasing hormone.                                    CT scanning is able to demonstrate tumours as
   In contrast to other pituitary tumours that rely   small as 4 mm in diameter. Macroadenomas en-
 PITUITARY TUMOURS                                                                                     117




                                                 (b)

(a)
Fig. 8.7 (a) CT showing hypodense microadenoma in pituitary gland. (b) MRI showing microadenoma.




Fig. 8.8 Axial and coronal CT scans showing large pituitary tumours.




hance after intravenous contrast and the exact           to haemosiderin (see Figs 8.5 and 8.9). Dynamic
nature of the extrasellar extension can be best ap-      scans taken at 30-second intervals following in-
preciated with direct coronal scans (Fig. 8.8).          travenous gadolinium may help demonstrate
   MRI has improved the identification of mi-             small microadenomas.
croadenomas, which appear as low-density focal              Plain skull X-rays may show enlargement of
lesions on T1-weighted scans and high intensity          the sella with thinning erosion or bulging of its
on T2-weighted scans (Fig. 8.9). Macroadenomas           contours (Fig. 8.11).
usually appear as isointense on the T1-weighted             In the past angiography has been performed to
images and moderately hyperintense on the T2-            exclude incidental aneurysms and to determine
images (Fig. 8.10). Haemorrhage into a tumour,           the position of the internal carotid arteries in the
such as occurs following pituitary apoplexy,             cavernous sinuses, but this information can now
shows as high-intensity areas because of                 be obtained satisfactorily from good-quality
methaemoglobin on the T1- and T2-weighted                MRI and, if necessary, magnetic resonance
scans intermingled with low-density regions due          angiography.
 118                                                                                               CHAPTER 8




                                                        (a)

     (a)




     (b)
                                                              (b)
Fig. 8.9 MRI scan (T1) showing large pituitary tumour
                                                        Fig. 8.10 Enhanced MRI showing large pituitary
with area of recent haemorrhage.
                                                        tumour extending up to the 3rd ventricle.




                                                                    Fig. 8.11 Plain lateral skull X-ray showing
                                                                    thinning of the dorsum sellae and
                                                                    destruction of the pituitary fossa in a patient
                                                                    with a large pituitary tumour.
 PITUITARY TUMOURS                                                                                   119


                                                        cent neural structures, particularly the visual
                                                        pathways
                                                        • GH-secreting tumours causing acromegaly
                                                        • ACTH-secreting tumours causing Cushing’s
                                                        disease
                                                        • the occasional treatment of a prolactin-secreting
                                                        adenoma, either microadenoma or macroade-
                                                        noma confined within the sella, when medical
                                                        treatment using bromocriptine is not tolerated.
                                                           Most tumours can be excised via the trans-
                                                        sphenoidal approach to the pituitary fossa (Fig.
                                                        8.13). The development of the surgical micro-
                                                        scope and fluoroscopic radiography has made
                                                        this a safe procedure. The sphenoid sinus is usu-
                                                        ally entered using a unilateral trans-septal ap-
Fig. 8.12 Hypothalamic glioma.
                                                        proach, with the incision either in the nasal
                                                        mucosa or sublabially. The mucosa is reflected
                                                        from the nasal septum and floor and the sphe-
Differential diagnosis
                                                        noid is opened. The anterior wall of the sella
The major differential diagnoses are:                   is removed and the pituitary fossa entered.
• craniopharyngioma                                     Microadenomas (tumours less than 10 mm in
• suprasellar meningioma (arising from the tu-          diameter) may be evident on the surface of
berculum sellae).                                       the gland or may become evident only once the
   Uncommon masses around the suprasellar re-           gland is incised. These tumours can be comple-
gion also include optic nerve and hypothalamic          tely excised, preserving pituitary function. The
glioma (Fig. 8.12), giant aneurysm arising from         suprasellar extension of the tumour can be gently
the carotid artery, Rathke’s cleft cysts, suprasellar   coaxed down into the pituitary fossa by slightly
germinomas and chordomas.                               raising the intracranial pressure using a Valsalva
                                                        manoeuvre or by the anaesthetist injecting small
                                                        increments of nitrous oxide and oxygen mixture
Treatment
                                                        into the lumbar theca until the intracranial pres-
The objectives of treatment of patients with pitu-      sure forces the suprasellar tumour into the oper-
itary tumours depend on whether the patient has         ative field. This will also have the additional
presented with features of endocrine disturbance        benefit that the intracranial gas will provide a
or problems related to compression of adjacent          pneumoencephalogram, outlining the remaining
neural structures. The methods of treatment used        suprasellar extension of tumour.
are:                                                       A transcranial operation is occasionally neces-
1 Operative procedures:                                 sary, particularly where there is a subfrontal or
   (a) trans-sphenoidal excision                        retroclival extension of the tumour.
   (b) transcranial excision.                              Postoperative management requires careful at-
2 Radiotherapy.                                         tention to the fluid balance and hormonal status.
3 Medical treatment with antisecretory drugs.           Endocrine deficiency in the immediate post-
                                                        operative period will require replacement with
                                                        parenteral hydrocortisone and possibly the use
Surgical excision
                                                        of vasopressin for the treatment of diabetes
This will be used as the primary method of treat-       insipidus, which often occurs at least transiently
ment for:                                               after the excision of a large pituitary tumour. In
• large tumours causing compression of adja-            the early postoperative period aqueous vaso-
 120                                                                                           CHAPTER 8


                                                           the postoperative endocrine studies demonstrate
                                                           residual excessive hormone secretion.
 Tumour

 Sphenoid                                                  Medical treatment
 sinus
                                                           Treatment of pituitary adenomas is undertaken
                                                           to restore the endocrine status of the patient by
                                                           replacement of either the pituitary hormone
                                                           itself or the hormone of the pituitary-dependent
                                                           glands. This will be a necessary preoperative pro-
 Nasal                                                     cedure in patients with evidence of hypopitu-
 speculum
                                                           itarism and will frequently be necessary after the
                                                           surgical excision of a macroadenoma.
                                                              Prolactin-secreting pituitary tumours are treat-
                                                           ed with bromocriptine, a dopamine agonist. This
  Endotracheal tube
                                                           is the preferred treatment for a symptomatic pro-
    (a)                                                    lactin-secreting microadenoma and may be used
                                                           either as the definitive treatment of larger pro-
                                                           lactin-secreting tumours or in conjunction with
                                                           surgery. Some patients show poor tolerance to
                                                           bromocriptine, as it may cause intractable
                                                           nausea, vomiting and postural hypotension, and
                                                           these patients will require surgical treatment of
                                                           the tumour.


                                                           Craniopharyngioma
                                                           This tumour may occur at any age, although
                                                           nearly half occur in the first 20 years of life. They
                                                           are thought to arise from the epithelial remnants
    (b)
                                                           of Rathke’s pouch.
Fig. 8.13 (a) Diagram of operative exposure in trans-
sphenoidal resection of pituitary tumour. A self-
                                                              The tumours occur in the region of the pitu-
retaining retractor is inserted and the anterior wall of   itary fossa and extend through the suprasellar
the sphenoid sinus is removed. (b) Intraoperative X-       cisterns to the hypothalamus. The majority are
ray showing the retractor in position and the forceps in   cystic, and the fluid is often yellow and sparkling
the pituitary fossa.                                       with cholesterol crystals. The cyst may be larger
                                                           than the solid component, which is often pale
pressin (Pitressin ®) should be given by intra-            and crumbly, consisting of epithelial debris.
muscular or subcutaneous injection and, if the di-            There are two histological types of tumours.
abetes insipidus persists, by the intranasal route.        The adamantinous type resembles adamantino-
Other long-term hormonal replacements may in-              ma of the jaw and is encountered in virtually all
clude cortisone acetate (12.5–25 mg twice daily),          children. The papillary type, so-called adult cran-
thyroxine and testosterone.                                iopharyngioma, occurs in about one-third of
                                                           adults and is rare in children.
Radiotherapy
                                                           Clinical presentation
Postoperative radiotherapy may be used if there
has been a subtotal excision of the tumour or if           Clinical features include:
 PITUITARY TUMOURS                                                                                 121


• raised intracranial pressure
• visual impairment
• endocrine dysfunction.

Raised intracranial pressure
This is common, particularly in children, who pre-
sent with headache, vomiting and papilloedema.

Visual impairment
This is due to papilloedema, chiasmal compres-
sion or a combination of both. Papilloedema is
due to hydrocephalus as a result of 3rd ventricu-
lar obstruction by the tumour. The visual field
defect is frequently similar to that produced by a
pituitary tumour, a bitemporal hemianopia, but
homonymous defects are more common than in
                                                          (a)
pituitary adenoma.

Endocrine abnormalities
These are frequent in children and consist of:
• hypogonadism
• stunting of growth
• diabetes insipidus.
   Endocrine failure due to craniopharyngioma
arising in adults is essentially similar to that
caused by a pituitary tumour, except that dia-
betes insipidus occurs more commonly in pa-
tients presenting with craniopharyngioma.


Investigations
The CT scan usually shows a cystic tumour in the
suprasellar region with calcification (Fig. 8.14).         (b)
Tumours in adults may be solid and are less calci-
                                                     Fig. 8.14 CT scan. Craniopharyngioma.
fied than those seen in younger patients. MRI is
useful in showing the full extent of the tumour
(Fig. 8.15).                                            On occasions craniopharyngioma and pitu-
  Changes in the sella turcica are seen in approx-   itary tumours need to be distinguished from a
imately 50% of patients. Suprasellar tumours and     Rathke’s cleft cyst (Fig. 8.16). Both craniopharyn-
the associated hydrocephalus press downwards         giomas and Rathke’s cleft cysts are thought to
on the dorsum sellae and anterior clinoids and       arise from embryonic remnants of Rathke’s
may enlarge the sella. Nearly 90% of tumours in      pouch. By the 6th week of embryonic life the
children have radiographically identifiable calci-    residual lumen of Rathke’s pouch is reduced to a
fication in the tumour, whereas only 40% of           narrow cleft that generally regresses. Persistent
adults have radiologically demonstrable calcifi-      enlargement of this cleft is said to be the cause of
cation. The calcification consists of aggregates of   Rathke’s cleft cyst. These cysts are epithelium-
small flecks of calcium and may be curvilinear,       lined cysts containing mucoid material. They are
outlining a portion of the cyst wall.                usually confined to the sella, but on occasions can
 122                                                                                     CHAPTER 8


form large cystic tumours extending into the         onal craniotomy or a bifrontal craniotomy with
suprasellar cisterns (Fig. 8.16).                    separation of the frontal lobes and division of the
                                                     lamina terminalis. Tumours extending into the
                                                     3rd ventricle may also need to be approached
Treatment
                                                     through the corpus callosum. An extended trans-
Preoperative visual and endocrine assessment         sphenoidal approach is sometimes advised for
is essential. The standard treatment for cranio-     those tumours extending down to the floor of the
pharyngioma is operative, with an attempt at         pituitary fossa.
maximal resection of the tumour. However, com-          Postoperative management will include care-
plete resection may not be possible due to the       ful attention to fluid and electrolyte balance as
extent of the tumour and the intimate attachment     many patients have at least a transient diabetes
to hypothalamic vital structures.                    insipidus following surgery. Other hormones
   The usual surgical approach is through a pteri-   may need replacement depending on endocrino-
                                                     logical assessment.
                                                        The role of postoperative radiotherapy in pa-
                                                     tients with a subtotal resection is controversial
                                                     but radiotherapy may be beneficial in decreasing
                                                     the production of cyst fluid and delaying recur-
                                                     rence of the tumour.


                                                     Empty sella syndrome
                                                     The empty sella refers to a communicating exten-
                                                     sion of the subarachnoid space into the pituitary
                                                     fossa (Fig. 8.17). This may occur as a result of an
                                                     incomplete anatomical formation of the di-
                                                     aphragma sellae which allows the arachnoid to
                                                     herniate directly into the pituitary fossa or as a
                                                     secondary phenomenon following either pitu-
Fig. 8.15 MRI. Craniopharyngioma.                    itary surgery or radiotherapy.




                                                                           Fig. 8.16 MRI showing large
                                                                           Rathke’s cleft cyst.
 PITUITARY TUMOURS                                                                                             123


                                                      Normal                                     Empty sella




                                                                  Basal cisterns
                                 Arachnoid                        (CSF)
                                                                             Diaphragma sellae




                                                                                                 CSF

Fig. 8.17 Empty sella. The       Dura
subarachnoid space is able to
enter the sella through an
incomplete diaphragma sellae.    Anterior lobe pituitary               Anterior lobe pituitary



   There is good reason to regard the empty sella
as an anatomical variant rather than a syndrome.
Bergland showed the presence of subarachnoid
space within the sella in 20%, and anatomical de-
fects of the diaphragma sellae of 5 mm or more in
nearly 40%, of an autopsy series without pitu-
itary disease. However, defects in the diaph-
ragma are not the only requirement for formation
of an empty sella. Increased intracranial pressure
associated with benign intracranial hypertension
or long-standing hydrocephalus will cause her-
niation of the subarachnoid space into the sella
and will result in the remodelling of the pituitary             (a)
fossa to produce the classic globular appearance
on plain X-ray and CT scan (Fig. 8.18). It is possi-
ble that the normal variations in CSF pressure
may be transmitted into the fossa through an in-
competent diaphragma and so result in the bony
changes.


Clinical presentation
Most patients with the radiological features of an
empty sella are asymptomatic. The majority of
patients presenting with symptoms are obese,
middle-aged, hypertensive women. Headache is
the most common symptom associated with the
empty sella but the features are so varied that                 (b)
their relevance to the intrasellar subarachnoid            Fig. 8.18 Empty sella. (a) The classic globular enlarged
space is dubious without an underlying cause for           sella. (b) CSF within the sella.
possible raised intracranial pressure.
   Visual field defects and endocrine abnormali-
ties are subtle and uncommon in patients with
 124                                                                                                CHAPTER 8


primary empty sella syndrome. In patients with a            Kaye AH, Black P McL (2000) Operative Neurosur-
secondary empty sella, e.g. following surgery or              gery. Churchill Livingstone, London, New York,
radiotherapy, field defects may be more pro-                   Edinburgh.
nounced but are rarely severe.                              Kaye AH, Galbraith JEK, King J (1981) Intracranial
                                                              pressure in patients with empty sella syndrome with-
  The most serious consequence of an empty
                                                              out benign intracranial hypertension. Journal of
sella is spontaneous CSF rhinorrhoea. This usual-
                                                              Neurosurgery 55, 453–456.
ly occurs only if there has been an underlying              Kovacs K, Horvath E (1985) Morphology of adenohy-
cause of raised intracranial pressure, such as                pophyseal cells and pituitary adenomas. In: Imura H,
benign intracranial hypertension. It is managed               ed. The Pituitary Gland. Raven Press, New York.
by repairing the leak in the floor of the sella with         Laws ER, Randle RV, Abboud CF (1982) Surgical treat-
crushed muscle and fascia lata and performing a               ment of acromegaly: results in 140 patients. In:
CSF shunt.                                                    Givens JR, ed. Hormone Secreting Pituitary Tumours.
                                                              Year Book. Medical Publishers, Chicago.
                                                            Molitch ME, Fahlbusch R (1995) Medical versus surgi-
Further reading                                               cal treatment of giant pituitary prolactinomas. In: Al-
Abboud CF, Laws ER (1988) Diagnosis of pituitary tu-          Mefty O, Origitano TC, Harkey HL, eds. Controversies
  mours. In: Young WF, Klee GG, eds. Endocrinology            in Neurosurgery. Thieme, New York.
  and Metabolism Clinics of North America. W B Saun-        Ross D, Wilson CB (1988) Results of transsphenoidal
  ders, Philadelphia, Vol. 17, 241–277.                       microsurgery for growth hormone secreting pitu-
Bergland RM, Ray BS, Torak RM (1968) Anatomical               itary adenoma in series of 214 patients. Journal of
  variations in the pituitary gland and adjacent struc-       Neurosurgery 68, 854–867.
  tures in 225 human autopsy cases. Journal of              Scheithauer BW (1984) Surgical pathology of the pitu-
  Neurosurgery 28, 93–99.                                     itary. The adenomas Part I. In: Sommers SC, Rosen
Black P McL, Zervas NT, Candia G (1987) Incidence and         PP, eds. Pathology Annual Part I. Appleton-Century-
  management of complications of transsphenoidal              Crofts, Connecticut, 317–374.
  operation for pituitary adenomas. Neurosurgery 20,        Scheithauer BW (1984) Surgical pathology of the pitu-
  920–924.                                                    itary. The adenomas Part II. In: Sommers SC, Rosen
Cushing H (1912) The Pituitary Body and its Disorders.        PP, eds. Pathology Annual Part I. Appleton-Century-
  Clinical States Produced by Disorders of the Hypophysis     Crofts, Connecticut, 269–329.
  Cerebri. JB Lippincott, Philadelphia.                     Thapar K, Laws ER (1995) Pituitary tumours. In: Kaye
Ebersold MJ et al. (1983) Pituitary apoplexy treated by       AH, Laws ER, eds. Brain Tumours. Churchill Living-
  transsphenoidal surgery. A clinicopathological and          stone, Edinburgh.
  immunocytochemical study. Journal of Neurosurgery         Trumble HC (1951) Pituitary tumours: observations on
  58, 315–320.                                                tumours which have spread widely beyond the con-
Hardy J (1968) Transphenoidal microsurgery of the nor-        fines of the sella. British Journal of Surgery 39, 7–24.
  mal and pathological pituitary. Clinical Neurosurgery     Wilson CB (1984) A decade of pituitary microsurgery.
  16, 185–217.                                                Journal of Neurosurgery 61, 814–833.
Kaufman B (1968) The ‘empty’ sella turcica: a mani-         Editorial (1982) The intrasella subarachnoid space.
  festation of the intrasellar subarachnoid space.            Lancet July 31, 249–250.
  Radiology 90, 931–941.
                            CHAPTER 9


  9                         Subarachnoid haemorrhage



The sudden onset of a severe headache in a pa-          rhage becomes more frequent than arteriovenous
tient should be regarded as subarachnoid haem-          malformations over the age of 20 years. Rare
orrhage until proven otherwise.                         causes of subarachnoid haemorrhage include
   Subarachnoid haemorrhage occurs when                 bleeding from a tumour, bleeding disorders,
bleeding is primarily within the subarachnoid           blood dyscrasias and rupture of a spinal arteri-
space rather than into the brain itself. It repre-      ovenous malformation (Table 9.1). The aetiology
sents about 5–10% of all non-traumatic intra-           of subarachnoid haemorrhage remains undis-
cranial haemorrhage with an incidence of                covered in approximately 15% of cases after thor-
approximately 15 per 100 000 population.                ough clinical and radiographic study. These
Apoplectic death has been mentioned in the ear-         patients often have associated intracranial vascu-
liest medical writings but its relationship to in-      lar atherosclerosis and hypertension.
tracranial haemorrhage and cerebral aneurysm
was not established until the latter part of the sev-
                                                        Subarachnoid haemorrhage —
enteenth century. The introduction of cerebral
                                                        presenting features (Table 9.2)
angiography by Moniz and Lima in Lisbon in
1927 allowed the diagnosis of cerebral aneurysm
                                                        Headache
to be made in living patients who had sustained
subarachnoid haemorrhage. Pioneering surgery            The sudden onset of a severe headache of a type
in the 1930s and 1940s, by Krayenbuhl in Switzer-       not previously experienced by the patient is the
land and Dandy in North America, showed                 hallmark of subarachnoid haemorrhage. A rela-
that aneurysms could be treated operatively, al-        tively small leak from an aneurysm may result in
though at that time with considerable morbidity         a minor headache, sometimes referred to as the
and mortality. Consequent improvements in mi-           ‘sentinel headache’, as this may be the warning
crosurgical techniques and neuroanaesthesia             episode of a subsequent major haemorrhage
have considerably improved the safety of                from the aneurysm. Naturally, recognition of a
surgery.                                                possible minor ‘warning’ haemorrhage is essen-
                                                        tial to avert a possible later catastrophic bleed, al-
                                                        though many are only recognized in retrospect.
Causes of subarachnoid haemorrhage
The most common cause of subarachnoid haem-
                                                        Diminished conscious state
orrhage in adults is rupture of a berry aneurysm.
Subarachnoid haemorrhage in children is much            Most patients have some deterioration of their
less common than in the adult population and            conscious state following subarachnoid haemor-
the most common paediatric cause is rupture             rhage. This varies from only a slight change
of an arteriovenous malformation. Cerebral              when the haemorrhage has been minor to
aneurysm as a cause of subarachnoid haemor-             apoplectic death resulting from massive haem-

                                                                                                          125
 126                                                                                         CHAPTER 9



  Table 9.1 Causes of subarachnoid haemorrhage
  (%).

  Cerebral aneurysm                               70
  Arteriovenous malformation                      10
  Undiscovered                                    15
  Other rare causes                                5
    Spinal arteriovenous malformation
    Tumour
    Blood dyscrasia




  Table 9.2 Subarachnoid haemorrhage —
  presenting features.

  Headache                                             Fig. 9.1 Intracerebral haematoma in temporal lobe
  Diminished conscious state                           due to rupture of a middle cerebral artery aneurysm.

  Meningism
   Neck stiffness, vomiting, photophobia, fever        noid haemorrhage due to concomitant intracere-
  Focal neurological signs                             bral haemorrhage, the local pressure effects of the
    Intracerebral haemorrhage                          aneurysm itself, or cerebral vasospasm.
    Focal pressure by aneurysm                            A cerebral aneurysm usually lies within the
    Vasospasm                                          subarachnoid cisterns but the aneurysm may be-
  Fundal changes                                       come adherent to the adjacent brain parenchyma
    Subhyaloid haemorrhage                             due to adhesions, frequently resulting from pre-
    Retinal haemorrhage                                vious leakage of blood. A haemorrhage from an
    Papilloedema                                       aneurysm in these circumstances may also ex-
                                                       tend into the brain and the position of the intra-
                                                       cerebral haematoma will determine the type of
                                                       neurological deficit. A middle cerebral artery
orrhage. It is a common cause of sudden death in       aneurysm frequently ruptures into the temporal
young adults.                                          lobe, resulting in hemiparesis and aphasia if the
                                                       dominant hemisphere is involved (Fig. 9.1). An-
                                                       terior communicating artery aneurysms may
Meningism
                                                       haemorrhage into the frontal lobes with subse-
Blood in the subarachnoid cerebrospinal fluid           quent akinetic mutism (Fig. 9.2). Defective
will cause the features of meningism — headache,       conjugate ocular movement may result from
neck stiffness, photophobia, fever and vomiting.       haemorrhage into a frontal lobe, persistent devia-
Irritation of the nerve roots of the cauda equina,     tion usually being towards the side of the lesion
which occurs when the blood extends down to            and purposeful gaze defective away from that
the lumbar theca, may result in sciatica-type pain     side.
and low back discomfort.                                  Occasionally, an aneurysm may also rupture
                                                       into the subdural space, resulting in a subdural
                                                       haematoma and brain compression causing lat-
Focal neurological signs
                                                       eralizing neurological signs. An arteriovenous
Focal neurological signs may occur in subarach-        malformation usually lies at least partially within
 SUBARACHNOID HAEMORRHAGE                                                                                 127




                                                       Fig. 9.3 Giant internal carotid artery aneurysm.



                                                       parasympathetic pupillary fibres arising from
                                                       the nucleus of Edinger–Westphal in the mid-
Fig. 9.2 Frontal intracerebral haematoma with blood    brain. An expanding aneurysm usually results in
in the Sylvian fissure and ventricles from a ruptured   more pain than the ischaemia associated with di-
anterior communicating artery aneurysm.                abetes mellitus, although this is an unreliable
                                                       guide. If there is any doubt about the cause of the
                                                       3rd nerve palsy then angiography must be per-
the brain parenchyma, so that when it ruptures         formed expeditiously. In a patient with impaired
intracerebral bleeding is frequently associated        conscious state, or in one with other abnormal
with the subarachnoid haemorrhage.                     neurological signs suggesting a massive haemor-
   Focal neurological signs may result from the        rhage, 3rd cranial nerve palsy may be secondary
position of the aneurysm itself. An aneurysm           to temporal lobe herniation.
arising from the internal carotid artery at the           A giant aneurysm (defined as larger than
origin of the posterior communicating artery           2.5 cm in diameter) may cause compression of
(known as a posterior communicating artery             adjacent neural structures resulting in focal signs
aneurysm) may cause pressure on the 3rd cranial        (Fig. 9.3). A large aneurysm of the internal carotid
nerve. Patients with an enlarging aneurysm in          artery or anterior communicating artery will
this position may present with features of a 3rd       cause compression of the optic nerve or chiasm,
cranial nerve palsy (ptosis, pupil dilatation, ex-     respectively, resulting in visual failure. Large
traocular muscle palsy) prior to a subarachnoid        vertebrobasilar aneurysms may cause brainstem
haemorrhage. It is vital that the correct diagnosis    compression.
of an enlarging cerebral aneurysm is made in this         Cerebral vasospasm following subarachnoid
situation, so as to avoid the possible catastrophic    haemorrhage does not usually result in clinical
effects of subarachnoid haemorrhage. The major         manifestations for 2 or 3 days after the initial
differential diagnosis of the aetiology of an ap-      bleed so that, although it may be the cause of
parently isolated 3rd cranial nerve palsy is an is-    subsequent focal signs resulting from brain is-
chaemic lesion such as those resulting from            chaemia, it is not the cause of focal signs imme-
diabetes mellitus or atherosclerosis. Pupil size is    diately after the haemorrhage.
a useful guide in differentiating between these
causes. The pupil is usually dilated, with an          Optic fundi
expanding aneurysm which compresses the                Mild papilloedema is common within the first
superior aspect of the nerve that contains the         few days of haemorrhage because of the sudden
 128                                                                                             CHAPTER 9


elevation of intracranial pressure resulting from         subarachnoid haemorrhage may be misdiag-
hydrocephalus or cerebral oedema. A transient             nosed as either migraine or tension headache. A
communicating hydrocephalus often occurs after            full neurological examination should be per-
subarachnoid haemorrhage due to blood block-              formed with particular attention given to the
ing the arachnoid villi. In about 10% of cases the        presence of neck stiffness, altered conscious state,
hydrocephalus persists and is severe enough to            pupillary status and fundal haemorrhage. Clini-
require a CSF shunt.                                      cal grading systems have been based on the
  Ophthalmoscopy may reveal fundal haemor-                severity of the headache and neck stiffness and
rhages, particularly in severe subarachnoid               on the level of conscious state. The two major
haemorrhage. Small, scattered retinal haemor-             systems are the Hunt and Hess classification and
rhages usually resolve satisfactorily, although           the World Federation of Neurological Surgeons
the large subhyaloid haemorrhages may break               (WFNS) system (Table 9.3).
into the vitreous, resulting in permanent visual
defect.
                                                          Investigations
                                                          The major differential diagnosis is meningitis, al-
Clinical assessment
                                                          though a minor haemorrhage is often misdiag-
The diagnosis is usually obvious when the histo-          nosed as migraine. Confirmation of the clinical
ry is obtained from the patient, relative or friend.      diagnosis of subarachnoid haemorrhage should
The classic sudden onset of severe headache with          be undertaken as soon as possible. Computer-
features of meningism and decreased conscious             ized tomography (CT) scanning (Fig. 9.4) is the
state is characteristic of a subarachnoid haemor-         best initial investigation as it will confirm the di-
rhage. However, difficulty may occur when the              agnosis in over 85% of cases. It will also provide
haemorrhage has been minor and, tragically, a             additional information on associated pathology




  Table 9.3 Subarachnoid haemorrhage grading systems.

  Hunt and Hess grading system*
  Grade     Description

  1          Asymptomatic, or minimal headache and slight nuchal rigidity
  2          Moderate to severe headache, nuchal rigidity, no neurological deficit (except cranial nerve palsy)
  3          Drowsiness, confusion or mild focal deficit
  4          Stupor, moderate to severe hemiparesis, possible early decerebrate rigidity and vegetative
               disturbances
  5          Deep coma, decerebrate rigidity, moribund

  WFNS grading system
  Grade              Glasgow Coma Score (GCS)                      Motor deficit

  1                     15                                         No deficit except a cranial nerve palsy
  2                     14–13                                      No deficit
  3                     14–13                                      Any deficit
  4                     12–7                                       With or without focal neurodeficit
  5                      6–3                                       Coma with or without abnormal posturing

  * Serious systemic disease such as hypertension, diabetes, severe arteriosclerosis, chronic pulmonary
  disease, and vasospasm on angiography result in placement in next less favourable category.
 SUBARACHNOID HAEMORRHAGE                                                                                   129


                                                          the subarachnoid haemorrhage and will deter-
                                                          mine the subsequent treatment. Intra-arterial
                                                          digital subtraction angiography has consider-
                                                          ably reduced the risks of conventional angio-
                                                          graphy and should be undertaken as soon as the
                                                          diagnosis has been confirmed and it is clear that
                                                          the patient will survive the initial haemorrhage.


                                                          Cerebral aneurysm
                                                          Cerebral aneurysms are the most common cause
                                                          of subarachnoid haemorrhage in the adult popu-
                                                          lation, with a maximal incidence in the 4th and
                                                          5th decades of life, although they can occur at any
                                                          age.


                                                          Surgical anatomy
Fig. 9.4 Blood in the Sylvian fissure and basal cisterns
indicative of subarachnoid haemorrhage.                   The great majority of aneurysms arise at the
                                                          branch points of two vessels, usually at an acute
                                                          angle, and are situated mainly on the circle of
such as intracerebral haemorrhage and hydro-              Willis and the trunks of the large arteries which
cephalus, and on the position of the haemor-              supply it. A few arise from its immediate branch-
rhage, which is helpful if there is more than one         es but aneurysms on peripheral vessels are rare
aneurysm. Arteriovenous malformation causing              (Fig. 9.5). The majority of aneurysms occur in
subarachnoid haemorrhage can frequently be di-            constant positions on the circle of Willis and
agnosed on the CT scan. If there is any doubt that        about 85% occur on the anterior half of the circle
subarachnoid blood is present on the CT scan, as          (Table 9.4). Aneurysms arise at approximately
may occur following more minor haemorrhages,              equal frequency from the internal carotid artery,
a lumbar puncture is essential. The presence of           anterior communicating artery and middle cere-
xanthochromia (yellow staining) in the CSF                bral artery. Those associated with the internal
will confirm subarachnoid haemorrhage. Xan-                carotid artery most frequently arise at the origin
thochromia resulting from breakdown of haemo-
globin in the red blood cells occurs within 6–8
hours after the initial haemorrhage and it will
confirm that the blood in the CSF is not due to                                       Anterior cerebral

trauma from the lumbar puncture needle. A fur-                                          Anterior communicating
ther method frequently suggested to exclude
                                                                                                  Middle cerebral
trauma from the passage of the lumbar puncture            Internal
                                                          carotid
needle as a cause of bloody CSF is to allow the                                                   Posterior
                                                                                                  communicating
CSF to drip into three consecutive tubes; if the
blood fails to ‘clear’ in the last tube subarach-
noid haemorrhage is confirmed. However, this                Posterior cerebral                  Superior cerebellar
                                                               Basilar                          Anterior inferior
method will result in many false positive diag-
                                                                                                cerebellar
noses. The CSF should also be immediately ex-
                                                                                                Posterior inferior
amined for the presence of white blood cells and                                                cerebellar
organisms.                                                                                      Vertebral
   Cerebral angiography will confirm the cause of          Fig. 9.5 Usual sites of cerebral aneurysms.
 130                                                                                        CHAPTER 9



  Table 9.4 Position of cerebral aneurysm.              Pathogenesis of cerebral aneurysms
                                                        The common type of cerebral aneurysm resulting
  Anterior circle of Willis
                                                        in a subarachnoid haemorrhage is a saccular
  Anterior communicating artery
  Middle cerebral artery — bifurcation or
                                                        aneurysm, which is also known as a berry or con-
  trifurcation                                          genital aneurysm. Fusiform aneurysms occur in
  Internal carotid artery                               the intracranial circulation, particularly the ver-
     Posterior communicating artery                     tebrobasilar arteries or internal carotid arteries,
     Terminal bifurcation                               and are due to diffuse atheromatous degenera-
     Anterior choroidal artery                          tion of the arterial wall, frequently associated
     Ophthalmic artery                                  with hypertension. Mycotic aneurysms result
     Intracavernous                                     from septic emboli. They may be situated on pe-
  Pericallosal artery                                   ripheral vessels, are frequently multiple and
  Posterior circulation (15%)                           have a high risk of haemorrhage.
  Terminal basilar artery — most common                    The saccular or berry aneurysm arises at the
  Vertebrobasilar junction                              junction of vessels where there is a congenital de-
  Posterior inferior cerebellar artery                  ficiency in the muscle coat. The elastic layer in
  Anterior inferior cerebellar artery                   cerebral arteries, in contrast with arteries else-
  Superior inferior cerebellar artery
                                                        where, is limited to the internal lamina, making
  Posterior cerebral artery
                                                        these vessels more susceptible to weakening ef-
                                                        fects of degeneration. Fragmentation and disso-
                                                        lution of the internal elastic membrane occurs at
                                                        the site of aneurysm development. The combina-
of the posterior communicating artery (the              tion of the muscle defect and the discontinuity of
so-called posterior communicating artery                the underlying internal elastic membrane is
aneurysm), less frequently at the terminal bifur-       probably necessary for the formation of a saccu-
cation, and occasionally at the origin of the oph-      lar aneurysm. Other factors that increase the risk
thalmic artery, the anterior choroidal artery or in     of aneurysm formation include atheroma and
the cavernous sinus. Middle cerebral artery             hypertension. There is an increased incidence
aneurysms arise from the middle cerebral artery         of atheroma in the vessels of the circle of Willis
at its bifurcation or trifurcation in the Sylvian fis-   and hypertension in patients with ruptured
sure (Fig. 9.6). Less commonly an aneurysm may          aneurysms. It is probable that these factors play a
arise from the pericallosal artery at the genu of       role in the growth of the aneurysm and its subse-
the corpus callosum.                                    quent rupture in some patients.
   Approximately 15% of aneurysms arise from
the posterior half of the circle of Willis, the most    Related diseases
common position being the basilar artery, most          There is no definite hereditary basis to the devel-
frequently at the terminal bifurcation into the         opment of intracranial aneurysms, although an
posterior cerebral arteries. However, an                epidemiology study has shown an increased inci-
aneurysm may arise from any of the main                 dence of approximately seven-fold in first-degree
branches of the vertebral or basilar arteries, in       relatives of patients who have had an aneurys-
particular the posterior inferior cerebellar artery,    mal subarachnoid haemorrhage, with a lifetime
anterior inferior cerebellar artery or superior         risk of 2–5% of developing an aneurysmal sub-
cerebellar artery (Fig. 9.7).                           arachnoid haemorrhage. Aneurysms do occur in
                                                        association with hereditary syndromes such as
Multiple aneurysms                                      Ehlers–Danlos syndrome, coarctation of the aorta
Aneurysms occur in more than one position in            and polycystic kidney disease.
approximately 15% of cases.
 SUBARACHNOID HAEMORRHAGE                                                                                   131




           (a)                                            (b)




           (c)                                            (d)
Fig. 9.6 (a) Anterior cerebral artery aneurysm. (b) Middle cerebral artery aneurysm. (c) Posterior communicating
artery aneurysm. (d) Terminal internal carotid artery aneurysm.




           (a)                             (b)                            (c)
Fig. 9.7 (a) Terminal basilar artery aneurysm. (b) Aneurysm arising from junction of basilar artery and superior
cerebellar artery. (c) Posterior inferior cerebellar artery aneurysm.



                                                          2 Rebleeding of the aneurysm.
Management of ruptured cerebral aneurysm
                                                          3 Cerebral vasospasm.
The management of patients following rupture
of a cerebral aneurysm is determined by three             Severity of the initial haemorrhage
major factors.                                            About 30% of all patients suffering a subarach-
1 Severity of the initial haemorrhage.                    noid haemorrhage from a ruptured aneurysm
 132                                                                                         CHAPTER 9


either have an apoplectic death or are deeply co-        jacent to the ruptured aneurysm, generalized
matose as a result of the initial haemorrhage.           vasospasm occurs frequently. The clinical mani-
                                                         festations resulting from vasospasm will be
Rebleeding                                               determined by the vessels which are most severe-
This occurs in about 50% of patients within 6            ly affected. Spasm of the internal carotid artery
weeks and 25% of patients within 2 weeks of the          and middle cerebral arteries produces hemipare-
initial haemorrhage. About half the patients that        sis and aphasia in the dominant hemisphere. Va-
have a subsequent haemorrhage will die as a re-          sospasm of the anterior cerebral vessels causes
sult of the rebleed. After the first year the risk of a   paralysis of the lower limbs and akinetic mutism.
further haemorrhage from the aneurysm is about           Severe vasospasm may cause widespread cere-
2–3% per year.                                           bral ischaemia so that the patient may become
   The only certain way to prevent an aneurysm           obtunded; if the vasospasm is sufficiently severe
rebleeding is to exclude it from the circulation.        it will result in death. Vasospasm does not usual-
Antifibrinolytic agents (such as epsilon amino            ly occur until 2 or 3 days after the initial haemor-
caproic acid or tranexamic acid) decrease the            rhage and its onset is rarely delayed beyond 14
risks of rebleeding but, as they are associated          days. The cause of delayed cerebral vasospasm
with increased incidence of thrombosis (such as          remains obscure but it is certainly related to vaso-
deep vein thrombosis and pulmonary embolus)              constrictor substances in the CSF as a result of the
and an increased risk of cerebral thrombosis as-         haemorrhage. Vasoactive substances isolated
sociated with vasospasm, these agents are now            from both the blood clot surrounding the spastic
rarely used.                                             vessels and the adjacent CSF include oxy-
                                                         haemoglobulin released from the erythrocytes,
Cerebral vasospasm                                       serotonin, thromboxane A2, prostaglandins (F2-
Angiographic vasospasm (Fig. 9.8) occurs in              alpha and E2), angiotensin and histamine. In ad-
about 50% of patients following subarachnoid             dition, unidentified vasoconstrictor substances
haemorrhage and in 25% it results in serious neu-        have been isolated from incubates of fibrinogen,
rological complications. There is a direct correla-      platelets, erythrocytes and blood/CSF mixtures.
tion between the amount of blood noted in the            The contractile process ultimately depends on
basal cisterns on the CT scan, the risk of develop-      the availability of cytosolic activator calcium
ing vasospasm and its severity. Although the             ions.
spasm may principally affect the vessels most ad-           Until recently there has been no satisfactory
                                                         treatment for established cerebral vasospasm. If
                                                         the aneurysm has been surgically occluded from
                                                         the circulation then hypertensive therapy com-
                                                         bined with hypervolaemia may overcome the hy-
                                                         poperfusion due to narrowing of the cerebral
                                                         blood vessels and reverse the ischaemic effects.
                                                         Calcium channel blocking agents such as nimod-
                                                         opine and nifedipine are frequently used in sub-
                                                         arachnoid haemorrhage to prevent and treat
                                                         vasospasm, although there is still some doubt as
                                                         to their effectiveness. Nimodopine, a substituted
                                                         1,4-dihydropyridine, is a calcium ‘antagonist’
                                                         that blocks the influx of extracellular calcium, the
                                                         primary source of calcium for contraction of large
Fig. 9.8 Spasm of the anterior cerebral arteries         cerebral arteries. Trials in North America, Britain
following subarachnoid haemorrhage from an anterior      and Scandinavia have shown promising results
communicating artery aneurysm.                           when the calcium channel blocking agents are
 SUBARACHNOID HAEMORRHAGE                                                                            133


used prophylactically, although there is debate as     • Blood pressure control. The blood pressure is fre-
to whether their effect is due to their action on      quently elevated immediately after the haemor-
the cerebral vessels or due to a ‘brain protection’    rhage and should be carefully controlled. Initially
effect.                                                this should be done using intravenous medica-
   Following the angiogram that confirms a cere-        tion and utilizing vasodilating agents (such as
bral aneurysm, a decision is then made as to the       hydralazine or glyceryl trinitrate) and beta-
definitive treatment of the aneurysm. This will         blockers. Although it is essential to control high
involve either:                                        blood pressure, as this may lead to rupture of
• surgery with clipping of the aneurysm or             the aneurysm, hypotension may result in cere-
• endovascular obliteration of the aneurysm.           bral ischaemia, particularly when vasospasm is
                                                       present. The appropriate desirable blood pres-
Surgery for ruptured aneurysm                          sure will depend upon the premorbid level.
The timing of the operation is critical in obtain-     • Fluids and electrolytes. Correct hydration is es-
ing optimal results following subarachnoid             sential to avoid electrolyte disturbance; in addi-
haemorrhage. Although better operative results         tion, overhydration may precipitate cerebral
may be achieved when the surgery is delayed,           oedema and insufficient fluids may increase
the longer the operation is deferred the greater       the risk of cerebral thrombosis associated with
the risk that the aneurysm will rebleed. In gener-     vasospasm. Electrolyte disturbances may also
al, the operation is performed as soon as possible     occur following subarachnoid haemorrhage due
after the cerebral angiogram. In the past surgery      to inappropriate antidiuretic hormone (ADH) se-
was avoided when the patient had clinical or an-       cretion, which results in hyponatraemia.
giographically severe vasospasm, but it is now         • Pain relief. Simple analgesic medication or
recognized that it is best to clip the aneurysm        codeine phosphate is best used for controlling
even in the presence of clinical or radiological va-   the headaches resulting from subarachnoid
sospasm as with the aneurysm excluded from the         haemorrhage.
circulation the spasm can be treated using hyper-
tensive hypervolaemic therapy and endovascu-           Surgical procedures
lar techniques.                                        The surgical procedures available are:
   Surgery is usually not performed on patients        • occlusion of the neck of the aneurysm
who are comatosed or have features of decere-          • reinforcement of the sac of the aneurysm
brate posturing response, unless the CT scan           • proximal ligation of a feeding vessel.
shows a large intracerebral haematoma resulting           Haemorrhage from an aneurysm is due to rup-
from the ruptured aneurysm which needs to be           ture of the fundus of the aneurysmal sac. There-
evacuated, or hydrocephalus as a cause of the          fore, the best surgical procedure is to occlude
poor neurological state.                               the neck of the aneurysm, thereby isolating the
                                                       aneurysm from the circulation. In brief, the oper-
Preoperative management                                ation involves a craniotomy which is usually
In those patients in whom it has been elected for      based on the pterion (pterional craniotomy) for
some reason to delay surgery, the management           aneurysms of the anterior circulation. This type
should include careful attention to the following.     of craniotomy may also be used for aneurysms
• Posture. The patient should lie flat in a quiet       arising from the terminal basilar artery, although
room with subdued lighting. Every attempt              some surgeons prefer an approach under the
should be made to avoid environmental situa-           temporal lobe via a temporal craniotomy. Micro-
tions which could cause sudden elevation of the        surgical techniques, utilizing the operating mi-
patient’s blood pressure and thus increase the         croscope and microneurosurgical instruments,
risk of rupture of the aneurysm. Sedation using        are employed. Access to the basal cisterns may be
barbiturates or diazepam may be necessary if the       aided by withdrawing CSF either using a ventric-
patient is agitated.                                   ular drain or from the lumbar theca. The arach-
 134                                                                                       CHAPTER 9


noid around the basal cisterns is opened, the neck     non-invasive ultrasound, may give useful infor-
of the aneurysm identified and dissected and a          mation on the degree of intracranial vasospasm.
clip placed across the neck to exclude the             Symptomatic vasospasm can be treated using
aneurysm from the circulation. During the dis-         hypervolaemic hypertensive therapy. This treat-
section of the aneurysm it is essential that vital     ment entails careful monitoring and requires the
adjacent vessels, including the perforating arter-     transfer of the patient to an intensive care unit.
ies, are not injured, as damage to these vessels       Recently, endovascular techniques to dilate the
may result in severe neurological disability.          vessels in spasm or administer intra-arterial pa-
   Occasionally it is not possible to safely place a   paverine into the intracranial vessels have been
clip across the neck of the aneurysm, usually as a     used to treat cerebral vasospasm postoperatively
result of branches of the parent vessel either aris-   with some success.
ing from the aneurysm or being inseparable from
the fundus. In this case the wall of the aneurysm
                                                       Endovascular procedures for
may be reinforced by a number of techniques, in-
                                                       ruptured aneurysms
cluding wrapping the wall with crushed muscle,
gauze or cotton wool or a combination of these.        Over the past 10 years endovascular techniques
Rapidly solidifying polymer (aneurysm cement)          (using detachable coils) have been used to oblit-
may be poured around the aneurysm to provide           erate cerebral aneurysms. These have been inves-
it with a solid covering.                              tigated in international trials, and have proven to
   Although ligation of the common or internal         be effective in excluding the aneurysm from the
carotid artery in the neck was commonly used for       circulation.
treatment of aneurysms of the internal carotid            The technique is usually performed by a spe-
artery, improved microneurosurgical techniques         cialist interventional radiologist, and almost al-
have made this operation almost obsolete. The          ways under general anaesthesia. As with surgery,
procedure has also been used for intracavernous        it is recommended that the aneurysm is ‘coiled’
aneurysms but these are now best treated by en-        as soon as possible after the angiogram has
dovascular techniques usually performed by a           been performed to confirm the presence of an
radiologist. Ligation of the internal carotid artery   aneurysm (Fig. 9.9).
may be performed for a giant internal carotid             The recent ISAT trial showed the possible
artery aneurysm which is not amenable to direct        superiority of endovascular coiling over surgery,
surgery, but an extracranial–intracranial bypass       although there has been some debate as to
procedure may need to be performed prior to the        these findings. The main concern remains as to
occlusion to prevent cerebral ischaemia.               whether the obliteration of the aneurysm is per-
                                                       manent, as the aneurysm can recur, particularly
Postoperative management                               with ‘impaction’ of the coils into the fundus of the
The usual postcraniotomy operative manage-             aneurysm, some months after the initial treat-
ment applies, with special attention to be given to    ment. In most centres a check angiogram is per-
the neurological state, hydration, posture, oxy-       formed at 6, 12 and 24 months after the treatment.
genation and blood pressure. Anticonvulsant               The decision as to whether an aneurysm
medication is recommended for 3 months to 1            should be ‘clipped’ by a surgeon or ‘coiled’ by an
year. Steroid medication is sometimes used in the      interventional neuroradiologist is best made
initial postoperative course to control cerebral       jointly by the treating specialist, cerebrovascular
oedema, although its effectiveness is not proven.      neurosurgeon and neuroradiologist. The inter-
  The major specific postoperative problem re-          ventional neuroradiologist will base his decision
sults from delayed cerebral vasospasm. As indi-        on
cated previously, prophylactic calcium channel         • the access to the aneurysm and
blocking agents may be of use in preventing this       • the configuration of the aneurysm.
complication. The transcranial Doppler, utilizing         Access to the aneurysm may be impaired by
  SUBARACHNOID HAEMORRHAGE                                                                             135


                                                          the aneurysm whilst maintaining patency of the
                                                          vessels. At The Royal Melbourne Hospital ap-
                                                          proximately 50% of aneurysms since the year
                                                          2000 have been treated by coiling.


