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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 Production Controller: Kate Charman For further information on Blackwell Publishing, visit our website: http://www.blackwellpublishing.com The publisher’s policy is to use permanent paper from mills that operate a sustainable forestry policy, and which has been manufactured from pulp processed using acid-free and elementary chlorine-free practices. Further- more, the publisher ensures that the text paper and cover board used have met acceptable environmental accreditation standards. 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 STROKE 145 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). STROKE 149 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 ti