Your Federal Quarterly Tax Payments are due April 15th Get Help Now >>

2009 01 15 Cooke Approach to CT head by fe7J72f

VIEWS: 127 PAGES: 111

									  CT Scans of the Head:
A Neurologist’s Perspective




       Lara Cooke
    January 15, 2009
            Objectives

• At the end of this session, residents
  should be able to:
  • Identify key anatomic structures on CT
  • Apply an approach to reading a CT of the
    head
  • List reasons to image a patient with headache
  • Identify CT signs of raised ICP, early ischemia
  • Describe the clinical presentation of dural
    sinus thrombosis
  • Distinguish between intracranial hemorrhages
General Principles of the CT

 • CT is basically a specialized X-Ray
 • We talk about “density” or
   “attenuation”
 • The image is a measure of
   absorption of X-rays through
   different angles through a given
   tissue and then transformed
   mathematically
 What is hyperdense vs
  hypodense on CT?
• Bone (dense calcium) (1000 HU)
• Metal
• Acute (but not hyperacute) blood (56-76
  HU)
• Thrombosis
• Grey matter>white matter (30, 20 HU)
• CSF (0 HU)
• Fat (-30-100 HU)
• Air (-1000)
    General Principles:

• Are there any fractures?
  • Use bone windows
  • Look around the orbits, skull base, zygoma


• Remember to look at the sinuses (frontal,
  maxillary, ethmoid, sphenoid, mastoid air
  cells)
  • Should be black & full of air--look for
    hyperdense fluid levels, thickening of mucosa,
    cysts….especially when the patient complains
    of headache
Bones




        Fracture
Sinuses

Sphenoid   Maxillary




Frontal


           Ethmoid
    General Principles

• Look at the dura
  • Is there anything ‘extra’ between the
    brain and the skull?
    •   Hygroma
    •   Blood
    •   Tumor
    •   Air
 Things between skull & brain
    that shouldn’t be there
           Hygroma




Subdural               Meningioma
hematoma




                          Epidural hematoma
                 Pneumocephaly
      General Principles

• Look at the brain:
  •   Grey-white differentiation
  •   Basal ganglia
  •   Internal capsule
  •   Corona radiata
  •   Is there blood? Is there edema? Is there
      CSF due to encephalomalacia/cysts? Is
      there a mass?
 GW Differentiation
Anatomic Structures
                          Anterior horn o
                  caudate lateral ventricle
                                  lentiform


                                    Interna
      Insular ribbon                capsule
           Sylvian                  (post.
           fissure                    limb)
             thalamus           Pineal glan
                        3rd
                        ventricle
    General Principles
• Look at the spaces
  • Ventricles:
     • Can you see all the ventricles?
     • Is there hydrocephalus?
  • Cisterns
     • Are the normal spaces around the brainstem still
       visible?
  • Dural Sinuses
     • Can you see them?
     • Are they thicker or brighter than usual?
              Case

• 43 yo woman with headache x 3
  weeks
• Presents to hospital with double
  vision
• Low grade fever
• On examination, weakness of EOM
  of left eye, mild proptosis, red eye
What do you see?




                   Sphenoid
                   sinusitis
CT is good at showing…

• Bony abnormalities
• Acute blood
• Large masses (and small enhancing
  masses if contrast is given)
• Calcified intracranial abnormalities
• Edema
• Large intracranial aneurysms (now we
  have CTA which is very good at this!!!)
• stroke
          CT might miss…
• Subacute subdural (isodense to brain)
• Isodense tumors/infections with little mass
  effect/edema associated
• Small aneurysms
• Vasculitis
• Vascular malformations
• Dural sinus thrombosis
• Lesions in the posterior fossa
• Demyelination/white matter disease
• Stroke
• Meningeal processes
• Diffuse axonal injury
Yield of CT for headache

• CT is generally low yield if a
  thorough neurologic exam is normal
  (including LOC/mentation)
• CT is higher yield with focal
  findings, decreased LOC
• In typical migraine with normal
  exam, yield is 0.18%
Normal CT