                                                          Management of an unruptured aneurysm
                                                          Multiple aneurysms occur in 15% of patients who
                                                          present following subarachnoid haemorrhage. In
                                                          general, an unruptured aneurysm will be clipped
                                                          at the same time as the surgery for the ruptured
                                                          aneurysm, provided it can be performed through
(a)
                                                          the same craniotomy. The indications for surgery
                                                          are controversial for an unruptured aneurysm
                                                          occurring in a patient who has suffered a sub-
                                                          arachnoid haemorrhage from another aneurysm,
                                                          or for an unruptured aneurysm found incidental-
                                                          ly. The debate regarding the optimal manage-
                                                          ment of patients with an unruptured aneurysm
                                                          revolves around the relative risk of rupture of the
                                                          aneurysm vs. the risk of treatment, by either
                                                          surgery or an endovascular approach. In the past
                                                          the risk of haemorrhage from an unruptured
                                                          aneurysm was usually quoted at 2–3% per year.
(b)                                                       However, in 1998 the New England Journal of
Fig. 9.9 (a) Endovascular treatment of internal carotid   Medicine published a large study of the natural
artery aneurysm. Figure (b) shows the aneurysm            history of unruptured intracranial aneurysms
excluded from the circulation following the
                                                          which indicated that the risk of haemorrhage was
endovascular insertion of coils.
                                                          very much lower, particularly for aneurysms less
                                                          than 10 mm in diameter and those arising from
stenosis or tortuosity within the carotid artery          the middle cerebral artery. There has been con-
(for anterior circulation aneurysms) and verte-           siderable debate in the neurosurgical literature
brobasilar artery (for posterior circulation              regarding the veracity of the so-called ISUIA
aneurysms). The ‘dome to neck’ ratio is an im-            (International Study of Unruptured Intracranial
portant consideration in deciding whether the             Aneurysms) study, with some experts question-
configuration of the aneurysm is appropriate for           ing the methodology. In general, the risk of rup-
coiling. In general, most neuroradiologists prefer        ture will depend on the size of the aneurysm, on
the ratio to be 2 : 1 or greater. New techniques in       the configuration of the aneurysm, in particular if
interventional radiology including the use of             there is a ‘daughter sac’ attached to the fundus,
stents and three-dimensional coils have in-               on a positive family history for aneurysmal sub-
creased the number of aneurysms that can be               arachnoid haemorrhage and on the age of the pa-
treated by endovascular techniques. At present,           tient. Symptomatic aneurysms of all sizes should
over 80% of terminal basilar aneurysms can be             be considered for treatment.
treated by endovascular techniques, but only
about half of the anterior circulation aneurysms
                                                          Arteriovenous malformation
are amenable to ‘coiling’. Most interventional ra-
diologists do not coil middle cerebral artery             Arteriovenous malformations are the most
aneurysms, as there is difficulty in obliterating          common cause of subarachnoid haemorrhage in
 136                                                                                     CHAPTER 9


children. Other types of vascular malformations
                                                      Surgical anatomy
of the brain include the following.
• Capillary telangiectasia — bleed infrequently       Most arteriovenous malformations are situated
but may result in fatal haemorrhage, particularly     in the cerebral hemispheres, although they may
in the pons.                                          occur in the posterior fossa involving either the
• Cavernous haemangioma (see Fig. 9.12) —             cerebellum or brainstem and they show consid-
often cause minor local extravasations of blood       erable variation in size. The malformations in-
but major haemorrhage is uncommon. Patients           volving the cerebral hemispheres frequently
frequently present following an epileptic seizure     form a pyramidal mass, the base of which may
if the haemangioma is in the cerebral hemi-           reach the cortical surface with the apex pointing
spheres. Posterior fossa haemangiomas may pre-        towards the lateral ventricle. There are frequent-
sent with a brainstem stroke.                         ly multiple, enlarged arteries feeding the malfor-
• Venous malformations.                               mation and arterialized draining veins extend
    The arteriovenous malformation is the most        superficially to the superior sagittal sinus or
common vascular malformation. Although it ac-         transverse sinus or deeply into the deep cerebral
counts for approximately 60% of all subarach-         venous system.
noid haemorrhage in children, by the 3rd decade
it is responsible for 20% and by the 5th decade for
                                                      Radiological investigations for arteriovenous
less than 5%.
                                                      malformations (Figs 9.10–9.12)
                                                      An arteriovenous malformation is often apparent
Clinical presentation
                                                      on the CT scan because of the vivid enhancement
Haemorrhage. This is the most frequent first symp-     of the enlarged feeding vessel and arterialized
tom of an arteriovenous malformation and, al-         draining veins after intravenous contrast. Cere-
though the bleeding may be subarachnoid, there        bral angiography is best performed using digital
is commonly an intracerebral component. The ar-       subtraction angiographic techniques and is es-
teriovenous fistulous communication results in         sential for adequate evaluation of the malforma-
the development of aneurysms within the lesion,       tion. Precise determination of the position of the
enlargement of the arteries which feed the            major feeding and draining vessels is vital prior
malformation and, consequently, the possible          to surgery. Magnetic resonance imaging is a valu-
secondary development of saccular aneurysms           able aid in determining the exact position of the
on the major feeding vessels. The haemorrhage         arteriovenous malformation and the vessels.
associated with an arteriovenous malformation            Preoperative occlusion of accessible major
may quite often be due to rupture of a saccular       feeding vessels close to the malformation by an
aneurysm on the feeding vessel.                       interventional radiologist may be useful if the
   Epilepsy. This is the second most common pre-      procedure is technically feasible. A flow-directed
senting manifestation of an arteriovenous mal-        catheter is positioned in the artery, which is oc-
formation.                                            cluded using cyanoacrylate glue or a polymeriz-
   Headache. Migraine characteristics are particu-    ing collagen mixture.
larly associated with headache due to arterio-
venous malformation.
                                                      Management
   Progressive neurological deficit. For example, a
slowly progressive hemiparesis may occur in a         As with cerebral aneurysms the aim of treatment
large malformation due either to local ischaemia      is to avoid either an initial haemorrhage or re-
induced by the shunt or to increasing size of the     bleed from the malformation. There has been
lesion.                                               controversy over the risk of haemorrhage and the
                                                      morbidity and mortality associated with rupture
                                                      of an arteriovenous malformation. Recent stud-
 SUBARACHNOID HAEMORRHAGE                                                                                 137




           (a)                            (b)                            (c)
Fig. 9.10 (a) The arteriovenous malformation enhances vividly on the CT scan after intravenous contrast and the
major dilated feeding vessels can be seen. (b) The MRI shows the position of the malformation in coronal and
axial planes and further information about the feeding vessels and draining veins (c).




           (a)                                           (b)
Fig. 9.11 Cerebral angiography (digital subtraction angiogram) demonstrates the vascular anatomy of the
arteriovenous malformation. (a) The major feeding vessels are shown on the arterial phase. (b) The draining
veins are demonstrated on the venous phase.


ies have shown that the chance of haemorrhage             Surgery for arteriovenous malformations
for both ruptured and unruptured arteriovenous            The principles of the operation involve isolation
malformations is about 3% each year and that the          and occlusion of the principal feeding arteries
combined morbidity and mortality of each haem-            followed by meticulous dissection of the malfor-
orrhage is at least 40%. However, unlike cerebral         mation, with occlusion and division of the nu-
aneurysms, haemorrhage from an arterioven-                merous small feeding vessels. The draining veins
ous malformation rarely causes symptomatic                should be ligated only after all the feeding vessels
vasospasm.                                                have been occluded, since premature obstruction
   Surgical excision, provided it is technically fea-     to the arterialized venous outflow will result in a
sible and would not result in a disabling neuro-          precipitous swelling and rupture of the vascular
logical deficit, should be performed if the                mass.
malformation has haemorrhaged.                               The surgical management of giant arterio-
   Unruptured arteriovenous malformations                 venous malformations is fraught with consid-
should be considered for excision if surgery is un-       erable risk. The lesions may be surrounded
likely to produce significant neurological deficit.         by chronically ischaemic brain ‘steal’ by the
 138                                                                                        CHAPTER 9


                                                      • Neonates present shortly after birth with
                                                      cyanosis and heart failure due to the shunt
                                                      through the malformation.
                                                      • Infants and young children present with
                                                      seizures and hydrocephalus due to obstruction of
                                                      the cerebral aqueduct.
                                                      • Adults may present with multiple subarach-
                                                      noid haemorrhage.


                                                      Subarachnoid haemorrhage
                                                      of unknown aetiology
                                                      In about 15% of patients the cause of subarach-
                                                      noid haemorrhage remains unclear, despite clini-
                                                      cal and radiological investigation. Many of these
                                                      patients are hypertensive and have evidence of
Fig. 9.12 Cavernous haemangioma.                      intracranial arterial atherosclerosis, although this
                                                      is not inevitable. Most patients make a good re-
                                                      covery following the subarachnoid haemorrhage
malformation and abrupt occlusion of the shunt        and rebleeding is uncommon.
through the malformation has led in some cases
to oedema and haemorrhage in the adjacent
                                                      Management
brain, a phenomenon first described by Spetzler
and which was called the ‘normal perfusion            It is essential to exclude a cause for the subarach-
pressure breakthrough’ theory. Methods that           noid haemorrhage and this may entail repeating
have been employed to avoid this complica-            the cerebral angiography, particularly if the ini-
tion include preoperative and intraoperative          tial angiography has been in some way imperfect
embolization and staged excision of the               and especially if not all the major vessel branches
malformation.                                         have been shown adequately. Systemic causes for
   The use of radiosurgical techniques, involving     the subarachnoid haemorrhage must be exclud-
either the gamma knife (a highly focused cobalt       ed, as well as rare causes such as pituitary
source of irradiation) or stereotactic radiosurgery   apoplexy.
using a linear accelerator, has been advocated for       The patient is managed symptomatically with
the treatment of small (less than 3 cm diameter),     bed rest until the headache has settled.
unruptured and surgically inaccessible arterio-
venous malformations with complete angio-
                                                      Further reading
graphic obliteration in greater than 80% of
lesions with a diameter of 3 cm or less at 3 years    Chyatte D, Fode N, Sundt T (1988) Early versus late in-
after radiation. However, as the radiotherapy ef-       tracranial aneurysm surgery in subarachnoid haem-
fect is slow, the patient remains at risk from          orrhage. Journal of Neurosurgery 69, 326–331.
haemorrhage for some years.                           Dorsch NWC, King MT (1994) A review of cerebral va-
                                                        sospasm in aneurysmal subarachnoid haemorrhage.
                                                        Journal of Clinical Neuroscience 1, 19–26.
Vein of Galen malformation                            Dorsch NWC, King MT (1994) A review of cerebral va-
                                                        sospasm in aneurysmal subarachnoid haemorrhage.
This unusual malformation results when arteries         Journal of Clinical Neuroscience 1, 78–92.
feed directly into the vein of Galen and produces     Dorsch NWC, King MT (1994) A review of cerebral va-
distinct clinical syndromes depending on the age        sospasm in aneurysmal subarachnoid haemorrhage.
at which the disease presents.                          Journal of Clinical Neuroscience 1, 151–160.
 SUBARACHNOID HAEMORRHAGE                                                                                  139


Drake CJ (1984) Early times in aneurysm surgery. Clini-     neurosurgical clipping versus endovascular coiling
  cal Neurosurgery 32, 41–50.                               in 2143 patients with ruptured intracranial
Freedman WA (1995) Linear accelerator radiosurgery          aneurysms: a randomised trial. Lancet 360,
  for arteriovenous malformations, the relationship of      1267–1273.
  size to outcome. Journal of Neurosurgery 82, 180–189.   Ljunggren B, Brandt L (1985) Timing of aneurysm
Heros RC, Tu YK (1987) Is surgical therapy needed for       surgery. Clinical Neurosurgery 33, 147–176.
  unruptured arteriovenous malformations? Neurology       Maraire JN, Awad IA (1995) Intracranial cavernous
  37, 279–286.                                              malformations: lesion behaviour and management
Heros RC, Zervas NT, Varsos V (1983) Cerebral va-           strategies (Review). Neurosurgery 37, 591–605.
  sospasm after subarachnoid haemorrhage: an up-          The International Study of Unruptured Aneurysm
  date. Annals of Neurology 14, 599–603.                    Investigators (1998) Unruptured intracranial
Jane JA et al. (1985) The natural history of aneurysms      aneurysms — risk of rupture and risks of surgical in-
  and arteriovenous malformations. Journal of Neuro-        tervention. New England Journal of Medicine 339 (24),
  surgery 62, 321–323.                                      1725–1733.
Kaye AH, Black P McL. (2000) Operative Neurosur-          Weir B (2002) Unruptured intracranial aneurysms; a re-
  gery. Churchill Livingstone, London, New York,            view. Journal of Neurosurgery 96, 3–42.
  Edinburgh.                                              Weir B, MacDonald MD (1992) Cerebral vasospasm.
International subarachnoid aneurysm trial (ISAT) of         Clinical Neurosurgery 40, 40–56.
                           CHAPTER 10


 10                        Stroke
                           Stephen M. Davis




                                                      blood into the surrounding tissues. The term
Introduction and terminology
                                                      ‘haemorrhagic infarction’ is used to describe
Stroke is the third most common cause of death in     an infarct into which there has been a secondary
most Western countries and the commonest              extravasation of blood. Although subarach-
cause of chronic adult disability. In many West-      noid haemorrhage (SAH) may not be associat-
ern countries, there has been an impressive fall in   ed with a focal neurological deficit, it is usually
population-based stroke mortality over the past       categorized as a stroke subtype. Old and mis-
few decades, averaging 4–5% each year. This has       leading terms such as ‘CVA’ (cerebrovascular
been chiefly attributed to the more effective          accident) and ‘RIND’ (reversible ischaemic
recognition and treatment of hypertension and         neurological deficit) have generally been aban-
other risk factors. Despite this progress, with the   doned.
increasing life expectancy of the population, a
marked increase in stroke prevalence has been
                                                      Stroke prevention
predicted. Stroke is generally a disease of ageing,
but young adults are also affected, with a some-      Stroke prevention involves primary and sec-
what different pathogenetic spectrum. The over-       ondary strategies. Primary prevention includes
all approach to stroke has undergone a dramatic       lifestyle modification and treatment of risk fac-
change in recent years, with important recent ad-     tors in individuals who have not experienced
vances in prevention strategies, the widespread       cerebrovascular symptoms. Risk factor manage-
introduction of acute stroke units, the application   ment can be categorized into the high risk ap-
of new imaging technologies and the introduc-         proach (detecting and treating patients at high
tion of thrombolysis for selected patients with       risk of stroke, such as those with atrial fibrillation
acute ischaemic stroke.                               or hypertension) and the mass or population ap-
   The term ‘stroke’ is used to describe a sudden     proach (such as reducing salt intake and hence
neurological deficit of vascular aetiology last-      attempting to lower blood pressure in the entire
ing more than 24 hours. A transient ischaemic         population). These two approaches are comple-
attack (TIA) indicates a transient neurological       mentary, although the population approach has
deficit of vascular origin lasting less than 24       the potential of much greater impact on stroke
hours, although many patients with TIAs last-         rates in society as a whole.
ing more than minutes have in fact suffered              Secondary prevention involves the use of
some neuronal damage and this time definition         strategies in a symptomatic individual after a
has been recently challenged. Stroke is classi-       stroke or TIA, generally tailored to the specific
fied as cerebral infarction or ischaemic stroke,      type of cerebrovascular pathology. Most stroke
signifying ischaemic brain damage, or cerebral        prevention studies have focused on a reduction
haemorrhage, where the primary pathology in-          in the incidence of stroke, neurological disabil-
volves vascular rupture and extravasation of          ity and other vascular endpoints. Recently,

140
 STROKE                                                                                                   141



  Table 10.1 Modifiable risk factors for ischaemic stroke.

  Risk factor                                                 Relative risk of stroke          Benefits proven

  Smoking                                                     1.0–4.0                          Yes
  Hypertension                                                2.0–4.0                          Yes
  Diabetes                                                    2.0–8.0                          Yes
  Heart disease (particularly atrial fibrillation)             6.0–8.0                          Yes
  Hypercholesterolaemia                                       1.0–2.0                          Yes




prevention of vascular dementia has also been               deep perforating vessels (intracerebral haemor-
recognized as an important additional goal.                 rhage).
                                                               A meta-analysis in 1990 showed that modest
                                                            reduction of systolic blood pressure (BP) re-
Primary prevention
                                                            duces stroke risk by about 40%. This benefit also
Primary prevention strategies target the modifi-             extends to those with mild hypertension. Most
able risk factors for stroke (Table 10.1). In the con-      of these earlier trials of antihypertensive agents
sideration of risk factors and stroke, the                  involved beta-blockers and diuretics, rather
population attributable risk is a useful concept            than the newer agents such as the angiotensin-
in evaluating the overall importance of a risk fac-         converting enzyme inhibitors, angiotensin II
tor, combining the relative risk of the individual          receptor blockers and calcium channel
factor and its prevalence.                                  antagonists. Blockade of the angiotensin recep-
                                                            tor has theoretical appeal, with potential bene-
Age and gender                                              fits beyond blood pressure reduction. However,
In general, the frequency of stroke increases with          there is still uncertainty about the relative bene-
advancing age. Overall, male gender is associat-            fits of different classes of antihypertensive
ed with increased stroke risk. Among older pa-              agents. Some still advocate diuretics as first-line
tients there is a slightly higher rate of stroke in         antihypertensive agents. One study suggested
females, but this may simply reflect the greater             class-specific benefits for angiotensin receptor
longevity of women.                                         blockade over beta-blockers, but recent meta-
                                                            analysis shows that the degree of benefit is not
Hypertension                                                related to drug class, but rather the extent of
Hypertension is the most important risk factor              blood pressure reduction.
for both cerebral infarction and haemorrhage.
The population attributable risk from hyperten-             Atrial fibrillation
sion has been estimated as 26%. Many popula-                Valvular heart disease has long been recognized
tion studies have demonstrated an increased                 as a cause of cerebral embolism. The decline in
frequency of stroke with both systolic and dias-            the incidence of rheumatic heart disease, associ-
tolic hypertension. Hypertension is correlated              ated with a 17-fold increase in stroke risk in those
with common pathogenetic stroke mechanisms.                 with atrial fibrillation, may have contributed to
These include cardiac disease (risk of cerebral             the reduction in population-based stroke mortal-
embolism), intracerebral small vessel disease               ity. Non-valvular atrial fibrillation (NVAF) is
(lacunar infarction, intracerebral haemorrhage),            now the most common cause of cardiogenic cere-
extracranial     atherosclerosis    (thromboem-             bral infarction in Western countries, associated
bolism), development of cerebral aneurysms                  with a 6–8 times increase in stroke risk. NVAF is
(subarachnoid haemorrhage) and rupture of                   age-related, affecting approximately 1.7% of the
 142                                                                                     CHAPTER 10


population aged 60 years and rising to 11% in          tion. Chronic smoking also lowers cerebral blood
those older than 75 years.                             flow.
   Clinical trials have demonstrated a relative
risk reduction of about 70% in the stroke rate in      Hypercholesterolaemia
patients with NVAF without prior cerebrovascu-         Hyperlipidaemia, and in particular hypercholes-
lar symptoms, treated with warfarin. In compli-        terolaemia, is a much weaker risk factor for
ant patients, there are low risks of major             stroke than ischaemic heart disease in epidemio-
haemorrhagic complications with careful moni-          logical studies. However, trials of the HMG-CoA
toring, with approximately a 1% major haemor-          reductase inhibitors (statins), which produce po-
rhage rate per year, aiming at an international        tent cholesterol reduction, have been shown in
normalized ratio (INR) in the 2–3 range. There is      high-risk patients (generally with ischaemic
a modest benefit with aspirin, but it is only about     heart disease) and cholesterol ranging from nor-
half as effective as warfarin. Aspirin is generally    mal to high levels, to markedly reduce the risk of
used when patients are not candidates for antico-      stroke. The efficacy of these drugs may also re-
agulation, and in those under the age of 60 years      flect other pharmacological actions, including ef-
with atrial fibrillation, but without risk factors or   fects on the endothelium and atherosclerotic
echocardiographic features of structural heart         plaque.
disease (termed ‘lone atrial fibrillation’). War-
farin is often combined with aspirin to convey         Heavy alcohol use
additional benefit in patients with prosthetic          Heavy alcohol usage is associated with an in-
heart valves and atrial fibrillation or prior throm-    creased risk of both ischaemic and haemorrhagic
bo-embolism.                                           stroke, particularly subarachnoid haemorrhage.
                                                       In contrast, some studies have suggested that low
Diabetes                                               to moderate alcohol intake is stroke-protective.
Diabetes mellitus is associated with a two- to
fivefold increase in the rate of stroke. This is due    Miscellaneous factors
to both accelerated atherogenesis in the extracra-     Polycythaemia is an important and treatable risk
nial and intracranial arteries (macrovascular dis-     factor for cerebral infarction. Leisure-time physi-
ease) and the development of small vessel,             cal activity has been linked with reduced risk of
lacunar infarcts (microvascular disease). The          ischaemic stroke. There has been interest in the
prognosis of acute stroke in diabetic and other        therapeutic role of vitamins such as folic acid and
hyperglycaemic patients is worse than in those         B6, given epidemiological links between homo-
with normal blood sugar levels, probably due to        cystinaemia and stroke, but further trial results
the production of excessive lactate and increased      are awaited.
tissue damage. Optimal control of blood glucose
is likely to reduce the vascular complications of      Asymptomatic carotid disease
diabetes.                                              Carotid bruits occur in at least 4% of asympto-
                                                       matic adults over the age of 40 years, of which
Smoking                                                only a proportion are due to severe internal
Smoking is an important risk factor for stroke,        carotid stenosis. There have been a number of
particularly ischaemic stroke and subarachnoid         randomized controlled trials to determine
haemorrhage. It at least doubles stroke risk in        whether carotid endarterectomy (CEA) is indi-
both men and women. Like diabetes, smoking             cated in patients with severe but asymptomatic
accelerates atherogenesis and has intravascular        carotid stenosis (Fig. 10.1). The most definitive of
effects on platelet adhesion and viscosity. The in-    these indicated that there was an 11% stroke rate
travascular effects appear to be particularly im-      in the hemisphere ipsilateral to a 60% or greater
portant, evidenced by a substantial reduction of       carotid stenosis, reduced significantly to 5% by
stroke risk within 2–4 years of smoking cessa-         CEA in good surgical hands. However, this study
 STROKE                                                                                                 143


                                                         indications for carotid endarterectomy and the
                                                         introduction of cerebral angioplasty/stenting.

                                                         Antiplatelet strategies
                                                         The benefits of aspirin were established by
                                                         pivotal studies more than 25 years ago, with a
                                                         relative risk reduction of about 22% for the com-
                                                         posite outcomes of stroke, death or myocardial
                                                         infarction. Meta-analysis of the 10 secondary pre-
                                                         vention trials where aspirin was tested against
                                                         placebo in secondary stroke prevention showed
                                                         no discernible difference between high, medium
                                                         and low doses of aspirin. The consensus amongst
                                                         stroke clinicians today is that doses in the ‘low’
                                                         50–325 mg range are preferred, given that bleed-
                                                         ing risk is lower than the high-dose regimens.
                                                            The effectiveness of aspirin depends on the in-
                                                         hibition of platelet cyclo-oxygenase, but other an-
                                                         tiplatelet strategies with differing actions have
                                                         also been proven in stroke prevention. Unlike as-
                                                         pirin, clopidogrel inhibits platelet ADP. It was
                                                         shown in the CAPRIE trial to be more effective
                                                         than aspirin in overall vascular protection in
                                                         high-risk patients, with a relative risk reduction
Fig. 10.1 Arterial digital subtraction angiogram         of 8.7% for clopidogrel over aspirin. If one as-
demonstrating severe, proximal internal carotid artery
                                                         sumes about a one-quarter reduction of all vascu-
stenosis (arrow).
                                                         lar events in high-risk patients with aspirin, this
                                                         can be improved to approximately one-third
                                                         with clopidogrel. However, because of the small
also confirmed that the natural history of asymp-         absolute risk reduction (approximately 0.5% per
tomatic carotid stenosis was relatively benign. A        year) and the cost of the drug, clopidogrel tends
large number of operations are required in stroke        to be used as second-line therapy in patients who
prevention, about 83 to prevent one stroke per           are either intolerant of aspirin or are aspirin fail-
year. The place of CEA for asymptomatic carotid          ures. Clopidogrel and aspirin have an additive
stenosis therefore remains controversial, and            or synergistic effect because of their different
should only be considered in highly selected             actions. This combination approach has been
patients.                                                proven in acute coronary syndromes and is cur-
                                                         rently being tested in patients with prior TIA or
                                                         stroke.
Secondary prevention
                                                            Dipyridamole reduces platelet aggregation by
Secondary prevention strategies after stroke or          raising the antiaggregating effects of cyclic AMP
TIA, unlike the primary prevention techniques,           and cyclic GMP. A synergistic effect between as-
are tailored to the underlying stroke pathology.         pirin and dipyridamole was demonstrated in the
The range of secondary prevention strategies             ESPS 2 trial. The relative stroke risk was
continues to expand (Table 10.2). These include          reduced by 18% with aspirin, 16% with dipyri-
the introduction of a number of new antiplatelet         damole, and an apparently additive 37% with the
strategies, proof of the efficacy of warfarin in          combination of the two therapies. This combina-
non-valvular atrial fibrillation, clarification of the     tion antiplatelet approach is also widely used.
 144                                                                                                 CHAPTER 10



  Table 10.2 Therapeutic opportunities in secondary prevention.

  Strategy                                    Indication                                       Level of evidence

  Antiplatelet and anticoagulant strategies
  Aspirin                                                                                      I
  Clopidogrel                                                                                  II
  Dipyrimadole                                                                                 II
  Combination antiplatelet strategies                                                          II (combined aspirin/
                                                                                                  dipyrimadole)
  Glycoprotein IIb/IIIa inhibitors                                                             Discarded I
  Warfarin                                    Non-valvular atrial fibrillation, valvular        I
                                               heart disease

  Surgical and interventional strategies
  Carotid endarterectomy                      Symptomatic carotid stenosis (< 70%)             I
                                              Asymptomatic carotid stenosis                    II
  Angioplasty/stenting                        Not yet proven; possible role in patients with   III
                                                extracranial, intracranial symptomatic
                                                atherosclerotic stenosis
                                              No randomized, controlled trials to date
                                                confirming benefits

  Quality of evidence ratings
  Level I: Evidence is obtained from a systematic review of all relevant randomized controlled trials.
  Level II: Evidence is obtained from at least one properly designed randomized controlled trial.
  Level III: Evidence is obtained from well-designed controlled trials without randomization; from well-
  designed cohort or case–control analytical studies.
  Level IV: Opinions of respected authorities, based on clinical experience, descriptive studies or reports of
  expert committees.




The platelet glycoprotein IIb/IIIa receptor is the             Carotid endarterectomy
final common pathway of platelet aggregation.                   Two large trials (the North American Sympto-
Oral platelet GPIIb/IIIa antagonists prevent                   matic Carotid Endarterectomy Trial — NASCET
the binding of fibrinogen to platelets but have                 and the European Carotid Surgery Trial — ECST)
proved hazardous in patients with coronary or                  showed major benefits for carotid endarterecto-
cerebrovascular disease and have now been                      my over optimal medical therapy in patients
abandoned.                                                     with greater than 70% carotid stenosis and ei-
                                                               ther TIA or non-disabling stroke. In the
Warfarin                                                       NASCET study, an absolute risk reduction of
The European Atrial Fibrillation trial compared                17% over 18 months was achieved, indicating
warfarin, aspirin and placebo in secondary                     that one stroke could be prevented for every six
stroke prevention. Warfarin was substantially                  patients.
more effective than aspirin and is the recom-
mended strategy in anticoagulation candidates.                 Cerebrovascular angioplasty/stenting
However, warfarin is not superior to aspirin                   Percutaneous transluminal angioplasty is in-
in patients with symptomatic cerebral                          creasingly used for symptomatic and asympto-
atherosclerosis.                                               matic carotid stenosis, usually combined with
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endovascular stenting. However, there is limited      to detect infarction or non-vascular pathology,
proof of efficacy and safety compared with en-         carotid duplex Doppler to diagnose major
darterectomy. One trial showed that the benefits       carotid disease, and ECG, sometimes followed by
and risks of surgery and angioplasty/stenting         echocardiography, to diagnose atrial fibrillation
were approximately equivalent. Large trials are       or another cardioembolic source.
now being conducted in patients with sympto-
matic carotid stenosis, comparing stenting with
                                                      Carotid-territory TIAs
endarterectomy. Distal protection devices, which
trap embolic debris at the time of the procedure,     These are due to transient ischaemia in the retina
represent an important advance. Stenting has          or cerebral hemisphere. Transient monocular
also been used in small series of patients with       blindness (‘amaurosis fugax’) is due to a tran-
symptomatic intracranial stenoses, in whom            sient reduction in retinal perfusion produced by
optimal medical therapy has failed.                   embolism or haemodynamic failure. The patient
                                                      often describes a shade pulled down over one
                                                      eye. In clinical practice it is vital to determine
Acute stroke
                                                      whether a visual disturbance is truly monocular,
It is estimated that approximately 20 million         indicating retinal ischaemia, or binocular, often
strokes occur around the world each year, with 5      implicating the vertebrobasilar circulation.
million deaths. Many stroke patients are left         Hemispheric symptoms most commonly consist
with significant neurological disability that can      of transient dysphasia and varying degrees of
threaten their independence, ability to work          hemiparesis or hemisensory disturbance, either
and quality of life. Better acute stroke treatments   singly or in combination.
are improving this dismal picture.

                                                      Vertebrobasilar TIAs
The spectrum of transient ischaemic
                                                      These are often more complex than carotid terri-
attacks and stroke
                                                      tory events and usually include two or more of
Transient ischaemic attacks (TIAs) and com-           the following symptoms:
pleted cerebral infarcts are caused by similar        • binocular visual disturbance
pathological mechanisms, most commonly large          • vertigo
vessel atherosclerotic disease, cardioembolism        • diplopia
and small vessel lacunar disease. Patients with       • ataxia
TIAs and completed infarcts, whether large or         • bilateral weakness or paraesthesiae
small, have a similar prognosis, with a 5–10-fold     • deafness
annual increase in stroke risk. Both conditions       • tinnitus
should be regarded as medical emergencies.            • amnesia.
   While TIAs by convention last less than              These symptoms are produced by transient is-
24 hours, most last only minutes. The majority of     chaemia of the brainstem, occipital and medical
TIAs lasting more than 1–2 hours produce tissue       temporal lobes and upper spinal cord.
damage on sensitive brain imaging techniques,
such as magnetic resonance imaging. The old 24-
                                                      Classification and pathogenesis
hour definition is therefore increasingly criti-
                                                      of stroke
cized and is not clinically useful. The recognition
of patients with minor ischaemic deficits presents
                                                      Cerebral infarction (ischaemic stroke)
a vital opportunity for prevention of major
stroke. Patients with TIAs should be urgently         Cerebral infarction accounts for approximately
evaluated within 24 hours of the episode. Investi-    80% of stroke patients and may be classified ac-
gations would typically include a CT or MR scan       cording to anatomical location or pathogenesis. It
 146                                                                                          CHAPTER 10


is useful to incorporate both classifications when       syndromes (see below). The obstruction of the
considering stroke in a particular patient.             origins of several of the deep perforating
                                                        branches can produce a larger subcortical infarct
Anatomical classification (Table 10.3)                   termed a striatocapsular infarct.
The anatomical location refers to the specific
arterial territory (e.g. internal carotid vs. verte-    Pathogenetic classification
brobasilar, anterior cerebral vs. middle cerebral)      Greater emphasis is now placed on the pathogen-
or specific location within the brain (e.g. lateral      esis of cerebral infarction, as this is useful for the
medullary syndrome, ventral pontine infarction          selection of secondary prevention therapies. This
or internal capsular infarction). Infarction most       classification is often referred to as the TOAST
commonly occurs in the middle cerebral arterial         system, after the TOAST trial.
territory and can be classified as cortical or deep      1 Large artery atherosclerosis.
(subcortical). The cortical middle cerebral syn-        2 Cardiogenic embolism.
dromes depend on whether a small branch has             3 Lacunar infarction.
been occluded, or whether one or both of the            4 Rare causes (e.g. dissection, vasculitis, pro-
main two divisions of the middle cerebral artery        thrombotic states).
is involved, the superior or inferior division.         5 Unclassified:
   Subcortical infarcts occur in the territory of the      • despite adequate investigation
deep perforating vessels supplying the internal            • due to inadequate investigation.
capsule, thalamus, basal ganglia and brainstem.
   The occlusion of a single perforating vessel         Large artery atherosclerosis (Figs 10.1–10.3)
produces a small deep infarct, less than 1.5 cm in      The development of extracranial atherosclerotic
diameter, called a lacunar infarct, particularly if     plaque produces a progressive arterial stenosis.
associated with one of the five classical clinical       Subsequent plaque complications include ulcera-




  Table 10.3 Anatomical stroke syndromes.

  Arterial territory                     Stroke syndrome

  Internal carotid artery                May be asymptomatic. Mixture of middle and anterior cerebral
                                          artery syndromes

  Middle cerebral artery occlusion       Contralateral hemiplegia (arm often more affected than leg),
                                           hemianaesthesia, homonymous hemianopia, aphasia,
                                           inattention, cortical sensory loss

  Anterior cerebral artery occlusion     Hemiparesis, chiefly in the leg

  Posterior cerebral occlusion           Homonymous hemianopia, disconnection syndromes,
                                          hemianaesthesia, amnesia, midbrain and thalamic syndromes

  Vertebrobasilar thrombosis (basilar    Quadriparesis, bulbar paralysis, impaired gaze, cortical blindness,
    occlusion)                            coma

  Ventral pontine infarction             Quadriparesis, bulbar paralysis, absent horizontal but retained
                                          vertical gaze. Normal conscious state; able to blink to command
                                          (‘locked in’ syndrome)

  Lateral medullary syndrome             Ipsilateral ataxia, Horner’s syndrome, nystagmus, facial numbness,
                                           9th and 10th nerve palsies, contralateral spinothalamic loss
 STROKE                                                                                                 147


tion, intraplaque haemorrhage and superim-                 stenosis and the absence of a cardiac source. An-
posed platelet–fibrin thrombus formation.                   terior circulation infarcts typically involve the
Stroke is most often due to the development of             cerebral cortex. Prodromal TIAs in the same arte-
thrombus (Fig. 10.4) followed by propagation               rial territory are another pointer.
and distal thromboembolism into the intracra-
nial vessels, sometimes embolism composed of               Cardiogenic embolism (Fig. 10.6)
atheromatous debris, or haemodynamic failure               A variety of cardiac diseases affecting the cardiac
due to the reduction of cerebral perfusion in the          walls, valves or chambers can lead to cerebral
arterial border zones (borderzone or watershed             embolism. These include:
infarction). Primary intracranial atherosclerosis          • non-valvular atrial fibrillation (the most
and atherothrombosis is rare in Caucasian popu-            common)
lations, but more common in African, African-              • valvular heart disease
American and Asian stroke patients (Fig. 10.5).            • myocardial infarction with ventricular throm-
   Clinical features include demonstration of rel-         bus formation
evant arterial pathology with 50% or greater               • post-cardiac surgery (valvular surgery or coro-
                                                           nary artery bypass grafts)
                                                           • prosthetic cardiac valves
                                                           • infective endocarditis
                                                           • atrial myxoma
                                                           • cardiomyopathy
                                                           • septal defect with paradoxical embolism.
                                                             Clinical features include delineation of a car-
                                                           diac source and lack of evidence of large artery
                                                           disease. Similarly, the cerebral cortex is usually
                                                           involved.

                                                           Lacunar infarction (Fig. 10.7)
                                                           The occlusion of single deep perforating arteries
                                                           supplying the internal capsule, basal ganglia or
                                                           brainstem can lead to the development of small
                                                           lacunar infarcts. These are most commonly the
                                                           result of hypertensive disease, which produces
Fig. 10.2 Carotid ultrasound of the carotid bifurcation,   localized arterial wall pathology, termed lipo-
demonstrating an ulcerated stenotic plaque (arrows) at     hyalinosis, in these small penetrating arteries, or
the common carotid bifurcation.                            localized microatheroma. Lacunar infarcts are




Fig. 10.3 Diffusion-weighted
imaging scan (left image)
showing large acute middle
cerebral artery (MCA) cortical
infarct. Magnetic resonance
angiography (right image)
shows lack of flow in the left
MCA.
 148                                                                                  CHAPTER 10




                                                   Fig. 10.6 Echocardiogram demonstrating clot (CL) in
                                                   left ventricle (LV).




Fig. 10.4 Internal carotid atherothrombosis from
autopsy specimen.


                                                   Fig. 10.7 Diffusion-weighted imaging scan showing
                                                   acute left thalamic lacunar infarct (hyperintense
                                                   lesion).


                                                   less often due to embolism from a proximal
                                                   source such as extracranial atherosclerosis or in-
                                                   tracardiac thrombus.
                                                      Classical lacunar syndromes include pure
                                                   motor hemiparesis, pure sensory stroke, sensori-
                                                   motor stroke, ataxic hemiparesis and the
                                                   dysarthria/clumsy hand syndrome. Clinical
                                                   pointers include clinical diagnosis of one of the
                                                   classical syndromes, usually exclusion of a large
                                                   artery or cardiac source and ideally neuroimag-
                                                   ing confirmation of a small, deep infarct.


Fig. 10.5 Magnetic resonance angiography           Oxfordshire classification
demonstrating severe distal vertebral/proximal     Another commonly used stroke classification,
basilar artery stenosis (arrow).                   termed the Oxfordshire classification, divides
                                                   ischaemic stroke into TACI (total anterior circula-
                                                   tion infarction) (Fig. 10.8), PACI (partial anterior
                                                   circulation infarction), POCI (posterior circula-
                                                   tion infarction) and LACI (lacunar infarction).
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Fig. 10.8 CT scan showing severe left middle cerebral
cortical infarction. Note sparing of anterior and
posterior cerebral arterial territories.
                                                        Fig. 10.9 CT scan showing hypertensive putaminal
                                                        haemorrhage.
This classification is also useful and the subtypes
correlate with prognosis.


Cerebral haemorrhage (haemorrhagic stroke)
Cerebral haemorrhage is generally classified into
intracerebral and subarachnoid haemorrhage.

Intracerebral haemorrhage (Figs 10.9–10.11)
Non-traumatic (primary) intracerebral haemor-
rhage is most commonly due to hypertension,
which leads to rupture of deep perforating arter-
ies in the putamen, thalamus, central white
matter, brainstem and cerebellum. The precise
mechanism of this vascular rupture is uncertain,
but may be related to the development of small
Charcot–Bouchard microaneurysms on the ves-
sel walls of these end-arteries, or direct rupture of
vessels affected by lipohyalinosis.
   ‘Lobar’ haemorrhage refers to superficial vascu-
lar rupture within the cerebral lobes, outside these
deep arterial territories. It is sometimes due to an
underlying structural lesion, such as an arteriove-
nous malformation, cerebral aneurysm, tumour,           Fig. 10.10 CT scan showing frontal and occipital lobar
vasculopathies or coagulation disorders. Amyloid        haemorrhages in a patient with amyloid angiopathy.
 150                                                                                    CHAPTER 10


                                                      identified at angiography. Some of these idio-
                                                      pathic bleeds are due to perimesencephalic
                                                      haemorrhage.


                                                      Modern principles of acute
                                                      stroke management
                                                      In Australia, the USA and Europe, guidelines for
                                                      acute stroke management have been developed,
                                                      based on the evidence from large controlled clin-
                                                      ical trials. Key principles of acute stroke manage-
                                                      ment include:
                                                      1 Urgent recognition of stroke symptoms by the
                                                      patient or their carer.
                                                      2 Urgent ambulance transport to a hospital with
                                                      adequate diagnostic facilities and organized
                                                      stroke care.
                                                      3 Urgent triage and investigation in the emer-
                                                      gency department including CT brain scanning.
                                                      4 Assessment for acute stroke therapy, particu-
                                                      larly thrombolysis.
Fig. 10.11 CT scan showing right cerebellar
                                                      5 Admission to a specialized stroke unit.
haemorrhage. The brainstem and 4th ventricle are
compressed.
                                                      Hospital arrival times: ‘Time is Brain’
angiopathy is an important cause of lobar cerebral    Delayed hospital arrival times are a worldwide
haemorrhage in elderly patients and is due to         problem. New therapies such as tPA (see below)
amyloid deposition in the walls of the cerebral ar-   are time-dependent. In many centres, only a
teries. These haemorrhages may be multiple and        quarter of stroke patients arrive within 3 hours.
typically occur in patients who are normotensive      Much of this delay is due to public ignorance and
and may show features of Alzheimer’s disease.         confusion about the nature of stroke and the need
   Clinical clues to ICH include the features of a    for urgent evaluation and treatment. However,
sudden rise in intracranial pressure with de-         professional nihilism is another barrier.
pressed conscious state, headache and vomiting.
The mortality is much higher than in ischaemic
                                                      Clinical assessment of stroke
stroke. However, patients with ICH may be sur-
prisingly alert and well looking. Conversely, pa-     The following questions should be considered in
tients with ischaemic stroke may have early           the management of any patient with a presumed
depression of conscious state. Hence, neuroimag-      stroke.
ing, usually with CT, is mandatory in all cases to    • Is it a stroke?
rapidly diagnose ICH.                                 • Is it an infarct or haemorrhage?
                                                      • Is the patient eligible for thrombolytic therapy
Subarachnoid haemorrhage (see Chapter 9)              or other urgent intervention?
Subarachnoid haemorrhage is classified accord-         • What is the arterial or anatomical localization
ing to pathological cause and site. The two most      and pathogenesis?
important identifiable causes include rupture of
a berry aneurysm and arteriovenous malforma-          Stroke and pseudostroke
tion, but in up to 15% of cases no bleeding can be    Non-vascular pathologies (‘pseudostroke’) such
 STROKE                                                                                               151


as cerebral tumour, subdural haematoma, ab-           area of the middle cerebral artery, are associated
scess, migraine, metabolic disturbances and           with a higher risk of haemorrhagic transforma-
epilepsy can mimic the stroke process. All pa-        tion. Up to 10% of ischaemic stroke patients can
tients with suspected stroke require an urgent CT     be treated in well-organized centres. In contrast
or MR scan to exclude non-cerebrovascular dis-        to the tPA trials, three trials evaluating the role of
orders, as well as to differentiate between infarct   intravenous streptokinase produced negative re-
and haemorrhage (Figs 10.8 and 10.9). Lumbar          sults, chiefly linked to the substantial risk of
puncture is reserved for those cases where            intracerebral haemorrhage associated with the
meningitis is considered (usually after a CT scan)    drug.
or where the diagnosis of subarachnoid haemor-           Direct infusion of thrombolytics via intra-arte-
rhage is still contemplated after a normal CT         rial catheters has been shown to be effective in
scan.                                                 one trial up to 6 hours after middle cerebral
                                                      artery occlusion. There is interest in experimental
The distinction between infarct and                   mechanical devices which can break up thrombi,
haemorrhage                                           with a much lower risk of cerebral haemorrhage.
The distinction between cerebral haemorrhage
and infarction is vital, as some haemorrhages are     Location and pathogenesis of infarction
considered for surgical evacuation, while pa-         Cortical infarcts (Fig. 10.3). Based on the clinical
tients with ischaemic stroke may be considered        examination, a distinction should be made
for thrombolysis or anticoagulation. While there      between an infarction in the carotid or in the
are clinical pointers (see above) this differentia-   vertebrobasilar territory. With regard to carotid
tion is usually based on CT scan findings. Al-         territory infarction, the presence or absence of
though CT scanning remains the workhorse for          cortical signs — dysphasia, apraxia, anosognosia
acute stroke assessment, recent studies indicate      (unawareness or denial of the stroke), sensory,
that MRI is at least as sensitive for intracerebral   motor or visual agnosia (inattention), acalculia,
haemorrhage as CT and far more sensitive for          right/left confusion, dysgraphia or cortical sen-
acute ischaemia. Patients with ischaemic stroke       sory loss (loss of two-point discrimination,
often have early infarct changes on CT, although      astereognosis, dysgraphaesthesia) — suggests an
these may be subtle. MRI with diffusion-              embolic source from either the extracranial ves-
weighted imaging (DWI) is increasingly used as        sels or the heart, rather than lacunar infarction.
this technique allows a sensitive diagnosis of           Subcortical infarcts (Fig. 10.7). As indicated ear-
cerebral ischaemia (Figs 10.3 and 10.7).              lier, lacunar infarcts (less than 1.5 cm in diameter)
                                                      rely on diagnosis of one of the classical lacunar
Is the patient eligible for thrombolysis?             syndromes. Cortical signs are not present. Lacu-
The thrombolytic agent tissue plasminogen acti-       nar syndromes reflect small vessel occlusions in
vator (tPA) has now been licensed in most parts       the internal capsule, thalamus and brainstem.
of the world as the first proven stroke drug thera-
py, given intravenously within 3 hours of stroke      Haemorrhage
onset in selected patients with ischaemic stroke.     Intracerebral haemorrhage (Fig. 10.9). As previous-
The approval of this acute therapy followed the       ly discussed, the rapid onset of a stroke with
positive results of a two-part pivotal trial, con-    early depression of conscious state favours the
ducted in the USA. Other European trials testing      diagnosis of a primary intracerebral haemor-
tPA up to 6 hours have shown a marked trend to        rhage. Primary intracerebral haemorrhage and
benefit over risk, and meta-analysis confirms the       aneurysmal subarachnoid haemorrhage can
3-hour window for tPA. Use of tPA increases the       overlap in their clinical presentations. For exam-
risk of symptomatic haemorrhagic complications        ple, a berry aneurysm can rupture primarily into
by three- to fourfold. Major early infarct changes    the brain parenchyma, presenting as an intra-
on CT, for example greater than one-third of the      cerebral haemorrhage, whereas a primary brain
 152                                                                                     CHAPTER 10


haemorrhage can rupture directly into the ven-        systematic overview of the benefits of stroke
tricular system and present with marked               units, it was shown that mortality could be re-
meningeal features due to subarachnoid blood.         duced by about 25%, also with evidence of re-
   For subarachnoid haemorrhage see Chapter 9.        duced disability. In addition, stroke units have
                                                      been found to reduce bed stay and hence hospital
                                                      costs.
Urgent assessment in the emergency
                                                         The components of team management in the
department
                                                      stroke unit include:
Rapid triage of suspected stroke patients should      1 Acute medical, surgical and nursing care.
be performed in an emergency department, with         2 Diagnosis of the pathological mechanism of
skilled medical evaluation and urgent investiga-      the stroke and the institution of tailored sec-
tions. These involve blood tests, including a         ondary prevention strategies.
blood glucose measurement to exclude hypogly-         3 Prevention, early detection and treatment of
caemia (which can mimic acute stroke), and an         complications such as aspiration pneumonia,
ECG to diagnose atrial fibrillation or acute my-       pressure sores, hyperglycaemia, seizures and
ocardial infarction, which can reveal the cause of    sepsis.
cerebral embolism. Most importantly, a CT brain       4 Use of measurement instruments and stroke
scan must be performed urgently in all patients       registers.
to differentiate between cerebral infarction and      5 Early integrated neurorehabilitation with eval-
cerebral haemorrhage. In addition, CT scanning        uation of premorbid status and therapy goals.
is essential to exclude the other brain pathologies   6 Involvement, education, and support for pa-
that can simulate stroke. As noted above, many        tient and family.
centres are now using acute MRI with DWI and          7 Early, coordinated discharge planning.
magnetic resonance angiography (MRA). Com-
puted tomographic angiography (CTA) is
                                                      Acute medical care
another useful tool. Duplex Doppler scanning is
of value in the diagnosis of large vessel athero-     Three key, evidence-based advances include the
sclerosis, while echocardiography (usually less       use of tPA, aspirin (see below) and stroke unit
urgent) can aid in the diagnosis of intracardiac      care. In the acute phase, close monitoring of vital
thrombi and valvular or cardiac wall kinetic ab-      and neurological signs is paramount, given that
normalities. Transoesophageal echocardiography        about a third of stroke patients deteriorate after
is superior to transthoracic echocardiography.        admission to hospital. Cardiac monitoring is
                                                      useful for many acute stroke patients. Initial clin-
                                                      ical evaluation should involve assessment of the
Acute stroke units
                                                      patient’s function and clinical state before the
One of the most important developments in             stroke, the stroke type and pathogenesis, docu-
acute stroke management in recent years has           mentation of the nature and severity of neuro-
been the proven value of stroke units, based on       logical deficits, and comorbid diseases. Early
the results of clinical trials which have compared    mobilization, range of motion exercises for
organized expert care in a special unit to the man-   hemiplegic limbs, frequent turning, fluid and
agement of patients in general medical wards.         nutritional maintenance, dysphasia manage-
The usual stroke unit model involves a geo-           ment, avoidance of aspiration, prevention of
graphical area in the hospital, incorporating a       deep venous thrombosis (DVT) and pneumonia,
skilled multidisciplinary stroke team, led by a       management of incontinence, treatment of uri-
neurologist or other physician with expertise in      nary tract infections and other causes of fever,
stroke management. Vascular surgeons and neu-         and maintenance of skin integrity are all key
rosurgeons should be readily available for con-       planks in the team treatment of the acute stroke
sultation and intervention in selected cases. In a    patient.
 STROKE                                                                                            153


  Patients should have oximetry, but there is no      tional Stroke Trial (IST) evaluated unmoni-
evidence of the value of routine supplemental         tored, subcutaneous heparin up to 48 hours
oxygen by mask or nasal prongs. Patients should       after stroke onset and showed that a slight re-
be well hydrated using normal saline rather than      duction in recurrent stroke was offset by an in-
glucose-containing solutions, because of the haz-     creased risk of haemorrhagic transformation.
ards of even mild degrees of hyperglycaemia. In       The rate of early, recurrent embolism in patients
general, blood pressure should not be acutely         with atrial fibrillation was much lower in recent
lowered, because this can compromise cerebral         trials than in a number of earlier clinical
perfusion in acute stroke. Hypertension is usual      studies.
in acute stroke and this usually settles sponta-         Systematic overview of the available evidence
neously over 2–3 days. We routinely use com-          leads to the conclusion that heparin is not
pression stockings and usually low-dose               generally indicated for most patients with acute
heparin, or low molecular weight heparin or he-       ischaemic stroke, but heparin should be
parinoid, in DVT prophylaxis. Airway assess-          considered for selected patients with non-
ment should be an urgent priority to avoid            disabling ischaemic stroke and a very high risk
aspiration pneumonia. We generally use naso-          of recurrent embolism.
gastric feeding after 24–48 hours if the patient’s
bulbar function is compromised.
                                                      Acute aspirin
  Adverse prognostic factors include advancing
age, depression of conscious state, severity of       Two large trials (the International Stroke Trial
neurological deficit, conjugate gaze palsy and         and the Chinese Acute Stroke Trial) both showed
early urinary incontinence. Causes of mortality       that, as for acute myocardial infarction, aspirin
in stroke patients are predominantly neurologi-       administered within 48 hours of stroke onset pro-
cal (transtentorial herniation) in the 1st week,      duced a modest improvement in outcomes at 6
and due to secondary systemic factors in the 2nd      months. Hence, aspirin should be used routinely
and 3rd weeks such as pneumonia, pulmonary            in acute ischaemic stroke, unless thrombolysis is
embolism and cardiac causes.                          being used.


Progressing stroke                                    Neuroprotective therapies
A deteriorating neurological deficit is seen in        A complex cascade of biochemical changes oc-
about one-third of stroke patients. Cerebral oede-    curs in stroke, secondary to the initial ischaemia.
ma, with progressive elevation of intracranial        Ischaemic brain injury is associated with ele-
pressure, is an important cause of death. Howev-      vated levels of the excitatory neurotransmitters
er, this oedema is generally cytotoxic and clinical   glutamate and aspartate. These lead to exces-
trials have demonstrated that corticosteroids are     sive stimulation of the N-methyl D-aspartate
of no value in either cerebral infarction or haem-    (NMDA) receptor on the cell surface. This activa-
orrhage. Intravenous mannitol and glycerol are        tion is followed initially by an influx of sodium
sometimes empirically used, but their value has       and water into the cells and secondly by a sudden
not been proven. In highly selected young pa-         rise in intracellular calcium. A range of neuropro-
tients with severe, early brain oedema, surgical      tective compounds has been designed to inhibit
decompression with hemicraniectomy should be          various points in the excitotoxic cascade. These
considered.                                           include calcium channel and NMDA antagonists,
                                                      glutamate release inhibitors, glycine antagonists,
                                                      free radical scavengers, inhibitors of the neu-
Heparin
                                                      trophil influx into the ischaemic region and vari-
Heparin has been the most widely used un-             ous growth factors. To date, none of these
proven therapy in most countries. The Interna-        compounds have proven effective in adequately
 154                                                                                      CHAPTER 10


powered, Phase III clinical trials, but there are
                                                       Young adult and rarer causes of stroke
several ongoing studies. Other approaches in-
clude the combination of thrombolysis with neu-        Stroke in young adults is due to a wide spectrum
roprotective drugs.                                    of causes. Those presenting with cerebral haem-
                                                       orrhage usually have an underlying lesion such
                                                       as an aneurysm or vascular malformation. Pa-
Cerebral hemorrhage
                                                       tients presenting with cerebral infarction have a
While routine surgical evacuation of haematoma         range of pathologies somewhat different to those
is unproven, we consider evacuation in selected        in older age groups, including:
patients with cerebral haemorrhage, particularly       • migraine
in the cerebellum, as well as younger patients         • oral contraceptive pill
with lobar haemorrhage. The general principles         • mitral valve prolapse
of acute stroke management apply equally to in-        • cerebral vasculitis
tracerebral haemorrhage as to infarction.              • extracranial arterial dissection
                                                       • fibromuscular dysplasia
                                                       • moya-moya disease
Prevention of recurrent stroke — secondary
                                                       • hypercoagulability states.
stroke prevention
                                                          Consequently, these patients require more in-
Patients with symptomatic high-grade carotid           tensive investigation than many older stroke pa-
stenosis should be considered for subacute             tients. Some form of cerebral angiography and
carotid endarterectomy. While surgery is               transoesophageal echocardiography are virtual-
awaited, or if endarterectomy is inappropriate,        ly mandatory in all cases. Many patients will also
antiplatelet therapy should be instituted. In          require a lumbar puncture, to look for evidence
cardioembolic stroke, there is uncertainty as to       of an underlying inflammatory condition, and
the optimal timing of anticoagulation, particu-        detailed haematological investigations directed
larly in patients with atrial fibrillation. Our ap-     at diagnosis of a hypercoagulability state.
proach is to employ heparin acutely if the patient
has a mild deficit and there is a high risk of recur-
                                                       Migraine
rent embolism. Many patients with atrial fibrilla-
tion are commenced on warfarin 7–10 days after         Migraine is a well-recognized cause of stroke in
onset, without prior heparin, because of the risk      young adults, but the precise mechanism of in-
of haemorrhagic transformation. Lacunar in-            farction is unclear. Although vasospasm is
farcts are less commonly embolic and generally         usually postulated, it has only rarely been
have a good prognosis.                                 demonstrated on cerebral angiography in pa-
                                                       tients with migraine and stroke. The diagnosis of
                                                       migraine as the cause of infarction should only be
Post-stroke rehabilitation
                                                       made in a migraineur who has a persisting neu-
While beyond the scope of this review, rehabilita-     rological deficit, in the wake of a classical attack,
tion after stroke is of immense importance. Many       and where other causes have been excluded by
models of care have been developed, including          detailed investigations, including angiography
home-based care as well as the more common in-         and echocardiography.
patient and outpatient models. Increasingly,
comparative trials of different therapeutic proto-
                                                       Oral contraceptive pill
cols are being conducted to provide a more ratio-
nal evidence-based approach to post-stroke             Oral contraceptive agents, particularly the high-
rehabilitation. In optimal stroke care, the rehabil-   er-dosage oestrogen-containing forms which
itation team should be integrated into the acute       can increase blood coagulability, have been
stroke unit.                                           linked with stroke. However, the relative risk of
 STROKE                                                                                             155


the oral contraceptive pill is probably very small,   tients with extracranial artery inflammation,
and should not be assumed to be the cause of a        headache, systemic symptoms and an elevated
young adult stroke without exclusion of other         erythrocyte sedimentation rate. The chief compli-
causes.                                               cation is ischaemic optic neuropathy due to in-
                                                      farction of the optic nerve, but cerebral infarction
                                                      occasionally occurs due to involvement of the
Cardiac causes
                                                      vertebral arteries. Ophthalmic herpes zoster can
Mitral valve prolapse is a common echocardio-         be followed by middle cerebral arteritis and
graphic finding in young women, but also fig-           infarction.
ures prominently in clinical series of young adult
stroke patients. Another cardiac embolic source
                                                      Dissection of the extracranial and
in young adults is patent foramen ovale (PFO)
                                                      intracranial arteries
with paradoxical embolism from the venous cir-
culation. The investigation of young adult stroke     Dissections are often due to trauma, although the
patients with transoesophageal echocardio-            preceding injury may be extremely mild. Recog-
graphy (TOE) not infrequently shows PFO at a          nized causes include motor car accidents with
higher rate than those seen in a control popula-      torsional neck or seat belt injuries, and cervical
tion, but their precise significance and therapeu-     manipulation. Spontaneous dissections also
tic implications are often uncertain. There is an     occur, some of these cases having an underlying
increased risk when PFO is associated with atri-      arteriopathy such as fibromuscular dysplasia.
al septal aneurysm. There are current trials eval-    Carotid artery dissection may be associated with
uating endovascular devices to close these            ocular pain and Horner’s syndrome. Neurologi-
lesions.                                              cal deficits may follow due to intimal thrombus
                                                      superimposed on the ruptured lining of the
                                                      artery and distal thromboembolism. The lateral
Cerebral vasculitis
                                                      medullary syndrome is a common clinical pre-
Cerebral vasculitis used to be commonly seen in       sentation of vertebral artery dissection. Diagno-
patients with an underlying basal meningitis due      sis is made by angiography or MRA, which
to tuberculosis or syphilis but it is now seen        shows a narrowed or tapered artery, the ‘string
mainly with aseptic, inflammatory conditions.          sign’, sometimes with the formation of an arterial
These include multisystem disorders such as           aneurysm. MRA may show intramural throm-
polyarteritis nodosa. Isolated central angiitis       bus. Anticoagulation is often used to prevent
(granulomatous angiitis) is an aseptic vasculitis     subsequent thromboembolic events. Intracranial
associated with multifocal cerebral infarcts and a    arterial dissections are much rarer, and can pre-
high mortality. The cause is unknown. As with         sent with brain ischaemia or subarachnoid
the other types of intracranial arteritis, some pa-   haemorrhage.
tients have ‘beading’ of arteries on angiography,
an excess of cerebrospinal fluid lymphocytes and
                                                      Fibromuscular dysplasia
an elevated erythrocyte sedimentation rate. De-
finitive diagnosis often depends on brain biopsy,      This arteriopathy chiefly affects females and
but a negative biopsy does not exclude the condi-     most commonly involves the distal portions of
tion. High-dose steroids are used, sometimes in       the extracranial carotid artery. It may be associat-
combination with other immunosuppressive              ed with renal fibromuscular dysplasia. It is usual-
agents, particularly cyclophosphamide.                ly asymptomatic, but is associated with an
   Cerebral arteritis can also be caused by illicit   increased risk of both TIAs and cerebral infarc-
drug use with heroin, oral or intravenous am-         tion. There is also an increased risk of subarach-
phetamines, cocaine and other agents. Giant cell      noid haemorrhage due to associated berry
arteritis (temporal arteritis) is seen in older pa-   aneurysms. The ischaemic events are probably
 156                                                                                       CHAPTER 10




Fig. 10.12 Cerebral angiography demonstrating
moya-moya disease.                                     Fig. 10.13 Sagittal MRI scan showing features of
                                                       cerebral venous thrombosis, with high signal (arrows)
                                                       due to blood clot in the superior sagittal sinus.
due to thromboembolism and occasionally arter-
ial dissection. Angiography demonstrates a clas-
sic saw tooth appearance. Treatment is usually
conservative with aspirin.
                                                       Cerebral venous thrombosis
                                                       Cerebral venous thrombosis is a rare type of
Moya-moya disease (Fig. 10.12)
                                                       stroke with variable clinical manifestations, but
Moya-moya disease is a rare obliterative arterial      increasingly recognized with the widespread use
condition where the terminal internal carotid ar-      of MRI. Septic and aseptic syndromes are recog-
teries are occluded and there is a fine, telang-        nized. Septic thrombosis is now very rare. It most
iectatic web of anastomotic, intracranial vessels      commonly involves the cavernous sinus but can
which produces the classic angiographic ‘puff of       also affect the superior sagittal and lateral
smoke’ appearance (Fig. 10.12). The posterior cir-     sinuses. Sources of infection include the face,
culation is usually spared. It is associated with an   paranasal sinuses, middle ear infection and bac-
increased risk of either cerebral infarction due to    terial meningitis. Aseptic cerebral venous throm-
brain ischaemia or haemorrhage due to rupture          bosis is most commonly seen in conditions
of the abnormal telangiectatic vessels. The cause      associated with hypercoagulability states such as
of the condition is unknown and medical therapy        the postpartum period, presence of the lupus an-
is ineffective. Surgical revascularization proce-      ticoagulant or the oral contraceptive pill. Clinical
dures constitute the mainstay of therapy.              features range from the insidious development of
                                                       headache and papilloedema, to more fulminant
                                                       focal syndromes in the cavernous sinus region,
Hypercoagulability states
                                                       hemiplegia, depressed conscious state, fever,
Disorders of blood haemostasis and coagulation         seizures, sinus tachycardia and meningismus.
are sometimes recognized as the cause of stroke        (Fig. 10.13). Therapy in septic cases is directed
in young adults. Various rare abnormalities of the     against the causative infection. Treatment in
coagulation process have been identified in some        aseptic cases involves the use of early anticoagu-
stroke patients. These include the presence of the     lation, which has been shown to improve the
lupus anticoagulant, which is an antiphospho-          outcome. Transdural thrombolysis is also used in
lipid antibody, activated protein C resistance,        selected cases, particularly when the patient’s
and deficiencies of protein S and C.                    condition worsens, despite heparin.
 STROKE                                                                                                        157


                                                             Furlan A, Higashida R, Wechsler L, Gent M, Rowley H,
Further reading
                                                               Kase C, Pessin M, Ahuja A, Callahan F, Clark WM,
Albers GW, Caplan LR, Easton JD, Fayad PB, Mohr JP,            Silver F, Rivera F (1999) Intra-arterial prourokinase
  Saver JL, Sherman DG; TIA Working Group (2002)               for acute ischemic stroke. The PROACT II study: a
  Transient ischemic attack — proposal for a new defin-         randomized controlled trial. Prolyse in Acute Cere-
  ition. New England Journal of Medicine 347, 1713–1716.       bral Thromboembolism. Journal of the American
Antiplatelet Trialists Collaboration (1994) Collabora-         Medical Association 282, 2003–2011.
  tive overview of randomised trials of antiplatelet         Heart Protection Study Collaborative Group (2002)
  treatment, Part 1. Prevention of death, myocardial in-       MRC/BHF heart protection study of cholesterol low-
  farction, and stroke by prolonged antiplatelet thera-        ering with simvastatin in 20536 high risk individuals:
  py in various categories of patients. British Medical        a randomized placebo-controlled trial. Lancet 360,
  Journal 343, 139–142.                                        7–22.
Atrial Fibrillation Investigators (1994) Risk factors for    International Stroke Trial Collaborative Group (1997)
  stroke and efficacy of antithrombotic therapy in atri-        The International Stroke Trial (IST): a randomised
  al fibrillation. Analysis of pooled data from five ran-        trial of aspirin, subcutaneous heparin, both, or nei-
  domized controlled trials. Archives of Internal              ther among 19 435 patients with acute ischemic
  Medicine 154, 1449–1457.                                     stroke. Lancet 349, 1569–1581.
Blood Pressure Lowering Treatment Trialists’ Collabo-        Madden KP, Karanjia PN, Adams HP Jr, Clarke WR
  ration (2003) Effects of different blood-pressure-low-       (1995) Accuracy of initial stroke subtype diagnosis in
  ering regimens on major cardiovascular events:               the TOAST study. Trial of ORG 10172 in acute stroke
  results of prospectively designed overviews of ran-          treatment. Neurology 45, 1975–1979.
  domised trials. Lancet 362, 1527–1535.                     Mohr JP, Thompson JL, Lazar RM, Levin B, Sacco RL,
Bucher HC, Griffith LE, Guyatt GH (1998) Effect of              Furie KL, Kistler JP, Albers GW, Pettigrew LC,
  HMG-CoA reductase inhibitors on stroke. A meta-              Adams HP Jr, Jackson CM, Pullicino P (2001) War-
  analysis of randomized controlled trials. Annals of          farin-Aspirin Recurrent Stroke Study Group. A com-
  Internal Medicine 128, 89–95.                                parison of warfarin and aspirin for the prevention of
CAPRIE Steering Committee (1996) A randomised,                 recurrent ischemic stroke. New England Journal of
  blinded, trial of clopidogrel vs. aspirin in patients at     Medicine 345, 1444–1451.
  risk of ischemic events (CAPRIE). Lancet 348,              The National Institute of Neurological Disorders and
  1329–1339.                                                   Stroke rt-PA Stroke Study Group (1995) Tissue plas-
CAVATAS Investigators (2001) Endovascular vs. surgi-           minogen activator for acute ischemic stroke. New
  cal treatment in patients with carotid stenosis in the       England Journal of Medicine 333, 1581–1587.
  Carotid and Vertebral Artery Transluminal Angio-           North American Symptomatic Carotid Endarterectomy
  plasty Study (CAVATAS): a randomised trial. Lancet           Trial Collaborators (1991) Beneficial effect of carotid
  357, 1729–1737.                                              endarterectomy in symptomatic patients with high
Diener H, Cunha L, Forbes C, Sivenius J et al. (1996) Eu-      grade carotid stenosis. New England Journal of
  ropean Stroke Prevention Study 2. Dipyridamole and           Medicine 325, 445–453.
  acetylsalicylic acid in the secondary prevention of        Stroke Unit Trialists’ Collaboration (1997) Collabora-
  stroke. Journal of Neurological Science 143, 1–13.           tive systematic review of the randomised trials of or-
European Carotid Surgery Trialists’ Collaborative              ganized inpatient (stroke unit) care after stroke.
  (ECST) Group (1991) MRC European Carotid                     British Medical Journal 314, 1151–1159.
  Surgery Trial: interim results for symptomatic pa-         Whisnant JP (1997) Modelling of risk factors for is-
  tients with severe (70–99%) or with mild (0–20%)             chemic stroke: The Wills Lecture. Stroke 28,
  carotid stenosis. Lancet 337, 1235–1243.                     1840–1844.
Executive Committee for the Asymptomatic Carotid             Zimmet PZ, Alberti KGMM (1997) The changing face of
  Atherosclerosis Study (1995) Endarterectomy for              macrovascular disease in non-insulin-dependent di-
  asymptomatic carotid artery stenosis. Journal of the         abetes mellitus: an epidemic in progress. Lancet 350,
  American Medical Association 273, 1421–1428.                 1–4.
                             CHAPTER 11


  11                         Developmental abnormalities



There are a number of neurosurgical conditions            Sylvian fissure
that are developmental in origin and that involve         The Sylvian fissure is the most common site for
the cranium, intracranial contents and spinal             arachnoid cysts and symptoms may become
column. The more important of these will be               manifest at any age. There is a marked male
described in this chapter.                                predominance. The most common presenting
                                                          features are:
                                                          1 Raised intracranial pressure:
Arachnoid cyst
                                                             (a) headaches
Arachnoid cysts are benign developmental cysts               (b) nausea
that occur along the craniospinal axis.                      (c) vomiting.
   Bright (after whom Bright’s disease was named)         2 Seizures.
was the first to accurately describe the condition in         Haemorrhage into the cyst following minor
1831. In 1964 Robinson described a large series of        head injury, although uncommon, will cause
middle cranial fossa arachnoid cysts and errone-          a sudden onset of neurological symptoms and
ously postulated that the primary defect was agen-        signs due to raised intracranial pressure and
esis of the temporal lobe; he later revised his opinion   compression of the underlying brain.
and recognized that the cysts were arachnoid mal-            However, as with arachnoid cysts in any other
formations. In 1958 Starkman recognized that the          location, the cyst may remain asymptomatic
cysts were developmental, were ‘intra-arachnoid’          throughout life.
in location, and that they resulted from splitting and
duplication of the arachnoid membrane.                    Cerebellopontine angle
   The cysts contain clear, colourless fluid which         The clinical features are similar to those of an
resembles normal cerebrospinal fluid; they occur           acoustic neuroma, with sensorineural hearing
in characteristic locations.                              loss as the most common initial symptom. A large
• Sylvian fissure                                   50%    cyst may cause minor impairment of 5th nerve
• Cerebellopontine angle                           10%    function, with depression of the corneal reflex
• Quadrigeminal                                    10%    and, rarely, ataxia due to cerebellar compression.
• Suprasellar                                      10%
• Vermian                                           8%    Suprasellar arachnoid cysts
• Cerebral convexity                                5%    The majority of cysts in this position present in
• Other                                             7%    children and adolescents and the clinical mani-
                                                          festations are due to:
                                                          • hydrocephalus
Clinical features
                                                          • visual impairment
The presenting features depend on the position            • endocrine dysfunction.
of the arachnoid cyst.                                      The hydrocephalus results from protrusion of

158
 DEVELOPMENTAL ABNORMALITIES                                                                             159


the cyst into the 3rd ventricle and occlusion of
the foramen of Monro. Visual failure results from
compression of the optic pathways, as well as
long-standing raised intracranial pressure caus-
ing optic atrophy. Endocrine dysfunction may be
due to intrasellar extension of the cyst and com-
pression of the pituitary gland, or long-standing
pressure on the hypothalamus, and is manifest as
hypopituitarism, growth retardation or isosexual
precocious puberty.

Cerebral convexity
In adults arachnoid cysts over the convexity
present with seizures, headaches or a progressive
hemiparesis. The presenting feature in infants
                                                             (a)
may be asymmetrical enlargement of the head.
  Convexity and Sylvian fissure cysts slightly
predispose the patient to subdural haematoma
formation.

Quadrigeminal cistern
The cysts arising in the supracollicular region
mimic pineal masses and the most common pre-
senting symptom is obstructive hydrocephalus
with raised intracranial pressure.


Radiological investigations
The computerized tomography scan or magnetic
resonance imaging will show the cyst in the
characteristic position and the fluid will have               (b)
the same density as CSF (Figs 11.1 and 11.2). The      Fig. 11.1 (a) Arachnoid cyst arising in the Sylvian
bone windows on CT scan or plain skull X-rays          fissure. (b) Suprasellar arachnoid cyst causing
may show remodelling and erosion of adjacent           obstructive hydrocephalus.
bone. The Sylvian fissure arachnoid cyst is char-
acteristically associated with expansion of the
                                                       Treatment
middle cranial fossa, elevation of the lesser wing
of the sphenoid, and outward expansion and             Arachnoid cysts are frequently diagnosed as an
thinning of the squamous portion of the temporal       incidental finding on CT scan. Surgery is not nec-
bone.                                                  essary if they are completely asymptomatic, with
   The suprasellar arachnoid cyst extending into       no distortion or enlargement of the ventricular
the 3rd ventricle and causing hydrocephalus may        system; the patient should be carefully reviewed
be difficult to differentiate from a dilated 3rd ven-   at regular intervals.
tricle due to aqueduct stenosis. MRI, particularly        There are two major surgical procedures for
sagittal views, will help to differentiate the         arachnoid cysts.
conditions.                                            1 Craniotomy, excision of the cyst wall and
                                                       opening of the membranes to allow drainage into
                                                       the basal cisterns.
 160                                                                                              CHAPTER 11


2 Shunting of the cyst into the peritoneal                 closely through both their underlying patho-
cavity.                                                    physiology and their clinical presentation.
  The type of surgical procedure will depend on               The Chiari malformation results from abnor-
the position of the cyst, the presenting features          malities at the craniocervical junction involving
and the surgeon’s preference.                              the caudal cerebellum, medulla and upper cervi-
                                                           cal region. In 1881 and 1885 Chiari reported the
                                                           anomaly of the cerebellum and medulla oblon-
Chiari malformations and
                                                           gata and described three types of malformation.
syringomyelia
                                                           The type I malformation consists of caudal dis-
Chiari malformations and syringomyelia are                 placement of the cerebellar tonsils below the
complex developmental malformations with a                 foramen magnum into the upper cervical canal.
wide spectrum of severity; they may present at             The type II malformation comprises caudal dis-
any stage of life. The conditions are linked               placement of the cerebellar vermis, 4th ventricle
                                                           and medulla oblongata below the foramen mag-
                                                           num. This is similar to the case reported by
                                                           Arnold in 1894 and consequently is also known
                                                           as the ‘Arnold–Chiari malformation’ (Fig. 11.3).
                                                           The type III malformation involves caudal dis-
                                                           placement of the cerebellum and brainstem into a
                                                           high cervical meningocele. Chiari also described
                                                           a type IV abnormality, comprising two cases of
                                                           hypoplastic cerebellum.
                                                              It is usual for Chiari type I malformations to
                                                           present clinically in adults and many of the
                                                           presenting features are related to the common as-
                                                           sociation of syringomyelia. The Chiari type II
                                                           malformation has an even higher incidence
                                                           of association with syringomyelia and it is
                                                           almost invariably present in patients with
                                                           myelomeningocele. Other frequent associations
                                                           are hydrocephalus due to aqueduct stenosis, atre-
                                                           sia or forking of the aqueduct, fusion of the supe-
Fig. 11.2 MRI. Posterior fossa arachnoid cyst.             rior and inferior colliculi on both sides into a


                Type I Chiari                       Type II Chiari

Fourth ventricle (normal position)           Fourth ventricle (displaced caudally)




Medulla
(normal
position)
                                                                       Medulla
                                                                       displaced
Cerebellar                                                             caudally
tonsils
                                                                       Herniated
                                                                       cerebellar    Fig. 11.3 Major features of
                                                                       vermis        Chiari types I and II
                                                                                     malformation.
 DEVELOPMENTAL ABNORMALITIES                                                                          161


single ‘beaked’ structure, and a small and ‘crowd-      returns to normal the reverse should occur, with
ed’ posterior fossa. Supratentorial anomalies           flow from the intracranial cavity into the spinal
include enlargement of the massa intermedia,            cavity. If this equalization of pressures is im-
microgyria and heterotopias, which may involve          paired and delayed by adhesions and tissue in
both the cerebral hemispheres and cerebellum.           the foramen magnum, a pressure differential is
Cranial lacunae or mesodermal defects of the            created between the intracranial and intraspinal
skull (luckenschadel) are common and the radi-          fluid compartments and alternative pathways
ographic appearance is of multiple ‘punched-out’        develop, such as through a patent obex into the
areas which usually resolve in the first 6 months        spinal central canal. In addition, the pressure dif-
of life. The Chiari type II malformation may also       ferential promotes progressive caudal displace-
be associated with anomalies of the cardiovascu-        ment of cerebellar tissue through the foramen
lar system, gastrointestinal system (imperforate        magnum.
anus) and genitourinary system.
   Syringomyelia is cavitation within the spinal
                                                        Clinical presentation
cord. However, the cavitation occurring in asso-
ciation with the Chiari malformation is usually         The clinical features of the Chiari type II malfor-
called hydromyelia, as it is a dilatation of the cen-   mation present in infancy, childhood or adoles-
tral canal which is lined by ependyma. The term         cence. A Chiari type I malformation causes
syringomyelia is reserved for cavitation lying          symptoms presenting in adolescence and adult-
outside the central canal area lined by glial tissue.   hood and the neurological features are almost al-
                                                        ways due to the development of a syrinx within
                                                        the spinal cord or lower brainstem.
Aetiology
                                                           In infancy the abnormality will be apparent
Gardner popularized the hydrodynamic theory             with its association with myelomeningocele.
of the origin of syringomyelia (hydromyelia) as-        Progressive hydrocephalus may develop. Severe
sociated with Chiari malformation. In brief, the        brainstem dysfunction may result in episodic
theory proposes that the CSF is unable to pass          apnoea, depressed gag reflex, nystagmus and
freely out of the 4th ventricle as the normal path-     spastic paresis of the upper limbs.
ways have either failed to open or are obliterated         In childhood the type II malformation may be
due to ‘crowding’ in the posterior fossa. The nor-      manifest by nystagmus, spastic paralysis and
mal pulsations of CSF are consequently transmit-        bulbar dysfunction.
ted down the central canal of the spinal cord. The         In adolescence the symptoms may be due to
close association of the Chiari type II malforma-       either a type I or type II Chiari malformation.
tion and meningomyelocele led to a theory that          The features will involve a progressive spastic
spinal cord tethering resulted in the caudal dis-       paralysis of the upper and/or lower limbs and
placement of the cranial structures as a result of      may also include the features of syringomyelia,
growth. Alternatively, the malformation may             including suspended thermoanaesthesia sensory
result from hindbrain maldevelopment during             loss, atrophic changes in the hands and upper
early fetal life.                                       extremities and bulbar problems due either to
   Williams has proposed a differential pressure        extension of the syrinx into the lower brainstem
between the intracranial and intraspinal fluid           or to the direct pressure from the Chiari type II
compartments as another mechanism for the de-           malformation itself.
velopment of the malformation. With a Valsalva             Adult symptoms are primarily due to a com-
manoeuvre, the engorgement of the spinal                bination of the Chiari type I malformation
epidural veins causes a rise in the intraspinal         and syringomyelia. The characteristic symptoms
pressure. The spinal subarachnoid space is com-         include occipital headache, exacerbated by
pressed and a pressure wave moves into the              coughing, and neck and arm pain. Nystagmus is
intracranial cavity. When the spinal pressure           common and may be either horizontal or vertical.
 162                                                                                         CHAPTER 11




                                                             (a)




Fig. 11.4 ‘Cape-like’ distribution of pain and
temperature loss typically resulting from syrinx or
other intramedullary lesion in the cervical and upper        (b)
thoracic regions.                                       Fig. 11.5 (a) Chiari type II malformation with
                                                        dysplastic cerebellum extending through foramen
                                                        magnum to C2 level and caudal displacement of 4th
Downbeat nystagmus, exacerbated by the pa-              ventricle and medulla. There is a syrinx (hydromyelia)
tient looking down and out, is characteristic of a      in the cervical and upper thoracic spinal cord. (b)
craniocervical junction abnormality.                    Chiari type I malformation with cervical syrinx
   The characteristic clinical features resulting       (hydromyelia).
from syringomyelia include:
• dissociated sensory loss (loss of pain and            gations of craniocervical junction abnormalities.
temperature sensation with preservation of              Sagittal and coronal scans will show displace-
joint position sense) occurring in a ‘cape-like’        ment of the cerebellum into the upper cervical
distribution (Fig. 11.4). The sensory loss will         canal, with caudal displacement of the 4th ventri-
often result in painless injury of the fingers or        cle and brainstem in the type II malformation.
hands and Charcot joints may develop                    MRI will also show the other associated intra-
• weakness and wasting of the small muscles of          cranial abnormalities (Fig. 11.5). However, it
the hand                                                may not adequately demonstrate the underlying
• progressive long tract signs resulting in spastic     anatomy of the bony structures.
paresis of the lower limbs and paralysis of the            MRI has virtually replaced CT scanning
upper limbs                                             with intrathecal contrast, and myelography is no
• bulbar features, if the syrinx extends into the       longer necessary.
lower brainstem.
                                                        Syringomyelia (hydromyelia)
                                                        As discussed earlier, intraspinal cavitation can be
Radiological investigations
                                                        either hydromyelia, where the syrinx is a dilata-
MRI has revolutionized the radiological investi-        tion of the central canal and there is usually com-
 DEVELOPMENTAL ABNORMALITIES                                                                        163


munication with the CSF pathways, or the non-         the posterior fossa decompression but others pre-
communicating syringomyelia, where the syrinx         fer to perform the operation only if there is con-
is separate from the central canal.                   tinuing progression of neurological disability.
   Hydromyelia (communicating syringomyelia)
usually results from Chiari type I and type II
                                                      Craniovertebral junction abnormalities
malformations and occasionally from basilar
arachnoiditis. Non-communicating syringomyelia        The craniovertebral junction region involves the
may be due to previous trauma or neoplasms, or        foramen magnum, the adjacent occipital bone
associated with spinal arachnoiditis. Occasion-       and the atlas and axis vertebrae. Numerous con-
ally, no underlying abnormality can be found as a     genital or acquired abnormalities occur in this
cause of the syrinx.                                  region which may result in compression of the
   The most valuable radiological investigation is    underlying neural structures. Some abnormali-
MRI, which will show the extent of the syrinx and     ties, including spina bifida of the anterior or pos-
associated abnormalities. This investigation has      terior arch of the atlas, remain asymptomatic.
almost completely replaced the use of CT scan
with water-based contrast injected into the sub-
                                                      Basilar invagination (impression)
arachnoid space. Delayed post-contrast CT scan-
ning shows intramedullary opacification as well        Basilar invagination is a deformation of the basi-
as the enlarged cord.                                 occiput in which there is an upward indentation
                                                      or invagination of the base of the skull, includ-
                                                      ing the rim of the foramen magnum, occipital
Treatment
                                                      condyles and neighbouring bone, into the poste-
There are two major surgical procedures.              rior fossa. The clivus is often shortened and the
1 Posterior fossa and upper cervical decom-           invagination reduces the diameter of the foramen
pression.                                             magnum. The odontoid process frequently pro-
2 Shunting of the syrinx.                             jects into the anterior part of the foramen mag-
   The posterior fossa operation involves decom-      num so that its diameter is reduced still further.
pression by removing the posterior rim of the         There is a frequent association with congenital
foramen magnum, posterior arch of the atlas and       fusion of the cervical vertebrae to each other or to
laminae of the upper cervical spine, extending        the occiput.
down to below the level of the descent of the            Acquired basilar impression may be due to
cerebellar tonsil. The dura is opened widely, as      softening of the bone by disease. The most
it often acts as a constricting band, particularly    common cause is Paget’s disease but it may also
at the level of the foramen magnum. A variety of      occur in osteomalacia, hyperparathyroidism and
other procedures may be performed at that time,       osteogenesis imperfecta.
including dissection of the subarachnoid adhe-           The clinical features resulting from basilar
sions, opening of the foramen of Magendie into        impression are due to compression of the neural
the 4th ventricle, plugging the enlarged opening      structures at the cervicomedullary junction — the
of the central canal at the obex with tissue, and     medulla oblongata, the cranial nerves, the cervi-
placing a stent through the foramen of Magendie.      cal roots and the spinal cord.
These procedures must be done with meticulous            The clinical features may include a progressive
microsurgery techniques to avoid further dam-         quadriparesis, dysphagia, respiratory difficul-
age to this extremely sensitive area. The dura is     ties, nystagmus (sometimes downbeat) and sub-
closed using a graft of cervical fascia.              occipital headache due to irritation of the 2nd
   The syringomyelia (hydromyelia) may be             cervical nerve.
shunted into either the subarachnoid space or the        Useful radiological investigations include CT
peritoneal or pleural cavity. Some surgeons pre-      scan (with sagittal reconstruction and intrathecal
fer to carry out this procedure at the same time as   contrast) (Fig. 11.6), MRI and plain X-rays.
 164                                                                                          CHAPTER 11




Fig. 11.6 Sagittal reconstruction of CT scan (with
intrathecal contrast) demonstrating the odontoid
process extending through the foramen magnum.




                                                          Fig. 11.8 Atlantoaxial subluxation in rheumatoid
                        Chamberlain's line
                                                          arthritis.



                                                          Atlantoaxial dislocation
                                                          Dislocations at the atlantoaxial joint can result
       Hard palate                      McGregor's line
                                                          from congenital malformations, involving in par-
Fig. 11.7 Plain X-ray measurement for basilar             ticular the congenital fusion of the occiput to the
invagination.                                             atlas and fusions of C2 and C3. Multiple congen-
                                                          ital cervical fusions occur in the Klippel–Feil syn-
                                                          drome. These types of fusions will increase the
Various measurements at the base of the skull can         strain on the ligaments of adjacent vertebrae,
be used to diagnose the anomaly. Chamberlain’s            resulting in instability. Atlantoaxial dislocation
line joins the tip of the dorsal lip of the foramen       may also result from inflammatory conditions
magnum to the dorsal margin of the hard palate            such as rheumatoid arthritis or following trauma
and, on a lateral skull X-ray or sagittal MRI,            (Fig. 11.8).
should normally lie above the tip of the odontoid
process of the axis and pass through the ventral
                                                          Dandy–Walker cyst
lip of the foramen magnum. McGregor’s line
joins the hard palate to the most caudal portion of       The Dandy–Walker cyst is a cystic enlargement
the occipital curve. In basilar invagination the tip      of the 4th ventricle, usually associated with hy-
of the odontoid lies more than 4.5 mm above this          poplasia or partial agenesis of the cerebellum and
line (Fig. 11.7).                                         hydrocephalus of the 3rd and lateral ventricles.
                                                             It is probable that the primary cause is an em-
                                                          bryological failure of the foraminal outlets of the
Platybasia
                                                          4th ventricle to open, resulting in cystic enlarge-
Platybasia is sometimes erroneously used syn-             ment of the 4th ventricle and hydrocephalus.
onymously with basilar impression. Platybasia             However, the Dandy–Walker cyst is sometimes
refers to an obtuse basal angle joining the plane of      associated with other congenital abnormalities,
the clivus with the plane of the anterior fossa           such as agenesis of the corpus callosum and
of the skull; it is said to be present if the angle       aqueduct stenosis, and it has been suggested that
exceeds 145°.                                             it may represent a cerebellar dysraphism.
   Although platybasia is often present with basi-           The clinical features are usually apparent in in-
lar impression it causes no symptoms by itself.           fancy and result primarily from hydrocephalus.
 DEVELOPMENTAL ABNORMALITIES                                                                             165


                                                            Myelomeningocele               Meningocele




                                                                          Dysplastic
                                                                         nerve roots




                                                                               Sac




                                                        a                              b

                                                        Fig. 11.10 Myelomeningocele and meningocele.
Fig. 11.9 Dandy–Walker cyst in posterior fossa with
hydrocephalus of lateral and 3rd ventricles.
                                                        rological involvement and the lesion is asympto-
                                                        matic throughout life.
   The cyst may be diagnosed in childhood, par-
ticularly if it does not produce significant hydro-
                                                        Myelomeningocele
cephalus, and the major presenting features are
ataxia and delayed motor development.                   Myelomeningocele is the most common and im-
   The diagnosis is made by CT scan (Fig. 11.9) or      portant form of spinal dysraphism presenting
MRI. The standard treatment is now shunting of          during the neonatal period (Fig. 11.10). It is char-
the cyst but, if aqueduct stenosis is present, a ven-   acterized by protrusion of the neural elements
tricular shunt may also need to be inserted.            through a vertebral defect into a meningeal-lined
                                                        sac. Typically, the cord at this level is not fused
                                                        but is in its flattened embryological state, with
Spinal dysraphism
                                                        the nerve roots arising from the ventral surface
Spinal dysraphism results from incomplete or            and the open central canal lying dorsally. The
faulty closure of the dorsal midline embryol-           major disability from this condition results from
ogical structures. The major forms of spinal dys-       the irreversible neurological deficit caused by
raphism are:                                            this spinal cord abnormality. Depending on the
1 Myelomeningocele.                                     level of the defect the spinal cord or conus
2 Meningocele.                                          and cauda equina may be involved. Although
3 Lipomyelomeningocele.                                 myelomeningocele may occur at any level, it is
4 Occult spinal dysraphism:                             most common in the lumbar and lumbosacral
  (a) dermoid tumours                                   segments.
  (b) diastematomyelia                                    This disorder occurs in approximately 1 in
  (c) intraspinal lipoma                                1000 live births. There is a greater frequency
  (d) hypertrophic filum terminale.                      among whites than blacks, with a slight female
  Spina bifida occulta is a bony deficit usually          predominance. There is a familial incidence: if
found in the laminae of the lumbosacral spine           one member of a family is affected the risk of the
and due to a midline fusion defect. It is an inci-      disorder occurring in subsequent offspring is
dental radiological finding and is present in up to      about 5%. Seasonal outbreaks of myelomeningo-
20% of adults. In the vast majority there is no neu-    cele have been reported and there are ethnic
 166                                                                                      CHAPTER 11


differences, with a higher incidence of the condi-      were developed and the children excluded from
tion in the western United Kingdom, northern            treatment were those with:
India and Egypt.                                        • paralysis at L2 to L3 or above
   Prenatal diagnosis of myelomeningocele and           • marked hydrocephalus
other open neural tube disorders is possible by         • kyphosis
measuring alpha-fetoprotein in the amniotic             • other major congenital abnormalities or birth
fluid at 14–16 weeks and by prenatal ultrasound          injuries.
examination. The widespread use of increasingly            However, although when these criteria are
accurate ultrasound examination in the first             used, a large number of untreated infants do not
trimester of pregnancy has led to detection of          live long, a significant minority do, and there is
myelomeningocele, and in many centres detec-            great concern about their quality of life.
tion is followed by parental decision to terminate         The initial operation aims to:
the pregnancy. Consequently there has been a            • preserve all the neural tissue and reduce it into
dramatic decrease in the incidence of children          the intervertebral canal; untether the spinal cord
born with this type of anomaly. The ultrasound          • obtain a watertight closure of dura lining the
findings can be confirmed by MRI.                         sac
   Myelomeningocele is frequently associated            • cover the defect with muscle, fascia and skin.
with other congenital abnormalities, most                  It will subsequently be necessary to make deci-
commonly the Chiari type II malformation,               sions concerning the treatment of hydrocephalus
aqueduct stenosis (forking) and hydromyelia             and other associated malformations.
(syringomyelia).                                           The continued care of these children requires a
   The management of myelomeningocele                   multidisciplinary approach including urologists,
involves:                                               orthopaedic surgeons, physicians, physiothera-
1 Assessment of the sac and its coverings.              pists and social workers. The children frequently
2 Neurological evaluation.                              have severe urological problems, which may re-
3 Examination for other associated conditions:          sult in renal failure as adolescents. The muscu-
   (a) within the CNS, e.g. hydrocephalus               loskeletal disorders, including talipes and hip
   (b) extracranial anomalies, e.g. gastrointesti-      dislocation, require careful orthopaedic man-
   nal, urinary.                                        agement to maximize any residual lower limb
4 Counselling and careful discussions with the          function.
parents.
5 Surgical procedures.
                                                        Lipomyelomeningocele
   Decisions concerning whether a patient should
undergo a surgical procedure with closure of the        This is a much less common disorder than
sac are among the most difficult in neurosurgical        myelomeningocele. The mass is covered by skin
practice. On the one hand, the child has a right to     and the lipomatous tissue extends intradurally
life but there is also a right to a life of sufficient   and is intimately interwoven with the rootlets
quality to be worth living. The immediate deci-         of the cauda equina and the conus medullaris,
sion is whether to close the myelomeningocele           which is not usually fused. Neurological exami-
sac. In 1959 physicians in Sheffield undertook a         nation is usually normal at birth and progres-
programme of immediate closure in all neonates,         sive neurological deficits occur, resulting from
with aggressive treatment of the hydrocephalus          growth and tethering of the spinal cord. The most
and other malformations. However, when the              common symptoms include bladder and bowel
series was examined, only 7% ‘had less than             disturbance, back pain and progressive paralysis
grossly crippling disability and may be consid-         in the legs with foot deformities and loss of
ered to have a quality of life not inconsistent with    sensation.
self respect, earning capacity, happiness and              Surgery is delayed until about 4 months. The
even marriage’. Consequently, selective criteria        lipoma is removed as completely as possible
 DEVELOPMENTAL ABNORMALITIES                                                                     167


without endangering the neural tissue; the          with tethering of the cord by an enlarged filum
primary surgical aim is to untether the spinal      terminale or fatty tissue.
cord.                                                  Diastematomyelia is a condition in which the
                                                    spinal cord is bifid and the two hemicords are
                                                    separated by a bony spur or dural band. Progres-
Meningocele
                                                    sive neurological dysfunction will occur due to
This is much less common than myelomeningo-         traction on the cord that is transfixed during
cele and is characterized by a cystic lesion        growth periods (Fig. 11.11).
containing only meninges and CSF; it does not          The cord is occasionally tethered by a short-
contain any neural tissue.                          ened, thickened filum terminale — hypertrophic
                                                    filum terminale — and the only associated abnor-
                                                    malities are spina bifida occulta and an occa-
Occult spinal dysraphism
                                                    sional hairy patch over the lower spine.
Occult spinal dysraphism includes a number of          Radiological assessment will utilize plain X-
spinal disorders, the vast majority of which are    ray, CT scan (with intrathecal contrast) and MRI.
situated in the lumbar region and produce           Plain X-rays will show a range of vertebral ab-
progressive neurological dysfunction, often as a    normalities including spina bifida, hemiverte-
result of tethering of the spinal cord. The more    brae, abnormal spinal curves, diastematomyelic
common lesions include:                             spurs and widened interpedicular distances.
• intraspinal lipomas (and lipomyelomenin-             The surgical treatment is aimed at:
gocele)                                             • removing the underlying pathological cause
• dermoid tumours                                   while preserving neural tissue
• diastematomyelia.                                 • untethering the cord.
   The underlying intraspinal lesion can often be
suspected from an overlying skin lesion such as a
                                                    Craniosynostosis
dimple, sinus tract, fatty mass, haemangioma or
abnormal tuft of hair. The neurological symp-       Craniosynostosis is premature closure of cranial
toms are usually first noted in childhood or ado-    sutures and occurs in 1 in 3000 births. It may
lescence. There is usually a slowly progressive     occur as a condition involving a single cranial su-
neurological dysfunction involving:                 ture or as part of a complex syndrome involving
• bowel and bladder disturbance                     multiple fusion abnormalities.
• progressive weakness of the legs and foot           The posterior fontanelle has usually closed by
deformities                                         2–3 months of age and the anterior fontanelle by
• back pain                                         about 16–18 months. The brain ceases to grow at
• sensory disability in the lower limbs             10–12 years of age, at which time the cranial
• progressive scoliosis.                            sutures are obliterated by firm fibrous tissue.
   Depending on the level of the abnormality, the   Complete ossification of the sutures does not
neurological examination will show evidence         occur until after the 3rd decade of life.
of either lower and/or upper motor neurone            The clinical features of craniosynostosis are
damage.                                             related to:
   Lipomas are the most frequent form of occult     • the cranial deformity
spinal dysraphism. The lumbosacral lipoma pre-      • raised intracranial pressure
sents at birth as a soft subcutaneous mass, usu-    • the presence of associated congenital abnor-
ally in the midline and covered by skin. In its     malities.
most severe form — lipomyelomeningocele — the
lipoma will involve neural tissue and will extend   Sagittal synostosis
through a spina bifida. Less severe abnormalities    This is by far the most common type of primary
will be associated with a low-lying conus and       craniosynostosis; the incidence is greater than
 168                                                                                    CHAPTER 11


                                                    that of all other types of craniosynostosis com-
                                                    bined. Males are most commonly affected and
                                                    the condition is usually not associated with other
                                                    congenital abnormalities.
                                                       Premature fusion of the sagittal suture results
                                                    in the head expanding in the occipitofrontal
                                                    diameter and produces a long narrow head
                                                    (scaphocephaly). Compensatory growth along
                                                    the metopic and coronal sutures causes the fore-
                                                    head to expand laterally (frontal bossing).
   (a)
                                                    Coronal synostosis
                                                    Coronal synostosis occurs more commonly in
                                                    females. The head expands superiorly and later-
                                                    ally (brachycephaly). This produces a short ante-
                                                    rior cranial fossa, shallow orbits, hypertelorism
                                                    and elevation of the forehead. Choanal atresia is
                                                    common.
                                                       Bilateral coronal synostosis commonly occurs
                                                    as one of several congenital defects in Crouzon’s
                                                    and Apert’s syndromes.
                                                       If only one coronal suture fuses prematurely
   (b)
                                                    there will be an asymmetrical cranial deformity.