                  Maxillary sinus
                  air-fluid
                  level

            Brainstem
            -medulla
Normal CT


            Superior ophthalmic vein



             Sphenoid sinus
             Temporal lobe
               Mastoid air cel
            4th ventricle
            Cerebellum
Normal CT




             Internal carotid
             artery
               Basilar artery
                Pons
        Temporal horn of right
        lateral ventricle
Normal CT




                   Left MCA
             Suprasellar cistern
            Cerebral aqueduct
Normal CT




                Cerebral peduncle
            Interpedulcular cister
            Normal CT    Anterior horn
                         of left lateral
                         ventricle
                         Caudate
                          Lentiform
                          Posterior limb
                          of internal
                          capsule
Insular ribbon
                        Thalamus
Sylvian fissure         3rd ventricle
Normal CT
           Normal CT




    Falx cerebrei


Superior sagittal sinus
Normal or Not Normal?
Normal or not normal?
Normal or Not Normal?
Normal or Not Normal?
Raised Intracranial Pressure:
      What to look for
 • Loss of basal cisterns
 • Loss of suprasellar cistern
   (unilateral or bilateral)
 • Loss of sulcal/gyral pattern
 • Loss of grey-white differentiation
 • Enlarged “trapped ventricles”
 • Slit-like ventricles
Valproic Acid Overdose
Valproic Acid Overdose
Posterior Fossa
Posterior Fossa Day 3
When not to do an LP
           Raised ICP
• Do not do an LP if:
  • you suspect raised ICP
  • You see a mass or structural lesion with mass
    effect (e.g. hematoma)
  • You see mass effect (displaced structures like
    the falx, uncus, ventricles)
  • You cannot see the basal cisterns
  • You see hydrocephalus
  • You have not done a CT, there are neuro
    findings/altered LOC and you work in a
    tertiary care centre where this test is readily
    available
When should you image a
  headache patient?
When should you order CT for
        headache?
  • Any unexplained neurologic signs
  • Altered LOC
  • New headache type in an older
    patient
  • Change in pattern of previous
    headache
  • Progressive headache
  • Thunderclap headache
  • Refractory headache
Headache Red Flags…CT
        please!
•   Abnormal neuro exam
•   Headache worst on waking in a.m.
•   Headache waking patient from sleep
•   Progressive headache
•   Worse with valsalva
•   Worse supine than upright
•   Abrupt onset headache
•   Other condition predisposing to CNS
    disease (immune suppressed, cancer,
    clotting disorder, anticoagulants, recent
    trauma, etc)
35 yo man, assaulted with pipe



    Subarachnoid       Obliteration of
    hemorrhage         ant horn of R
                       lateral ventricle
    Epidural
    hematoma
       Intracerebral
       hemorrhage
assault




          Midline shift
66 yo man with subacute onset
     of language difficulty




                        Hypodense mas
                        Edema
                     Midline shift
wet




      Ring enhancin
47 yo man with RA and vertigo




                      Cerebellar
                      hemorrhage
             Case

• 39 yo man with polycystic kidney
  disease
• CT head was done for headache
• Normal neuro exam
             What do you see?




Small hyperdense
lesion
             Case

• 18 yo girl with a history of ITP
• Presents with bizarre behaviour,
  difficulty walking and headache
• On exam appears ‘indifferent’ to her
  ‘state’
• Moves both sides well with
  encouragement
• Left side ‘lags’ behind when she
  gets off bed
CT




     Enlarged cortic
     veins
MRV & MRI
Dural Sinus Thrombosis

• May present with chronic
  progressive headache
• May present with thunderclap
  headache
• May or may not have abnormal
  neurosigns
  Predisposing Factors
• OCP +/-smoking
• Pregnancy/post-partum
• Clotting disorder (APA, ACA, Pr C, ATIII,
  S deficiencies, Factor V Leiden, cancer,
  IBD, nephrotic syndrome)
• Dehydration
• Local occlusion by trauma/tumor
• Infection (meningitis, mastoiditis,
  sinusitis, dental abscess)
What you might see on CT
• Nothing at all
• Hyperdense/misshapen/thickened dural
  sinus or cortical vein
• Hyperdense/empty delta (empty on
  enhanced CT) (do not hang your hat on
  this to r/o DST)
• Venous infarct (wedge shaped, grey-
  white junction, associated hemorrhage,
  deeper white matter, non-arterial
  territory
• May be bilateral
• Diffuse edema/raised ICP
              DST