                                                    Metopic synostosis
                                                    Metopic synostosis produces a narrow, triangu-
                                                    lar forehead (trigonocephaly) associated with
                                                    hypotelorism.

                                                    Lambdoid synostosis
                                                    Lamboid synostosis is uncommon. There is sym-
                                                    metrical flattening of the posterior cranium.


                                                    Operative treatment
                                                    Surgery is performed to:
                                                    • correct the cranial deformity
                                                    • relieve the effects of raised intracranial pressure.
                                                       If only one suture is fused, compensatory
                                                    growth along the open suture lines will reduce
                                                    the risk of raised intracranial pressure, although
                                                    there have been studies showing raised intracra-
                                                    nial pressure, usually only moderate, in children
                                                    with single suture fusion. However, if two or
                                                    more cranial sutures fuse prematurely there is a
   (c)
                                                    risk of increased intracranial pressure as growth
Fig. 11.11 Lumbar diastematomyelia with bone spur
                                                    proceeds. This may lead to mental and motor
and dural band (arrow) passing through the cauda
                                                    retardation and to optic atrophy.
equina.
 DEVELOPMENTAL ABNORMALITIES                                                                                 169


   The operative procedure has usually involved              diagnosis and surgical correction. Child’s Brain 2,
a strip craniectomy of the fused suture. However,            145–151.
as the long-term results have been somewhat dis-           Humphreys RP (1985) Spinal dysraphism. In: Wilkins
appointing, the trend is now to undertake a more             RH, Rengochary SS, eds. Neurosurgery. McGraw-Hill,
                                                             New York, 2041–2052.
major vault reconstruction to obtain a permanent
                                                           Kaye AH, Black P McL (2000) Operative Neurosur-
effect.
                                                             gery. Churchill Livingstone, London, New York,
   Surgery is usually best delayed until the child           Edinburgh.
is 3–6 months old, but if two or more cranial su-          Levy WJ, Mason L, Hahn JF (1983) Chiari malformation
tures are fused then it may be undertaken earlier            presenting in adults: a surgical experience in 127
to minimize the effects of brain compression.                cases. Neurosurgery 12, 377–390.
   The operation involves resection of the                 Little JR, Gomez MR, McCarty CS (1973) Infratentorial
affected sutures. It should be carefully planned             arachnoid cysts. Journal of Neurosurgery 39, 380–386.
and meticulously performed to minimize blood               Lorber J (1971) Results of treatment of myelomeningo-
loss, which is the greatest risk of the procedure.           coele: an analysis of 524 unselected cases, with
                                                             special reference to possible selection for treatment.
                                                             Developmental Medicine and Child Neurology 18,
Further reading                                              279–303.
                                                           Mapstone T (1994) Management of tethered cord
Delashaw JB et al. (1989) Cranial vault growth in cran-
                                                             syndrome. Neurosurgery Quarterly 4, 82–91.
 iosynostosis. Journal of Neurosurgery 70, 159–166.
                                                           Matson DD (1969) Neurosurgery in Infancy and Child-
Dyste GN, Menezes AH, Vanglider JC (1989) Sympto-
                                                             hood. Charles C Thomas, Springfield.
 matic Chiari malformations. An analysis of presenta-
                                                           Milhorat TH (1978) Paediatric Neurosurgery. Contempo-
 tion, management and long term outcome. Journal of
                                                             rary Neurology Series. F A Davis, Philadelphia.
 Neurosurgery 71, 159–168.
                                                           Milhorat TH, Miller JI, Johnson WD (1993) Anatomical
Gardner WJ (1965) Hydrodynamic mechanism of
                                                             basis of syringomyelia. Neurosurgery 32, 748–754.
 syringomyelia: its relationship to myelocoele. Journal
                                                           Robinson RG (1964) The temporal lobe agenesis syn-
 of Neurology, Neurosurgery and Psychiatry 28, 247–259.
                                                             drome. Brain 87, 87–106.
Hockley AD, Wake MJ, Goldin H (1988) Surgical
                                                           Robinson RG (1971) Congenital cysts of the brain:
 management of craniosynostosis. British Journal of
                                                             arachnoid malformations. Progress in Neurological
 Neurosurgery 2, 307–314.
                                                             Surgery 4, 133–174.
Hoffman HJ et al. (1982) Investigation and management
                                                           Shillito J, Matson DD (1968) Craniosynostosis: a review
 of suprasellar arachnoid cysts. Journal of Neurosurgery
                                                             of 519 surgical patients. Paediatrics 41, 829–853.
 57, 597–602.
                                                           Starkman SP, Brown TC, Linell EA (1958) Cerebral
Hoffman HJ, Hendrick EB, Humphreys RP (1975) Man-
                                                             arachnoid cysts. Journal of Neuropathology and Experi-
 ifestations and management of Arnold Chiari
                                                             mental Neurology 17, 480–500.
 malformation in patients with myelomeningocoele.
                                                           Williams B (1980) On the pathogenesis of syringo-
 Child’s Brain 1, 255–259.
                                                             myelia: a review. Journal of the Royal Society of
Hoffman HJ, Hendrick EB, Humphreys RP (1976) The
                                                             Medicine 73, 298–806.
 tethered spinal cord: its protean manifestations,
                           CHAPTER 12


 12                        Infections of the
                           central nervous system


Infections involving the nervous system present       terial meningitis are related to the patient’s age
in a variety of ways, many of which result in         and to the presence and nature of any underlying
death or severe morbidity if not diagnosed and        predisposing disease. Although a few types of
treated promptly. The infections usually occur as     bacterial organisms account for most cases of
the result of haematogenous spread or direct ex-      acute pyogenic meningitis there is a wide range
tension from adjacent bone, soft tissue or sinuses.   of organisms that may be responsible. Table 12.1
A large variety of pathogens are involved, in-        shows the most common causes of bacterial
cluding viruses, fungal agents and bacteria. The      meningitis related to age.
most common infections involving the neurosur-           The bacteria reach the meninges and cere-
geon are:                                             brospinal fluid by three main routes.
• acute bacterial meningitis                          1 Haematogenous spread from extracranial foci
• cerebral abscess.                                   of infection.
   Neurosurgeons are involved in the manage-          2 Retrograde spread via infected thrombi within
ment of nervous system infections because             emissary veins from infections adjacent to the
patients frequently present with manifestations       central nervous system, such as sinusitis, otitis or
of a rapidly progressive neurological illness, as     mastoiditis.
well as the systemic manifestations of sepsis.        3 Direct spread into the subarachnoid space,
   Infection may involve any part of the nervous      such as from osteomyelitis of the skull and infec-
system or its coverings and can be classified in       tions of the paranasal sinuses.
the following way.                                       The CSF is a good culture medium which will
1 Cranial vault infections.                           support the growth of many microorganisms.
2 Extradural abscess/empyema.                         Normal CSF contains very low concentrations of
3 Subdural abscess/empyema.                           immunoglobulins and complement components
4 Meningitis.                                         and is devoid of polymorphonuclear phagocytes.
5 Brain:                                              Furthermore, phagocytosis is impaired by the
   (a) brain abscess                                  low opsonic activity of CSF and organisms
   (b) encephalitis.                                  such as Streptococcus pneumoniae, Haemophilus in-
                                                      fluenzae type B, Group B streptococci, Escherichia
                                                      coli and Klebsiella pneumoniae have a polysaccha-
Meningitis
                                                      ride capsule that hinders phagocytosis.
Bacterial meningitis is a serious, life-threatening
infection of the meninges. Viral meningitis is
                                                      Clinical presentation
the more common infection but is usually
self-limiting, and the neurosurgeon is rarely         Bacterial meningitis is usually an acute illness
involved.                                             with rapid progression of clinical signs. Many
  Most of the common organisms that cause bac-        cases are preceded by symptoms of an upper

170
 INFECTIONS OF THE CENTRAL NERVOUS SYSTEM                                                                 171



  Table 12.1 Common organisms causing primary bacterial meningitis related to age.

  Age                               Organism

  Neonate (0–4 weeks)               Group B streptococcus, Escherichia coli
  4–12 weeks                        Group B streptococcus, Streptococcus pneumoniae, Salmonella, *Haemophilus
                                      influenzae, Listeria monocytogenes
  3 months–5 years                  Haemophilus influenzae*, Streptococcus pneumoniae, Neisseria meningitidis
  Over 5 years and adults           Streptococcus pneumoniae, Neisseria meningitides

  *In countries with routine Haemophilus influenzae immunization this organism is a rare cause of meningitis.




respiratory tract infection. The major presenting
                                                         Diagnosis
features are:
• high fever                                             The diagnosis is made by CSF examination ob-
• meningismus, including headaches, neck                 tained by lumbar puncture which should be per-
stiffness, photophobia, vomiting and an altered          formed immediately the diagnosis is suspected.
mental state in terms of clinical presentation.          If the patient is drowsy, has other signs of raised
   Although patients are usually alert at the com-       intracranial pressure or there are focal neurologi-
mencement of the illness they will frequently be-        cal signs, an urgent computerized tomography
come drowsy and confused. If treatment is not            scan must be performed prior to the lumbar
commenced promptly there may be further dete-            puncture to exclude an intracranial space-
rioration of the conscious state as a result of a di-    occupying lesion.
rect septic effect on the underlying brain, septic          The CSF features on lumbar puncture are:
thrombosis of the cerebral arteries and veins, or        • Macroscopically cloudy CSF.
the development of hydrocephalus. Focal neuro-           • Raised white cell count. This is usually in
logical signs may develop as a result of cortical        excess of 500 cells/mm3 and is predominantly a
infarction secondary to thrombosis.                      polymorphonuclear leukocytosis.
   In infants, neonates, the elderly and the im-         • The protein level is greater than 0.8 g/l; it is
munocompromised, the presentation of bacterial           often substantially higher.
meningitis may be different. Neck stiffness and          • The glucose level is less than 2 mmol/l,
fever are often absent and the presentation in-          frequently much lower. A useful index is the
cludes listlessness and irritability in the young        CSF : serum ratio which is less than 0.4 in a bacte-
and confusion or obtundation in the elderly/             rial infection.
immunocompromised.                                       • The Gram stain will be positive in over 70% of
   A careful search should be made for a skin            patients if common pathogens are involved, and
rash. Meningococcal infection frequently has a           in approximately 50% of patients for Gram-
coexisting petechial rash, which occurs less fre-        negative bacilli.
quently in other bacterial (e.g. staphylococcal          Other tests which should be performed on the
bacteraemia, Haemophilus influenzae infection) or         CSF include:
viral infections. The original source of infection,      • examination for Cryptococcus neoformans using
e.g. sinusitis, bacterial endocarditis, otitis media     an India ink preparation and an agglutination
or mastoiditis, may be evident and many patients         test for cryptococcal antigen
have evidence of pharyngitis — bacterial menin-          • investigation for Mycobacterium tuberculosis
gitis sometimes follows an upper respiratory             (Ziehl–Neelsen stain for acid-fast bacilli) and
tract infection.                                         amoebae.
 172                                                                                          CHAPTER 12


  Difficulties arise in diagnosis of partially treat-         There are many antibiotic regimes but if there
ed bacterial meningitis because the CSF culture is        is no obvious site of infection initial therapy
often negative. Other investigations include:             should commence immediately as follows.
• blood cultures                                          • Neonates (under 3 months) — cefotaxime or
• radiological investigations to detect the source        ceftriaxone plus benzyl penicillin or amoxy-/
of infection — chest X-ray, CT scan or skull X-ray        ampicillin.
for sinusitis.                                            • Three months to 15 years — cefotaxime or
  The differential diagnosis includes:                    ceftriaxone.
1 Other types of meningitis:                              • 15 years to adult — benzyl penicillin plus
  (a) viral                                               cefotaxime/ceftriaxone.
  (b) fungal (Cryptococcus neoformans)                    • Add vancomycin if Gram-positive strepto-
  (c) amoebic                                             cocci are seen and there is any suspicion of
  (d) tuberculous                                         intermediate and/or resistant Streptococcus
  (e) carcinomatous (Chapter 6).                          pneumoniae.
2 Subdural empyema.                                          When the organism has been identified the
3 Subarachnoid haemorrhage (Chapter 9).                   most appropriate antibiotic should be used, de-
4 Viral encephalitis (especially herpes simplex           pending on sensitivities and the ability of the
encephalitis).                                            antibiotic to penetrate into the CSF. Table 12.2
                                                          shows the CSF penetration of antibiotics.
                                                             The usual specific antimicrobial therapy fol-
Treatment
                                                          lowing identification of the organism is:
High-dose intravenous antibiotic therapy should           • Pneumococcus or meningococcus — benzyl
be commenced immediately, and the selection of            penicillin (child: 60 mg/kg up to 1.8–2.4 g intra-
the antibiotic depends on:                                venously 4-hourly). If patient is sensitive to peni-
• the initial expectation of the most likely organ-       cillin use cefotaxime (child: 15 mg/kg 6-hourly or
ism involved, taking into account the age of the          ceftriaxone 100 mg/kg daily). About half the
patient and the source of infection                       patients with meningococcal meningitis have
• CSF microbiology studies                                petechiae or purpura. Subclinical or clinical
• the antibiotic that has the best penetration into       disseminated intravascular coagulation often ac-
the CSF.                                                  companies meningococcaemia and may progress




  Table 12.2 Antibiotic penetration into cerebrospinal fluid.

  Good penetration with or without      Good penetration only with
  meningeal inflammation                 meningeal inflammation                Fair to poor penetration

  Chloramphenicol*                      Penicillins                          First-generation cephalosporins
  Metronidazole                           Penicillin                         Aminoglycosides
  ‘Third-generation’ cephalosporins       Amoxycillin                          Gentamicin
    Ceftriaxone/Cefotaxime                Flucloxacillin                       Tobramycin
                                        Rifampicin
                                        Trimethoprim/sulphamethoxazole
                                        Vancomycin
                                        Carbapenems
                                          Meropenem

  *Limited availability in most countries. Rarely used.
 INFECTIONS OF THE CENTRAL NERVOUS SYSTEM                                                             173


to haemorrhagic infarction of the adrenal glands,      overt signs of meningitis. There is frequently a
renal cortical necrosis, pulmonary vascular            coexisting ventriculitis.
thrombosis, shock and death. The antibiotic ther-        The diagnosis is confirmed by examination of
apy must be accompanied by intensive medical           the CSF via a lumbar puncture or occasionally by
supportive therapy.                                    withdrawal of CSF from the reservoir mecha-
• H. influenzae — amoxy-/ampicillin if organism         nism of the shunt. The treatment consists of ad-
is susceptible. If the patient is allergic or organ-   ministration of antibiotics and removal of the
ism-resistant use cefotaxime or ceftriaxone.           shunt.
• Listeria — benzyl penicillin or amoxy-/ampi-           The most frequently isolated organisms in
cillin plus trimethoprim and sulfamethoxazole.         meningitis following neurosurgical operations
• Hospital-acquired meningitis — vancomycin            are Staph. aureus, Staph. epidermidis and Gram-
plus cefotaxime, ceftriaxone or meropenem.             negative aerobic bacilli. The clinical features of
                                                       bacterial meningitis may be masked, or confused
                                                       with the underlying neurosurgical illness and
Complications of bacterial meningitis
                                                       operation. Although the meningitis may present
Complications are more likely to occur if treat-       as a rapidly fulminating infection, it is also possi-
ment is not commenced immediately. The major           ble for the clinical features to evolve slowly. The
complications are as follows.                          diagnosis must be suspected if there is unex-
• Cerebral oedema.                                     plained fever, impaired conscious state, seizures
• Seizures.                                            or neck stiffness following surgery.
• Hydrocephalus — communicating hydroceph-               CSF must be obtained and treatment with the
alus. This may occur early in the disease or as a      appropriate antibiotics commenced. However, it
late manifestation.                                    may be difficult to identify the causative organ-
• Subdural effusion, particularly in children.         ism, as perioperative prophylactic antibiotics
Most resolve spontaneously but some may                may make isolation of the organism difficult.
require drainage.
• Subdural empyema. A rare complication that
                                                       Brain abscess
usually requires drainage.
• Brain abscess, which occurs as a rare complica-      Cerebral abscess may occur at any age, may be
tion of meningitis.                                    single or multiple and, although most are supra-
                                                       tentorial, can also occur in the cerebellum or
                                                       brainstem.
Bacterial meningitis following
neurosurgical procedures
                                                       Pathogenesis
Bacterial meningitis may complicate any in-
tradural neurosurgical procedure, often with           Pyogenic inflammation of the brain leading to
devastating consequences. It is a much feared          cerebral abscess may result from:
complication following insertion of a CSF shunt        • haematogenous spread from a known septic
(Chapter 3).                                           site or occult focus
   The majority of shunt infections are caused by      • direct spread from an adjacent infected
Staphylococcus epidermidis and diphtheroids,           paranasal or mastoid sinus
species that are present in the normal skin flora.      • trauma causing a penetrating wound.
However, other pathogens such as Staph. aureus,           The metastatic brain abscesses arising by
pneumococcus and Haemophilus species may               haematogenous dissemination of infection are
also be involved. Unlike primary bacterial             frequently multiple and develop at the junction
meningitis, the clinical presentation is frequently    of white and grey matter. The incidence in each
subacute or chronic and patients present with          part of the brain is proportional to its regional
a low-grade fever before developing the more           blood flow, so that most abscesses occur in the
 174                                                                                     CHAPTER 12


distribution of the middle cerebral artery, princi-   circulation and which surround the area of devel-
pally the parietal lobe, although they can also be    oping infective necrosis. The necrotic centre
found in the cerebellum and brainstem.                enlarges and pus is formed by the release of
   The most common sources of infection include       enzymes from the inflammatory cells. At the
skin pustules, chronic pulmonary infection (e.g.      periphery of this necrotic centre fibroblasts lay
bronchiectasis), diverticulitis, osteomyelitis and    down a reticulin network and, as the abscess
bacterial endocarditis. Patients with congenital      enlarges, a collagen capsule develops. The wall of
heart disease and who have a right-to-left shunt      the abscess develops more slowly on the ventric-
are particularly prone to brain abscesses because     ular side because of the poorer vascularity of the
their blood does not filter through the capillary      deep white matter compared with the cortical
beds within the lungs. The site of origin of the      grey matter. Consequently, the abscess tends to
haematogenous spread is unknown in approxi-           enlarge into the deep white matter, and it may
mately 25% of patients.                               rupture into the lateral ventricle.
   Direct spread from paranasal sinuses, mastoid
air cells or the middle ear are the most common
                                                      Bacteriology
pathogenic mechanisms in most series. Infection
from the paranasal sinuses spreads, by retro-         In the preantibiotic era brain abscess was caused
grade thrombophlebitis, through the diploic           predominantly by Staph. aureus and streptococci.
veins into either the frontal or temporal lobe. The   After the introduction of antibiotics the inci-
abscesses are usually single and are located          dence of staphylococcal abscesses declined and
superficially. Frontal sinusitis may cause a brain     most abscesses were thought to be due to strep-
abscess in the frontal lobe, sphenoid sinusitis an    tococci, although up to 50% of culture results
abscess in either the frontal or temporal lobe,       in some series were ‘sterile’. When improved
maxillary sinusitis an abscess in the temporal        anaerobic culture techniques became available
lobe and ethmoid sinusitis an abscess in the          the incidence of positive cultures increased, and
frontal lobe. Middle ear infection may spread         many of the abscesses previously thought to be
into the temporal lobe and, uncommonly, a cere-       sterile were found to have been caused by an-
bellar abscess may result from infection spread-      aerobic organisms, particularly streptococci
ing from the mastoid air cells. The mechanism of      and Bacteroides species. Meticulous culture tech-
abscess formation is either by erosion of the adja-   niques have resulted in considerable improve-
cent bone and spread through the dura or due to       ment in the definition of the bacterial spectrum in
retrograde septic thrombophlebitis in an emis-        brain abscesses and have confirmed that strepto-
sary vein.                                            cocci are the most common organisms isolated in
   A cerebral abscess may result from craniocere-     brain abscesses of all origins, but the exact bacte-
bral trauma which has caused a penetrating brain      rial flora depends on the cause of the abscess
injury, particularly if foreign bodies such as bone   (Table 12.3).
or hair have been implanted in the brain. A less         Streptococci are isolated from approximately
common but well-documented cause of brain             80% of brain abscesses. The most common single
abscess results from infection spreading from         species is the beta-haemolytic carboxyphilic Strep.
skull tongs used in skeletal traction for cervical    milleri, a microaerophilic streptococcus which
dislocation.                                          grows in anaerobic culture and also 10% carbon
                                                      dioxide. The major habitat of Strep. milleri is the
                                                      alimentary tract, including the mouth and dental
Histopathology
                                                      plaque. The association between frontal lobe ab-
The abscess begins as a small area of focal in-       scesses, Strep. milleri and sinusitis indicates that
flammation — cerebritis — consisting of polymor-       the source of infection in many brain abscesses is
phonuclear leukocytes, lymphocytes and plasma         the upper respiratory tract, the organism passing
cells, which migrate from the peripheral blood        into the brain from the paranasal sinuses.
 INFECTIONS OF THE CENTRAL NERVOUS SYSTEM                                                                    175



  Table 12.3 Cerebral abscess — pathogenesis and principal organisms.

  History                                 Site of abscess               Predominant organisms

  Sinusitis — frontal                     Frontal lobe                  Aerobic and anaerobic streptococci
                                                                          Streptococcus milleri
                                                                        Haemophilus species

  Mastoiditis, otitis                     Temporal lobe                 Mixed flora
                                                                         Aerobic and anaerobic streptococci
                                                                         Enteric bacteria or Enterobacteria
                                                                         Bacteroides fragilis
                                                                         Haemophilus species

  Haematogenous, cryptogenic              Brain                         Aerobic streptococci
                                                                        Anaerobic streptococci
                                                                        Enterobacteria
                                                                        Staphylococcus aureus

  Trauma                                  Brain                         Staphylococcus aureus




  Otogenic abscesses usually yield a mixed flora,            the abscess involves an eloquent intracerebral
including bacteroides (Bacteroides fragiles),               location it may present when quite small. Alter-
various streptococci and members of the Entero-             natively, an abscess in the frontal lobe may reach
bacteriaceae (Escherichia coli, Proteus and                 a large size before producing any major neuro-
Pseudomonas species).                                       logical deficit. About half the patients with brain
  Metastatic haematogenous infection may be                 abscess have systemic symptoms, including
due to various aerobic and anaerobic strepto-               fever, at the time of the diagnosis. Marked toxic
cocci, enterobacteria and other Gram-negative               symptoms may be attributable to the abscess rup-
bacilli.                                                    turing into the ventricle or associated meningitis.
  Staph. aureus is often the pathogen in abscesses
resulting from trauma and can also be seen in
                                                            Diagnosis
postoperative abscesses.
                                                            CT scanning has been responsible for a dramatic
                                                            reduction in the mortality from cerebral abscess
Presenting features
                                                            because of its ability to diagnose single and
Patients present with features of:                          multiple abscesses and to localize the lesion
1 An intracranial mass:                                     accurately.
   (a) raised intracranial pressure                           The CT scan or magnetic resonance imaging
   (b) focal neurological signs, e.g. hemiparesis,          appearance is typically a ring-enhancing mass
   dysphasia                                                often surrounded by considerable oedema (Figs
   (c) epileptic seizures.                                  12.1–12.4). The enhancing capsule is usually thin-
2 Systemic toxicity — fever and malaise.                    ner adjacent to the ventricle compared with the
3 Clinical features of the underlying source of             more superficial capsule. The lesions may be
the infection — sinusitis, bacterial endocarditis,          multiple (Fig. 12.2b) or multiloculated (Fig. 12.3).
diverticulitis.                                             In the early stages of development of the abscess,
   The clinical features develop over 2–4 weeks,            when the infection is localized as ‘cerebritis’, the
although a slower progression is not unusual. If            CT scan or MRI appearance will be an area of low
 176                                                                                            CHAPTER 12


density which enhances after intravenous con-                 Peripheral blood examination may show a
trast but without the typical ‘ring’ appearance           leukocytosis. Raised erythrocyte sedimentation
and usually with marked adjacent oedema. MRI              rate and positive blood cultures may be obtained
is a more sensitive investigative tool and can help       if there is a coexisting septicaemia.
differentiate between an abscess and tumour. If
the abscess is due to haematogenous spread it is
                                                          Management
usually located at the grey/white matter junction
(Fig. 12.1).                                              The principles of treatment are to:
                                                          • identify the bacterial organisms
                                                          • institute antibiotic therapy
                                                          • drain or excise the abscess.
                                                            A specimen of the pus is essential for accurate
                                                          identification of the organism so that the appro-
                                                          priate antibiotic therapy can be commenced. Oc-
                                                          casionally, the organism can be identified from a
                                                          positive blood culture or other obvious source of
                                                          infection. A lumbar puncture is absolutely
                                                          contraindicated (and of no diagnostic benefit) in
                                                          the presence of a cerebral abscess.

                                                          Surgical treatment
                                                          Surgical treatment of the abscess involves either:
                                                          • aspiration of the abscess through a burr hole,
                                                          with repeated aspirations as required or
                                                          • excision of the abscess.
                                                             Drainage of the abscess through a burr hole, if
Fig. 12.1 Cerebral abscess early in its development. A    necessary using CT-guided stereotaxis, is a safe,
small contrast-enhancing lesion surrounded by low-        effective way of obtaining the pus and emptying
density cerebral oedema.                                  the abscess. It is frequently necessary to repeat




         (a)                                                (b)
Fig. 12.2 (a) Typical ring-enhancing cerebral abscess in the frontal lobe with surrounding cerebral oedema.
(b) Multiple cerebral abscesses.
 INFECTIONS OF THE CENTRAL NERVOUS SYSTEM                                                           177


                                                     Antibiotic therapy
                                                     As soon as pus has been obtained, antibiotic ther-
                                                     apy should commence. The initial choice of an-
                                                     tibiotic, before culture results are available, will
                                                     depend on the probable cause of the brain ab-
                                                     scess and the Gram stain. The usual initial
                                                     treatment is high-dose penicillin, ceftriaxone and
                                                     metronidazole. Strep. milleri is the organism most
                                                     frequently found in abscesses of sinusitic origin
                                                     involving the frontal lobe; it is highly sensitive to
                                                     penicillin. Abscesses of otitic origin, usually
                                                     occurring in the temporal lobe, are caused by a
                                                     wide range of aerobic and anaerobic bacteria. A
                                                     combination of penicillin with cefotaxime, ceftri-
                                                     axone or metronidazole should be used. Abs-
Fig. 12.3 Multiloculated cerebral abscess.           cesses of metastatic or cryptogenic origin may be
                                                     caused by streptococci or by a mixture of bacte-
                                                     ria, and broad-spectrum therapy, including peni-
                                                     cillin, should be used until bacteriological results
                                                     are available. As many of the organisms are resis-
                                                     tant to penicillin, it has been suggested that a
                                                     penicillinase-stable penicillin (e.g. flucloxacillin)
                                                     should be substituted. For postsurgical brain ab-
                                                     scess it is recommended that vancomycin be
                                                     used with cefotaxime or ceftriaxone.
                                                        As soon as the culture results are available
                                                     the appropriate antibiotic should be used intra-
                                                     venously in high doses and selection should be
                                                     made bearing in mind the antibiotic’s penetra-
                                                     tion into the brain and CSF.
                                                        Corticosteroid therapy (dexamethasone) may
                                                     be necessary to reduce cerebral oedema and
                                                     should be considered in patients who are drowsy
                                                     or have a deteriorating neurological state despite
                                                     surgery and antibiotic treatment.
Fig. 12.4 CT scan. Large cerebral abscess.              Anticonvulsant medication should be com-
                                                     menced as there is an incidence of seizures in
                                                     between 30 and 50% of cases.
the aspirations and this is best evaluated by
follow-up CT scans.
                                                     Prognosis
   Surgical excision of the abscess should be con-
sidered if:                                          The improvements in antibiotic therapy and CT
• there is persistent reaccumulation of pus de-      scanning have dramatically reduced the mortality
spite repeated aspirations                           of bacterial abscesses from 50% to less than 10%.
• the abscess is in an accessible site
• there is a well-formed fibrous capsule which
                                                     Epidural abscess
fails to collapse despite repeated aspirations
• there is a cerebellar abscess.                     Cranial epidural abscess results following:
 178                                                                                      CHAPTER 12


• trauma                                               penetrating wounds, or may follow surgery. In
• surgery — craniotomy or insertion of skull trac-     infants subdural empyema may occur as an
tion tongs                                             infection of the subdural space following
• paranasal sinusitis or mastoiditis.                  meningitis.
   The condition is frequently associated with
osteomyelitis of the cranial vault.
                                                       Microbiology
                                                       The most common organism responsible for
Clinical features
                                                       subdural empyema following frontal sinusitis is
The clinical features of an epidural abscess are       Strep. milleri. However, other aerobic and anaero-
primarily those of osteomyelitis, with acute local-    bic streptococci, other anaerobes and Staph. au-
ized pain and tenderness and localized pitting         reus may also be responsible, with a pattern
oedema of the scalp over the affected area, de-        similar to that indicated for intracerebral
scribed by Percival Pott and known as ‘Pott’s          abscesses.
puffy tumour’. There are usually systemic symp-
toms of infection. When the epidural collection
                                                       Clinical presentation
enlarges the patient will start to have symptoms
of raised intracranial pressure and, if the mass is    In contrast to patients with extradural abscesses,
large enough, associated symptoms of a neuro-          patients presenting with subdural empyemas are
logical deficit.                                        usually seriously ill, being toxic and febrile, with
   The most common organisms are aerobic and           features of meningeal irritation. They frequently
anaerobic streptococci and Staph. aureus.              have rapidly progressive neurological signs, in-
                                                       cluding depressed conscious state, hemiparesis
                                                       and dysphasia. Epileptic seizures occur in most
Treatment
                                                       patients.
Treatment involves evacuation of the pus, exci-          The classic presentation is a patient with a his-
sion of any infected bone and surgical eradica-        tory of acute frontal sinusitis who develops
tion of the underlying cause (e.g. sinus infection).   severe headaches and high fever and has a rapid
High-dose antibiotic therapy should be com-            neurological deterioration with seizures.
menced with di-/flucloxacillin plus gentamycin.
This must be utilized until the organism is identi-
                                                       Diagnosis
fied and sensitivity determined.
   The diagnosis is made on CT scan or MRI,            The differential diagnosis includes:
which will show the extradural collection of pus       • viral encephalitis
as well as osteomyelitis and the infected sinuses.     • bacterial meningitis
                                                       • brain abscess
                                                       • septic cavernous sinus thrombosis.
Subdural abscess
A subdural abscess is an uncommon but poten-
                                                       Investigations
tially life-threatening infection with possible
serious neurological sequelae in the patients          Evidence of underlying sinusitis will be present
who survive. The abscess follows infection in the      on plain skull X-ray and CT scan. The CT scan or
paranasal sinuses, particularly frontal sinusitis      MRI findings may be subtle, as the abscess is usu-
and, less commonly, infection in the mastoid air       ally iso- or hypodense. The interhemispheric col-
cells. The infection in the subdural space is an ex-   lection can easily be overlooked and thus must be
tension of the sinusitis through emissary veins        considered in patients with this sort of clinical
and retrograde thrombophlebitis.                       presentation. There may be contrast enhance-
   Subdural empyema may also result from               ment of the underlying inflamed membranes and
 INFECTIONS OF THE CENTRAL NERVOUS SYSTEM                                                          179


evidence of underlying cerebral oedema, al-
                                                       Tuberculosis
though these features are not universal.
  Lumbar puncture should not be performed if           Tuberculosis involving the brain is unusual in
the diagnosis is suspected clinically, as it is haz-   Western countries but is not uncommon in India,
ardous and frequently not diagnostic. There is         Africa, Asia, the Middle East, South America and
usually a pleocytosis in the CSF with elevated         eastern Europe. In developed countries tubercu-
protein, but the sugar may be normal and organ-        losis is more likely to present in patients who
isms cannot usually be cultured.                       are immunocompromised — HIV-positive and
                                                       immunosuppressed patients.
                                                         The infection may occur as:
Treatment
                                                       • tuberculous meningitis
Subdural empyema is a surgical emergency. The          • intracranial tuberculomas.
principles of treatment, as for any abscess, are:
• treat the source of sepsis — sinus surgery (if
                                                       Tuberculous meningitis
indicated)
• drain the abscess                                    Tuberculous meningitis is usually a subacute ill-
• identify the organism                                ness; patients present with headaches, confusion
• treat with appropriate high-dose antibiotics.        and features of meningitis. It occurs more fre-
   The surgical techniques used to drain the ab-       quently in children and will result in secondary
scess are either multiple burr holes, craniotomy       pathological changes and neurological deficit,
or craniectomy. The advantage of the multiple          including:
burr hole technique is that the pus may be wide-       • basal arachnoiditis causing hydrocephalus
spread and bilateral and the patient is frequently     • visual failure due to arachnoiditis around the
seriously ill. However, it may be difficult to drain    optic pathways
the pus adequately through burr holes, as the          • multiple cranial nerve palsies due to the basal
underlying oedematous brain may swell up to            arachnoiditis
occlude the hole. In addition, it is difficult to       • arteritis causing cerebral infarction.
provide adequate drainage for the parafalcine             CSF examination will show:
pus, which frequently lies between the falx and        • lymphocytic pleocytosis (100–500 cells/mm3)
the medial aspect of the hemispheres, through          • elevated protein (greater than 0.8 g/l)
burr holes.                                            • low glucose (less than 2 mmol/l)
   The subdural space should be irrigated with         • low chloride (less than 110 mmol/l)
antibiotic solution at the time of surgery and sub-    • acid-fast bacilli in 20% of patients using a
dural catheters should be left in place for further    Ziehl–Neelsen stain.
drainage of pus and postoperative antibiotic irri-        The definitive diagnosis is often only made on
gation. It is arguable whether the antibiotic irri-    culture of M. tuberculosis, which may take up to
gation is useful but it is probably worthwhile, in     6 weeks.
view of the seriousness of the situation.                 Antituberculous therapy should be com-
   High-dose systemic antibiotic therapy should        menced if tuberculous meningitis is suspected, as
be commenced as soon as pus is obtained for cul-       it is invariably fatal within 6 weeks and is often
ture. The initial therapy will depend on the un-       more rapidly fatal. The antituberculous medica-
derlying cause, as for cerebral abscess, bearing in    tion includes isoniazid, rifampicin, ethambutol
mind that the most common infecting organism           and pyrazinamide.
is penicillin-sensitive Strep. milleri from frontal       Hydrocephalus should be treated with a ven-
sinusitis. Further antibiotic therapy will depend      triculoperitoneal shunt. Steroid therapy has been
on the results of the culture.                         used to diminish the risk of arachnoid adhesions
   Anticonvulsant therapy is important as the pa-      and arteritis but is probably of little benefit. A
tients have a high incidence of seizures.              brief course may be indicated in patients with
 180                                                                                       CHAPTER 12


raised intracranial pressure. The serum sodium           Cerebral cryptococcosis presents as:
in older patients may drop, probably due to inap-      • meningitis
propriate antidiuretic hormone secretion, and          • meningoencephalitis
should be treated by fluid restriction.                 • cerebral granuloma.

                                                       Meningitis
Intracranial tuberculoma
                                                       The most common presentation is meningitis,
An intracranial tuberculoma or abscess origi-          which is usually subacute, and the patients pre-
nates by haematogenous spread from tubercu-            sent with increasing headaches followed by
lous lesions in other parts of the body, especially    vomiting, seizures and impaired conscious state.
the lung. They are frequently multiple and are         Papilloedema occurs in up to half of patients and
predominantly located in the posterior fossa in        cranial nerve palsies may develop.
children and young adults, but may occur
throughout the cerebral hemispheres.                   Meningoencephalitis
   The clinical presentation is similar to an in-      This will develop if the meningeal infection ex-
tracranial tumour, with features of raised in-         tends along the Virchow–Robin spaces into the
tracranial pressure, focal neurological signs and      brain.
epileptic seizures. Systemic symptoms of tuber-
culosis, such as fever, excessive perspiration and     Intracerebral granulomas
lethargy, occur in less than 50% of cases.             These are uncommon in cryptococcal infection
   The CT scan or MRI appearance of a tubercu-         but may develop in conjunction with meningitis
lous granuloma will show an area of low attenu-        or in isolation (Fig. 12.5).
ation with surrounding vasogenic oedema. The              Patients present with symptoms of raised in-
enhancement on this occasion tends to be periph-       tracranial pressure, convulsions and neurologi-
eral. Once again there may be multiple lesions.        cal deficit including lower cranial nerve palsies.
There is usually surrounding oedema and the               The CSF studies will show:
lesions may be multiple. The tuberculoma is
occasionally calcified.
   The preoperative diagnosis is usually appreci-
ated only after recognition of tuberculous foci
elsewhere in the body.
   The optimal treatment is surgical excision of
the tuberculoma, if it is in a surgically accessible
region, and antituberculous chemotherapy.


Cerebral cryptococcosis
Cryptococcosis (torula) is a fungal infection that
may involve the CNS.
   Cryptococcus neoformans is commonly found in
avian habitats, and particularly among pigeons.
The usual portal of entry is by inhalation of the
airborne cryptococcus.
   Up to half of patients with CNS involvement
have an underlying predisposing condition such
as AIDS, intravenous drug use, sarcoidosis, lym-
phoma or prolonged steroid therapy, and some           Fig. 12.5 Cryptococcal granuloma. A contrast-
patients also have cryptococcal lesions in the lung.   enhancing mass with surrounding oedema.
 INFECTIONS OF THE CENTRAL NERVOUS SYSTEM                                                             181


• elevated pressure
• pleocytosis — usually lymphocytes
• elevated protein
• decreased glucose (in 50%)
• Cryptococcus neoformans on wet preparation
stained with India ink
• positive latex cryptococcal agglutination test
which detects cryptococcal capsular antigen in CSF.


Treatment
Treatment consists of anticryptococcal therapy
using amphotericin B, 5-flucytosine or flucona-
zole. Intracerebral granulomas may need to be
excised and a thoracotomy may be necessary for
a lung lesion.
   Hydrocephalus is a common complication of
                                                      Fig. 12.6 Hydatid daughter cyst or ‘brood capsule’.
cryptococcal infection of the CNS system and
should be treated with a shunt.
                                                         The neurosurgeon is involved when the hyda-
                                                      tid cyst lodges in the brain, vertebrae or orbit.
Hydatid
Hydatid disease is endemic in rural areas, par-
                                                      Intracerebral hydatid cyst
ticularly those involved with sheep and cattle
raising such as the western region of Victoria        Intracerebral hydatid cyst presents as a mass
in Australia, South America and South Africa.         lesion with slowly developing neurological in-
Echinococcus granulosus is a small tapeworm,          volvement. Hydatid cysts in the brain are usually
about 6 mm long and with approximately four           single and large and are often primary. In rare in-
segments, which lives in the small bowel of ca-       stances they are embolic and multiple and can
nines. The ova are shed in the faeces of dogs and     arise from cysts in the left ventricle of the heart.
the intermediate hosts are cattle and sheep, al-      Cysts can also arise from rupture of a cerebral
though humans may also serve in this capacity.        cyst and secondary seedings. The MRI or CT scan
Following ingestion the egg capsule is digested       (Fig. 12.7) shows a hypodense cyst with minimal
and the hexocanth oncosphere penetrates the           or low enhancement around the margins.
intestinal mucosa and passes into the portal cir-        The surgical treatment is excision and great
culation. Most are trapped in the liver (65%) or      care should be taken to remove the cyst intact. If
lungs (20%) and less than 5% pass to the bone or      the contents are spilled the hydatid disease may
CNS. The embryos lodge within the capillaries         be disseminated through the CNS and anaphy-
and will develop into cysts, which progres-           lactic shock has occasionally been reported.
sively increase in size. The cyst is filled with         Orbital involvement is usually manifest by
the clear hydatid fluid, around which is an           unilateral proptosis. If the vertebral column is in-
inner nucleated germinative layer and an outer        volved there will be destruction of cancellous
opaque non-nucleated layer with delicate lami-        bone with vertebral collapse and possible cord
nations. Daughter cysts develop from the ger-         compression.
minative layer (Fig. 12.6). The inflammatory             If cerebral hydatid disease is suspected, clinical
reaction occurring in the tissue which sur-           examination and radiological investigation may
rounds the laminated layer does not usually           show involvement of the liver and lung. Serolog-
occur in the brain.                                   ical investigations help in the diagnosis.
 182                                                                                        CHAPTER 12




                                                        Fig. 12.8 MRI following gadolinium showing
                                                        intracerebral toxoplasmosis.




Fig. 12.7 Hydatid cyst in frontal lobe extending into
the lateral ventricle.


  Medical therapy is with prolonged use of
albendazole.


AIDS
Acquired immune deficiency syndrome (AIDS)
is due to the T-cell lymphotrophic virus type III,      Fig. 12.9 MRI of herpes simplex encephalitis with
also known as the human immunodeficiency                 major involvement of the right temporal lobe and less
                                                        severe changes in the left temporal lobe.
virus (HIV) type I.
   The virus attacks the patient’s immune system,
rendering the patient prone to opportunistic            scan and MRI (Fig. 12.8). Cerebral toxoplasma
infection or malignancy. The virus is also neu-         infections are treated with sulfadiazine and
rotrophic and can involve the CNS directly.             pyrimethamine. Cryptococcus neoformans is the
Approximately 10% of patients are diagnosed             second most common cause of CNS infection and
due to CNS symptoms at presentation and up to           other infections include tuberculosis, Candida al-
70% of patients have central nervous symptoms           bicans, herpes simplex encephalitis (Fig. 12.9) and
at death.                                               progressive multifocal leukoencephalopathy.
   CNS manifestations have several causes.              • Malignant disease of the brain may be either
• Secondary infection. The most common infec-           primary CNS lymphoma, secondary lymphoma
tion is Toxoplasma gondii, which is a mass lesion       from systemic disease or secondary Kaposi’s
and may present with features indistinguishable         sarcoma.
from a tumour. The lesions may be solitary or           • The AIDS virus may infect the nervous system
multiple and are usually ring-enhancing on CT           directly, causing the AIDS dementia complex in
 INFECTIONS OF THE CENTRAL NERVOUS SYSTEM                                                                183


over 90% of patients. This may present as a be-         lesions or hydrocephalus. Medical treatment is
havioural change similar to presenile dementia.         with albendazole or praziquantel. Steroids are
Transverse myelitis and peripheral neuropathy           used in the early stage of treatment to attenuate
may also occur.                                         the acute inflammatory response.
   The advisability of biopsy of intracerebral le-
sions in AIDS patients and the possible benefits
                                                        Herpes simplex encephalitis
are not clear at this stage, as there is no satisfac-
tory treatment of the underlying disease process.       This viral infection can present with rapid onset
A reasonable approach is to treat HIV-positive          of fever, headaches, vomiting and progressive
patients with cerebral lesions that have the radio-     neurological deterioration. The type 1 virus is the
logical appearance typical of toxoplasmosis with        causative organism in most of the adult cases. It
therapy for Toxoplasma infection, and to reserve        presents as an acute necrotizing encephalitis and
biopsy for patients who do not respond to               has a high morbidity and mortality in the absence
therapy, or if the radiological appearance is           of early antiviral therapy.
atypical for toxoplasmosis.                                Patients present with symptoms of meningitis,
                                                        a progressive deteriorating neurological state
                                                        and seizures. Diagnosis can be reached with elec-
Neurocysticercosis
                                                        troencephalography that reveals focal slowing,
This is the most common parasitic disease of the        periodic spikes or sharp and wave patterns.
central nervous system. It is caused by the larval      CT scanning can be normal initially or reveal
stage of a tapeworm Taenia solium. Human beings         oedema-like changes in the temporal or frontal
are the only definitive host for this parasite,          lobes. This can be associated with areas of haem-
whilst both humans and pigs are the intermedi-          orrhage. MRI is the investigation of choice, re-
ate hosts for the embryonic form. Infestation oc-       vealing the signal changes within the temporal
curs by eating poorly cooked infested food or           lobe with oedema and haemorrhage (Fig. 12.9).
through contamination of food by fertilizer con-        The diagnosis is confirmed by the presence of
taining the eggs. The larva penetrates the intesti-     mononuclear cells in the CSF and the detection of
nal wall and gains access to brain, muscle or eye       viral DNA. Early treatment with aciclovir is the
via the bloodstream.                                    treatment of choice and can be life-saving. Very
   There are multiple forms of neurocysticercosis,      rarely does the patient develop raised pressure
the commonest form being parenchymal disease.           to the extent of requiring intracranial pressure
However, the cyst can also be concentrated in the       monitoring, ventricular drain or a decompres-
subarachnoid space, intraventricular space, in-         sive craniotomy.
trasellar region or spinal canal.
   Neurocysticercosis commonly has multiple
                                                        Further reading
cysts at various stages of the disease process from
calcified lesions to cysts of varying sizes in vary-     Becker GL et al. (1980) Amoebic abscesses of the brain.
ing locations and often variations in terms of en-        Neurosurgery 6, 192–194.
hancement (when present).                               Bell WE (1981) Treatment of bacterial infections of
   The lesions can present with hydrocephalus,            the central nervous system. Annals of Neurology 9,
                                                          313–327.
coma, convulsions and neurological deficits.
                                                        Brown E (1987) Antimicrobial prophylaxis in neuro-
   A lumbar puncture examination of the CSF can
                                                          surgery. British Journal of Neurosurgery 1, 159–162.
be diagnostic provided it is not contraindicated.       Chan KH, Mann KS, Yue DP (1989) Neurosurgical
This cyst can occasionally be found in the                aspects of cerebral cryptococcosis. Neurosurgery 25,
CSF; however, the presence of a lymphocytosis,            44–48.
eosinophilia and a positive complement fixation          Everett ED, Stausbaugh LJ (1980) Antimicrobial agents
test will contribute to the diagnosis.                    and the central nervous system. Neurosurgery 6,
   Surgical intervention is indicated for mass            691–714.
 184                                                                                               CHAPTER 12


Garvey G (1983) Current concepts of bacterial infec-         management of bacterial brain abscesses: a review of
  tions of the central nervous system. Journal of Neuro-     102 cases over 17 years. Neurosurgery 23, 451–458.
  surgery 59, 735–744.                                     Mandel GL, Douglas RG, Bennett JE (1985) Principles
Gotvai P, De Louvis J, Hurley R (1987) The bacteriology      and Practice of Infectious Diseases, 2nd edn. John Wiley,
  and chemotherapy of acute pyogenic brain abscess.          New York.
  British Journal of Neurosurgery 1, 189–204.              Richards P (1987) AIDS and the neurosurgeon. British
Haines SJ (1989) Efficacy of antibiotic prophylaxis in        Journal of Neurosurgery 1, 163–172.
  clean neurosurgical operations. Neurosurgery 24,         Rosenblum ML, Levy RM, Bredesen DE (1986) Neuro-
  401–405.                                                   logical implications of the acquired immunodefi-
Hlavin ML, Kaminski HJ, Fenstermaker RA, White RJ            ciency syndrome (AIDS). Clinical Neurosurgery 34,
  (1994) Intracranial suppuration: a modern decade of        419–445.
  postoperative subdural empyema and epidural ab-          Stephanov S (1988) Surgical treatment of brain ab-
  scess. Neurosurgery 34, 974–981.                           scesses. Neurosurgery 22, 724–730.
Mampalam TJ, Rosenblum ML (1988) Trends in the
                            CHAPTER 13


  13                        Low back pain and leg pain



About 90% of the population suffer from
                                                         Sciatica
low back pain at some time and 30% of these
will develop leg pain due to lumbar spine
                                                         Aetiology (Table 13.1)
pathology.
   The critical factor in assessing patients with        The most common cause of sciatica is a lumbar
low back pain is whether there are also features of      disc prolapse causing nerve root compression.
lumbosacral nerve root compression, such as leg          Sciatica-type pain may also occur as a result of
pain or focal signs of neural compression in the         bony compression of the nerve root, usually by
lower limbs. In general, neurosurgeons are prin-         an osteophyte, and is often associated with lum-
cipally concerned with lumbar spine pathology            bar canal stenosis or spondylolisthesis. Narrow-
that causes nerve root compression.                      ing of the ‘lateral recess’ of the spinal canal
   Sciatica is the clinical description of pain in the   may also occur in conjunction with lumbar canal
leg due to lumbosacral nerve root compression            stenosis, and may cause compression of a nerve
which is usually in the distribution of the sciatic      root. Sciatica may occasionally be caused by tu-
nerve. Sciatica was first mentioned in an Egypt-          mours of the cauda equina or by pelvic tumours,
ian manuscript dated 2500–3000 BC. In 1934               such as spread from carcinoma of the rectum.
Mixter and Barr established that a prolapsed
lumbar intervertebral disc was commonly the
                                                         Anatomy and pathology
cause of sciatica.
   Lumbar canal stenosis, a narrowing of the lum-        Nearly 75% of the lumbar flexion–extension and
bar spinal canal, is the other major spinal cause of     of total spinal movement occurs at the lumbo-
leg pain. In 1949 Verbiest specifically defined the        sacral junction, 20% of lumbar flexion–extension
clinical significance of the narrow spinal canal          occurs at the L4/5 level and the remaining 5% is
and the syndrome of intermittent neurogenic              at the upper lumbar levels. Consequently, it is not
claudication of the legs.                                surprising that 90% of lumbar disc prolapses
   A lumbar disc prolapse can occur at any age in        occur at the lower two lumbar levels; the most
adults but is uncommon in teenagers. The symp-           frequently affected disc is at the L5/S1 level.
toms of lumbar canal stenosis usually commence              The lumbar disc consists of an internal nucleus
after the 5th decade. Although lumbar canal              pulposus surrounded by an external laminar
stenosis and lumbar disc prolapse may be pre-            fibrous container, the annulus fibrosus. A disc
sent in the same patient, they each produce a            prolapse may consist of the nucleus pulposus
distinct clinical entity which will be described         bulging, with the annulus being stretched but
separately.                                              intact. Alternatively, the nucleus may rupture
                                                         through the annulus and sequestrate as a free
                                                         fragment under the posterior longitudinal liga-
                                                         ment or lie in the extradural space. Prolapse of

                                                                                                        185
 186                                                                                         CHAPTER 13



  Table 13.1 Causes of sciatica.

  Prolapsed lumbar disc
  Lumbar spondylosis (osteophyte)
  Lumbar canal stenosis (lateral recess)
  Lumbar spondylolisthesis
  Cauda equina tumours (e.g. ependymoma)
  Pelvic tumours (e.g. rectal carcinoma)
  Spinal arteriovenous malformation (rare)




the disc is usually in a posterolateral direction, as
                                                        (a)                          (b)
the posterior longitudinal ligament prevents
                                                        Fig. 13.1 The diagram shows (a) a posterolateral
direct posterior herniation. Less frequently the
                                                        lumbar disc proplapse causing compression of lumbar
disc may herniate laterally to trap the nerve in
                                                        nerve root passing across the disc to enter the neural
the neural foramen.                                     canal below the pedicle and (b) a lateral disc prolapse
   A prolapsed intervertebral disc causes com-          causing compression of the nerve root passing beneath
pression of the nerve which runs along the              the pedicle above the disc prolapse.
posterior aspect of the disc and down under
the pedicle of the vertebra below (Fig. 13.1). Con-
sequently, an L4/5 posterolateral intervertebral        may be present, the important feature is the pain
disc prolapse will usually compress the L5 nerve        which radiates down the leg in the distribution of
root, which runs caudally across the disc to enter      the affected nerve. The pain usually radiates into
the neural foramen below the L5 pedicle. Simi-          the buttock, along the posterolateral aspect of the
larly, a lumbosacral (L5/S1) disc prolapse will         thigh and calf into the foot (S1 nerve root); it may
usually affect the S1 nerve root. The less common       extend into the dorsum of the foot and great toe
lateral disc prolapse will cause compression of         (L5 nerve root). An L3/4 disc herniation may pro-
the nerve root at one level higher than expected        duce pain in the posterior thigh but, as with an
(e.g. L4 nerve root compression due to L4/5             L2/3 disc prolapse, the pain is frequently along
lateral disc prolapse). In the case of a large disc     the anterior aspect of the thigh. L4 root pain fre-
prolapse, there may be evidence of more than            quently radiates into the anterior aspect of the
one nerve root compression.                             lower leg. Depending on the degree of nerve root
   Cauda equina compression may result if the           compression, the patient may complain of senso-
disc herniation is sufficient to rupture the pos-        ry disturbance such as numbness or tingling in
terior longitudinal ligament and produce a pos-         the leg or foot, and weakness may be present. The
terior central disc prolapse.                           history must include an assessment of sphincter
                                                        function, as a large disc prolapse may cause
                                                        cauda equina compression.
Patient assessment
The patient suffering from sciatica will be in ob-
                                                        Examination features
vious discomfort, which will be reflected by
movements and posture when lying supine. The            Lumbar back movements may be restricted and a
patient lies tilted, usually to the side opposite to    scoliosis may be seen, usually concave to the side
the sciatica, with the affected hip and knee            of the affected leg. Straight leg raising (Lasegue’s
slightly flexed taking pressure off the stretched        test) will be restricted on the affected side and, in
nerve. The pain is worse on movement, cough-            severe cases, pain in the affected leg will be re-
ing, sneezing or straining. Although back pain          produced when the opposite leg is raised.
 LOW BACK PAIN AND LEG PAIN                                                                                187



  Table 13.2 Segmental innervation of lower limb musculature.

  L1     Psoas major; psoas minor
  L2     Psoas major; iliacus; sartorius; gracilis; pectineus; adductor longus; adductor brevis
  L3     Quadriceps; adductors (magnus, longus, brevis)
  L4     Quadriceps; tensor fasciae latae; adductor magnus; obturator externus; tibialis anterior; tibialis
           posterior
  L5     Gluteus medius; gluteus minimus; obturator internus; semimembranosus; semitendinosus; extensor
           hallucis longus; extensor digitorum longus and peroneus tertius; popliteus
  S1     Gluteus maximus; obturator internus; piriformis; biceps femoris; semitendinosus; popliteus;
           gastrocnemius; soleus; peronei (longus and brevis); extensor digitorum brevis
  S2     Piriformis; biceps femoris; gastrocnemius; soleus; flexor digitorum longus; flexor hallucis longus;
           some intrinsic foot muscles
  S3     Some intrinsic foot muscles (except abductor hallucis; flexor hallucis; brevis; flexor digitorum brevis;
           extensor digitorum brevis)




   Examination of the neurological disability
                                                            Table 13.3 Segmental innervation of lower limb
should proceed in an ordered fashion. Initially a
                                                            joint movements.
search is made for ‘wasting’ in specific muscle
groups, particularly the quadriceps, calf muscles,
                                                            Hip       Flexors, adductors, medial       L1, 2, 3
extensor digitorum brevis muscle and the small                          rotators
muscles of the foot. The patient is then examined                     Extensors, abductors, lateral    L5, S1
for weakness in each of the muscle groups (Tables                       rotators
13.2 and 13.3). Weakness of dorsiflexion of the
                                                            Knee      Extensors                        L3, 4
foot and extension of the great toe (extensor
                                                                      Flexors                          L5, S1
hallucis longus) is most commonly caused by
a prolapsed L4/5 intervertebral disc with in-               Ankle     Dorsiflexors                      L4, 5
volvement of the L5 nerve root; severe cases may                      Plantar flexors                   S1, 2
result in a complete foot drop.                             Foot      Invertors                        L4, 5
   Plantar flexion weakness is caused by com-                          Evertors                         L5, S1
pression of the S1 nerve root, usually due to a                       Intrinsic muscles                S2, 3
prolapsed lumbosacral disc. However, plantar
flexion is a very strong movement and any weak-
ness may be difficult to elicit unless tested by ask-
ing the patient to stand on the toes of the affected
side. A large prolapsed disc at the L4/5 level may
result in some plantar flexion weakness because           Sensation should be tested in the foot and leg
of compression of the S1 nerve root, and simi-           (Fig. 13.2).
larly a large lumbosacral disc prolapse may be             At the end of the examination the patient
associated with dorsiflexion weakness due to L5           should be turned prone so that the buttocks can
nerve root compression.                                  be inspected for atrophy of the gluteal muscles,
   The deep tendon reflexes should be carefully           sensation can be tested along the back of the legs
tested as they provide objective evidence of             and in the perianal region, and anal tone can be
nerve root compression. The ankle jerk is de-            assessed. A rectal examination should be per-
pressed or absent when the S1 nerve root is com-         formed if there are clinical features suggestive of
pressed, usually by a lumbosacral disc prolapse.         a pelvic tumour.
 188                                                                                            CHAPTER 13


                                                              L3/4 prolapsed intervertebral disc
                                                              • Pain in the anterior thigh
                                     S4         L2            • Wasting of the quadriceps muscle
              L1
                          Ventral                             • Weakness of the quadriceps function and dor-
                                          S3
                          axial                               siflexion of foot
                          line
              L2                                              • Diminished sensation over anterior thigh,
                                                              knee and medial aspect of lower leg
                                           S2
                                                     Dorsal   • Reduced knee jerk.
                                                     axial
                   L3                L3              line
Extension                                                     Management
forwards            L4
from dorsal                                                   Most patients with sciatica achieve good pain
axial line
               L5                                             relief with simple conservative treatment and
                                     L4
                                                L5            less than 20% will require surgery. The likelihood
                                                              of symptomatic relief without surgery is related
                                                              to the pathology of the disc prolapse. A ‘bulging’
                                                              disc is likely to settle with simple conservative
               S1                                             measures, but sciatica due to a nucleus pulposus
                    L5                    S1                  that has herniated out of the disc space and ‘se-
                                    L5
                                                              questrated’ outside the annulus will probably
                                                              need surgery for satisfactory relief of symptoms.
Fig. 13.2 Segmental distribution of nerves of the
lumbar and sacral plexuses to the skin of the anterior        Conservative treatment
and posterior aspect of the lower limb.                       Most patients achieve good pain relief following
                                                              bed rest, usually for a period of about 7–10 days,
                                                              and the use of simple analgesic agents and
                                                              non-steroidal anti-inflammatory medication. Al-
Summary of clinical features
                                                              though traction is sometimes recommended it
Clinical localization of the disc prolapse should             probably has only limited benefit and may result
be possible in the majority of patients with scia-            in lower leg complications. Resolution of the
tica. The following features are typical (but not             pain is probably due to a combination of some
invariable) of disc herniation.                               resorption of the prolapsed disc material, the
                                                              oedema of the nerve decreasing and possible
L5/S1 prolapsed intervertebral disc                           adaptation of the pain fibres to pressure. Spinal
• Pain along the posterior thigh with radiation to            manipulation is not recommended and the con-
the heel                                                      cept that a disc prolapse can be ‘reduced’ by ma-
• Weakness of plantar flexion (on occasion)                    nipulation is a myth. Initially, the only necessary
• Sensory loss in the lateral foot                            investigations are a plain lumbar spine X-ray and
• Absent ankle jerk.                                          an erythrocyte sedimentation rate (ESR). The
                                                              lumbar spine X-ray will diagnose an associated
L4/5 prolapsed intervertebral disc                            spondylolisthesis which may contribute to the
• Pain along the posterior or posterolateral thigh            sciatica, and it also helps to exclude sinister
with radiation to the dorsum of the foot and great            pathology, such as metastatic tumour involving
toe                                                           the spinal vertebrae. The ESR will also exclude
• Weakness of dorsiflexion of the toe or foot                  systemic disease.
• Paraesthesia and numbness of the dorsum of                    Some clinicians advocate the use of high-dose
the foot and great toe                                        corticosteroids in the conservative management
• Reflex changes unlikely.                                     of sciatica due to lumbar disc prolapse. Whilst
 LOW BACK PAIN AND LEG PAIN                                                                              189


steroid therapy may help to give transient pain          mobilizing despite adequate relief with bed rest.
relief, the limited benefit is probably outweighed        In this group of patients physiotherapy and a
by the possible complications of corticosteroid          limited trial of a spinal brace might be tried, but
treatment.                                               they usually have only limited success.
   Chemonucleolysis has, in the past, been advo-
cated as a treatment for lumbar disc prolapse. It        Neurological deficit. A significant weakness or in-
involves the intradiscal injection of a proteolytic      creasing amount of weakness is an indication for
enzyme, such as chymopapain, which dissolves             early investigation and surgery.
disc material. Chymopapain was first isolated in
1941 and has been used intermittently since 1963         Central disc prolapse. Patients with bilateral sciati-
in clinical studies. There is a small risk of serious    ca or other features indicating a central disc
anaphylactic reaction following intradiscal injec-       prolapse, such as sphincter disturbance and di-
tion. Although chymopapain dissolves the nor-            minished perineal sensation, should be investi-
mal nucleus pulposus it has a high failure rate in       gated promptly. An acute central disc prolapse
the treatment of prolapsed disc, as it fails to affect   may lead to acute, severe, irreversible cauda
the extruded disc material, and further nerve            equina compression and should be investigated
compression may occur following chemonucle-              and treated as an emergency.
olysis from the disc dissolving and collapsing, re-
sulting in narrowing of the intervertebral neural        Tumour. Surgery is indicated if the clinical fea-
foramen. The procedure is not recommended for            tures suggest that a tumour could be the cause of
use at this time.                                        sciatica.

Indications for surgery
                                                         Investigations
Pain. The most common indication for surgery in
patients with disc prolapse is pain in the follow-       Lumbar myelography (Fig. 13.3) was the time-
ing situations.                                          honoured investigation for lumbar disc prolapse.
• Incapacitating pain despite 7–10 days of bed           The use of water-soluble non-ionic contrast
rest.                                                    material avoids the risk of the postmyelogram
• Continuing episodes of recurrent pain when             arachnoiditis previously seen with the oil-based




          (a)                               (b)
Fig. 13.3 Lumbar myelogram using water-soluble contrast medium showing (a) posterolateral L4/5 disc
prolapse and (b) complete block due to a large central L5/S1 disc protrusion.
 190                                                                                             CHAPTER 13


mediums. Although myelography is now much
safer, there is a very small risk of reaction to the
contrast medium, particularly epileptic seizures.
Some patients suffer headaches following the
myelogram. These are due to the lumbar punc-
ture (Chapter 2) and/or the effects of the contrast
material.
   High-quality computerized tomography scan-
ning (Figs 13.4 and 13.5) and magnetic resonance
imaging (Fig. 13.6) have largely superseded
myelography for the diagnosis of lumbar disc
prolapse. The MRI is especially helpful in show-
ing the size, configuration and position of the disc
prolapse, as well as any associated nerve root or
thecal compression. In addition the MRI will also
demonstrate pathology at other discs, such as de-
generative changes as evidenced by decreased
signal in the disc on the T2-weighted scans.


Operative procedure for lumbar disc prolapse
The operation involves excision of the disc pro-
lapse with decompression of the affected nerve
root.
   In the past the operation usually entailed a                 (a)
complete or partial laminectomy, identification
of the compressed nerve root, its mobilization off
the disc prolapse and excision of the herniated
disc. However, with improvements in instru-
mentation and magnification, e.g. the operating
microscope, most disc prolapses can be excised
with minimal disturbance to the normal bony
anatomy and with the removal of only a small
amount of bone, usually from the adjacent lami-
nae on the side of the prolapse.
   A full laminectomy may occasionally be neces-
sary prior to the disc excision of a large central
disc prolapse causing cauda equina compression.                 (b)
   A percutaneous lumbar discectomy to remove             Fig. 13.4 (a) CT scans of lumbar spine showing
the nucleus pulposus is sometimes advocated for           posterolateral disc prolapses. (b) CT scan of left
the ‘bulging’ lumbar disc. However, if the disc is        posterolateral disc prolapse after intrathecal contrast.
‘bulging’ the sciatica will nearly always settle
with conservative treatment and surgery is not
                                                          Postoperative mobilization
necessary. A percutaneous discectomy of the in-
tradiscal contents will fail to relieve the sciatica if   Most patients commence walking the day after
the disc has ruptured through the annulus, be-            surgery and are discharged from hospital on day
cause it will not remove the herniated disc mate-         2 or 3 following the operation. A gently graduat-
rial causing the nerve root compression.                  ed mobilizing programme should be carefully
 LOW BACK PAIN AND LEG PAIN                                                                          191


                                                     and straining for the first 4 weeks. A graduated
                                                     active exercise programme can commence after
                                                     the first month.


                                                     Prognosis following surgery
                                                     The results following lumbar disc surgery are
                                                     directly related to the accuracy of the preopera-
                                                     tive clinical evaluation. Excellent results can be
                                                     achieved if:
                                                     • there is a good history of sciatica
                                                     • there are good signs of nerve root irritation
                                                     • the investigations show evidence of a
Fig. 13.5 CT scan of left lateral disc prolapse.     herniated disc
                                                     • at surgery the nerve root is stretched by a disc
                                                     prolapse
                                                     • the patient is well motivated.
                                                        If any of the above criteria are absent the results
                                                     following surgery are disappointing.
                                                        Recurrent sciatica following surgery occurs in
                                                     about 10% of cases and is usually due to further
                                                     disc prolapse, either at the same level or at
                                                     another level. The principles of management are
                                                     similar to those described for the initial treatment
                                                     of sciatica. Recurrent sciatica is sometimes due to
                                                     adhesions developing around the nerve root
                                                     causing perineural fibrosis. The treatment is con-
                                                     servative, with judicious use of bed rest followed
                                                     by gentle mobilizing exercises, simple analgesic
                                                     medication and non-steroidal anti-inflammatory
                                                     agents. Surgery to excise the adhesions is suc-
                                                     cessful in relieving the pain in less than 60% of
                                                     patients.
                                                        Rarely, recurrent sciatica is due to intradural
                                                     arachnoiditis. Treatment is conservative and
                                                     surgery to divide the intradural adhesion is
                                                     rarely successful.


                                                     Lumbar canal stenosis
                                                     The patient with lumbar canal stenosis usually
                                                     complains of pain radiating diffusely into the
Fig. 13.6 MRI of lumbar disc prolapse.               legs, particularly when standing or walking. The
                                                     pain may be a diffuse ache, or is sometimes de-
explained to the patient, often with the help of a   scribed as having a ‘burning’ quality; it is usually
physiotherapist. Gentle back strengthening exer-     relieved with sitting and patients often adopt a
cises commence after 10 days, and the patient        posture of bending the body forward when walk-
should avoid prolonged periods of sitting, lifting   ing to help relieve the discomfort. The pain may
 192                                                                                     CHAPTER 13


be similar to that described by patients with vas-
cular occlusive disease, although a key feature is
the presence of pain when standing only.
   On occasions there may be features of sciatica-
like pain in association with the diffuse pain of
lumbar canal stenosis due to entrapment of a
nerve root by an osteophyte or within the ‘lateral
recess’ of the canal.
   The patient often complains of a subjective
feeling of weakness and of a diffuse ‘numbness’
and ‘tingling’ radiating down the legs. Sphincter
difficulties may occur if the stenosis is particul-
arly severe.


Examination findings                                   Fig. 13.7 CT scan of lumbar spine showing severe
                                                      lumbar canal stenosis.
The examination of the lower limbs and back
often reveals little or no abnormality. Focal wast-
ing may occur in the lower limbs if the compres-
sion is severe, and the ankle jerks may be            usually straightforward, but it should be con-
depressed or absent. Definite sensory disturbance      firmed by radiological investigations. High-
or weakness occur only in the most severe cases.      quality CT scanning (Fig. 13.7) and MRI (Fig.
   The peripheral pulses should be checked as the     13.8) have replaced the need for myelography
symptoms may mimic those due to peripheral            (Fig. 13.9). All these radiological studies demon-
vascular disease.                                     strate the canal stenosis. The myelogram will
                                                      show marked indentation of the contrast column
                                                      and, if the stenosis is severe, there may be a com-
Pathology and anatomy
                                                      plete block to the flow of contrast. The MRI will
The stenosis of the lumbar canal may involve re-      show the extent and severity of the stenosis as
duction of the sagittal diameter of the canal, nar-   well as other pathology related to the lumbar
rowing of the ‘lateral recess’ and stenosis of the    discs such as degenerative disease and prolapse.
neural foramen. The pathology is frequently due          The clinical features of lumbar canal stenosis
to a combination of congenital canal stenosis and     do not respond favourably to conservative treat-
degenerative pathology, such as lumbar spondy-        ment, and surgery is almost invariably successful
losis with hypertrophy of the facet joints and        in relieving the symptoms. The operation con-
ligamentum flavum, osteophyte formation and            sists of a decompressive lumbar laminectomy
thickening of the laminae causing further nar-        extending over the whole region of the stenosis
rowing of the canal and bulging of the discs such     with decompression of the lumbar theca and
that the space for the neural elements becomes        nerve roots.
compromised.                                             The patient can be mobilized promptly after
   The most frequently affected levels are L4/5       the operation and a course of gently graduated
and L3/4. The lumbosacral level may be in-            active exercises prescribed, usually with the help
volved, but this is less common. The stenosis may     of a physiotherapist.
also be related to a degenerative spondylolisthe-
sis, particularly at the L4/5 level.
                                                      Back pain
                                                      Low back pain without leg pain or signs of nerve
Management
                                                      root compression is a common problem. The
The clinical diagnosis of lumbar canal stenosis is    usual presentations are:
 LOW BACK PAIN AND LEG PAIN                                                                      193




Fig. 13.8 MRI showing severe canal stenosis.


• acute low back pain, often following minor
trauma
• chronic or recurrent low back pain.
   Acute sudden-onset back pain, following a rec-
ognized episode of trauma, is usually due to soft     Fig. 13.9 Lumbar myelogram showing lumbar canal
tissue strain. If the injury was severe it may have   stenosis.
caused a fracture or disc herniation. The manage-
ment of patients with an acute onset of back pain
following trauma involves:
• history and examination to exclude symptoms
and signs of nerve root compression
  194                                                                                        CHAPTER 13


• radiological evaluation to exclude fracture or          clinician to the possibility of a more sinister basis
disc herniation (if severe trauma)                        for the back pain.
• conservative management with initial bed rest              Intra-abdominal pathology should also be con-
followed by gentle mobilization and simple anal-          sidered in patients presenting with back pain,
gesic medication.                                         especially:
   Most of the pain and stiffness should settle           • pancreatic disease — pancreatitis or tumours
after a few days, although mild discomfort may            • aortic aneurysm
linger for some weeks.                                    • renal disease — calculus, infection or tumour.
   The more difficult problem is chronic or recur-            Lumbar spondylosis, a degenerative disease
rent back pain, where the patient gives a history         involving the vertebral column, is the most
of less severe or even trivial trauma. In some            common demonstrable cause of low back pain.
cases no pathological cause will be found. The            The arthritic process may involve any of the
most common aetiology is degenerative disease             spinal joints and be associated with degenera-
which includes:                                           tive disc disease. Low back pain, without fea-
• lumbar spondylosis                                      tures of sciatica, is only rarely caused by disc
• spondylolisthesis                                       prolapse, and then only if the prolapse is large
• degenerative disc disease.                              and central.
   Other uncommon but important causes of low
back pain which, in the early stages, may present
                                                          Spondylolisthesis
without pain radiating into the legs or radicular
signs, include:                                           Spondylolisthesis is a subluxation of one verte-
• spinal tumours (Chapter 15)                             bral body on another, usually involving the L4 or
• thoracic disc prolapse (Chapter 15)                     L5 levels, and may be due to congenital defects
• spinal abscess (Chapter 15)                             involving the neural arch or to degenerative
• arteriovenous malformation (Chapter 15).                changes. Spondylolysis describes a defect in the
   These serious but unusual causes may present           pars interarticularis, often the precondition for
with acute or chronic back pain but nearly always         spondylolisthesis (Fig. 13.10).
have other features, e.g. symptoms or signs of              Various classifications have been used to
nerve root involvement, which would alert the             categorize spondylolisthesis; most subdivide the




(a)




Fig. 13.10 Lumbar spondylolysis with bilateral defects in the
                                                                   (b)
pars interarticularis.
 LOW BACK PAIN AND LEG PAIN                                                                                195



  Table 13.4 Classification of spondylolisthesis.

  Congenital
  Dysplastic          Congenital deficiency of superior facet of sacrum or inferior facet of 5th lumbar vertebra
  Isthmic             Lesion in pars interarticularis
                        Lytic fatigue fracture
                        Elongated but intact pars
                        Acute fracture

  Degenerative        In adults, usually at L4/5; a cause of lumbar canal stenosis

  Traumatic

  Pathological        Paget’s disease, neoplastic, osteogenesis imperfecta and achondroplasia




forms into those of congenital and those of de-
generative origin (Table 13.4).
   The congenital dysplastic variety results from
congenital deficiencies of the superior facets of
the sacrum or the inferior facets of the 5th lumbar
vertebra. The lumbosacral junction is incapable
of withstanding the truncal forces imposed by
the erect stance and there is gradual forward slip-
page of the 5th vertebral body. This is frequently
associated with spina bifida occulta of L5 or S1.
The congenital isthmic category involves a defect
of the pars interarticularis, either a lytic fatigue
fracture or, rarely, when the interarticularis frac-
ture occurs following severe trauma.                      Fig. 13.11 CT scan showing lumbar spondylolisthesis
   A further subtype is when the pars is elongated
but intact.
   Degenerative spondylolisthesis, also known as
pseudospondylolisthesis, results from severe              pain, which may radiate into the buttocks, but
localized arthritis of the facets (apophyseal             patients often complain of a ‘tight’ feeling in the
joints) of the slipped vertebrae.                         upper thighs. Symptomatic children and adoles-
   Radiological investigations, including plain X-        cents often have a gait disturbance, the so-called
rays, CT scan and MRI, will show the type of              ‘tight hamstring’ syndrome.
spondylolisthesis, the amount of slippage and                The vertebral slippage may produce compres-
the associated narrowing of the neural canals             sion of the lumbar nerve roots in the neural fora-
(Fig. 13.11). The degree of subluxation is com-           men. This causes sciatica, the symptoms of which
monly described by the percentage of slip (Tail-          may be indistinguishable from those due to disc
lard method) or assigned a grade (I–IV) based on          prolapse. Narrowing of the bony canal may
the number of quarters of the adjacent body               result in clinical symptoms of ‘lumbar canal
spanned by the slip.                                      stenosis’.

Clinical presentation                                     Treatment
The presenting features involve back pain and             Children and adolescents
leg pain. The initial symptom is usually back             In the majority of children and adolescents
 196                                                                                       CHAPTER 13


symptomatic spondylolisthesis responds to con-        conservative treatment, where the radiological
servative treatment. The following indications        findings show a relative absence of degenerative
are guidelines for lumbar fusion.                     disease as a cause for the pain. This is an uncom-
• Pain unrelieved by conservative measures.           mon situation since, in most cases, it is not possi-
• Progression of subluxation on serial radiologi-     ble to identify that the spondylolisthesis is the
cal studies.                                          sole cause of the back pain.
• Subluxation of greater than 30%.                    • Documented progressive subluxation. This is
• Tight hamstring gait.                               uncommon in adults but is a definite indication
  The usual surgical procedure is a spinal fusion.    for spinal fusion.
Only rarely is a laminectomy necessary, and it          In general, the treatment of symptomatic grade
should never be performed unless the spine is         I spondylolisthesis by fusion and fixation re-
fused as there will be a progressive slip.            mains controversial and should be considered on
                                                      an individual basis. Symptomatic patients with a
Adults                                                grade II slip usually benefit from surgery, and
In most patients conservative therapy involving       symptomatic patients with grade III or IV benefit
short periods of bed rest during exacerbations of     greatly.
discomfort, gentle mobilizing exercises, simple
analgesic medication and non-steroidal anti-in-
                                                      Further reading
flammatory medication will be sufficient. If some
pain persists following bed rest a period with a      Bogduk N (2004) Management of chronic low back
properly fitted lumbar brace may be of value.            pain. Medical Journal of Australia 180 (2), 79–84.
Surgery involves either a laminectomy to decom-       Branch CL, Handley EN, Ducker T (1995) Treatment of
press the neural structures and/or a spinal             lumbosacral spondylolisthesis. In: Al-Mefty O, Orig-
                                                        itano TC, Harkey HL, eds. Controversies in Neuro-
fusion to prevent instability. The indications for
                                                        surgery. Thieme, New York.
laminectomy include:
                                                      Hardy RW (1982) Lumbar disc disease. Seminars in Neuro-
• symptomatic spinal canal stenosis (that is,           logical Surgery. Raven Press, New York.
symptoms of lumbar canal stenosis)                    Kaye AH, Black P McL (2000) Operative Neurosurgery.
• clinical features of nerve root compression           Churchill Livingstone, London, New York,
(e.g. sciatica) unrelieved by conservative therapy.     Edinburgh.
   A laminectomy decompresses the lumbar              Maroon JC, Young P, Tarlov E, Haines SJ (1995) Treat-
theca and nerve roots, usually with satisfactory        ment of lumbar disc protusion, percutaneous discec-
relief of lower limb symptoms. However, a               tomy, microdiscectomy, conservative treatment. In:
laminectomy may increase the instability and            Al-Mefty O, Origitano TC, Harkey HL, eds. Contro-
some surgeons prefer to combine a decompres-            versies in Neurosurgery. Thieme, New York.
                                                      Mixter W, Barr J (1934) Rupture of the intervertebral
sive laminectomy with a spinal fusion. An
                                                        disc with involvement of the spinal canal. New Eng-
intertransverse fusion between the transverse
                                                        land Journal of Medicine 211, 210–214.
processes has been the traditional method of          Sherman FC, Rosenthal RK, Hall JE (1979) Spine fusion
fusion, but more recently internal pedicle screw        for spondylolysis and spondylolisthesis in children.
fixation and/or interbody ‘cages’ placed in the          Spine 4, 59–67.
emptied disc space between the vertebral bodies       Vierbiest H (1954) A radicular syndrome from develop-
have become the preferred method.                       mental narrowing of the lumbar vertebral canal.
   Spinal fusion, without laminectomy, is occa-         Journal of Bone and Joint Surgery 36B, 230–237.
sionally indicated and should be considered in        Wiltse LL, Newman PH, MacNab I (1976) Classification
patients with the following conditions.                 of spondylolysis and spondylolisthesis. Clinical Or-
• Incapacitating low back pain unrelieved by            thopaedics 177, 23–29.
                          CHAPTER 14


 14                       Cervical disc disease and
                          cervical spondylosis


Cervical spine disorders predominantly cause
                                                     Anatomy and pathology
neck pain and/or arm symptoms. Cervical disc
prolapse and cervical spondylosis are the two        The structure of the cervical disc is essentially the
common cervical spine disorders. Degenerative        same as in the lumbar region and consists of an
changes in the vertebral column are the basic un-    internal nucleus pulposus surrounded by the ex-
derlying pathological processes in both these        ternal fibrous lamina, the annulus fibrosus. The
conditions. Although the two conditions may be       role of trauma in the degenerative process and
distinct clinical entities, the shared common        disc herniation is not clear. It is probable that
pathogenetic mechanism results in a spectrum of      repetitive excessive stresses do exacerbate the
clinical presentation depending upon whether         normal ageing process and cause disc degenera-
the degenerative disease has resulted primarily      tion. Although it is frequently possible to identify
in disc rupture or cervical spondylosis. As in the   some minor episode of trauma prior to the onset
lumbar region the critical clinical feature de-      of an acute disc prolapse, a readily identifiable
pends on whether there is nerve root entrapment      episode of more major trauma as the precipitat-
causing arm pain and/or focal signs of neural        ing event is much less frequent.
compression in the upper limb. Cervical cord            The cervical disc prolapse is usually in the
compression due to disc prolapse or cervical         posterolateral direction, because the strong
spondylosis is discussed in Chapter 15.              posterior longitudinal ligament prevents direct
                                                     posterior herniation. The posterolateral disc
                                                     herniation will cause compression of the adja-
Cervical disc prolapse
                                                     cent nerve root as it enters and passes through
In the 1934 report of their experiences with rup-    the intervertebral neural foramen. Unlike the
tured intervertebral discs, Mixter and Barr          lumbar region, the nerves pass directly laterally
described four cases with cervical disc disease.     from the cervical cord to their neural foramen,
Prolapse of an intervertebral disc is less common    so that the herniation compresses the nerve at
in the cervical region than in the lumbar area.      that level (Fig. 14.1). The arrangement of the
The disc herniation occurs most frequently at        cervical nerve roots and the relationship to
the C6/7 level and slightly less commonly at the     the vertebral bodies differ from the lumbar
C5/6 level. Disc herniation above these levels       region — the C1 nerve root leaves the spinal
and at the C7/T1 level is much less common. The      canal between the skull (the foramen magnum)
predominant frequency of disc prolapse at C6/7       and the atlas, and the C8 root, for which there is
and C5/6 is due to the force exerted at these        no corresponding numbered vertebra, passes
levels which act as a fulcrum for the mobile         through the C7/T1 foramen. Consequently, a
spine and head.                                      C5/6 disc prolapse will cause compression of
                                                     the C6 nerve root, a C6/7 prolapse causes com-
                                                     pression of the C7 nerve root and the C7/T1 disc

                                                                                                      197
 198                                                                                         CHAPTER 14


                                                          lesions, middle finger (and sometimes index fin-
                                                          ger) in C7 lesions, and little and ring fingers in C8
                                                          lesions. The patient may notice weakness of the
                                                          arm, particularly if the C7 root is affected, as this
                                                          causes weakness of elbow extension and the
                                                          movement has only very little supply by other
                                                          nerve roots (C8). A severe C5 root lesion may
                                                          cause weakness of shoulder abduction and the
                                                          patient may complain of difficulty in elevating
                                                          the arm.


                                                          Examination features
                                                          Cervical spine movements will be restricted and
Fig. 14.1 Posterolateral cervical disc prolapse causing   the head is often held rigidly to one side, usually
compression of the adjacent nerve root.                   moderately flexed, and tilted towards the side of
                                                          the pain in some patients but occasionally away
                                                          from it in others. Lateral tilt relaxes the roots on
prolapse causes compression of the C8 nerve               the side of the concavity but diminishes the inter-
root.                                                     vertebral foraminae, and flexion slightly sepa-
   Occasionally a cervical disc may herniate              rates the posterior part of the intervertebral space
directly posteriorly, causing compression of the          and lessens the tension in the prolapse. If the disc
adjacent cervical spinal cord (Chapter 15) which          herniation is long standing there may be wasting
is a neurosurgical emergency.                             in the appropriate muscle group, particularly the
                                                          triceps in a C7 root lesion. The patient is then ex-
                                                          amined for weakness in each of the muscle
Clinical presentation
                                                          groups (Tables 14.1 and 14.2). Weakness of elbow
The characteristic presenting features of a patient       extension and finger extension is most common-
with an acute cervical disc herniation consist of         ly caused by a C6/7 prolapse with compression
neck and arm pain and the neurological manifes-           of the C7 nerve root. Less commonly, disc hernia-
tations of cervical nerve root compression.               tion with compression of the C5 root will cause
   Although the pain usually begins in the cervi-         weakness of shoulder abduction, compression of
cal region it characteristically radiates into the        the C6 root will cause mild weakness of elbow
periscapular area and shoulder and down the               flexion, and compression of C8 may cause weak-
arm (brachial neuralgia). The neck pain com-              ness of the long flexor muscles, triceps, finger ex-
monly regresses while the radiating arm pain be-          tensors and intrinsic muscles.
comes more severe. It is usually described as a              The deep tendon reflexes provide objective ev-
‘deep’, ‘boring’ or ‘aching’ pain and the patient is      idence of nerve root compression in the following
usually severely distressed and debilitated by the        distribution.
discomfort. The distribution of the pain is wide-         • Biceps reflex                                    C5
spread and conforms to sclerotomes (segmental             • Brachioradialis (supinator) reflex               C6
distribution to muscle and bone) rather than to           • Triceps reflex                                   C7
dermatomes. The patient frequently complains                 Sensation should be tested in the arm and hand
of sensory disturbance, particularly numbness or          and the sensory loss will be characteristic for the
tingling in the distribution of the dermatome af-         nerve root involved (Fig. 14.2) although there
fected. The location of the sensory disturbance is        may be some overlap.
more useful than the pain as an indication of root           A full neurological examination must be per-
level: thumb (and sometimes index finger) in C6            formed and particular care taken to assess the
 CERVICAL DISC DISEASE AND CERVICAL SPONDYLOSIS                                                                      199



  Table 14.1 Segmental innervation of upper limb musculature.

  C3, 4     Trapezius; levator scapulae

  C5        Rhomboids; deltoids; supraspinatus; infraspinatus; teres minor; biceps

  C6        Serratus anterior; latissimus dorsi; subscapularis; teres major; pectoralis major (clavicular head);
            biceps; coracobrachialis; brachialis; brachioradialis; supinator; extensor carpi radialis longus

  C7        Serratus anterior; latissimus dorsi; pectoralis major (sternal head); pectoralis minor; triceps;
            pronator teres; flexor carpi radialis; flexor digitorum superficialis; extensor carpi radialis longus;
            extensor carpi radialis brevis; extensor digitorum; extensor digiti minimi

  C8        Pectoralis major (sternal head); pectoralis minor; triceps; flexor digitorum superficialis; flexor
            digitorum profundus; flexor pollicis longus; pronator quadratus; flexor carpi ulnaris; extensor carpi
            ulnaris; abductor pollicis longus; extensor pollicis longus; extensor pollicis brevis; extensor indicis;
            abductor pollicis brevis; flexor pollicis brevis; opponens pollicis

  T1        Flexor digitorum profundus; intrinsic muscles of the hand (except abductor pollicis brevis; flexor
            pollicis brevis; opponens pollicis); hypothenar muscles




  Table 14.2 Segmental innervation of upper limb                                C3
  joint movements.                                                                                        C4
                                                                              C4

  Shoulder     Abductors and lateral           C5                                                   T2
                                                                         C5                                C5
                rotators
               Adductors and medial            C6, 7, 8                         T2
                rotators

  Elbow        Flexors                         C5, 6
               Extensors                       C7, 8

  Forearm      Supinators                      C6
                                                                                   T1                T1
               Pronators                       C7, 8

  Wrist        Flexors and extensors           C6, 7

  Digits       Long flexors and extensors       C7, 8                  C6
  Hand         Intrinsic muscles               C8, T1

                                                                                                          C8
                                                                 C6        C8                                        C6
                                                                                                                C7
                                                                    C7
presence in the lower limbs of long tract signs,
such as increased tone, a pyramidal pattern of
weakness, hyperreflexia or an upgoing plantar
response. If there is a cervical disc herniation
                                                             Fig. 14.2 Upper limb dermatome distribution.
these features will indicate that it is compressing
the spinal cord.


Summary of clinical features
Clinical localization of disc prolapse is possible in
 200                                                                                      CHAPTER 14


most patients with brachial neuralgia due to cer-
                                                       Management
vical disc prolapse. The following features are
typical (but not invariable) for disc herniation:      Most patients with arm pain due to an acute soft
                                                       cervical disc herniation achieve good pain relief
C6/C7 prolapsed intervertebral disc (C7 nerve root)    with conservative treatment. This should include
• Weakness of elbow extension                          bed rest, a cervical collar, simple analgesic
• Absent triceps jerk                                  medication, non-steroidal anti-inflammatory
• Numbness or tingling in the middle or index          medication and muscle relaxants. Manipulation
finger.                                                 of the neck is potentially hazardous and is
                                                       contraindicated.
C5/6 prolapsed intervertebral disc (C6 nerve root)        The following are indications for further inves-
• Depressed supinator reflex                            tigation and surgery.
• Numbness or tingling in the thumb or index           1 Pain:
finger                                                     (a) continuing severe arm pain for more than
• Occasionally mild weakness of elbow flexion.             10 days without benefit from conservative
                                                          therapy
C7/T1 prolapsed intervertebral disc (C8 nerve root)       (b) chronic or relapsing arm pain.
• Weakness may involve long flexor muscles,             2 Significant weakness in the upper limb that
triceps, finger extensors and intrinsic muscles         does not resolve with conservative therapy.
• Diminished sensation in ring and little finger        3 Evidence of a central disc prolapse causing
and on the medial border of the hand and forearm       cord compression — this should be investigated
• Triceps jerk may be depressed.                       urgently.


Differential diagnosis                                 Radiological investigations
The clinical features of an acute cervical disc pro-   High-quality MRI is now the investigation of
lapse, with severe neck and arm pain and com-          choice and has almost completely replaced both
monly diminished sensation in the dermatome of         myelography and CT (Fig. 14.3). The cervical
the affected cervical root, are so characteristic      myelogram using water-based non-ionic iodine
that in the vast majority of cases the diagnosis is    contrast material was a most useful investigation
self-evident. The most common cause of radiat-         for determining the presence and site of the disc
ing arm pain, other than acute prolapse, is            herniation (Fig. 14.4). CT scanning by itself is fre-
spondylosis but, as has been indicated, disc pro-      quently not helpful, but if performed following
lapse and spondylosis are aspects of one continu-      intrathecal iodine contrast it will demonstrate a
ing degenerative process and, in the cervical          disc herniation, and smaller volumes of intra-
region, the distinction between them becomes           thecal contrast are necessary than with myelo-
blurred. Other unlikely but possible differential      graphy (Fig. 14.5).
diagnoses include:
• cervical nerve root compression by a spinal
                                                       Operative procedure
tumour (e.g. meningioma, neurofibroma)
(Chapter 15)                                           The two most commonly performed operations
• thoracic outlet syndrome (Chapter 17)                for cervical disc prolapse are:
• Pancoast’s tumour infiltrating the roots of the       1 Cervical foraminotomy with excision of the
brachial plexus                                        disc prolapse.
• peripheral nerve entrapments, such as carpal         2 Anterior cervical discectomy, with subsequent
tunnel syndrome, median nerve entrapment in            fusion.
the cubital fossa and tardy ulnar palsy (Chapter
17).                                                   Cervical foraminotomy. This involves fenestration
 CERVICAL DISC DISEASE AND CERVICAL SPONDYLOSIS                                                        201




       (a)




                                                       (b)




                                                       Fig. 14.3 MRI of cervical disc prolapse. (a) Cervical
                                                       axial T1-weighted image (arrow shows disc prolapse).
                                                       (b,c) Sagittal MRI showing disc prolapse compressing
                                                       the spinal theca and distorting the cervical cord.
       (c)


of the bone posteriorly, to provide direct access to   recurrent disc herniation, but this is very uncom-
the cervical nerve root and disc prolapse. A small     mon. In general, the results of the procedure are
amount of bone from the lateral margins of the         very satisfactory, with excellent relief of arm pain
adjacent lamina and articular facets is removed to     and, provided the nerve has not been irreparably
identify the nerve root in the foramen. Further        damaged by long-standing disc herniation, re-
bone can then be removed from around the nerve         turn of full strength to the arm.
root to enlarge the neural canal. The nerve root is
gently retracted and the disc herniation excised.      Anterior cervical discectomy. This involves an ante-
The major advantages of the technique are that         rior approach to remove the cervical disc and the
the nerve is directly decompressed both by re-         prolapse. Some surgeons perform formal fusion
moval of the disc herniation and by enlargement        at the level using bone taken from the iliac crest,
of the foramen, and cervical fusion is not neces-      bovine bone, artificial bone, or an intervertebral
sary. The major disadvantage is the possibility of     cage, usually filled with bone chips. The fusion
 202                                                                                        CHAPTER 14




                                                        Fig. 14.5 CT myelogram showing a posterolateral
                                                        cervical disc protrusion.



                                                        Cervical spondylosis
                                                        Cervical spondylosis is a degenerative arthritic
Fig. 14.4 Cervical myelogram showing a postero-         process involving the cervical spine and affecting
lateral cervical disc protrusion with compression
                                                        the intervertebral disc and zygapophyseal joints.
of the cervical nerve root.
                                                        Radiological findings of cervical spondylosis are
                                                        present in 75% of people over 50 years of age who
may be supplemented by a metal (usually titani-         have no significant symptoms referable to the
um) plate screwed onto the anterior vertebral           cervical spine.
surface, bridging the disc space. Some surgeons
do not perform a formal fusion, as spontaneous
                                                        Pathological changes
fibrous or bony fusion will occur across the disc
space provided all the disc has been excised. The       The degenerative process resulting in cervical
major disadvantage is that the fusion will result       spondylosis and its progression occur in most
in additional stress at the adjacent cervical levels,   cases largely as a result of the inevitable stresses
thereby rendering them more prone to degenera-          and traumas that occur to the cervical spine as a
tive disease.                                           result of the normal activities of daily living. It is
   An anterior approach with disc excision is           probable that the process is aggravated by repet-
mandatory for a central disc protrusion.                itive or chronic trauma, as may occur in some oc-
                                                        cupations, and as a result of an episode of severe
Postoperative care                                      trauma.
Whatever approach is used, the patient is encour-          The process principally involves the interver-
aged to mobilize the day after surgery. A soft cer-     tebral discs and zygapophyseal joints. Reduced
vical collar may be useful in the first week after a     water content and fragmentation of the nuclear
foraminotomy to minimize the neck pain. A firm           portion of the cervical discs are natural ageing
collar is usually worn for the first 4–6 weeks after     processes. As the disc degenerates there is
anterior discectomy, or until there is evidence of      greater stress on the articular cartilages of the
fusion.                                                 vertebral end-plates and osteophytic spurs de-
  The prognosis for pain relief following the op-       velop around the margins of the disintegrating
eration is excellent provided the diagnosis has         end-plates, projecting posteriorly into the spinal
been accurate and the nerve decompressed.               canal and anteriorly into the prevertebral space.
 CERVICAL DISC DISEASE AND CERVICAL SPONDYLOSIS                                                       203


The degenerative process involving the zy-              disc prolapse, in that the pain radiates diffusely
gapophyseal joints will also lead to osteophyte         into the periscapular area and shoulder, and into
formation. The intervertebral foramen may be            the upper limb in a scleratomal distribution.
narrowed by these osteophytes, so causing com-          There may be other features of nerve root com-
pression of the nerve root. The osteophyte forma-       pression, including numbness and tingling in the
tion that causes compression of the nerve in the        appropriate dermatome distribution, and weak-
neural foramen, and which is seen around a              ness of the arm. Although the clinical features
bulging annulus, is sometimes called a ‘hard disc       may be almost indistinguishable from those due
protrusion’, as distinct from the acute ‘soft’ cervi-   to an acute soft disc prolapse, the process is usu-
cal disc herniation.                                    ally not as acute and the patient often has a histo-
   The spondylitic process may cause narrowing          ry of intermittent or chronic pain. Wasting of a
of the spinal canal as a result of osteophyte for-      muscle group in the appropriate nerve root dis-
mation, particularly the formation of hyper-            tribution is more common because of the longer
trophic bony ridges at the anterior intervertebral      history, but the examination findings will other-
spaces of the spinal canal and hypertrophy of           wise be similar to those seen with an acute soft
the ligamenta flavum. This may result in com-           disc protrusion.
pression of the underlying cord. Such compres-
sion is maximal during hyperextension of                Cervical myelopathy. This may result from cervical
the neck and may cause cervical myelopathy              spondylosis causing narrowing of the spinal
(Chapter 15).                                           canal with compression of the underlying spinal
                                                        cord. The features of progressive weakness and
                                                        sensory disability are described in Chapter 15.
Presenting features
There are three major manifestations of cervical
                                                        Radiological findings
spondylosis, depending on whether there is com-
pression of a cervical nerve root or the spinal         Plain cervical spine X-rays (Fig. 14.6) show:
cord.                                                   • narrowing of the disc space (the C5/C6 and
1 Neck pain.                                            C6/C7 levels are the most commonly affected)
2 Radiating arm pain.                                   • osteophyte formation with encroachment into
3 Cervical myelopathy (Chapter 15).                     either the spinal canal or neural foramen
                                                        • reduced mobility at positions of fusion and in-
Neck pain. This is the most common clinical man-        creased mobility at adjacent levels.
ifestation of cervical spondylosis and its onset           The indications for further radiological investi-
may be precipitated by minor trauma. The pain           gations depend on the clinical presentation.
usually settles over a period of a few days or          Although CT scan will clearly show the bony
weeks but frequently recurs and is associated           changes seen on the plain cervical spine X-rays, it
with increasing stiffness of the neck.                  is not indicated for the investigation of cervical
                                                        spondylosis which is causing only neck pain.
Radiating arm pain. Brachial neuralgia (radiating       Nerve root entrapment, causing arm pain, is best
arm pain) results from a nerve root being com-          visualized by high-quality MRI. A CT scan fol-
pressed in the neural foramen by osteophyte for-        lowing intrathecal contrast or a cervical myelo-
mation, with subsequent narrowing of the bony           gram with water-based non-ionic iodine contrast
canal. The patient frequently has a history of          will also show the nerve root compression, but
intermittent neck pain as a result of cervical          are now only rarely necessary as MRI provides
spondylosis for some months or years, and the           such excellent visualization of the pathology and
onset of the arm pain may be precipitated by an         nerve root compression. The radiological assess-
episode of minor trauma. The clinical features are      ment of cervical myelopathy is discussed in
similar to the neuralgia caused by an acute soft        Chapter 15.
 204                                                                                         CHAPTER 14


                                                        gesics. During an acute episode the patient may
                                                        be more comfortable in a soft cervical collar. As
                                                        the pain subsides the patient should be encour-
                                                        aged to perform simple mobilizing exercises
                                                        which may be best undertaken with the supervi-
                                                        sion of a physiotherapist. If the episodes become
                                                        frequent and severe the patient may need to con-
                                                        sider a change of lifestyle, particularly work
                                                        practices and recreational behaviour, which
                                                        might be aggravating the cervical spondylosis.

                                                        Arm pain
                                                        The symptoms frequently settle with the man-
                                                        agement described above. The following are in-
                                                        dications for surgery.
                                                        • Severe pain that does not settle with conserva-
                                                        tive treatment over 2–3 weeks.
                                                        • Chronic or recurrent pain.
                                                        • Progressive weakness in the arm which causes
                                                        functional disability. The most frequently in-
                                                        volved nerve root producing significant func-
Fig. 14.6 Cervical spondylosis. There is narrowing of
                                                        tional weakness is the C7 root, but the C8 or C5
the C5/6 and C6/7 disc spaces, osteophyte formation
                                                        roots may also result in functional disability as a
and a subluxation at the C4/5 level.
                                                        result of long-standing root compression.
                                                           The choice of surgical procedure is similar to
Differential diagnosis                                  that for an acute soft disc prolapse. Cervical fora-
                                                        menotomy, with decompression of the nerve
Neck pain
                                                        root, excision of the osteophytes and enlarge-
There are numerous possible causes of neck pain,
                                                        ment of the neural foramen, is an effective surgi-
depending on the mode of clinical presentation
                                                        cal technique. As the spondylitic process is often
and the presence of neurological signs in the
                                                        at multiple levels, two roots often need to be de-
limbs. The most common cause of neck pain is a
                                                        compressed. Some surgeons favour an anterior
minor muscular or ligamentous strain which
                                                        approach and cervical discectomy with excision
usually follows minor trauma. If there has been a
                                                        of the osteophyte extending into the neural fora-
major injury then a fracture dislocation or acute
                                                        men. The decompression is followed by a fusion
disc herniation should be considered and exclud-
                                                        as described in the previous section on cervical
ed. Other rare causes of neck pain are spinal tu-
                                                        disc prolapse.
mours or spinal abscess.
  The other possible diagnoses in a patient
                                                        Cervical myelopathy
presenting with arm pain have been described
                                                        (See Chapter 15.)
earlier in the chapter.

                                                        Further reading
Management
                                                        Adams CBT, Logue V (1971) Studies in cervical
Neck pain due to cervical spondylosis                    spondylitic myelopathy: 1. Movement of the cervical
The pain usually resolves with simple conserva-          roots, dura and cord and their relationship to the
tive measures, including the use of non-steroidal        course of the extrathecal roots. Brain 94, 557–568.
anti-inflammatory medication and simple anal-            Hoff J (1980) Cervical spondylosis. In: Wilson CB, Hoff
 CERVICAL DISC DISEASE AND CERVICAL SPONDYLOSIS                                                              205


  JT, eds. Current Surgical Management of Neurological       Martins AN (1976) Anterior cervical discectomy with
  Disease. Churchill Livingstone, New York.                    and without interbody bone graft. Journal of Neuro-
Kaye AH, Black P McL (2000) Operative Neurosurgery.            surgery 44, 290–295.
  Churchill Livingstone, London, New York,                   Simeone FA, Vise WM, Grob D, Henderson F (1995)
  Edinburgh.                                                   Treatment of soft cervical disc herniation. In: Al-
Lees F, Aldren-Turner JW (1963) Natural history and            Mefty O, Origitano TC, Harkey HL, eds. Controversies
  prognosis of cervical spondylosis. British Medical           in Neurosurgery. Thieme, New York.
  Journal 2, 1607–1610.                                      Zeidman SM, Ducker TB (1992) Cervical disc diseases
Lunsford LD et al. (1980) Anterior surgery for cervical        (Review). Neurosurgery Quarterly 2, 116–159.
  disc disease. Part 1. Treatment of lateral cervical disc
  herniation: 253 cases. Journal of Neurosurgery 53, 1–11.
                           CHAPTER 15


 15                        Spinal cord compression



Compression of the spinal cord is a common neu-         (c) extradural
rosurgical problem. Although the initial clinical       (d) intradural.
manifestations vary considerably, if the condi-       4 Haematoma:
tion is unrecognized and untreated the eventual         (a) spontaneous (trauma)
outcome will inevitably be disabling paralysis          (b) arteriovenous malformation.
and sphincter disturbance. Spinal cord compres-       5 Developmental:
sion requires early diagnosis and urgent treat-         (a) syrinx
ment if these disastrous consequences are to be         (b) arteriovenous malformation
avoided.                                                (c) arachnoid cyst.
    The compression may occur at any position           Although there is a large range of possible
from the cervicomedullary junction to the conus       causes of cord compression, in clinical practice
medullaris. Although compression of the cauda         the large majority are due to the following.
equina is not strictly spinal cord compression, the   1 Extradural:
pathophysiology and treatment is so similar that        (a) metastatic tumour
it is considered with cord compression.                 (b) extradural abscess.
    Spinal trauma may also cause cord compres-        2 Intradural, extramedullary:
sion but will be discussed separately in the next       (a) meningioma
chapter (Chapter 16).                                   (b) schwannoma.
                                                      3 Intramedullary:
                                                        (a) glioma (astrocytoma and ependymoma)
Pathology
                                                        (b) syrinx.
The spinal cord may be compressed by lesions            Table 15.1 shows a list of the possible causes
that are:                                             of spinal cord compression and their primary
• extradural (80%)                                    positions.
• intradural, extramedullary (15%)
• intramedullary (5%).
                                                      Presenting features
  The major groups of pathological causes are:
1 Tumour:                                             There are two major presenting features that are
  (a) metastatic                                      the hallmarks of spinal cord compression.
  (b) primary.                                        1 Pain.
2 Degenerative:                                       2 Neurological deficit.
  (a) disc prolapse                                     There is considerable variation in the manner
  (b) osteoporosis/spondylosis.                       in which these two major features present, de-
3 Infection:                                          pending on:
  (a) vertebral body                                  • the site of the compression and the involve-
  (b) disc space                                      ment of adjacent nerve roots

206
 SPINAL CORD COMPRESSION                                                                              207


                                                       compression, with involvement of the thoracic
  Table 15.1 Spinal cord compression.
                                                       nerve roots, will often be associated with pain
                                                       radiating around the chest wall. This ‘girdle’ pain
  Extradural
                                                       is an important feature associated with a lesion
  Metastatic tumour
  Lymphoma
                                                       which may cause cord compression. Whereas
  Myeloma                                              back pain in general is a non-specific common
  Leukaemia                                            symptom, usually associated with degenerative
  Primary vertebral body tumour                        disease, ‘girdle’ pain should arouse the suspicion
  Chordoma                                             of an underlying sinister cause. The pain is often
  Disc prolapse                                        aggravated by coughing and straining.
  Osteoporosis/spondylosis                             • ‘Central’ pain due to spinal cord compression
  Extradural abscess                                   itself is an unpleasant diffuse dull ache, often
  Extradural haematoma                                 with a ‘burning’ quality, and is frequently de-
  Intradural, extramedullary                           scribed with difficulty. It may involve a limb or
  Meningioma                                           side of the trunk, depending on the segment
  Schwannoma                                           involved.
  Arteriovenous malformation                              Flexion or extension of the neck may cause
  Spinal seeding from intracranial tumour              ‘electric shock’ or tingling radiating down
    (medulloblastoma, ependymoma)
                                                       through the body to the extremities of the limbs.
  Intramedullary                                       This is called Lhermitte’s sign, and is typically as-
  Glioma — ependymoma, astrocytoma                     sociated with cervical cord involvement, either
  Arteriovenous malformation, haematoma                by a compressive lesion or due to an inflammat-
  Abscess                                              ory process.
  Metastatic tumour
  Syrinx
                                                       Neurological deficit
  Haemangioma
                                                       The neurological features of spinal cord compres-
                                                       sion consist of:
                                                       • progressive weakness
                                                       • sensory disturbance
• the speed of the compression                         • sphincter disturbance.
• the pathological cause and the nature of the
compressive lesion                                     Motor impairment
• the involvement of the blood supply of the           The level of paralysis will depend on the position
spinal cord.                                           of the cord compression. Thoracic cord compres-
                                                       sion will result in a progressive paraparesis of the
Pain                                                   lower limbs and if the cervical cord is involved
Pain is a common early feature of cord compres-        the upper limbs will also be affected. The com-
sion and often precedes the onset of any neuro-        pression of the corticospinal pathways will result
logical disturbance, sometimes by many months.         in an upper motor neurone weakness with little
• Pain is due to involvement of local, pain-           or no wasting, increased tone, increased deep
sensitive structures, such as the bone of the verte-   tendon reflexes and positive Babinski response.
bral column. Pain in the back may also be caused       As the cord becomes more severely compressed a
by spasm of the erector spinae muscles.                complete paraplegia will result. The weakness
• Pain of spinal root origin is due to involvement     has an initial ‘pyramidal’ pattern, with the flexor
of the nerve root at the level of the compression.     movements being most severely affected, whilst
In cervical compression nerve root involvement         the extensor movements, e.g. hip extension, knee
will cause pain radiating into the upper limb in       extension and plantar flexion, are relatively
the distribution of the nerve root. Thoracic cord      preserved.
 208                                                                                                  CHAPTER 15


   As described in Chapter 1, the pattern of weak-
ness may also be influenced by the position of
the compressing lesion. The descending corti-
cospinal pathways decussate at the level of the
                                                                                      C3
cervicomedullary junction so that lateral com-
                                                                             C4
pression in the spinal cord will initially cause                              T3
                                                                                           T2
weakness, predominantly on the side of the com-                                              4
                                                                                  5
pressing lesion.                                                                             6
   The compressing mass will cause weakness of                                    7               T
                                                                                             8    2
the nerve root segment at the involved level. In                         T        9
                                                                        1                  10
the cervical region this will result in a lower
                                                                                   11
motor neurone weakness of the involved nerve                                            12
                                                                              L1
roots in the upper limb, with the other associated
                                                                                                        C
features of focal wasting and depressed reflexes                                                          8
at that level. A mass below T1 in the thoracic area                                          L2
will cause no clinically demonstrable nerve root
weakness. In the lumbar region, involvement of
the conus medullaris may produce a mixture of
lower motor neurone features and upper motor
neurone signs in the lower limbs.
   Cauda equina compression produces a lower
motor neurone pattern of weakness.

Sensory disturbance
A sensory level is the hallmark of spinal cord
compression. In the thoracic region the sensory
level will be to all modalities of sensation over
                                                       Fig. 15.1 Dermatomes of the trunk (thoracic) and
the body or trunk, although there may be spar-         adjacent cervical and lumbar areas. The sensory level
ing of some modalities in the early stages of com-     will be a useful guide to the level of cord compression.
pression. A useful guide to remember is the T4         (See also Figs 13.2 and 14.2.)
dermatome lies at the level of the nipple, the T7
at the xiphisternum and the T10 at the umbilicus.
Careful examination will often reveal a band of        eral spinothalamic tracts, whereas the fibres of
minor hyperaesthesia at the level of the com-          proprioception ascend in the dorsal columns of
pression. If the compression is in the cervical        the spinal cord and do not cross until they reach
area there will be sensory loss in the upper limb      the low medullary region. Intrinsic lesions affect-
in the appropriate dermatomal pattern (Fig.            ing the central cord in the cervicothoracic region
15.1).                                                 and damaging the sensory neurones crossing to
   Specific patterns of sensory loss will occur de-     the lateral spinothalamic tract will initially cause
pending on the tracts within the cord that are         a ‘cape-like’ distribution of thermoanalgesia,
initially involved. A laterally placed mass will       such as occurs in syringomyelia (Chapter 11, Fig.
initially cause a ‘Brown-Séquard’ syndrome.            11.3). The sacral fibres lie peripherally in the lat-
There will be contralateral impairment of pain         eral spinothalamic tracts and so some degree of
and temperature sensation, with ipsilateral pyra-      sacral sparing can occur, even with large intrinsic
midal weakness and impairment of joint position        lesions. Analgesia affecting primarily the saddle
sense, vibration and fine touch. This is because        area (buttocks and upper posterior thigh) occurs
the fibres of pain and temperature cross to the op-     particularly in cauda equina or conus medullaris
posite side of the spinal cord to ascend in the lat-   lesions.
 SPINAL CORD COMPRESSION                                                                              209


Sphincter involvement                                  ular planning the most appropriate surgical
Sphincter disturbance occurs following compres-        approach.
sion of the spinal cord, conus medullaris or cauda
equina. The first symptom is difficulty in initiat-      Spinal myelography, using water-soluble, iodine-
ing micturition and this is followed by urinary        based contrast agents injected intrathecally, was
retention, which is often relatively painless.         the benchmark investigation for confirming the
Constipation and faecal incontinence will subse-       diagnosis and the level of spinal cord compres-
quently occur. The clinical signs include an en-       sion prior to MRI. The contrast is injected in-
larged, palpable bladder, diminished perianal          trathecally in the lumbar region and the level of
sensation and decreased anal tone.                     the compression can be identified. If there is a
                                                       complete block to the flow of contrast it is often
In summary the clinical features of spinal cord        helpful to inject further contrast using a Cl/2
compression are:                                       puncture, so as to ascertain the upper level of the
• pain — local and radicular                           block. The pattern of ‘block’ on the myelogram
• progressive weakness of the limbs                    will usually demonstrate whether the cord has
• sensory disturbance — often a sensory level          been compressed by an extradural mass or an ex-
• sphincter disturbance.                               tramedullary intradural tumour, or whether the
                                                       cord is swollen by an intramedullary lesion (Fig.
                                                       15.2).
Management
The general principles of management are simi-         Computerized tomography scanning at the level of
lar whatever the cause of the cord compression.        the compression and just above and below the
It is again emphasized that the investigations         area will often help to further demonstrate the
and treatment must be undertaken as a matter of        nature and cause of the compression and give
urgency once the diagnosis is suspected, so as to      more detail about the adjacent bony structures.
reduce the possibility that the neurological
deficit will progress or become permanent.              Plain spinal X-rays are essential in patients with
Spinal cord compression is a neurosurgical             spinal cord compression. The important radio-
emergency.                                             logical features are:
                                                       • focal bony destruction indicating a metastatic
Radiological investigations                            lesion, e.g. erosion of a pedicle, vertebral collapse
The radiological studies undertaken to confirm          • evidence of multiple destructive or sclerotic
the diagnosis of spinal cord compression include:      lesions, indicating multiple metastatic tumours
• plain spinal X-rays                                  • thinning of a pedicle and widening of the
• MRI                                                  interpedicular distance, suggestive of long-
• myelography                                          standing intradural compression
• CT scan (with intrathecal contrast).                 • scalloping of the posterior surface of the verte-
                                                       bral body, indicating a long-standing intradural
Magnetic resonance imaging is of considerable          lesion
value in diagnosing the cause and position of          • expansion of an intervertebral foramen on
spinal cord compression, and has replaced myel-        oblique X-rays, indicative of a neurofibroma
ography as the definitive investigation. It is by far   • destruction of a disc space, suggestive of
the best investigation for spinal cord compres-        infection.
sion as it is a non-invasive investigation and will
clearly show the pathological changes in the ver-      Other investigations
tebral body, spinal canal, spinal cord and par-        • Further investigations to evaluate the extent of
avertebral region, thereby helping considerably        the disease and site of origin may be useful in pa-
with treatment planning in general, and in partic-     tients with metastatic disease prior to surgery.
 210                                                                                        CHAPTER 15


       Extradural                              Intradural
         Complete                Extramedullary             Intramedullary
           block                      block                      block
Uneven edge to contrast   Rounded edge of contrast material
material                                    Cord displaced to one side




                                                                               Fig. 15.2 Diagram of
                                                                               myelographic appearance due
                                                                               to extradural, intradural and
                          Contrast material is splayed
                          around the swollen cord
                                                                               extramedullary, or
                                                                               intramedullary lesions.



However, these investigations should not delay           monly affected but metastases may occur at any
the definitive treatment.                                 site and are often multiple. The compression is
• Many patients with malignant disease have a            due to the tumour itself or to vertebral collapse,
poor general medical condition and require car-          or a combination of these.
diorespiratory and biochemical assessment prior             The clinical features are basically as described
to surgery.                                              in the previous section. The patient invariably
                                                         complains of pain local to the involved region
                                                         and a radicular girdle pain is frequently present.
Treatment
                                                         Although, in retrospect, minor symptoms of cord
The standard treatment for spinal cord compres-          compression may have been present for a few
sion is urgent surgery, except in some cases of          weeks or even months, there is often a rapid neu-
compression due to malignant tumour, in which            rological deterioration resulting in paralysis, sen-
treatment with high-dose glucocorticosteroids            sory disturbance and sphincter difficulties.
and radiotherapy is indicated. This will be dis-            Urgent investigation and treatment is essential
cussed further in the next section.                      if permanent severe disability (Figs 15.3–15.5) is
                                                         to be avoided.
                                                            Surgical treatment for malignant spinal cord
Malignant spinal cord compression
                                                         compression utilizes either:
By far the most common cause of spinal cord              • decompressive laminectomy (posterior ap-
compression results from extradural compres-             proach) or
sion by malignant tumours. The most common               • vertebrectomy and fusion (anterior approach).
tumours are:                                                The decision regarding the type of surgery will
• carcinoma of the lung                                  depend on the position of the compressive lesion
• carcinoma of the breast                                (whether anterior or posterior to the spinal cord)
• carcinoma of the prostate                              and the extent of the compression.
• carcinoma of the kidney                                   The standard treatment has been a decompres-
• lymphoma                                               sive laminectomy over the affected levels. The
• myeloma.                                               exposed tumour is resected as much as possible
   Less common tumours include leukaemias,               to relieve the cord compression. Glucocortico-
melanoma, carcinoma of the thyroid and primary           steroids (e.g. dexamethasone) are often used to
sarcomas.                                                reduce local oedema of the spinal cord, and the
   The thoracic region is by far the most com-           surgery is usually followed by radiotherapy.
 SPINAL CORD COMPRESSION                                                                            211


   If the metastatic tumour is localized to one or        anterior tumour and reconstruction with fixation
two vertebral bodies only, and is causing com-            may be appropriate. However, this entails a more
pression anterior to the spinal cord, a posterior         major operative procedure and may not be toler-
decompressive laminectomy may not relieve the             ated or indicated in debilitated patients with
compression and may result in vertebral instabil-         widespread metastatic tumour.
ity. Vertebral body resection, excision of the               The initial results following surgical decom-
                                                          pression depend largely on the severity and
                                                          length of time of the preoperative compression.
                                                          Patients with a complete paraplegia of more than
                                                          36 hours have a poor prognosis for neurological
                                                          recovery.
                                                             Some studies have shown that urgent radio-
                                                          therapy, with high-dose glucocorticosteroids,
                                                          may be effective in controlling the tumour caus-
                                                          ing spinal cord compression. The treatment must
                                                          be commenced immediately following diagnosis
                                                          and should be considered:
                                                          • if the patient has a known primary tumour
                                                          that is radiosensitive (e.g. carcinoma of the
                                                          prostate, lymphoma)
                                                          • if there is a partial incomplete neurological
                                                          lesion that is only slowly progressive
Fig. 15.3 Extensive destruction of vertebral body and     • if sphincter function is retained.
adjacent neural arch with invasion into spinal canal by      This form of treatment is also particularly
metastatic carcinoma.                                     advantageous if the tumour is mostly anterior




Fig. 15.4 Extradural block on
myelogram due to metastatic carcinoma.       (a)                         (b)
 212                                                                                      CHAPTER 15



                                                       Schwannoma (neurofibroma)
                                                       Schwannomas are the most common of the in-
                                                       trathecal tumours and may occur at any position.
                                                       They arise invariably from the posterior nerve
                                                       roots and grow slowly to compress the adjacent
                                                       neural structures. Occasionally the intrathecal tu-
                                                       mour extends through the intervertebral fora-
                                                       men to form a ‘dumb-bell’ tumour, and the
                                                       tumour may rarely present as a mass in the tho-
                                                       rax, neck or posterior abdominal wall.
                                                          The presenting features are those of a slowly
                                                       growing tumour causing cord compression. Pain
                                                       in a radicular distribution is the most common
     (a)
                                                       first symptom and is often present for several
                                                       years. In the cervical region there may be evi-
                                                       dence of long-standing neurological involve-
                                                       ment of the cervical nerve root prior to the
                                                       features of cord compression becoming apparent.
                                                       There is frequently some degree of a Brown-
                                                       Séquard syndrome due to the lateral position of
                                                       the tumour.
                                                          The plain X-rays show radiological evidence of
                                                       bone erosion, and enlargement of the interverte-
                                                       bral foramen is typical (Fig. 15.6). A large tumour




     (b)
Fig. 15.5 (a,b) MRI of metastatic tumour in cervical
vertebral bodies and compression of spinal cord.



to the spinal cord over a number of vertebral
levels because the compression from this type
of lesion may not be satisfactorily relieved
following a posterior decompressive lamin-
ectomy.
   Conversely, radiotherapy as the primary form
of treatment is not appropriate if:
• the tumour is known to be radioresistant
• the compression is primarily due to bone col-
lapse rather than tumour mass
• the origin of the tumour is not known
• there is a rapidly progressive neurological          Fig. 15.6 Enlarged neural foramen due to
deficit and/or sphincter disturbance.                   schwannoma.
 SPINAL CORD COMPRESSION                                                                                213




       (a)




                                                        (b)




       (c)
Fig. 15.7 (a) ‘Dumb-bell’ schwannoma extending through intervertebral neural foramen. The intrathecal contrast
medium outlines the tumour in the spinal canal causing spinal cord compression. (b) MRI of schwannoma.
(c) MRI of cervical schwannoma.

will erode the adjacent part of the vertebral body        The treatment is surgical excision of the
and there is frequently an increase in the inter-       tumour. Access to the tumour is obtained
pedicular distance.                                     by a laminectomy. If there is a large extraspi-
   The myelogram and CT scan (following in-             nal extension it may be necessary to obtain
trathecal contrast) will show an intradural tu-         additional exposure through the neck, chest or
mour with cord compression (Fig. 15.7) and the          abdomen.
CT scan will also show the extraspinal extension.
MRI with intravenous gadolinium contrast has
                                                        Spinal meningioma (Fig. 15.8)
replaced myelography for the diagnosis of these
lesions (Fig. 15.7b).                                   Spinal meningiomas occur particularly in mid-
 214                                                                                   CHAPTER 15




         (a)                                       (b)




                                                   Fig. 15.8 (a) Intradural extramedullary block on
                                                   myelogram due to meningioma. (b) Meningioma with
                                                   severe compression of adjacent spinal cord. (c) MRI of
                                                   spinal meningioma.
         (c)




dle-aged or elderly patients and show a marked     is usually a long history of ill-defined back pain,
female predominance. The thoracic region of the    often nocturnal, and a very slowly progressive
spinal cord is the most common site and they are   paralysis prior to diagnosis.
invariably situated intradurally, causing marked      Plain X-rays may show erosion of the pedicles
compression of the adjacent cord.                  due to long-standing intradural compression.
  The tumours grow extremely slowly and there      Hyperostosis, which is frequently present in
 SPINAL CORD COMPRESSION                                                                             215


cranial meningiomas, does not occur in spinal          sensory loss over the saddle area and eventually
meningiomas.                                           sphincter disturbance.
   The diagnosis will be made using the radio-            Spinal rigidity and pain are common features
logical investigations mentioned earlier in the        in patients with intrinsic spinal cord tumours,
chapter. MRI with intravenous gadolinium con-          particularly in children, and there is a progres-
trast will give an accurate diagnosis of these         sive paralysis and sensory loss. A ‘cuirasse’
tumours and has replaced myelography (Fig.             (cape-like) pattern of sensory loss may be seen
15.8c).                                                initially but there is invariably progression to in-
   The treatment of spinal meningioma is resec-        volve all lower segments below the level of the
tion of the tumour and the involved dura. The tu-      tumour. Tumour expansion and involvement of
mour often lies lateral to the cord and, following     the anterior horn cells may produce a lower
the excision, there is an excellent chance of neuro-   motor neurone weakness and wasting of the cor-
logical improvement, even when there is sub-           responding muscle groups, but long tract in-
stantial neurological disability at the time of        volvement causes upper motor neurone
diagnosis. Occasionally the tumour lies directly       weakness below the level of the lesion.
anterior to the spinal cord and resection without         The progression of the spinal cord involve-
further injury to the cord in these circumstances      ment will depend on the histological nature of
is difficult.                                           the tumour. Although the tumours are initially
                                                       low grade, they may evolve into a more aggres-
                                                       sive morphology.
Intramedullary tumours
Intrinsic intramedullary tumours are uncommon
                                                       Radiology
and much less frequent than the extradural or in-
tradural extramedullary tumours mentioned              MRI is the investigation of choice. It will show
previously. The tumours usually present in the         expansion of the cord which may enhance fol-
3rd and 4th decades, although they may occur at        lowing intravenous injection of gadolinium. A
any age. The two most common tumours of the            syrinx is frequently associated with an in-
spinal cord are:                                       tramedullary tumour (Fig. 15.9b,c). Plain X-rays
1 Ependymoma.                                          or CT will show expansion of the spinal canal
2 Astrocytoma.                                         with increase of the interpedicular distance
   Ependymomas comprise about 60% of intrin-           through several segments, scalloping of the ver-
sic spinal tumours. They can occur at any level in     tebral bodies and sometimes thinning of the
the spine, but the majority arise from the filum        neural arches.
terminale where they usually have a myxopapil-
lary histological appearance and cause compres-
                                                       Treatment
sion of the cauda equina.
   Astrocytomas of the spinal cord may occur at        It is often possible to obtain a complete macro-
any level and frequently initially have a low-         scopic excision of an ependymoma arising from
grade histological appearance.                         the filum terminale which is causing compres-
                                                       sion of the cauda equina (Fig. 15.10). Meticulous
                                                       microsurgical techniques are necessary to dissect
Presenting features
                                                       the tumour from the nerve roots. In some
The presenting features of the tumours depend          ependymomas of the spinal cord it is possible to
on the level of cord involved. Ependymomas             obtain a plane of cleavage and perform a partial
arising in the filum terminale will cause features      or even complete resection. However, it is not
of cauda equina compression. There is often a his-     possible to resect astrocytomas of the cord, and
tory of low back and leg pain, progressive weak-       surgery is usually restricted to obtaining a diag-
ness in the legs (often with radicular features),      nosis by biopsy, aspiration of cyst cavities and
 216                                                                                      CHAPTER 15




             (a)




             (b)




                                                        Fig. 15.10 MRI showing myxopapillary ependymoma
                                                        of the filum terminale.



                                                        of cervical nerve root compression causing arm
             (c)                                        pain (Chapter 14) and lumbar nerve root com-
Fig. 15.9 Cervical cord intramedullary ependymoma
                                                        pression causing sciatica (Chapter 13). The nerve
in a 24-year-old female. (a) Myelogram shows typical    root compression results from posterolateral disc
features of intramedullary tumour with ‘splaying’ of    herniation. Occasionally, the disc may prolapse
contrast around the expanded cervical cord. (b,c) MRI   directly posteriorly (centrally) causing compres-
shows the tumour and the associated syrinx cavity       sion of the spinal cord in the cervical or thoracic
extending up into the medulla.                          region and cauda equina in the lumbar region
                                                        (Chapter 13).
exclusion of other possible rare resectable le-
sions. Radiotherapy is usually administered.
                                                        Cervical disc prolapse
   The prognosis is good if an ependymoma can
be resected. However, although patients with as-        Central posterior cervical disc herniation causes
trocytomas may have prolonged survival, there           a rapidly progressive paralysis with upper motor
is frequently progressive tumour growth result-         neurone features below the level of the compres-
ing in permanent, severe neurological disability.       sion and lower motor neurone features at the
Death will result if the tumour extends into the        level of the compression. There is frequently a
high cervical level or brainstem.                       preceding history of some neck discomfort and
                                                        occasionally brachial neuralgia. However, the
                                                        patient often presents following the sudden
Intervertebral disc prolapse
                                                        onset of severe neck pain with rapidly progres-
Intervertebral disc herniation is a common cause        sive paralysis.
 SPINAL CORD COMPRESSION                                                                               217


                                                          quence of disc degeneration. The thoracic spinal
                                                          canal is small and there is very little space be-
                                                          tween the disc and the thoracic cord. In addition,
                                                          the circulation to the low thoracic region is a
                                                          ‘water shed’ and the region is often largely sup-
                                                          plied by a single unilateral radicular vessel — the
                                                          artery of Adamkiewicz — which usually arises
                                                          between T8 and L2, particularly on the left side.
                                                             The most common presenting symptom is
                                                          poorly localized back pain related to the degener-
                                                          ative disc disease and stretching of the pain-
                                                          sensitive posterior longitudinal ligament. There
                                                          are often features of radicular involvement with
                                                          girdle pain. The neurological features of thoracic
                                                          cord compression may progress rapidly or pro-
                                                          ceed only slowly.
                                                             There are numerous possible differential diag-
                                                          noses for thoracic disc prolapse. It is extremely
                                                          difficult to exclude spinal degenerative disease as
                                                          the cause when back pain is the only symptom
                                                          and there are no neurological signs. The clinical
Fig. 15.11 MRI of cervical disc prolapse causing spinal
                                                          picture associated with the neurological deficit
cord compression.
                                                          could be due to any other cause of spinal cord
                                                          compression, as well as to multiple sclerosis.
   Urgent MRI is the best investigation and will             The plain X-rays show disc space narrowing
show the disc prolapse and anterior cord com-             and there is often evidence of calcified disc mate-
pression, which is usually at the C5/6 or C6/7            rial either in the intervertebral space or within
level (Fig. 15.11). If MRI is not readily available       the canal. Disc space calcification is highly sug-
myelography followed by a CT scan will also               gestive of thoracic disc herniation and is present
demonstrate the disc prolapse. Plain X-rays will          in up to 70% of cases, as opposed to an incidence
show narrowing of the disc space.                         of less than 4% in the normal population. As with
   Urgent surgery is necessary to relieve the com-        other causes of spinal cord compression the di-
pression. The disc is excised by an anterior ap-          agnosis is best made with MRI (Fig. 15.12). If
proach which involves removing the disc at that           MRI is not available myelography or CT scan-
level and, using microsurgical techniques, excis-         ning following intrathecal contrast will show
ing the disc fragments which have usually                 an anterior compression at the level of the
prolapsed through the posterior longitudinal              disc space and is also helpful in confirming the
ligament. It is sometimes necessary to drill away         diagnosis.
the adjacent margins of the vertebral body to                It is essential that an accurate preoperative
obtain adequate exposure and a formal vertebral           diagnosis is made because treatment involves
fusion is usually necessary.                              excision of the disc protrusion by an anterior
                                                          or anterolateral approach. The disc herniation
                                                          should not be resected using a laminectomy for
Thoracic disc prolapse
                                                          access because the protrusion lies in front of the
A central posterior thoracic disc prolapse is less        spinal cord and any manipulation of the thoracic
common. It usually occurs in males, predomi-              cord will inevitably result in devastating
nantly between the ages of 30 and 55, and                 neurological consequences. The usual surgical
usually occurs below the T8 level.                        approach is via either a thoracotomy or a
  The thoracic disc protrusion is usually a conse-        costotransversectomy at the involved level, with
 218                                                                                           CHAPTER 15


                                                          excision of the disc and disc prolapse from in
                                                          front of the dura without any manipulation of the
                                                          cord.


                                                          Spinal abscess
                                                          Spinal epidural abscess is an uncommon condi-
                                                          tion requiring urgent treatment. The abscess usu-
                                                          ally occurs in the low thoracic or thoracolumbar
                                                          region but may occur in the cervical or upper tho-
                                                          racic levels. It is due either to haematogenous
                                                          spread from obvious distant or occult infection or
                                                          to direct spread from the adjacent intervertebral
                                                          disc or vertebral column, particularly the pedicle
                                                          or neural arch. Osteomyelitis of the body of the
                                                          vertebra is less likely to infect the extradural
                                                          space because there is no loose, anterior, fatty
                                                          areolar tissue and the posterior longitudinal
                                                          ligament helps to restrain the intraspinal spread
                                                          of infection (Table 15.2).
Fig. 15.12 MRI of thoracic disc prolapse causing spinal
                                                             The most common organism is Staphylococcus
cord compression.
                                                          aureus but other causative organisms include
                                                          streptococci, pneumococci and Pseudomonas
                                                          species (Table 15.3).




  Table 15.2 Reported sources of infection of epidural spinal abscess vary with the patient population
  studied. Sources of infection are changing over time as spinal surgery, other invasive procedure and
  immunosuppression become more common and diagnosis and treatment of distant infection improve.

  Source                                 Incidence (%)                  Site of primary infection

  Unknown                                20–50                          Skin/soft tissue
                                                                        Pharynx/respiratory tract
                                                                        Sinus/middle ear
                                                                        Dental
                                                                        Genitourinary tract
                                                                        Infected vascular access
                                                                        Infected prosthesis
                                                                        Endocarditis/phlebitis
                                                                        Intravenous drug use
                                                                        Infected surgical/traumatic wound

  Contiguous focus                       15–75                          Osteomyelitis/discitis
                                                                        Postoperative infection
                                                                        Lumbar puncture/epidural catheter
                                                                        Paraspinal abscess
                                                                        Decubitus ulcer
 SPINAL CORD COMPRESSION                                                                                     219



  Table 15.3 The incidence of microorganisms causing epidural spinal abscess varies with the population
  studied. In particular, infections due to Mycobacterium tuberculosis are more common in developing nations
  and among the underprivileged. The incidence of unusual infections, such as fungi and parasites, is
  increasing as a result of the rising numbers of immunosuppressed patients.

  Type of infection    Microorganism                                                                Incidence (%)

  Unknown              Unknown                                                                       3–13

  Bacterial            Staphylococcus species
                         Staph. aureus                                                              45–70
                         Others                                                                      3–14

                       Streptococcus species: pyogenes, pneumoniae, viridans; anaerobic species      5–17

                       Gram-negative bacteria: Escherichia coli, Pseudomonas, Klebsiella,            3–18
                         Proteus, Enterobacter species

                       Anaerobes: Bacteroides, Proprionibacterium species                            3–10

                       Multiple microorganisms                                                       5–10

  Mycobacterial        Mycobacterium tuberculosis                                                    3–10

  Fungal               Aspergillus, Actinomyces, Nocardia, Cryptococcus, Sporotrichium               3–4

  Other                Parasites, syphilis                                                          Rare




   Spinal cord compression is due to inflammat-             pus is obtained from the needle it should be ad-
ory swelling and pus. Involvement of the ex-               vanced no further, to avoid the risk of meningitis.
tradural spinal veins causes thrombophlebitis              If there is no pus in the extradural space at the
which can spread into the veins of the spinal              level of lumbar puncture the needle can be ad-
cord, and the radicular arteries may develop an            vanced into the subarachnoid space and the
arteritis and thrombosis. Consequently, the cord           myelogram can proceed. Not infrequently the
is not only compressed by the abscess itself, but it       cerebrospinal fluid contains increased protein
is also at risk from infarction due to venous and          and sometimes a mild polymorphonuclear
arterial thrombosis.                                       pleocytosis.
   The presenting features consist of:                        Treatment consists of urgent laminectomy (or
• severe local spinal pain                                 anterior approach if necessary) and complete
• neurological signs of a rapidly progressive              evacuation of the extradural abscess. The patient
spinal cord compression                                    should be started on high-dose antibiotics.
• constitutional features of infection such as
high fever, sweating and tachycardia.                      Subdural spinal abscesses (Fig. 15.13). These
   MRI is the preferred investigation; it will best        are rare. Some are associated with congenital
show the level, extent and position of the abscess.        dermal sinuses and others are a consequence of
MRI has replaced the need for a lumbar puncture            haematogenous spread from sepsis at a different
and myelography, which should only be per-                 site.
formed if MRI is not available. Lumbar puncture               The clinical presenting features are similar to
for myelography should be performed carefully              those of extradural spinal abscess and meningitis
if a spinal extradural abscess is suspected and as-        is more likely to occur.
piration of the extradural space should be under-
taken before the subarachnoid space is entered. If         Intramedullary     abscesses.    These   result   from
 220                                                                                       CHAPTER 15


                                                        approach with access by a costotransversectomy
                                                        or a more extensive vertebral resection.


                                                        Spinal arteriovenous malformation
                                                        Although spinal vascular malformations only oc-
                                                        casionally cause actual compression of the spinal
                                                        cord, the presenting features are those of primary
                                                        spinal cord involvement and may mimic a com-
                                                        pressive lesion.
                                                           There are numerous morphological and patho-
                                                        logical classifications of spinal vascular malfor-
                                                        mations. Arteriovenous malformations (AVMs)
                                                        constitute the most common type of vascular
                                                        anomaly and occur with a frequency of approxi-
                                                        mately 4% of all primary spinal tumours. They
                                                        are much more frequent in males, occurring
                                                        four times more frequently than in females.
                                                        Other uncommon morphological types include
                                                        telangiectasia (capillary angiomas), cavernous
                                                        malformations and venous malformations com-
Fig. 15.13 MRI of subdural spinal abscess.
                                                        posed entirely of veins.
                                                           The gross appearance of the spinal AVM is
haematogenous spread, from a penetrating in-            highly variable. The malformation may be a sim-
jury or in association with a congenital dermal         ple arteriovenous fistula involving a single coiled
sinus. They are rare, and patients present with         vessel and resulting in a fistulous communica-
features of rapidly progressive spinal cord             tion or, at the other extreme, it may be the so-
involvement.                                            called ‘juvenile’ type, in which there are multiple,
                                                        large feeding arteries supplying an extensive di-
                                                        lated vascular mass that may fill the spinal canal
Spinal tuberculosis (Pott’s disease)
                                                        and permeate throughout the cord. This is the
Although spinal tuberculosis is uncommon in             type most frequently seen in children. The
Western countries it is still relatively prevalent in   so-called ‘glomus’ type consists of single or mul-
some Asian regions and in South America. The            tiple vessels converging on a highly localized
osteomyelitis affects two or more adjacent verte-       vascular plexus which is drained by one or more
bral bodies and destroys the intervening disc           arterialized veins.
space.                                                     The malformations may occur at any level and
  Spinal cord compression occurs as an early fea-       not only involve the surface of the cord but fre-
ture due to tuberculous granulation tissue and          quently have an intramedullary component.
pus, extruded sequestrae and fragments of                  The most common type of spinal AVM in-
intervertebral disc and vertebral collapse.             volves the ‘nidus’ of the malformation being em-
Alternatively, the compression may be a late            bedded in the dura covering the nerve root, and
manifestation resulting from the cord being dis-        the intradural malformation being the dilated ar-
torted over the apex of an angular kyphus.              terialized veins of the dural nidus. This type of
  Treatment involves the use of antituberculous         malformation was first recognized in the 1970s. It
chemotherapy. If there is progressive cord com-         is confined to the thoracolumbar and sacral re-
pression the abscess, granulation tissue and dis-       gions and in nearly all cases there is a solitary
eased bone may be excised by an anterolateral           feeding vessel supplying the nidus of malforma-
 SPINAL CORD COMPRESSION                                                                              221


tion in the dura. Most cases occur in middle-aged
or elderly men.


Presenting features
The clinical manifestations of AVM involving the
spinal cord may be due to a number of mecha-
nisms.
• A steal phenomenon. It is possible that the
malformation steals blood from the normal neur-
al tissue and that this shunt causes local spinal
cord hypoxia.
• Thrombosis, which may cause catastrophic
symptoms.
• Compression or, more appropriately, a pul-
satile compression, which probably plays only a
small role.
• Chronic increase of venous pressure, which
could explain the progressive myelomalacia.
• Haemorrhage.
   The presenting features include the following.      Fig. 15.14 Spinal angiogram of arteriovenous
1 Back pain and root pain.                             malformation and major feeding vessel.
2 Progressive neurological disability involving:
   (a) paresis
   (b) sensory disturbance                             Myelography is now rarely necessary but may
   (c) sphincter dysfunction                           show the tortuous vessels which will also be
   (d) impotence.                                      seen on CT scan following intrathecal iodine
3 A sudden catastrophic neurological event             contrast. The exact nature of the malformation
due to either haemorrhage within the cord or           can only be determined by highly selective
thrombosis.                                            spinal angiography (Fig. 15.14). The technique,
4 Subarachnoid haemorrhage.                            requiring considerable expertise, has been
   Pain is a common feature. Most patients pre-        facilitated by the use of digital subtraction
sent with a progressive neurological loss which,       angiography.
in half of the cases, is intermittent and recurrent.
   About 15% of patients present with subarach-
                                                       Treatment
noid haemorrhage. The diagnosis is obvious
when the haemorrhage is accompanied by para-           The previous surgical technique of stripping the
plegia or quadriplegia. However, there may not         malformation from the surface of the cord has
be any obvious associated cord manifestations          now been largely replaced by the recognition that
and the diagnosis of spinal subarachnoid haem-         the majority of these angiographic intradural
orrhage may be difficult. The onset of subarach-        malformations are merely the arterialized dilated
noid haemorrhage associated with sudden                veins of the dural AVM. All that is necessary is to
severe back pain is strongly indicative of an AVM      excise the dural nidus or obliterate the arterial-
of the spinal cord.                                    ized draining vein from the nidus. It is not neces-
                                                       sary to ‘strip away’ the intradural component
                                                       covering the cord.
Investigations
                                                         The surgical treatment of the true intradural
MRI facilitates the diagnosis of these lesions.        AVM, which often has a major intramedullary
 222                                                                                       CHAPTER 15


component, is fraught with hazard. The surgical       the neurological disability to increase rapidly,
technique involves accurate identification of the      particularly following an injury.
draining vessels at the level of the malformation        The presenting features are pain and neurolog-
and meticulous microsurgical dissection to pre-       ical disturbance attributable to cervical cord
serve the normal cord tissue. The large, in-          involvement.
tramedullary, juvenile-type malformations are
frequently inoperable because an attempted            Neck pain. This is not due to the cervical myelo-
surgical excision would inevitably result in          pathy itself but may occur as part of the degen-
devastating consequences. It may be possible to       erative disease of the cervical spine. Narrowing
combine angiographic embolization of these            of a neural foramen may result in entrapment of a
malformations with surgical excision.                 cervical nerve root causing brachial neuralgia.
                                                      This is discussed in Chapter 14.

Cervical myelopathy
                                                      Muscular weakness. This is the most common ini-
Cervical myelopathy results from cervical cord        tial symptom and usually occurs earlier in the
compression due to a narrow cervical vertebral        lower limbs. The patient initially notices clumsi-
canal. The constriction of the canal enclosing the    ness involving the hands and fingers, particular-
cervical cord is due to:                              ly in fine skilled movements, and dragging or
• congenital narrowing                                shuffling of the feet. According to the level and
• cervical spondylosis involving hypertrophy of       extent of the cord lesion the signs in the upper
the facet joints and osteophyte formation             limbs will be predominantly of a lower or upper
• hypertrophy of the ligamenta flava                   motor neurone type and there will be a spastic
• bulging (or prolapse) of a cervical disc            paraparesis of the lower limbs.
• excessive mobility, usually associated with            Depending on the level of the compression
cervical spondylosis.                                 there may be wasting of the suboccipital spinal
  The myelopathy results from:                        muscles, shoulder girdle muscles and biceps and
• direct pressure on the spinal cord                  triceps. Fasciculation may be present but is usu-
• ischaemia of the cord due to compression and        ally not severe. The deep tendon reflexes in the
obstruction of small vessels within the cord, or to   upper limbs will be depressed at, or exaggerated
compression of the feeding radicular arteries         below, the level of compression corresponding
within the intervertebral foramen.                    with the presence of lower motor neurone and
  The morphological changes within the cord in-       upper motor neurone damage, respectively. The
clude:                                                supinator (brachioradialis) reflex may be of value
• degeneration and loss of nerve cells, cavitation    in localizing the level. If it is absent, but the reflex
and proliferation of glia within the grey matter      evokes flexion of the digits and sometimes the bi-
• demyelination of the lateral and posterior          ceps or triceps, this is regarded as evidence of a
columns                                               lesion restricted to the C6 segment (the inverted
• Wallerian degeneration in ascending tracts          supinator reflex).
above and descending tracts below the                    The lower limbs will show upper motor neu-
compression                                           rone changes due to corticospinal tract involve-
• proliferation of small blood vessels with thick-    ment with increased tone, a pyramidal pattern of
ening of the vessel walls                             weakness, exaggerated reflexes and upgoing
• rare involvement of the anterior columns.           plantar responses.

                                                      Sensory symptoms. These frequently occur as dif-
Clinical features
                                                      fuse numbness and paraesthesiae in the hands
There is frequently a long history of slowly pro-     and fingers. Severe sensory loss is unusual in
gressive disability, although it is not unusual for   spondylolytic myelopathy, but an entirely nor-
 SPINAL CORD COMPRESSION                                                                                  223


mal sensory examination is also rare. The sensory
changes may be limited to the upper limbs and
may involve a dermatomal pattern if a particular
nerve root is being compressed. Posterior column
involvement will be reflected by a loss of joint po-
sition and vibration sense.
   The major differential diagnoses are:
• spinal tumour
• multiple sclerosis
• motor neurone disease (particularly if only
minor sensory changes)
• syringomyelia (Chapter 11)
• subacute combined degeneration of the cord.


Radiological investigations
Plain X-rays of the cervical spine may show a nar-
row vertebral canal which could be either con-
genital and/or due to spondylolytic degenerative             (a)
disease and osteophyte formation. Flexion–
extension views testing the mobility of the cer-
vical spine may show excessive movement of
the vertebrae.
   Although a CT scan without intrathecal con-
trast may confirm a narrow canal, it is necessary
to perform MRI to confirm the nature and extent
of the cord compression. An MRI will show the
exact pathological basis for the compression and,
in particular, whether it is primarily an anterior
compression due to disc bulging or osteophyte
formation or whether the compression is
mostly from a posterior bulging hypertrophied
ligamentum flava.
   These are critical issues to be considered in the
planning of surgery (Fig. 15.15). An additional
benefit of MRI is that it may show myelomalacia
(high signal within the cord) indicating the sever-
ity of the compression and a poorer prognosis fol-
lowing surgery.                                              (b)
                                                       Fig. 15.15 Cervical canal stenosis. (a) Severe cervical
Treatment                                              canal stenosis with incomplete block on myelogram
                                                       which has now been superceded by MRI. (b) MRI of
Surgery is definitely indicated for clinically pro-     cervical canal stenosis.
gressive or moderate or severe myelopathy.
There is some controversy over the indications         cluding rest in a cervical collar. However, surgery
for the surgery in patients with a mild, non-pro-      is usually advisable, and is definitely indicated if
gressive myelopathy because these patients will        there is marked compression of the cervical cord
often improve with conservative treatment, in-         because these patients may suffer a severe cord
 224                                                                                         CHAPTER 15


injury resulting in quadriparesis or quadriplegia      Further reading
following even a minor injury to the cervical re-
                                                       Hulme A (1960) A surgical approach to thoracic inter-
gion, such as a jolt or ‘whiplash’ type of injury. A
                                                         vertebral disc protrusion. Journal of Neurology, Neuro-
further reason for advising early surgery is that
                                                         surgery and Psychiatry 23, 133–137.
any existing neurological deficit may not im-           Kaye AH, Black P McL (2000) Operative Neurosurgery.
prove following an operation, due to irreversible        Churchill Livingstone, London, New York,
changes within the cervical cord, so that it is          Edinburgh.
preferable that the condition be arrested in its       Logue V (1979) Angiomas of the spinal cord: Review of
early stage.                                             the pathogenesis, clinical features and results of
   The type of surgical procedure performed will         surgery. Journal of Neurology, Neurosurgery and Psychi-
depend upon:                                             atry 42, 1–11.
• the extent of the compression                        Mack P (1979) Spinal metastases: Current status and
• the number of vertebral levels involved                recommended guidelines for management. Neuro-
                                                         surgery 5, 726–746.
• whether the compression is predominantly in
                                                       Malis LI (1978) Intramedullary spinal cord tumours.
front of or behind the cord
                                                         Clinical Neurosurgery 254, 512–540.
• the presence of cervical instability.                Perin N, O’Laoire S, Benzel E, Connolly ES (1995) Treat-
   A decompressive cervical laminectomy is the           ment of thoracic disc herniation. In: Al-Mefty O,
preferred operation if there is a narrow canal over      Origitano TC, Harkey HL, eds. Controversies in Neu-
a number of levels and if there is significant pos-       rosurgery. Thieme, New York.
terior compression, usually from hypertrophied         Rosenblum B et al. (1987) Spinal arteriovenous malfor-
ligamenta flava.                                          mations: a comparison of dural arteriovenous fistu-
   If the compression is predominantly anterior          las and intradural arteriovenous malformations in 81
to the cord at one or two levels, usually due to an      patients. Journal of Neurosurgery 67, 795–802.
osteophyte or disc bulge, an anterior approach         Simeone FA, Rashbaum R (1977) Transthoracic disc ex-
                                                         cision. In: Schymidek HH, Sweet WH, eds. Current
with excision of the compressive lesion and ante-
                                                         Techniques in Operative Neurosurgery. Grune and
rior cervical fusion is preferred.
                                                         Stratton, New York, 324–333.
   Whatever surgical procedure is used, extreme        Solero CL et al. (1989) Spinal meningiomas: review of
care must be taken in removing the compression           174 operated cases. Neurosurgery 25, 240–252.
to avoid further injury to the highly sensitive cer-   Stein BM (1979) Surgery of intramedullary spinal cord
vical cord.                                              tumours. Clinical Neurosurgery 26, 529–542.
   As indicated previously, surgery should arrest      Stein BM (1985) Spinal intradural tumours. In: Wilkins
the progress of the cervical myelopathy and only         RH, Rengachery SS, eds. Neurosurgery. McGraw Hill,
in a minority of patients will there be marked im-       New York, 1048–1061.
provement of neurological function following           Sundaresan N et al. (1979) Spinal chordomas. Journal of
the operation. A small percentage of patients who        Neurosurgery 50, 312–319.
                                                       Symon L, Kuyama H, Kendall B (1984) Dural arterio-
have severe neurological impairment and evi-
                                                         venous malformations of the spine. Journal of Neuro-
dence of myelomalacia on MRI may have further
                                                         surgery 60, 238–247.
neurological deterioration following surgery.
                           CHAPTER 16


 16                        Spinal injuries



Trauma to the spinal column occurs at an inci-        damage. In general the injuries can be classified
dence of approximately 2–5 per 100 000 popula-        by mechanism of the trauma.
tion. Although the majority of spinal injuries do
not affect the cord or spinal roots, about 10% will
                                                      Cervical spine
result in quadriplegia or paraplegia.
   Adolescent and young adult males are the           Flexion and flexion–rotation injuries
most commonly affected group. Most of the seri-       This is the most frequent type of injury to the
ous spinal cord injuries are a consequence of road    cervical spine; C5/6 is the most common site.
traffic accidents (involving cars, motor bikes and     Usually, one or both of the posterior facets are
bicycles) although there are other major causes of    subluxed or dislocated and may be locked in this
spinal cord injury, for example water sports, es-     position. There is extensive posterior ligamen-
pecially diving into shallow water, and injuries      tous damage and these injuries are usually unsta-
following skiing and horse riding accidents and       ble. The spinal cord may be compressed and
drunken falls.                                        distracted, sustaining both direct damage and
                                                      vascular impairment from involvement of the
                                                      anastomotic segmental vessels or feeders and
Mechanisms of injury
                                                      secondary compression from subluxation with or
Although severe disruption of the vertebral           without instability (Fig. 16.1).
column usually causes serious neurological
damage, it is not always possible to correlate the    Compression injuries
degree of bone damage with spinal cord injury.        The vertebral body is decreased in height and
Minor vertebral column disruption does not            there may be a wedge compression fracture or a
usually cause neurological deficit, but occasion-      comminuted fracture with the posterior aspect of
ally may be associated with severe neurological       the body (retropulsed fragment) encroaching
injury. The mechanism of injury will determine        upon the spinal canal. C5/6 is the most common
the type of vertebral injury and neurological         level for this fracture. The wedge fracture injuries
damage.                                               are usually stable because the posterior bony
   Trauma may damage the spinal cord by               elements and longitudinal ligaments are intact.
direct compression by bone, ligament or disc,         However those with a significant retropulsed
haematoma, interruption of the vascular supply        fragment are likely to have disruption of the as-
and/or traction.                                      sociated ligaments and thus have to be consid-
   The X-rays taken following a potential spinal      ered unstable. When combined with a rotation
cord injury show the vertebral alignment at that      force in flexion, a ‘tear drop’ fracture may occur,
time but do not necessarily indicate the amount       with separation of a small anteroinferior frag-
of disruption that may have occurred at the           ment from the vertebral body, and these should
moment of injury, or the degree of ligamentous        also be considered unstable. Of the patients who

                                                                                                      225
226                                         CHAPTER 16


       do have spinal cord injuries about half have com-
       plete neurological deficit below the level of the
       lesion, the remainder having incomplete deficit
       with the most damage being to the anterior
       aspect of the cord.

       Hyperextension injuries
       These injuries are most common in the older age
       groups and in patients with degenerative spinal
       canal stenosis. Bony injury is often not demon-
       strated and the major damage is to the anterior
       longitudinal ligament secondary to hyperexten-
       sion. Most of the injuries result in incomplete
       cord damage resulting from compression of the
       cord between the degenerative body and disc
       anteriorly, and the hypertrophic ligamentum
 (a)   flavum protruding posteriorly. The injuries are
       nearly always stable and a central cervical cord
       syndrome (p. 228) is the most common neurolo-
       gical impairment.


       Thoracolumbar spine
       Flexion–rotation injuries
       These injuries occur most frequently at the
       T12/L1 level and result in anterior dislocation of
       the T12 on the L1 vertebral body. There is usually
       disruption of the posterior longitudinal ligament
       and posterior bony elements. The inferior verte-
       bral body often sustains an anterior superior
       wedge compression fracture. These are unstable
 (b)   injuries which usually result in complete neuro-
       logical deficit of either the spinal cord, conus or
       cauda equina.

       Compression injuries
       These injuries are common and the vertebral
       body is decreased in height. They are usually
       stable injuries and neurological damage is
       uncommon.

       Hyperextension injury
       This is a very uncommon mechanism of injury at

       Fig. 16.1 (a) Cervical spine X-ray with C5/6 fracture
       dislocation. (b) Cervical spine CT reconstruction with
 (c)   C5/6 fracture dislocation. (c) Cervical spine CT
       reconstruction showing a perched facet with a fracture.
 SPINAL INJURIES                                                                                    227


the thoracolumbar spine. It involves rupture of
                                                     Types of neurological impairment
the anterior longitudinal ligament, rupture of the
intervertebral disc and fracture through the in-     Immediately after a severe cord injury there is a
volved vertebral body anteriorly. The injuries are   state of diminished excitability of the isolated
unstable and usually cause severe cord injury.       spinal cord. This is referred to as ‘spinal shock’ or
                                                     ‘altered reflex activity’. The transient depression
Chance fractures                                     in the segments caudal to the cord lesion is due to
This injury needs to be considered in patients       sudden withdrawal of a predominantly facilitat-
who are involved in a high-speed accident wear-      ing or excitatory influence from supraspinal cen-
ing lap belts without a shoulder harness. They       tres. There is an areflexic flaccid paralysis. The
sustain a hyperflexion distraction injury to the      duration of spinal shock varies: minimal reflex
thoracolumbar spine. The forward flexion and          activity may appear within a period of 3–4 days
bending result in two potential types of injuries,   or may be delayed up to 6–8 weeks, the average
and they can cause a fracture through the spinous    duration being 3–4 weeks.
process pedicle and vertebral body (Fig. 16.2a) or      The spinal cord injury is caused by:
a fracture through the end-plate with disruption     • the direct force applied to the cord
of the facet joint and ligamentous structures        • ischaemia due to vascular injury
(Fig. 16.2b). These injuries can easily be missed    • secondary haemorrhage in and around the
because of the unusual radiological findings.         cord.
They could well be associated with internal             The degree of neurological injury will be
injuries, especially abdominal injuries.             determined by the extent and severity of these
                                                     mechanisms.
Open injuries
                                                     Complete lesions
These may result from stab injuries or gunshot
wounds resulting in cord damage due to the blast     The most severe consequence of spinal trauma is
injury, vascular damage and/or cord penetration      complete transverse myelopathy, in which all
by the missile or bony fragments.                    neurological function is absent below the level of




Fig. 16.2 Chance fracture: (a)
through vertebral body and
pedicle; (b) through end-        (a)                                (b)
plate, facet and ligament.
 228                                                                                        CHAPTER 16


the lesion, causing either a paraplegia or quadri-
                                                       Incomplete lesions
plegia, depending on the level. There will also
be impairment of autonomic function including          Anterior cervical spinal cord
bladder and bowel function.                            Acute anterior cervical spinal cord syndrome is
                                                       due to compression of the anterior aspect of the
Motor deficit                                           cord. This causes damage to the corticospinal and
Injuries to the spinal cord will result in an upper    spinothalamic tracts, with motor paralysis below
motor neurone paralysis characterized by loss of       the level of the lesion and loss of pain, tempera-
voluntary function, increased muscle tone and          ture and touch sensation but relative preserva-
hyperreflexia. Injuries to the lumbar spine caus-       tion of light touch, proprioception and position
ing cauda equina injuries result in lower motor        sense, which are carried in the posterior columns.
neurone paralysis characterized by reduced             The exact pathophysiological process causing
muscle tone, wasting and loss of reflexes. A com-       this syndrome has not been precisely defined and
bination of upper and lower motor neurone              it may be due either to stretch applied by the at-
lesions results from a thoracolumbar injury            tachment of the dentate ligaments at the equator-
involving the conus medullaris and cauda               ial plane of the cord or to ischaemic injury from
equina.                                                compromise of the anterior spinal artery which
                                                       supplies the anterior two-thirds of the cord
Sensory deficit                                         (Fig. 16.3c).
In complete lesions the afferent long tracts carry-
ing the various sensory modalities are inter-          Central spinal cord
rupted at the level of the lesion, abolishing          Acute central spinal cord syndrome is usually
sensory appreciation of pain, temperature, touch       due to a hyperextension of the cervical spine with
and position and tactile discrimination below the      compression of the spinal cord between the
lesion. Visceral sensation is also lost. Sensation
may decrease over a few spinal segments before                                                   Dorsal
                                                       Corticospinal tract
being lost altogether. Occasionally there is a level                                             columns
                                                              Lower limb
of abnormally increased sensation, hyperaesthe-                                                  Lateral
                                                       Chest & abdomen                           spinothalamic
sia and hyperalgesia at or just below the lesion.                                                tract
                                                              upper limb
                                                                                                 Anterior
                                                       (a)                                       spinothalamic
Autonomic deficit                                                                                 tract
Vasomotor control. Cervical and high thoracic le-
sions above the sympathetic outflow at T5 may
cause hypotension. Interruption of the sympa-
thetic splanchnic vasomotor control will initially
cause a severe postural hypotension as a result of
impaired venous return.                                (b)
                                                                                    (c)
Temperature control. The patient with a complete
spinal lesion will not have satisfactory thermal
regulation as there will be impairment of the au-
tonomic mechanisms for vasoconstriction and
vasodilatation.
                                                       (d)                          (e)
Sphincter disturbance                                  Fig. 16.3 (a) Normal cord cross-section. (b) Central
There is impairment of bowel and bladder               cord syndrome. (c) Anterior spinal artery syndrome.
control; this is discussed later.                      (d) Brown-Séquard syndrome. (e) Posterior column
                                                       syndrome.
 SPINAL INJURIES                                                                                   229


degenerative intervertebral disc and osteophyte
                                                       Initial treatment
anteriorly and the thickened ligamentum flavum
posteriorly. The cord damage is located centrally,     The first aid management of patients with
with the most severe injury to the more centrally      injuries to the spinal column and spinal cord
lying cervical tracts which supply the upper           requires the utmost caution in turning and lifting
limbs. There is disproportionately greater weak-       the patient. The spine must be handled with great
ness in the upper limbs in comparison to the           care to avoid inflicting additional damage. Before
lower extremities below the level of the injury.       moving the patient sufficient help should be
Sensory loss is usually minimal, although this         available to provide horizontal stability and
is variable and frequently occurs in no specific        longitudinal traction. Spinal flexion must be
pattern (Fig. 16.3b).                                  avoided. A temporary collar should be applied if
                                                       the injury is to the cervical spine. An assessment
Brown-Séquard syndrome                                 should be made for other injuries to the chest,
The Brown-Séquard syndrome results from                abdomen or limbs.
hemisection of the spinal cord (Chapter 1) as             Hypotension and hypoventilation imme-
from a stab wound, although it infrequently fol-       diately following an acute traumatic spinal cord
lows a blunt injury. There is ipsilateral paralysis    injury may not only be life-threatening but may
of the limbs below the level of the lesion with loss   also increase the extent of neurological impair-
of pain, temperature and touch on the opposite         ment. Resuscitation techniques may need to be
side of the body. The posterior columns will be in-    modified to ensure that the spine remains stable.
terrupted ipsilaterally, but as some fibres cross       Respiratory insufficiency may require oxygen
there is not a great deficit (Fig. 16.3d).              therapy and ventilatory assistance. Loss of sym-
                                                       pathetic tone may result in peripheral vaso-
                                                       dilatation with peripheral vascular pooling
Spinal cord concussion
                                                       and hypotension. Treatment will include the
There may be a transient loss of function from         use of intravascular volume expanders, alpha-
concussion of the spinal cord. The exact patho-        adrenergic stimulators, intravenous atropine and
logical processes involved in spinal cord concus-      occasionally the use of a transvenous pacemaker.
sion are not clear but they are probably similar to    There must be careful attention to the body tem-
those occurring in cerebral concussion, resulting      perature — the spinal patient is poikilothermic
in temporary impairment of neuronal function.          and will tend to assume the temperature of the
Recovery usually begins within 6 hours and             environment. Body temperature must be pre-
should be detected within 48 hours.                    served in cold weather and the patient must not
                                                       be overheated in warm weather. A nasogastric
                                                       tube should be passed to avoid problems associ-
Management of spinal injuries
                                                       ated with vomiting due to gastric stasis and par-
As with head injuries, there is little that can be     alytic ileus. A urinary catheter should be passed
done to repair the damage caused by the initial        to prevent the complications of bladder overdis-
injury and therefore the major efforts are directed    tension, although intermittent catheterization
towards prevention of further spinal cord injury       may become preferable later. Prophylaxis for
and the complications resulting from the neuro-        deep vein thrombosis and subsequent pul-
logical damage. The general principles of man-         monary embolus should be commenced as soon
agement are:                                           as possible using low-dose heparin (5000 units
• prevention of further injury to the spinal cord      subcutaneously twice daily) or low molecular
• reduction and stabilization of bony injuries         weight heparins. Some centres also favour using
• prevention of complications resulting from           various types of compression stockings on the
spinal cord injury                                     lower limbs.
• rehabilitation.
 230                                                                                           CHAPTER 16




                                                        (a)
Fig. 16.4 MRI of spinal injury showing the bone
damage and cord injury with localized syrinx.




Radiological investigations
Plain cervical spine X-rays and computerized to-
mography scan will show the bony injuries, and
magnetic resonance imaging is very helpful in
showing the associated cord, soft tissue and liga-
                                                        (b)
mentous pathology (Fig. 16.4). If a cervical spine
injury is suspected (in the absence of neurologi-
cal signs or symptoms) but the plain X-ray and
CT scan show no abnormality, the X-rays should
be carefully repeated in flexion and extension to
exclude instability due to ligamentous damage.

Spinal reduction and stabilization
As soon as the systemic parameters have been
stabilized, attention should be directed to align-
ment and stabilization of the spine. The use of         (c)

skeletal traction for the restoration and/or main-      Fig. 16.5 The reduction of fractures following traction
tenance of the normal alignment of the spinal col-      in patients illustrated in Fig. 16.1. (a) The plain X-ray
umn is a time-honoured and effective treatment.         shows the distracted disc spaces. (b,c) The CT
                                                        reconstruction shows normal alignment and
There are various types of cervical traction de-
                                                        correction of perched facet.
vices. The spring-loaded tongs have become
popular because of their ease of application and
maintenance. The usual practice is to apply             patients will require analgesia. Their body
weight to the traction device to a maximum of           weight is utilized for counter traction by tilting
5 lb or 2.25 kg for each level below the occiput        the entire bed in a head-up position. It is impor-
(e.g. C6 = 30 lb or 13.5 kg). It is usual to commence   tant to maintain a neutral spine. Extreme care
with half the maximum weight and, under X-ray           should be taken to avoid distraction at the frac-
or fluoroscopic control, gradually add weights           ture site as the traction on the underlying cord
up to the maximum if necessary (Fig. 16.5). These       may worsen the neurological injury. Reduction of
 SPINAL INJURIES                                                                                           231


facet dislocations may be more difficult and re-
quire more weight for the traction. Some advo-
cate manipulation of the neck under fluoroscopic
control while weight is being applied to accom-
plish reduction of locked facets. In Australia and
Europe cervical traction under general anaesthe-
sia has been used for closed reduction of some
fracture dislocations but this has not been popu-
lar in the United States. Open surgery may be
necessary to reduce the fracture — subluxation
with overriding and locked facet joints.
   Following reduction the position may be
maintained with skeletal traction or halo              Fig. 16.6 Postoperative X-ray — anterior cervical
immobilization.                                        discectomy and bone and plate fusion.
   Injuries of the thoracolumbar spine can
usually be managed conservatively by postural          elevate bone spicules and, if possible, repair the
reduction in bed. The correct posture must be          dura.
maintained during positioning on the side, as          4 The most common indication for operative in-
well as on the back; this is achieved by the appro-    tervention is to stabilize the spine. This is usually
priate placement of bolsters and pillows by a          undertaken:
turning team.                                            (a) if there is gross instability, particularly in
                                                         the presence of an incomplete neurological
Indications for surgical intervention                    lesion
There has been considerable controversy over             (b) if it has not been possible to reduce locked
surgical intervention in patients with spinal cord       facets by closed reduction — posterior reduc-
injuries. The damage to the spinal cord occurs           tion and fusion is appropriate
principally at the time of the injury and it is not      (c) if operative procedures are needed to stabi-
surprising that there has been no evidence to            lize the unstable cervical spine and so avoid
show improved neurological function from acute           prolonged bed rest; these are favoured by
operative decompression of the spine. The fol-           many spinal injury units (Fig. 16.6).
lowing are the general indications for surgical
intervention.                                          Other treatments for spinal cord injury
1 Progression of neurological deficit is an ab-         Numerous pharmacological agents have been
solute indication. It requires emergency interven-     investigated in experimental laboratory models
tion if a compressive lesion is demonstrated by        but as yet there has been no controlled clinical
either MRI or CT scan.                                 study to show the usefulness of these agents in
2 Patients who have a partial neurological injury,     spinal cord injury. The treatments include gluco-
with preservation of some distal neurological          corticoids, diuretics, local hypothermia, barbitu-
function, and who fail to improve should have          rates and endogenous opiate agonists. Although
further radiological assessment. Surgery should        there is no proven benefit, some spinal units use
be considered if this shows persisting extrinsic       glucocorticoids and osmotic diuretics for the
compression of the spinal cord within the canal        treatment of oedema. The early use of high-dose
(particularly from a herniated cervical disc), a de-   dexamethasone may be beneficial, but there is no
pressed fractured lamina or an osteophytic bar,        conclusive proof.
although removal of the compression may not
result in any neurological improvement.
                                                       Further management
3 An open injury from a gunshot or stab wound
should be explored to remove foreign particles,        Following reduction and immobilization of the
 232                                                                                       CHAPTER 16


fractures the principles of the continuing care in-     tarily as it fills with urine. The capacity may be
volve the avoidance of potential complications in       less than normal, but there is good voiding pres-
patients who are paraplegic or quadriplegic, and        sure capacity. There is no sensation of bladder
early rehabilitation, which commences as soon as        fullness. In a lower motor neurone lesion the
the injury is stabilized.                               spinal micturitional reflex is interrupted and an
                                                        autonomous bladder results. Bladder function is
                                                        governed by a myogenic stretch reflex inherent in
General care
                                                        the detrusor fibres themselves. This type of dys-
Careful attention to the general condition and          function is characterized by a linear increase in
metabolic state is essential following the injury;      intravesical pressure, with filling until capacity is
patients frequently develop a negative nitrogen         reached. Urine may then flow past the sphincter
balance and may become anaemic. Urinary tract           by overflow incontinence. In a mixed upper and
or other infections will aggravate the metabolic        lower motor neurone lesion, such as with a conus
disorders. The patients and their relatives will re-    medullaris and cauda equina injury, it is possible
quire skilled counselling and emotional support         to have a flaccid lower motor neurone detrusor
during the treatment and rehabilitation period.         and a spastic sphincter, as well as the reverse.
                                                           The principles of management of the bladder
                                                        consist of maintaining proper bladder drainage
Skin care
                                                        to prevent dilatation of the upper urinary tract
Meticulous attention to pressure areas will avoid       and renal impairment, and the treatment of uri-
the development of pressure sores which would           nary tract infections. A catheter is passed initially
seriously complicate the recovery and rehabilita-       and bladder training is commenced after the
tion of the patient.                                    period of spinal shock. The details of bladder
                                                        training and management depend on whether
                                                        the neurogenic bladder has resulted from an
Gastrointestinal complications
                                                        upper or a lower motor neurone lesion and on the
Paralytic ileus occurs in acute spinal cord paraly-     results of a cystometrogram showing the intra-
sis and if this is unrecognized, the patient is at      vesical volume pressure relationship.
risk from vomiting and aspirations. A nasogastric
tube should be passed in the initial management
                                                        Limb care
of the patient. Acute gastric dilatation may also
develop and is also treated by nasogastric suc-         It is essential that the paralysed limbs should be
tion. In 3–5% of patients with acute spinal cord        put through their full range of movements regu-
injuries acute peptic ulceration occurs.                larly. Physiotherapy, in particular, is essential
                                                        to prevent contractures as the tone returns and
                                                        spasticity develops.
Bladder care
Urinary tract problems are a major cause of
                                                        Special cervical spine injuries
potential morbidity and mortality. During the pe-
riod of spinal shock the areflexic, flaccid paralysis
                                                        Jefferson’s fracture
below the level of the lesion includes bladder
function. The patient will develop acute retention      Jefferson described bilateral fractures of the pos-
with overflow incontinence and a catheter is             terior arch of the atlas from a direct vertical blow
required. Reflex activity returns in upper motor         to the head in four patients. The mechanism of
neurone lesions as the phase of spinal shock pass-      the fracture is due to the head pressing down on
es. The spinal micturitional reflex arc is intact in a   the spinal column and the atlas being squeezed
lesion above the conus and an autonomic type of         between the occipital condyles above and the
bladder results. The bladder will empty involun-        axis below. The grooves for the vertebral artery
 SPINAL INJURIES                                                                                         233




Fig. 16.7 Fractures of the            Odontoid                   Odontoid                    Odontoid
odontoid process.                      Type I                     Type II                     Type III



                                                      by immobilization in a firm brace or halo for 4
                                                      months. If there is non-union and instability a
                                                      posterior C1/2 fusion will be necessary. Anterior
                                                      screw internal fixation of the odontoid fracture
                                                      has been advocated but is indicated in certain
                                                      situations.


                                                      Hangman’s fracture (Fig. 16.8)
                                                      This fracture is the avulsion of the laminar arches
                                                      of C2 with dislocation of the C2 vertebral body on
                                                      C3. It is the characteristic lesion resulting from
                                                      judicial hanging.


                                                      Further reading
                                                      Dickman C, Kalfas I, Traynel V, Cooper DR (1995) Treat-
Fig. 16.8 Hangman’s fracture.
                                                        ment of transmutic instability of the cervical spine.
                                                        In: Al-Mefty O, Origitano TC, Harkey HL, eds.
are the sites where the arches of the atlas are         Controversies in Neurosurgery. Thieme, New York.
weakest, and when fractures occur at this site        Harris P et al. (1980) The prognosis of patients sustain-
bursting fragments are displaced outwards.              ing severe cervical spine injury (C2–C7 inclusive).
                                                        Paraplegia 18, 324–330.
                                                      Heiden JS et al. (1975) Management of cervical spinal
Fractures of the odontoid process                       cord trauma in Southern California. Journal of Neuro-
A fracture of the odontoid process may occur at         surgery 43, 732–736.
                                                      Norrell H (1978) The treatment of unstable fractures
the tip (type I) through the base of the dens (type
                                                        and dislocations. Clinical Neurosurgery 25, 193–208.
II) or at the base and extend into the adjacent C2
                                                      Norrell H (1980) The early management of spinal in-
vertebral body (type III). The fractures that occur
                                                        juries. Clinical Neurosurgery 27, 385–400.
at the base of the dens are the most common and       Sherk HH (1978) Fractures of the atlas and odontoid
may cause disruption of the blood supply to             process. Orthopaedic Clinics of North America 9,
the dens, resulting in non-union of the fracture        973–984.
(Fig. 16.7).                                          Wood-Jones F (1913) The ideal lesion produced by judi-
   Many of the odontoid fractures can be treated        cial hanging. Lancet i, 533.
                           CHAPTER 17


  17                       Peripheral nerve entrapments,
                           injuries and tumours


Peripheral nerves may be trapped, compressed           ment; women are affected four times more often
or injured at any position along their course, al-     than men.
though there are certain regions where they are           The carpal tunnel is a fibro-osseous tunnel on
especially vulnerable. Nerve entrapments occur         the palmar surface of the wrist (Fig. 17.1). The
particularly where the peripheral nerve passes         dorsal and lateral walls consist of the carpal
through a tunnel formed by ligaments, bone             bones, which form a crescentic trough. A tunnel is
and/or muscle. Traumatic injury to the nerve           made by the fibrous flexor retinaculum (trans-
occurs when it is either relatively superficial and     verse carpal ligament) which is attached
exposed, or lying adjacent to bone, where it may       medially to the pisiform and hook of the hamate
be directly injured by the jagged, fractured ends      and laterally to the tuberosity of the scaphoid and
of the bone.                                           crest of the trapezium. The contents of the tunnel
                                                       are the median nerve and the flexor tendons of
                                                       the flexor digitorum superficialis, flexor digito-
Peripheral nerve entrapment
                                                       rum profundis and flexor pollicis longus.
Entrapment neuropathies occur when nerves                 Although the features of carpal tunnel syn-
pass near joints. In this position they are particu-   drome may present at any stage throughout the
larly vulnerable to compression:                       adult years, the initial symptoms often occur in
• due to bone and joint disorders in the region        women during pregnancy and in both sexes
• because they frequently pass under a tendi-          when they are performing unusually strenuous
nous arch                                              work with their hands. There are a number of
• which may be exacerbated by movement of              systemic conditions which are associated with,
the adjacent joint.                                    and may predispose to, carpal tunnel syndrome;
   Less common forms of entrapment neuropa-            these include:
thy may lie at a distance from a joint. Table 17.1     • pregnancy and lactation
shows a list of the common and less frequent en-       • contraceptive pill use
trapment neuropathies. Although thoracic outlet        • rheumatoid arthritis
syndrome does not cause compression of a               • myxoedema
peripheral nerve, it will be considered in this        • acromegaly.
chapter because the clinical features may mimic           Any local condition that will decrease the size
peripheral nerve entrapment and because the            of the carpal tunnel will also predispose to carpal
pathophysiology is similar to compression of a         tunnel syndrome. Such conditions include a
peripheral nerve.                                      ganglion, tenosynovitis, unreduced fractures or
                                                       dislocations of the wrist or carpal bones, and
                                                       any local arthritis.
Carpal tunnel syndrome
                                                          The principal clinical features of carpal tunnel
This is by far the most common nerve entrap-           syndrome are:

234
 PERIPHERAL NERVE ENTRAPMENTS, INJURIES AND TUMOURS                                                               235


• pain                                                    the patient has to shake the hand to obtain any re-
• numbness                                                lief. The pain is also aggravated by activity of the
• tingling.                                               hand.
   The pain, which may be described as burning               Although the numbness and tingling is princi-
or aching, is frequently felt throughout the whole        pally in the lateral three and a half fingers, in the
hand and not just in the lateral three digits. There      distribution of the median nerve, the patient
is often a diffuse radiation of pain up the forearm       frequently complains of more diffuse sensory
to the elbow and occasionally into the upper arm.         loss throughout the fingers. This symptom is also
The symptoms are worse at night, and on waking            worse at night and with activity.
                                                             The patient frequently complains that the hand
                                                          feels ‘clumsy’, but with no specific weakness.
                                                             There are often only minimal signs of median
  Table 17.1 Entrapment neuropathies.                     nerve entrapment at the wrist. The Tinel’s sign
                                                          may be elicited by tapping over the median nerve
  Median nerve
                                                          but its presence or absence has little diagnostic
    Carpal tunnel syndrome*
                                                          value.
    Supracondylar entrapment
    Cubital fossa entrapment
                                                             If the compression has been prolonged and
    Anterior interosseus nerve entrapment                 severe there may be signs of median nerve
  Ulnar nerve                                             dysfunction, including:
    Tardy ulnar palsy*                                    • wasting of the thenar muscle
    Deep branch of ulnar nerve                            • weakness of muscles innervated by the distal
  Radial nerve — posterior interosseus nerve              median nerve, especially abductor pollicis brevis
  Suprascapular nerve                                     • diminished sensation over the distribution of
  Meralgia paraesthetica — lateral femoral                the median nerve in the hand.
    cutaneous nerve of thigh                                 Some patients, particularly the elderly or
  Sciatic nerve
                                                          diabetic, may present with only minor discom-
  Tarsal tunnel syndrome
                                                          fort but rapid wasting, weakness and numbness
  Thoracic outlet syndrome*
                                                          in the hand.
  *The more common entrapment neuropathies.
                                                             The clinical diagnosis can be confirmed by
                                                          electromyographic examination (EMG). The



                                 Tendons of flexor digitorum superficialis and profundus

                                 Flexor retinaculum         Median nerve
                                 Ulnar nerve                     Flexor pollicis longus
                                 and artery                                 Extensor pollicis brevis




                                                                                                           Trapezium

                                                                                   Hamate




                                 Pisiform
Fig. 17.1 The carpal tunnel,          Triquetrum                        Trapezium
just distal to the wrist.                      Capitate   Lunate Scaphoid                  Pisiform    Scaphoid
 236                                                                                       CHAPTER 17


earliest feature of carpal syndrome is prolonged        ing the fingers and wrist, to avoid stiffness of the
sensory latency, and the sensory action potentials      joints.
may show a diminished amplitude and are often
absent. The distal motor latency may also be
                                                        Other median nerve entrapments
prolonged. Needle examination may show loss
of motor units and presence of denervation              The median nerve may occasionally be com-
potentials in the thenar muscles.                       pressed at other sites, particularly:
                                                        • in the cubital fossa
Treatment                                               • under a supracondylar process of the humerus
Surgery is a simple and effective method of             and Struther’s ligament.
relieving the compression and curing the
symptoms. However, conservative treatment is            Cubital fossa
appropriate if:                                         The median nerve may occasionally be com-
• the symptoms are mild or intermittent                 pressed in the region of the cubital fossa:
• there is a reversible underlying precipitating        • under the bicipital aponeurosis
condition such as pregnancy or oral contracep-          • as it passes between the two heads of the
tive pill use.                                          pronator teres muscle
   Conservative treatment includes the use of a         • as it passes under the fibrotendinous arch of
wrist splint, particularly at night, and non-           the origin of the flexor digitorum superficialis
steroidal anti-inflammatory medication. Corti-           muscle.
costeroid injection into the carpal tunnel is              It is not usually possible to differentiate the
sometimes advocated but, at best, this offers only      exact cause of the compression prior to explo-
temporary relief and may damage the median              ration. The symptoms are similar and have an in-
nerve.                                                  sidious onset. There is usually a vague pain in the
   The operation involves the division of the           forearm, with increasing weakness of the hand
flexor retinaculum through a curvilinear incision        and numbness in the thumb and index finger.
made in the palm of the hand extending from the         The clinical findings are of weakness of the medi-
distal wrist crease and exposing the whole of the       an nerve-innervated muscles, especially the flex-
flexor retinaculum in the hand. The operation can        or pollicis longus, the radial half of the flexor
be performed under general, regional or local           digitorum profundus and the thenar muscles,
anaesthesia, with or without a tourniquet. It is        and of numbness in the distribution of the
essential to divide the whole of the retinaculum        median nerve.
and to avoid damage to the recurrent branch of             Although the symptoms may resolve with con-
the median nerve that innervates the thenar mus-        servative treatment, which should include rest of
cles. Although this important nerve usually             the limb and avoidance of heavy work, it is usu-
arises distally, from the median nerve on the           ally necessary to explore the nerve and relieve the
radial side in the carpal tunnel, it is common for it   compression.
to have an anomalous origin and course before              The anterior interosseous nerve arises from
entering the thenar muscles. Recently an endo-          the lateral aspect of the median nerve as it passes
scopic approach to decompress the nerve has             between the two heads of the pronator teres mus-
been advocated as a means of reducing postoper-         cle. The anterior interosseous nerve syndrome is
ative wound discomfort. However, endoscopic             usually due to compression of the nerve by the
decompression does have a higher risk of injury         tendinous origin of the deep head of pronator
to the median nerve and most surgeons prefer an         teres and is characterized by selective paralysis of
open decompression.                                     the flexor digitorum profundus of the second and
   Although some surgeons advocate postopera-           third fingers, the pronator quadratus and the
tive immobilization of the hand it is preferable to     flexor pollicus longus. There are no sensory
encourage movement of the upper limb, includ-           changes and the patient is classically unable to
 PERIPHERAL NERVE ENTRAPMENTS, INJURIES AND TUMOURS                                                    237


push the distal phalanges of the thumb and index         though the features of ulnar nerve entrapment do
finger together. Surgery to decompress the nerve          not usually appear for some years. This delay in
is often necessary.                                      the appearance of symptoms led to the term
   Compression of the median nerve under a               ‘tardy ulnar palsy’.
supracondylar process of the humerus is rare. A             In most cases there is no particular predispos-
fibrous ligament (Struther’s ligament) extends            ing cause. In a minority there are underlying
from the anomalous bony process arising from             factors which predispose to nerve entrapment,
the anteromedial surface of the humerus — the            including lengthy periods of bed rest from coma
supracondylar process — to the region of the             or major illness and poor positioning of the
medial epicondyle, and forms a fibro-osseous              upper limbs during long operations, causing
foramen through which the median nerve and               prolonged pressure on the nerve, arthritis of
brachial artery pass. The clinical features are of a     the elbow, ganglion cysts of the elbow joint and
progressive median nerve palsy, particularly             direct trauma.
with pronator weakness, which distinguishes                 The clinical features consist of:
this syndrome from more distal median nerve              • paraesthesia and numbness in the ring and
entrapment. Surgery consists of excision of              little fingers of the hand and the adjacent medial
Struther’s ligament and removal of the bony              border of the hand
spur.                                                    • wasting of the ulnar innervated muscles of the
                                                         hand (particularly the hypothenar eminence and
                                                         interossei muscles)
Ulnar nerve entrapment at the elbow
                                                         • weakness.
The ulnar nerve runs behind the medial epi-                 The most common initial presenting feature is
condyle of the humerus. It enters the forearm            paraesthesia in the ring and little fingers and the
through a fibro-osseous tunnel formed by the              adjacent ulnar border of the hand. The patient
aponeurotic attachment of the two heads of flex-          may complain of a painful ‘burning’ or ‘aching’
or carpi ulnaris, which span from the medial epi-        in the forearm and/or the hand, but pain is usu-
condyle of the humerus to the olecranon process          ally not a prominent symptom. There will be pro-
of the ulnar, forming the cubital tunnel (Fig. 17.2).    gressive clumsiness of the hand with impairment
The ligament tightens during flexion of the elbow         of fine movements.
and the volume of the cubital tunnel decreases              In advanced cases there will be wasting of the
with increasing pressure over the underlying             ulnar-innervated muscles, particularly notice-
nerve. Injuries in the region producing deformity        able in the hypothenar eminence and dorsal in-
of the elbow predispose to compression, al-              terossei. Entrapment of the ulnar nerve will lead
                                                         to weakness of the muscles of the hypothenar
                                                         eminence, the interossei, the two medial lumbri-
                                                         cals, the adductor pollicis, the flexor digitorum
                                                         profundus (ring and little fingers) and the flexor
                                                         carpi ulnaris. Paralysis of the small muscles of the
                                                         hand causes ‘claw hand’, this posture being
Medial                                                   produced by the unopposed action of the
epicondyle
Ulnar nerve
                                                         antagonists of the paralysed muscles. Since
                                               Radius    the interossei cause flexion of the fingers at the
Fascial roof                                   Flexor
of cubital tunnel                              carpi     metacarpophalangeal joints and extension at the
                                               ulnaris   interphalangeal joints, when these muscles are
Olecranon                                      Ulna
                                                         paralysed the opposite posture is maintained by
Fig. 17.2 The ulnar nerve passing behind the medial      the long flexors and extensors, which cause flex-
epicondyle of the humerus and through the cubital        ion at the interphalangeal joints and hyperexten-
tunnel.                                                  sion at the metacarpophalangeal joints. This is
 238                                                                                    CHAPTER 17


most pronounced in the ring and little fingers as      nerve is often noted to be compressed. If the
the two radial lumbricals, innervated by the me-      elbow is then flexed the nerve may be found to be
dian nerve, compensate to some degree for the         also trapped behind the medial epicondyle, so
impaired action of the interossei on the index and    that it is further traumatized during movement
middle fingers. Froment’s sign is demonstrated         of the elbow, despite the bridge of fibrous tissue
by asking the patient to grasp a piece of card-       being divided. Excision of the medial epicondyle
board between the index finger and thumb               through a subperiosteal resection of the condyle
against resistance. There will be flexion of the       allows the nerve to move freely during a full
interphalangeal joint of the thumb because the        range of movement of the elbow. Transposition of
median-innervated flexor pollicis longus is used,      the nerve is not usually necessary although it is
rather than the weakened adductor pollicis. The       recommended by some surgeons.
sensory disturbance will be in the little finger and
medial half of the ring finger and medial border
                                                      Ulnar nerve compression at the wrist
of the hand.
   The diagnosis will be confirmed by nerve            The ulnar nerve may occasionally be trapped and
conduction studies. The conduction velocity in        compressed at the wrist, and the clinical features
the ulnar nerve across the elbow is slowed, the       of this compression depend on the exact position
amplitude of the motor response in the abductor       of the entrapment.
digiti minimi is decreased, and the sensory              The deep branch of the ulnar nerve may be
latency is prolonged. Needle examination of the       compressed at the pisohamate hiatus. The condi-
ulnar-innervated muscles will show reduction          tion can sometimes arise spontaneously, but
in the voluntary motor unit action potentials.        there is usually a history of injury, often of a
                                                      heavy and repetitive type. Most of the patients
Treatment                                             are men and it classically occurs in those using
Conservative treatment may be tried if the            heavy jack hammers or wire-cutting shears, and
clinical features are minor and not progressive.      in motor cyclists, where there is repetitive trauma
It should include the advice to avoid pressure        over the ulnar aspect of the hand. There is
on the nerve at the elbow during reading, sitting     marked wasting and weakness of the hand mus-
or lying and to cease heavy work with the             cles innervated by the ulnar nerve. Flexor carpi
arms. Non-steroidal anti-inflammatory medica-          ulnaris and the medial half of the flexor digito-
tion may be helpful.                                  rum profundis are not impaired. Although there
   Surgery is indicated if there are progressive      is often spontaneous improvement after the
symptoms or signs and if there is any wasting or      trauma is ceased, surgery may be necessary to
weakness. The surgical procedure must release         relieve the compression.
the nerve from compression and prevent further           Less commonly the ulnar nerve is compressed
damage to the nerve from flexion and extension         at the wrist a little more proximally in ‘Guyon’s
movement of the elbow. The surgical techniques        canal’ which is an oblique fibro-osseous tunnel
have included:                                        that lies within the proximal part of the hy-
• neurolysis                                          pothenar eminence. The roof of the tunnel is
• medial epicondylectomy                              formed by the palmar fascia and palmaris brevis
• transposition of the nerve.                         muscle. The floor is formed by the flexor retinac-
   The nerve is explored through a curvilinear in-    ulum and the pisohamate ligament. The terminal
cision centred just behind the medial epicondyle.     part of the tendon of flexor carpi ulnaris and the
The dense fascia over the nerve, forming the roof     pisiform bone form the medial wall. The distal
of the cubital tunnel, is divided, extending from     part of the lateral wall is formed by the curved
the medial intermuscular septum above distally        ulnar surface of the hook of the hamate. The canal
to where the nerve runs between the two heads         contains the ulnar nerve and ulnar artery. In the
of the flexor carpi ulnaris at which position the      middle of the canal the ulnar nerve divides into
 PERIPHERAL NERVE ENTRAPMENTS, INJURIES AND TUMOURS                                                 239


the superficial and deep branches. The superfi-
cial branch continues distally and supplies a
small branch to the palmaris brevis muscle and
sensation to the medial half of the ring finger and
little finger. The deep motor branch passes later-
ally around the hook of the hamate and under the
pisohamate hiatus, a fibrotendinous arch.
   Compression in Guyon’s canal, often by a gan-
glion (Fig. 17.3), leads to features similar to the
more distal compression of the deep branch of
the ulnar nerve, as well as to sensory loss and in-
volvement of the palmaris brevis muscle. Sensa-           (a)
tion is retained on the dorsal aspect of the hand,
as the distal branch of the ulnar nerve arises prox-
imal to the wrist. The symptoms may resolve
with conservative therapy but surgical decom-
pression is often required.


Suprascapular nerve entrapment
The suprascapular nerve is occasionally com-
pressed in the suprascapular notch under the
suprascapular ligament.
   There is an occasional acute, precipitating trau-
matic event, although there is usually no readily
identifiable prior injury. The earliest presenting         (b)
feature is deep pain around the suprascapular re-      Fig. 17.3 MRI showing ganglion compressing ulnar
gion and shoulder. The frequent clinical finding        nerve in Guyon’s canal.
is marked atrophy of the supra- and infraspina-
tus muscles. There is often weakness of external
rotation of the arm.                                   cle. The nerve traverses the supinator muscle,
   The important differential diagnoses are a          winds around the lateral side of the radius and
rotator cuff injury of the shoulder, or a C5 nerve     emerges on the dorsal aspect of the forearm,
root compression which will cause weakness of          where it supplies the extensor muscles of the
shoulder abduction. Nerve conduction studies           wrist and fingers. The usual site of entrapment
will aid in the diagnosis. Section of the supras-      is at the origin of the supinator muscle under the
capular ligament usually satisfactorily relieves       fibrotendinous ring (arcade of Frohse), although
the compression and provides good sympto-              other adjacent skeletal abnormalities may also
matic relief.                                          cause a traumatic neuritis in the region.
                                                          The clinical presentation involves an inability
                                                       to extend the fingers at the metacarpophalangeal
Posterior interosseous nerve entrapment
                                                       joints (finger drop). There is not usually any wrist
The radial nerve divides into two terminal             drop because the extensor carpi radialis longus is
branches — the superficial radial nerve, and the        supplied by the radial nerve proximal to its
posterior interosseous nerve which supplies ex-        terminal branching.
tensor carpi radialis brevis and the supinator            If symptoms do not improve spontaneously
muscles before it passes under a tough fibro-           with conservative therapy, exploration and divi-
tendinous ring at the origin of the supinator mus-     sion of the compressing band is necessary.
 240                                                                                         CHAPTER 17


                                                          of either one of these will usually predominate. If
                                                          there is a cervical rib the patient may present with
                                                          vascular features of increasing pallor and cold-
                                     Scalenus medius
                                                          ness of the hand which, if variable in intensity,
                                                          may simulate Raynaud’s syndrome. The clinical
                                     Scalenus anterior    features of neural compression are usually grad-
                                                          ual and are more likely to occur with a fibrous
                                                          band than a full cervical rib. The major present-
                                                          ing features are:
                                      C5, C6
                                      C7       Brachial   • arm pain
                                               plexus     • motor weakness and sensory loss caused by
                                      C8, T1
                                                          compression of the lower trunk of the brachial
                                      Subclavian artery
             1                                            plexus.
                                                             The syndrome occurs typically in young to
             2                                            middle-aged females and the pain may be diffuse
                                                          or in the distribution of the lower trunk of the
Fig. 17.4 The brachial plexus passing through the         brachial plexus. Atrophy may be present in the
cervicobrachial junction.                                 thenar and hypothenar eminence and other in-
                                                          trinsic hand muscles, and weakness may involve
                                                          not only the small muscles of the hand but some-
Thoracic outlet syndrome
                                                          times the long flexors, particularly on the ulnar
Thoracic outlet syndrome is an entrapment                 side of the forearm. There may be diminished
neuropathy of the brachial plexus at the root of          sensation in the distribution of the C8 and T1 der-
the neck. Numerous upper limb pain problems               matomes.
are frequently and erroneously attributed to                 Plain X-rays may show the characteristic elon-
compression at the thoracic outlet. Although the          gated transverse process of C7. Nerve conduc-
brachial plexus may be trapped at the cervico-            tion studies and electromyography may help
brachial junction, it is a relatively uncommon            with the diagnosis. Preoperative MRI is helpful
cause of upper limb symptoms.                             in excluding other cervical pathology as a basis
   The neurovascular bundle, consisting of the            for the presentation.
roots and trunks of the brachial plexus and the              Surgery should only be performed if there is
subclavian artery (Fig. 17.4), emerges from               unequivocal clinical evidence of neural entrap-
the neck into the axilla through a slit or triangle       ment. As indicated earlier the condition has often
with a narrow base bounded anteriorly by the              been erroneously diagnosed as the cause of non-
scalenus anterior, posteriorly by the scalenus            specific arm pain. If there are objective neurologi-
medius and inferiorly by the first rib.                    cal signs of entrapment the surgical procedure is
   Historically, a cervical rib was thought to be         division of the fibrous band or, in the case of a cer-
the cause of compression of the neurovascular             vical rib, excision of the bone to relieve com-
bundle. However, in the majority of patients the          pression. These procedures are best performed
symptoms are due to a compressive fibrous band,            through a supraclavicular approach using mag-
continuous with the medial edge of scalenus               nification to identify and protect the neural struc-
medius, which extends from an elongated trans-            tures. A transaxillary approach may also be used
verse process of C7 (a ‘forme fruste’ of a cervical       to remove a cervical rib.
rib) to the first rib and produces its symptoms by
compression of the brachial plexus, particularly
                                                          Lower limb entrapment neuropathies
the lower trunk.
   The presenting features may be due to either           Entrapment neuropathies of the lower limb are
neural or vascular compression and the features           uncommon.
 PERIPHERAL NERVE ENTRAPMENTS, INJURIES AND TUMOURS                                                  241


Meralgia paraesthetica                                 principal symptoms are pain, numbness and
Meralgia paraesthetica results from entrapment         tingling along the plantar aspect of the foot and
of the lateral cutaneous nerve of the thigh            toes.
beneath the inguinal ligament, just medial to the         Electrodiagnostic studies will help confirm the
anterior superior iliac spine. At this position the    diagnosis. Operation involves division of the
nerve passes between two roots of attachment of        retinaculum and decompression of the nerve,
the inguinal ligament to the iliac bone and there      usually with excellent results.
is a sharp angulation of the nerve as it passes
from the iliac fossa into the thigh.                   Sciatic nerve palsy
   Prolonged standing or walking and an obese          A sciatic nerve pressure palsy typically occurs in
pendulous anterior abdominal wall accentuates          patients following a prolonged period of uncon-
the downward pull on the inguinal ligament and         sciousness and is most frequently seen after drug
may predispose to entrapment of the nerve. The         overdose. It is not a true entrapment neuropathy
syndrome is most frequently seen in middle-            but rather a direct pressure palsy.
aged, overweight men, and also in young army
recruits during strenuous training.                    Common peroneal (lateral popliteal)
   The principal symptom is a painful dysaesthe-       nerve palsy
sia in the anterolateral aspect of the thigh. The      Entrapment of the common peroneal nerve may
patient often describes the sensation as ‘burning’,    occur rarely as it winds around the neck of the
‘pins and needles’ or ‘prickling’ which may be         fibula deep to the peroneus longus muscle, re-
accentuated by standing up straight and relieved       sulting in a foot drop. More commonly, paralysis
by flexion of the hip.                                  of the nerve will occur as a result of direct trauma
   The only neurological sign is diminished sen-       in this superficial vulnerable position.
sation over the anterolateral aspect of the thigh in
the distribution of the lateral cutaneous nerve of
                                                       Acute nerve injuries
the thigh.
   The symptoms may only be minor and the
                                                       Peripheral nerve anatomy
patient may be satisfied with reassurance. The
unpleasant features may resolve with conserva-         The axon projects from the cell body (the
tive treatment, which should include weight            perikaryon) and is surrounded by a basement
reduction in an obese patient. Surgery may be          membrane and myelin sheath. The axon is cov-
necessary if the symptoms are debilitating. This       ered by the endoneurium, the innermost layer of
involves decompression of the nerve or, if that        connective tissue, and a number of axons are
fails, division of the nerve.                          grouped together in a bundle called a fascicle,
                                                       which is invested by a further connective tissue
Tarsal tunnel syndrome                                 sheath called the perineurium. A peripheral
The tarsal tunnel is the counterpart of the carpal     nerve consists of a group of fascicles covered by
tunnel of the wrist and is located posterior and       an outermost layer of connective tissue, the
inferior to the medial malleolus. The flexor            epineurium. The nerve fibres can be classified ac-
retinaculum extends from the medial malleolus          cording to their diameter and function. The nerve
above to the medial tubercle of the os calcis          conduction velocity is proportional to the square
below. The posterior tibial nerve, a terminal          root of the fibre diameter. The largest myelinated
branch of the sciatic nerve, enters the foot           axons which produce the most rapidly conduct-
through the tarsal tunnel with the posterior tibial    ing potential are known as A fibres, which can be
vessels and the tendons of the tibialis posterior,     further subdivided into alpha, beta, gamma and
flexor digitorum longus and flexor hallucis              delta, based on their size and conduction velo-
longus muscles.                                        city. The smaller, slower conducting B fibres are
  Men and women are equally affected. The              mostly responsible for autonomic conduction
 242                                                                                           CHAPTER 17


and the unmyelinated C fibres have the slowest             autonomic function. Electrical studies will show
conduction.                                               absence of voluntary muscle potentials and
                                                          evidence of denervation after 2–3 weeks.
                                                             Although the term neurotmesis implies a cut-
Classification of nerve injuries
                                                          ting of the nerve, the term is also used when the
There is no single classification system that can          epineurium of the nerve is still in continuity but
describe all the many variations of nerve injury.         the axons have been so destroyed and replaced
Most systems attempt to correlate the degree of           by scar tissue that spontaneous regeneration is
injury with symptoms, pathology and prognosis.            impossible. The most common injuries to cause
In 1943, during the Second World War, Seddon              neurotmesis are laceration and a missile injury,
introduced a classification of nerve injuries based        but it can also result from other types of trauma
on three main types of nerve fibre injury and              including a crush or traction injury.
whether there is continuity of the nerve (Table              If the nerve has been completely divided, ax-
17.2).                                                    onal regeneration causes a neuroma to form in
                                                          the proximal stump.
Neurotmesis. This is the most severe injury, in
which the nerve has been completely divided               Axonotmesis. This is characterized by complete
and complete distal Wallerian degeneration oc-            interruption of the axons and their myelin
curs. There is complete loss of motor, sensory and        sheaths, although the encapsulating tissue, the



  Table 17.2 Classification of nerve injuries (Seddon).

                              Neurotmesis                  Axonotmesis               Neurapraxia

  Pathological
  Anatomical continuity       May be lost                  Preserved                 Preserved
  Essential damage            Complete disorganization.    Nerve fibres interrupted   Selective
                                Schwann sheaths              by larger fibres, no       demyelination
                                preserved                    degeneration of axons

  Clinical
  Motor paralysis             Complete                     Complete                  Complete
  Muscle atrophy              Progressive                  Progressive               Very little
  Sensory paralysis           Complete                     Complete                  Usually much sparing
  Autonomic paralysis         Complete                     Complete                  Usually much sparing

  Electrical phenomena
  Reaction of degeneration    Present                      Present                   Present
  Nerve conduction distal     Absent                       Absent                    Preserved to the lesion
  Motor unit action           Absent                       Absent                    Absent potentials
  Fibrillation                Present                      Present                   Occasionally detectable

  Recovery
  Surgical repair             Essential                    Not necessary             Not necessary
  Rate of recovery            1–2 mm/day after repair      1–2 mm/day                Rapid; days or weeks
  March of recovery           According to order of        According to order        No order
                                innervation                  of innervation
  Quality                     Always imperfect             Perfect                   Perfect

  Adapted from Seddon (1975). Reproduced with permission.
 PERIPHERAL NERVE ENTRAPMENTS, INJURIES AND TUMOURS                                                  243


epineurium and perineurium, are preserved.              • Traction and stretch trauma may also result in
Spontaneous regeneration will occur because the         either complete disruption of the nerve or, if
intact endoneurial sheaths guide the regenerat-         minor, a neurapraxia. This type of mechanism is
ing fibres to their distal connections. There is         particularly responsible for brachial plexus in-
complete and immediate loss of motor, sensory           juries following motor bike accidents, or radial or
and autonomic function distal to the lesion with        peroneal nerve injuries. It is a common mecha-
an EMG picture similar to that of neurotmesis.          nism of nerve injuries associated with skeletal
Regeneration occurs at a rate of 1–2 mm per day,        fractures.
so that the time of recovery will depend on the         • Fractures or fracture dislocation may cause
distance between a lesion and the end-organ and         nerve injuries when the adjacent nerve is either
on the age of the patient.                              compressed by the displaced bone fragments,
  The major types of injuries causing an ax-            causing injury by stretch or ischaemia, or less
onotmesis include compression, traction, missile        commonly, severed by the jagged edge of the
and ischaemic.                                          bone. Axonotmesis is the most common type of
                                                        injury.
Neurapraxia. The mildest form of injury, neu-           • Compression ischaemia may produce a neu-
rapraxia, is akin to a transient ‘concussion’ of the    rapraxia in mild cases or, if prolonged and severe,
nerve. Neurapraxia is a physiological block in          axonotmesis or neurotmesis. It is the cause of the
conduction along one segment of the nerve with          pressure palsies following improper application
structural changes confined primarily to de-             of a tourniquet, or the ‘Saturday night palsy’ in
myelination, if present at all. There is a tempo-       which the radial nerve has been compressed
rary loss of function, which is reversible within       against the humerus. Increased pressure in a
hours to months of the injury (the average is 6–8       closed fascial compartment, as can occur follow-
weeks). If there is a complete, initial loss of func-   ing a musculoskeletal injury, may cause is-
tion, neurapraxia cannot be distinguished from          chaemic damage to a peripheral nerve and delay
the more serious type of injury but will be recog-      in treatment will result in severe ischaemic
nized only in retrospect when recovery of func-         damage to the nerves and muscles resulting in
tion has occurred sooner than would be possible         paralysis and contraction deformities, such as in
following Wallerian degeneration. There is fre-         Volkmann’s ischaemic contracture.
quently greater involvement of motor than sen-          • Injection injury results from either direct
sory function with autonomic function being             trauma by the needle or the toxic effect of the
retained.                                               agent injected. As would be expected, the sciatic
                                                        and radial nerves are the most commonly affected.
                                                        • Electrical and burn injuries are uncommon
Causes of peripheral nerve injury
                                                        causes of serious peripheral nerve damage.
The type of trauma will determine the nature of
the injury to the nerve. In practice there are nu-
                                                        Management of nerve injuries
merous possibilities, but these can be grouped
into the major types.                                   The basis of the management depends on a pre-
• Lacerations cause neurotmesis with complete           cise assessment of the damage that has been done
or partial division of the nerve. The usual injury      to the nerve. The types of injuries vary consider-
results from a knife wound, laceration by glass or      ably from an isolated single nerve lesion to a
extensive contusion of the area with a chainsaw.        complex nerve injury in a patient with multiple
• Missile injuries may cause the spectrum of            trauma. The following are the general guidelines
nerve injury from complete disruption of the            for management.
nerve to a mild neurapraxia. If the brachial            1 Determination of the exact nerve involved by:
plexus is injured a variety of these injury types          (a) the clinical deficit
may occur to various parts of the plexus.                  (b) the position of the injury.
 244                                                                                         CHAPTER 17


2 Assessment of the type of nerve damaged by              bike or motor vehicle accident. The trauma may
the mechanism of the injury.                              result in damage to any part of the plexus, but
3 If a neurapraxia or axonotmesis is suspected            severe axial traction may result in tearing of the
on clinical grounds there is no specific surgical          arachnoid and dura with nerve root avulsion.
treatment for the nerve but physiotherapy                    The management involves determination of
should commence as soon as possible to prevent            the exact neurological injury, and particularly the
stiffness of the joints and contractures. However,        part of the brachial plexus involved. A Horner’s
a neurotmesis will not recover without surgery.           syndrome is useful evidence for avulsion of the
4 Immediate or early exploration of the nerve             nerve roots from the spinal cord.
should be undertaken in the following situations:            Magnetic resonance imaging or a myelogram
   (a) if it is highly probable that the type of injury   (or CT scan/myelogram) may show the pseudo-
   (e.g. laceration) will have caused the nerve to        meningocele, which is characteristic of nerve
   be severed                                             root avulsion.
   (b) if the nerve injury has been caused by a dis-         Electrical studies rarely add any new diagnos-
   placed fracture that needs reduction by open           tic information concerning the neurological dam-
   surgery, when exploration of the nerve can be          age but they do provide useful baseline studies
   carried out at the same time.                          for future comparison. It is reasonable to obtain
The operative procedure involves identification            these studies 8 weeks after the injury.
of the nerve and relieving any compression. If the           There is controversy concerning the exact
nerve has been severed the nerve ends should be           indications for surgical intervention for closed
isolated and continuity restored by either direct         brachial plexus injuries in adults. Obviously, if
suture or inserting a nerve graft. Some surgeons          the injury is partial and improving there is no
advocate performing a graft as a secondary pro-           indication for surgery, and supportive manage-
cedure only, and delaying this until the wound            ment, including intensive physiotherapy and
has healed and the risk of infection has subsided.        mobilization of the joints, should be commenced
5 Delayed exploration of the nerve will be indi-          as soon as possible. Similarly, there is no place for
cated if the clinical and EMG findings indicate            surgery if there is clinical or radiological evi-
failure of regeneration of the nerve beyond the           dence of nerve root avulsion from the cord. In
time expected, that is, if the injury has resulted in     general there is little benefit from exploration of
a neurotmesis rather than an axonotmesis or               the plexus in closed injuries, although some sur-
neurapraxia.                                              geons do advocate exploration approximately 4
                                                          months after the injury if clinical and electrical
                                                          evidence show the lesion to be complete.
Brachial plexus injury
The mechanisms of injury are the same as for any
                                                          Pain following nerve injuries
peripheral nerve. Birth injuries usually have one
of three patterns.                                        A number of pain problems occur specifically
1 Erb’s palsy due to damage to the upper trunk            after nerve injuries. These include:
of the brachial plexus.                                   • causalgia (Chapter 20)
2 Klumpke’s paralysis due to damage to the                • phantom limb pains (Chapter 20)
lower trunk of the brachial plexus (C8 and T1), re-       • irritative nerve lesions — neuroma
sulting from the arm being held up while traction         • brachial plexus trauma pain.
was applied to the body during a breech delivery.            Phantom limb pain and causalgia are de-
3 Paralysis of the whole arm as a result of severe        scribed in more detail in Chapter 20. Causalgia
birth trauma.                                             occurs rarely; it is a burning pain that follows a
   In adolescents and adults the most common              partial or minor nerve injury and is relieved by
cause is severe traction on the brachial plexus re-       sympathectomy. Phantom limb pain may occur
sulting from violent trauma, frequently a motor           following traumatic amputation of a limb or after
 PERIPHERAL NERVE ENTRAPMENTS, INJURIES AND TUMOURS                                                  245


surgical amputation for tumours or peripheral
                                                         Table 17.3 Peripheral nerve tumours.
vascular disease.
   There is a diffuse range of pain problems fol-
                                                         Benign tumours
lowing peripheral nerve injuries that is broadly
                                                         Schwannoma
termed ‘irritative nerve lesions’. The pathological      Neurofibroma
cause of the pain is often not evident, although in        Cutaneous neurofibroma
some cases a neuroma may be demonstrable and               Intraneural (plexiform) neurofibroma
the pain is relieved following excision.
                                                         Malignant tumours
   A particularly severe form of pain following
                                                         Malignant schwannoma
nerve injury occurs after brachial plexus trauma.        Nerve sheath fibrosarcoma (neurofibrosarcoma)
The onset of the pain is frequently delayed by
some weeks or months and the pain is described           Non-neoplastic
                                                         Morton’s neuroma
as having both deep and superficial components.
                                                         Traumatic neuroma
The deep pain is continuous and is described as
an ‘ache’ throughout the affected limb. The
superficial ‘burning’ pain is particularly severe
distally in the limb and is associated with a
hyperpathia. The skin is usually dry and cool and        The nerve sheath tumours originating from the
hyperthermia and sweating are uncommon.                neuroectoderm may arise from the Schwann
   The management of these pain problems               cells, which form the axonal myelin, or from the
involves an assessment of the particular pain          perineurial cells. Those of mesodermal origin
pattern and the underlying pathological cause. In      arise from the fibrocytes that lie in the endoneuri-
general, treatment consists of simple conserva-        um and throughout the nerve sheath. The neu-
tive measures, including supportive care and           ronal or nerve cell tumours nearly always arise in
simple analgesic medication. If a neuroma is           the ganglia of the autonomic nervous system.
thought to be the cause of the pain it should be         The more common peripheral nerve tumours
excised. The pain from brachial plexus injuries is     are shown in Table 17.3.
notoriously difficult to treat and is often unre-
sponsive to conservative therapies. The dorsal
                                                       Benign tumours
root entry zone (DREZ) operation has been mod-
erately successful in controlling the pain in a        Schwannoma
significant percentage of these patients. The           Schwannomas may arise from intracranial
operation involves ablation of the DREZ over the       nerves (Chapter 7) or intraspinal nerves (Chapter
involved segments by thermocoagulation. There          15). The extraspinal schwannomas derived from
is a small risk of further damage to the cord by the   the Schwann cell may arise from motor, sensory
procedure but most patients are willing to accept      or autonomic nerves and are usually encoun-
this because of the severity of the pain.              tered as solitary lesions in adults. They may be
                                                       associated with von Recklinghausen’s neurofi-
                                                       bromatosis (neurofibromatosis type 1, NF1).
Peripheral nerve tumours
                                                       They are sometimes classed together with neu-
The classification and nomenclature of peripher-        rofibromas as ‘benign nerve sheath tumours’.
al nerve tumours has been confusing, mainly due        They are discrete, smooth and sometimes lobu-
to disagreements as to the embryological origin        lated; they originate focally in a fascicle. As they
of the various tumours. Peripheral nerve tu-           grow the discrete mass deflects the other fascicles
mours may arise from the nerve sheath or be of         over its surface. Malignant transformation is
neuronal origin. The nerve sheath tumours may          rare.
be neuroectodermal or mesodermal in origin; the           As in other schwannomas there are two dis-
neuronal tumours arise from the neuroectoderm.         tinct architectural patterns, Antoni A and B. The
 246                                                                                      CHAPTER 17


histological features of Antoni A typically consist
of strands and whorls of closely packed spindle
cells with elongated, darkly staining nuclei. The
nuclei show a tendency to aggregate and often
show striking pallisading. The type B pattern
consists of loosely arranged stellate cells and a
spongy meshwork of vacuolated cells.
   Benign schwannomas are usually asympto-
matic and most patients present with a painful
lump or local tenderness if the tumours are su-
perficial. Occasionally, the benign tumours may
present with pain or neurological disturbance,
particularly if they arise in an enclosed space
such as the carpal or tarsal tunnel. Most of the tu-
mours arise in the head, neck and extremities.
   The treatment, if indicated, involves tumour
resection and, using microsurgical techniques,
preservation of nerve function. The nerve fasci-
cles passing by the tumour are reflected over the
tumour surface, thereby making it possible to re-
sect the tumour and preserve neural function.

Neurofibroma
Neurofibromas arise spontaneously or in the
                                                       Fig. 17.5 Numerous cutaneous neurofibromatoma in
context of NF1 (see also Chapter 6) (Fig. 17.5).       a patient with von Recklinghausen’s disease (NF1).
Dermal neurofibromatosis may be isolated or nu-         Other cutaneous features include café au lait spots
merous as part of NF1. The deeper solitary neu-        and fibromas.
rofibromas that are associated with NF1 in about
50% of cases have a clinical presentation similar
to that of a schwannoma.                               Intraneural neurofibromas. Less common than the
   As with schwannomas the management of               cutaneous variety, intraneural neurofibromas
neurofibroma depends upon the clinical symp-            usually arise from larger nerves, have a frequent
toms. NF1 patients may have hundreds of                association with von Recklinghausen’s disease
dermal and visceral neurofibromas that require          and have a potential for malignant transforma-
no treatment and if they are asymptomatic they         tion. They commonly occur in the cervical,
can be followed clinically. Potential indications      brachial or lumbosacral plexus. The tumour
for surgery are pain, progressive neurological         is formed by an intraneural proliferation of
deficit, cosmetic reasons and rapid growth that         Schwann cells and is usually a diffuse transfor-
might be suspicious for malignant transforma-          mation of long segments of nerves and their
tion. The operation involves neurosurgical             branches. This plexiform neurofibroma is
techniques aided by intraoperative electro-            pathognomonic for von Recklinghausen’s
physiological testing in order to preserve func-       disease (NF1).
tional nerve fascicles. If functional fascicles           The nerve containing the plexiform neurofi-
cannot be preserved it might be necessary to           broma has a macroscopic appearance similar to
perform a subtotal resection or, if clinically indi-   rope, with the enlarged fascicles forming the
cated, to proceed with a complete resection fol-       braids of the rope.
lowed by an interposition nerve graft for neural          The surgical treatment provides a dilemma.
restoration.                                           Approximately 10% may undergo malignant
 PERIPHERAL NERVE ENTRAPMENTS, INJURIES AND TUMOURS                                                      247


transformation, but radical resection will usually    neurovascular bundle. The ‘neuroma’ can be
result in serious neurological impairment. In         excised simply and the problem cured.
general, an initial partial resection, with preser-      Traumatic neuromas appear macroscopically
vation of neurological function, should be at-        as a fusiform enlargement of the nerve or, if there
tempted. The patient should be observed closely       has been transection of the nerve, as a bulbous
and if there is evidence of malignant transforma-     expansion of the proximal stump.
tion a radical resection should be performed.            A painful neuroma can be excised. This is par-
                                                      ticularly appropriate if a nerve block proximal to
                                                      the neuroma gives total pain relief.
Malignant tumours
                                                         The treatment of a neuroma of a nerve in conti-
Malignant tumours of peripheral nerves can            nuity is more difficult when there is retained
arise spontaneously in a normal nerve from            nerve function. Neurolysis, with division of the
Schwann cells of neuroectodermal origin or fi-         epineurium, may relieve the pain. Occasionally
brocytes of mesodermal origin, or in a plexiform      excision of the neuroma in continuity and re-
neurofibroma of von Recklinghausen’s disease           suture of the nerve may be necessary.
(NF1). The tumours are classified as either malig-
nant schwannoma or a nerve sheath fibro-
                                                      Further reading
sarcoma. Sometimes, more overt mesenchymal
characteristics such as osteoid, chondroid and        Brain WR, Wright AD, Wilkinson M (1947) Sponta-
rhabdomyoblasts are contained in malignant              neous compression of both median nerves in a carpal
peripheral nerve neoplasms.                             tunnel. Six cases treated surgically. Lancet i, 277–282.
   The patient usually presents with an enlarging     Burger PC, Vogel FS (1982) Surgical Pathology of the Ner-
                                                        vous System and its Coverings, 2nd edn. John Wiley,
painful mass with a progressive neurological
                                                        New York.
disturbance in the distribution of the nerve
                                                      Ebeling P, Gilliat TRW, Thomas PK (1960) A clinical and
involved.                                               electrical study of ulnar nerve lesions in the hand.
   The tumour presents macroscopically as a             Journal of Neurology, Neurosurgery and Psychiatry 23,
lobulated, fusiform enlargement of the nerve that       1–8.
may extend over a long length, both proximal          Kaye AH, Black P McL (2000) Operative Neurosurgery.
and distal to the major mass. The surrounding           Churchill Livingstone, London, New York,
tissues are compressed and histological examina-        Edinburgh.
tion may show microscopic invasion.                   Kline DG, Judice DJ (1983) Operative management of
   Surgery will entail a radical resection provided     selected brachial plexus lesions. Journal of Neuro-
there is no evidence of widespread metastases.          surgery 58, 631–649.
                                                      Pang D, Wessel HB (1988) Thoracic outlet syndrome.
                                                        Neurosurgery 22, 105–121.
Non-neoplastic tumours                                Seddon H (1975) Surgical Disorders of the Peripheral
                                                        Nerves, 2nd edn. Churchill Livingstone, London.
Morton’s neuroma is a reactive fibrosis asso-          Sunderland S (1978) Nerves and Nerve Injuries. Churchill
ciated with degeneration of a nerve. It occurs pre-     Livingstone, Edinburgh.
dominantly in women in the plantar digital nerve      Tindall SC, McGillicuddy JE, Kline DG (1995) Treat-
between the heads of the 3rd and 4th metatarsals.       ment of ulnar entrapment. In: Al-Mefty O, Origitano
The patient presents with pain and, macroscopi-         TC, Harkey HL, eds. Controversies in Neurosurgery.
cally, the lesion is a discrete enlargement of the      Thieme, New York.
                            CHAPTER 18


  18                        Facial pain and
                            hemifacial spasm


Facial pain may result from local pathology in-          extended by Gardner, at the Cleveland Clinic, to
volving the face, mouth, jaw, temporomandibu-            form the basis of hemifacial spasm due to pres-
lar joint, paranasal sinuses or salivary glands, or      sure on the 7th cranial nerve. The concept has
it may be due to distinct pain disorders such as         been popularized by Jannetta, who proposed
trigeminal neuralgia, glossopharyngeal neural-           that trigeminal neuralgia is the result of compres-
gia and postherpetic neuralgia. These specific            sion of the root entry zone, which is a junctional
pain entities are relatively uncommon but the            area between the central and peripheral myelin
clinical manifestations are stereotyped so that a        on the nerve adjacent to the brainstem. However,
diagnosis should be apparent.                            others suggest that the pain is due to central dys-
                                                         function in the brainstem in structures related to
                                                         the nucleus of the 5th nerve, or pathology within
Trigeminal neuralgia
                                                         the gasserian ganglion.
Trigeminal neuralgia consists of excruciating               Trigeminal neuralgia may occasionally present
paroxysmal pain, which lasts for seconds to min-         as a symptom of multiple sclerosis, which should
utes, in the distribution of the 5th cranial nerve. It   therefore be considered as a cause in patients
was described by Avicenna 900 years ago and the          under 40 years of age.
term ‘tic douloureux’ was applied by André in               In approximately 3% of cases there may be a
1756. Charles Bell demonstrated the anatomical           mass, such as a meningioma, epidermoid or arte-
basis for sensation in the face in the 1820s and dis-    riovenous malformation, in the posterior fossa.
tinguished the sensory component of the trigem-          This mass distorts the nerve and produces pain
inal nerve from the motor function of the facial         similar to trigeminal neuralgia.
nerve, consequently defining an anatomical basis
for trigeminal neuralgia. It is estimated that it
                                                         Clinical features
occurs in about 1 in every 70 000 people.
                                                         The main clinical feature is the sudden, severe
                                                         pain that lasts for a moment and then goes, leav-
Aetiology
                                                         ing nothing behind — except the fear of its return.
There is some controversy concerning the precise         Shaving, talking, eating, washing or even a cold
aetiology of trigeminal neuralgia. The microvas-         wind may disturb the skin and trigger a parox-
cular compression theory is popular and postu-           ysm of pain which is so severe that the patient is
lates that the 5th cranial nerve is compressed at        immobilized in agony.
the brainstem junction by a vascular loop. In 1934         The particular characteristics of trigeminal
Dandy first proposed that trigeminal neuralgia            neuralgia are as follows.
was caused by the nerve being compressed and             • The pain is strictly limited to one or more
distorted by the superior cerebellar artery, and         branches of the trigeminal nerve. It most com-
this theory of microvascular compression was             monly affects the 2nd and/or 3rd division.

248
 FACIAL PAIN AND HEMIFACIAL SPASM                                                                  249


• The pain is sudden and short lived, usually         • pain of dental origin, such as malocclusion or
lasting seconds, or at the most, minutes.             dental abscess
• The pain is frequently provoked by light            • pain from the temporomandibular joint
mechanical stimuli within the trigeminal area. In     • postherpetic neuralgia
particular, it is often ‘triggered’ by touching the   • migrainous neuralgia (cluster headache).
side of the face, or is brought on by facial move-
ment, such as chewing. These patients are often
                                                      Treatment
unable to shave and they shield their faces when
outside in the wind.                                  Management of a patient with trigeminal neural-
• There is no detectable abnormality of trigemi-      gia may involve the use of a number of treatment
nal nerve function.                                   modalities including:
   The incidence of trigeminal neuralgia reaches      • drugs
its maximum between the ages of 50 and 70 years,      • local procedures on peripheral branches of the
is very rare below the age of 25 and is uncommon      trigeminal nerve
under the age of 35. The pain affects the territory   • percutaneous procedures involving the
of the 2nd and 3rd divisions of the trigeminal        trigeminal ganglion or the retrogasserian rootlets
nerve with equal frequency, and may involve           • posterior fossa craniotomy procedures.
both territories simultaneously. The area of the
1st division of the trigeminal nerve is involved      Drugs
less frequently. In about 5% of cases the neuralgia   Carbamazepine initially relieves the pain in the
affects both sides of the face, but not usually si-   great majority of patients although doses of 200-
multaneously, so that each bout of pain remains       mg tablets up to 4–5 times a day are often neces-
strictly unilateral. Bilateral trigeminal neuralgia   sary for adequate pain control. However, the
occurs more commonly in patients with multiple        patients frequently have a relapse of pain and
sclerosis.                                            need further treatment. In addition, many pa-
   Remissions of the pain are frequent and may        tients are unable to tolerate the side-effects of
last for months or even years; occasionally com-      carbamazepine which occur at the doses neces-
plete freedom from the pain occurs.                   sary to control the discomfort. The most frequent
   There are no physical signs. The patient may       adverse reactions are dizziness, drowsiness, un-
present with a scarf shielding the head and will      steadiness, nausea and vomiting. Haemopoietic
talk from the corner of the mouth so as not to pre-   complications due to bone marrow depression
cipitate a spasm of pain. If the pain has been very   occur rarely. Other drugs that can be tried include
severe the patient may be emaciated and dehy-         phenytoin, baclofen and clonazepam, although
drated from being unable to eat or drink and the      they are not as effective.
face may be dirty and unshaven from fear of
precipitating an attack of pain.                      Procedures involving peripheral branches
                                                      of the trigeminal nerve
                                                      Infraorbital or supraorbital nerve section may be
Investigations
                                                      performed in the uncommon situation of the pain
MRI of the brain should be performed to exclude       being localized to the area in the distribution of
a mass in the cerebellopontine angle in the poste-    these nerves. However, the pain frequently re-
rior fossa or intrinsic brainstem lesion such as      curs and these procedures should probably be
demyelination, especially in younger patients.        limited to the elderly frail patient.

Differential diagnosis                                Percutaneous thermocoagulation
The pain of trigeminal neuralgia is characteristic    Percutaneous thermocoagulation of the retro-
but must be differentiated from:                      gasserian rootlets or ganglion of the trigeminal
• atypical facial pain                                nerve can result in analgesia in selected areas of
 250                                                                                       CHAPTER 18


the trigeminal distribution. In this procedure a        10–15% have some relapse of trigeminal neural-
needle is passed percutaneously, under X-ray            gia over the next 5 years.
control, through the foramen ovale into the gan-
glion and nerve roots just behind the ganglion in       Summary of treatment
Meckel’s cave. The nerve rootlets and ganglion          There are a number of methods of treating
are heated with a radiofrequency current, which         trigeminal neuralgia and the treatment chosen
results in a differential loss of pain sensation but    will frequently depend on the patient’s prefer-
retention of light touch sensation. Alternatively,      ence when the various options are explained. In
glycerol may be injected into Meckel’s cave so as       general, carbamazepine is used first. If the med-
to bathe the retrogasserian nerve rootlets. Al-         ication is not tolerated, or when the pain relapses,
though these procedures have a high initial suc-        the main choice is between a radiofrequency
cess in relieving pain, they may produce facial         percutaneous rhizotomy or a posterior fossa
numbness and the trigeminal neuralgia fre-              craniotomy and microvascular decompression.
quently recurs. The procedures may be repeated          Unless the patient is elderly and very frail, mi-
when the pain recurs or alternative treatments          crovascular decompression is the preferred op-
may be considered.                                      tion, as it has the greatest chance of producing
                                                        permanent relief of pain with no facial
Posterior fossa craniotomy procedures                   numbness.
Total or partial trigeminal nerve section. Trigeminal
root section, by either a posterior fossa cranio-
                                                        Glossopharyngeal neuralgia
tomy or a middle cranial fossa approach
(Frazier’s operation), used to be a common pro-         Glossopharyngeal neuralgia is much less com-
cedure for trigeminal neuralgia but is now almost       mon than trigeminal neuralgia, there being ap-
obsolete. Section of the nerve results in facial        proximately one case for every 50 of trigeminal
numbness and the morbidity may be quite dis-            neuralgia. It was first defined as a clinical entity
abling, particularly if the ophthalmic division         by Harris in 1921. It is characterized by intense at-
supplying the cornea is affected. However, a par-       tacks of pain in the distribution of the glossopha-
tial section of the posterior half of the nerve         ryngeal nerve and the auricular and pharyngeal
causes only relatively minor disturbance of facial      branches of the vagus nerve.
sensation and may result in lasting pain relief for
trigeminal neuralgia involving the 2nd and/or
                                                        Aetiology
3rd divisions. An uncommon, but feared, dis-
abling complication of nerve section is a painful       The precise cause of glossopharyngeal neuralgia
dysaesthesia of the face, ‘anaesthesia dolorosa’,       is unclear, although Janetta proposed the theory
for which there is no treatment. Anaesthesia            of microvascular compression of the 9th nerve, as
dolorosa only rarely results from percutaneous          for trigeminal neuralgia and the 5th cranial
radiofrequency rhizotomy.                               nerve.

Microvascular decompression. This is now the pro-
                                                        Presenting features
cedure of choice. The operation is performed via
a small retrosigmoid posterior fossa craniotomy         The patient presents with attacks of severe pain
using the operating microscope. The compres-            involving the throat, tongue or ear. The pain may
sive vessel, most commonly the superior cerebel-        start anywhere in the territory of the glosso-
lar artery, is dissected away from the 5th cranial      pharyngeal nerve or auricular and pharyngeal
nerve at the brainstem entry junction and the           branches of the vagus nerve. The tonsil, root of
nerve is then shielded from the vessel by a small       the tongue and ear are common sites and the pain
patch of sponge. Over 90% of patients have an           often extends into the base of the jaw and the
initial complete relief of pain, although about         neck. At times the pain may be confined to the
 FACIAL PAIN AND HEMIFACIAL SPASM                                                                   251


throat and occasionally only the ear is involved.     usually in the distribution of the ophthalmic divi-
In some patients the pain involves the area of        sion, is severe, constant and unremitting, and is
the mandibular division of the trigeminal nerve,      described as ‘burning’ or a ‘crawling’ sensation
which may lead to a wrong diagnosis.                  under the skin.
  The attacks are frequently induced by talking,         The diagnosis is usually obvious by the
swallowing or chewing, and consequently, in se-       herpetic rash. Occasionally, however, the rash
vere cases, the patient may become cachectic. Oc-     may be minor and barely noticeable.
casionally, an episode of throat pain precipitated       There is no surgical treatment for postherpetic
by swallowing may be associated with bradycar-        neuralgia of the trigeminal nerve and sensory
dia, hypotension and syncope.                         root section is of no benefit. Carbamazepine may
                                                      alleviate some of the discomfort, although unfor-
                                                      tunately its benefit is usually limited.
Differential diagnosis
                                                         There is some evidence that the early use of
The distribution of the pain will distinguish glos-   steroids and acyclovir in patients presenting with
sopharyngeal neuralgia from trigeminal neural-        herpes zoster may reduce the risk of postherpetic
gia. Geniculate neuralgia, described by Hunt, is      neuralgia.
rare and involves the sensory component of
the facial nerve (nervus intermedius). Geniculate
                                                      Atypical facial pain
neuralgia has two major forms, one affecting the
ear, with secondary radiation into the deep struc-    Facial pain which has no pathological basis is
tures of the face, the other involving primarily      relatively common and most frequently affects
the deep facial structures.                           middle-aged females. The pain presents a diag-
                                                      nostic problem which can often only be solved
                                                      after underlying pathology has been excluded by
Treatment
                                                      clinical and radiological investigations.
Patients with glossopharyngeal neuralgia may             The pain is usually situated in the central
derive benefit from treatment with carba-              portions of the face or cheek and is described as
mazepine, although with less effect than for          boring, dull or aching. The lancinating parox-
trigeminal neuralgia. However, surgery for glos-      ysms of pain characteristic of trigeminal neural-
sopharyngeal neuralgia is straightforward and         gia and glossopharyngeal neuralgia are absent.
effective. The operation involves a small posteri-    Dental malocclusion and pain from the temporo-
or fossa craniotomy with section of the 9th nerve     mandibular joint, Costen’s syndrome, should be
and the upper 10% of the fibres of the vagus           excluded.
nerve. The sensory loss resulting from these
nerve sections results in no disability. Some sur-
                                                      Hemifacial spasm
geons advocate microvascular decompression as
for trigeminal neuralgia, but the nerve section       Hemifacial spasm is a facial disorder that is not
operation is effective and the microvascular          painful, but its proposed aetiology is so similar to
decompression may require manipulation of the         trigeminal neuralgia that it is best described in
lower cranial nerves resulting in morbidity.          this chapter. The condition is characterized by
                                                      unilateral spasms of the facial muscles supplied
                                                      by the facial nerve.
Postherpetic neuralgia
Herpes zoster may involve the distribution of the
                                                      Aetiology
trigeminal nerve, particularly the ophthalmic di-
vision. In a manner similar to shingles involving     The aetiology is similar to that proposed for
the trunk or limbs, postherpetic neuralgia occurs     trigeminal neuralgia and the microvascular com-
more frequently in elderly patients. The pain,        pression theory postulates that the 7th cranial
 252                                                                                       CHAPTER 18


nerve is compressed at the brainstem junction by     treatment. Injections of botulinum toxin into the
a vascular loop, usually an artery. Gardner advo-    affected muscles have limited, transient success,
cated this theory in the 1960s and it has been       but need to be repeated every few months.
popularized by Jannetta who proposed that, as           At present the only long-term effective treat-
for trigeminal neuralgia and the 5th cranial         ment is surgical and the operation is a microvas-
nerve, hemifacial spasm is due to pulsatile com-     cular decompression of the 7th cranial nerve.
pression at the root exit zone of the 7th cranial    However, as the condition is benign and painless
nerve, which is a junctional area between the cen-   the principal indication for operation is social
tral and peripheral myelin where the 7th nerve       embarrassment. In many patients the hemifacial
leaves the brainstem. Very uncommonly, hemifa-       spasm is so annoying and socially distressing
cial spasm is associated with a compressive mass     that they are keen to proceed with an operation,
such as an epidermoid, aneurysm or menin-            bearing in mind its possible risks. Surgery is def-
gioma. Occasionally, hemifacial spasm and            initely inappropriate if the patient is not troubled
trigeminal neuralgia may coexist in the same         by the spasm.
patient (known as ‘tic convulsif’).                     The microvascular decompression is per-
                                                     formed through a small posterior fossa cranio-
                                                     tomy and, using the operating microscope, the
Clinical features
                                                     vessel, often the anterior inferior cerebellar
The onset of hemifacial spasm usually com-           artery, compressing the 7th nerve at the brain-
mences in middle or old age and there is a slight    stem junction is carefully mobilized away from
female predominance. The spasms usually com-         the nerve. The nerve is then protected from the
mence around the orbicularis oculi muscles and       vessel by a small patch of sponge. The operation
subsequently spread down the face to involve the     is usually highly effective in relieving the spasm.
other facial muscles innervated by the facial        There is a small risk of unilateral hearing loss due
nerve. The spasms are episodic and are fre-          to the proximity of the 8th nerve and its blood
quently precipitated by emotional distress,          supply. As the operation involves a craniotomy,
chewing, talking or laughing. The condition          often in elderly patients, there is a small risk
causes the patient considerable social embarrass-    of serious complication, mostly as a result of
ment and the spasms of the orbicularis oculi re-     cerebrovascular complications. This possibility
sult in eye closure, making driving difficult.        should temper an obvious enthusiasm for an
  In contrast to trigeminal neuralgia, where         effective operation.
there is no clinical evidence of 5th cranial nerve
dysfunction, there is frequently minor facial
                                                     Further reading
weakness between the episodes of spasm. Other-
wise, there are no neurological findings.             Adams CBT (1989) Microvascular compression, an
                                                       alternative view and hypothesis. Journal of
                                                       Neurosurgery 57, 1–12.
Management                                           Apfelbaum RI (1983) Surgery for tic douloureux.
                                                       Clinical Neurosurgery 31, 351–368.
The diagnosis is self-evident, with the spasms
                                                     Burchiel KJ et al. (1981) Comparison of percutaneous
being located on one side of the face. In the very
                                                       radiofrequency gangliolysis and microvascular
early stages hemifacial spasm needs to be differ-      decompression for the surgical management of tic
entiated from simple blepharospasm, but this is        douloureux. Neurosurgery 9, 111–119.
confined to the muscles around the eye and is         Dandy WE (1929) An operation for the cure of tic
usually bilateral.                                     douloureux: partial section of the sensory root at the
   An MRI should be performed to exclude the           pons. Archives of Surgery 18, 687–734.
unlikely possibility of a posterior fossa mass       Dandy WE (1934) Concerning the cause of trigeminal
lesion causing the condition.                          neuralgia. American Journal of Surgery 24, 447–455.
   There is currently no lasting effective medical   Gardner WJ (1962) Concerning the mechanism of
 FACIAL PAIN AND HEMIFACIAL SPASM                                                                             253


  trigeminal neuralgia and hemifacial spasm. Journal of      Nugent GR, Brown JA, Hakanson S, Matsushima T,
  Neurosurgery 19, 947–948.                                    Wilkins RH (1995) Treatment of patient with trigemi-
Jannetta PJ (1980) Neurovascular compression in cra-           nal neuralgia. In: Al-Mefty O, Origitano TC, Harkey
  nial nerve and systemic disease. Annals of Surgery           HL, eds. Controversies in Neurosurgery. Thieme, New
  192, 518–525.                                                York.
Jannetta PJ et al. (1977) Aetiology and definitive micro-     Resnick DK, Jannetta PJ, Bissonett D (1995) Microvas-
  surgical treatment of hemifacial spasm: operative            cular decompression for glossopharyngeal neural-
  techniques and results in 47 patients. Journal of Neuro-     gia. Neurosurgery 36, 64–69.
  surgery 47, 321–328.                                       Stookey B, Ransohoff J (1959) Trigeminal Neuralgia: its
Kaye AH, Black P McL (2000) Operative Neurosurgery.            History and Treatment. Charles C Thomas, Springfield.
  Churchill Livingstone, London, New York,                   Taha J, Tew S (1996) Comparison of surgical treatment
  Edinburgh.                                                   for trigeminal neuralgia. Neurosurgery 38, 865–871.
Lunsford LD, Apfelbaum RI (1985) Choice of surgical
  therapeutic modalities for treatment of trigeminal
  neuralgia. Clinical Neurosurgery 32, 319–333.
                           CHAPTER 19


  19                       Pain — neurosurgical
                           management


Pain is the most common symptom in patients            the spatial, temporal and magnitude properties
presenting to a neurosurgeon; in fact it is often      of pain and is subserved mostly by neo-
the only symptom that the patient will complain        spinothalamic projections to the ventrobasal
of. The features of the pain are often characteris-    thalamus and then to the somatosensory cortex
tic of the particular underlying disease; these fea-   (Fig. 19.1). The pain pathways are described in
tures include:                                         Chapter 1. The receptors for pain consist of
• mode of onset                                        unencapsulated endings of peripheral nerves.
• pattern of the pain — continuous or intermittent     The neural responses are mediated through the
• duration                                             myelinated A-delta and unmyelinated C fibres.
• position of the pain                                 Pain may be felt as two waves, separated by a
• quality of the pain                                  very short interval. The first is sharp and local-
• features that alleviate or exacerbate the pain.      ized, with conduction along group A fibres. The
   There are three major clinical groups of pain       second wave, which is rather diffuse and more
problems.                                              disagreeable, depends on the slower conduction
1 Benign specific pain syndromes.                       of group C fibres. The cell bodies are in the dor-
2 Benign non-specific pain syndromes.                   sal root ganglia. Their axons traverse the dorsal
3 Cancer pain.                                         roots and enter the dorsolateral fasciculus (tract
                                                       of Lissauer) of the spinal cord, in which ascend-
                                                       ing and descending branches travel for one or
Mechanisms of pain
                                                       two segments. These fibres, which give off many
There is no ‘pain centre’ in the brain — such a con-   collateral branches in their short course, termi-
cept would be quite inadequate to account for          nate in the substantia gelatinosa of the dorsal
the complexity of pain. There are three major          grey horn. The substantia gelatinosa consists of
psychological–anatomical–physiological com-            Golgi type II neurones whose axons are either
ponents to pain which aid in the understanding         confined to the nucleus or run for short distances
of the mechanisms of pain and in treating              in the tract of Lissauer, connecting adjacent re-
patients. These are:                                   gions of the