• Often missed
• 25% don’t have predisposing factors
• Ask yourself if this is a possibility
  whenever you want to scan a patient
  for headache
• Remember the redflags
• Remember to look at the fundi
            Case II

• 89 yo woman with progressive
  confusion and intermittent spells
  lasting 10-20 min of word-finding
  difficulties
• Headache for two weeks--
  moderate, dull, holocephalic
• 1) additional history you would like?
• 2) do you want to do a CT?
Acute on chron
SDH
         Key Points:

• Older people are at risk due to
  atrophy + tearing of bridging veins
• Ask about anticoagulants
• Ask about recent minor trauma
• Scan older people who have new
  headache
• Scan people with ‘TIAs’
Small SDH
Acute on chronic
SDH
             Case

• 29 yo male involved in a bar-fight
  this evening
• Punched in the head - brief LOC
  then went home with his girlfriend
• Brought in 2 hours later with
  progressive decrease in LOC
• On exam, comatose, right pupil
  sluggish
• Do you want to do a scan?
            Management?




Epidural hematoma
  Acute on chronic
  SDH




Epidural hematoma
                     Midline shift
Epidural hematoma
                Case

• 55 yo man fell off of a stool and struck head
  on concrete floor
• Had had some EtOH
• Wife brought him in because he had some
  slurred speech and inappropriate behaviour
• Headache
• On exam, smells like EtOH. Slurred speech.
  Behaviour inappropriate. Nil focal.
• What do you want to do?
Subarachnoid
hemorrhage
Blood follows the pattern of
         gyri/sulci




Subarachnoid
hemorrhage
         “Pentagon Sign”




Subarachnoid
hemorrhage
Pentagon sign + hydrocephalus




Temporal horn of
lateral ventricle
               Case

• 40 y.o. man with new onset mild
  incoordination of the Left hand &
  behavioural change
• What do you want to know?
• What do you want to do?
 Loss of lentiform
 nucleus


Hypodense region
& loss of G-W in M1
Early Ischemic Changes: Clues
           to Stroke
                • ASPECTS
                • Out of 10
                • M1, M2, M3, M4, M5,
                  M6
                • Caudate
                • Lentiform nucleus
                • Internal capsule
                • Insular ribbon
                • Also, look at MCA
ASPECT Score

        • M1,2,3, IC, L, C
         ASPECTS

• M4-6
     Looking for stroke

• Time is brain
• Stroke more than 12 hours old begins to
  look quite hypodense (dark) in the affected
  arterial territory
• Acutely, there ARE subtle signs--which
  may alter likelihood of getting TPa and risk
  of hemorrhage
       Subtle findings

• Look at:
  • Grey-white differentiation
  • Presence/loss of sulcal/gyral pattern
  • Compare side to side - stroke is usually
    unilateral--so you have a built-in comparator
  • Look for hyper dense, asymmetric, vessels
  • Look for loss of signal in deep structures (basal
    ganglia, thalami, internal capsule)
  • Know the basics of vascular anatomy
80 yo man with dysphasia x 3hrs

                       Loss of G-W
                       Differentiation
                       In M1, M2, M3
                        Loss of insular
                        ribbon
Same scan, superiorly



                  Loss of GW
                  differentiation
                  in M4, M5, M6
12 hrs later
               Case

• 68 yo man with DMII, htn.
• Woke up with left-sided weakness, leg more
  than hand.
         What do you see?




Hypodense
Region - ACA
                 Case

•   43 yo waiter
•   Binge drinking
•   Awoke at 4 am feeling nauseated/headache
•   Awoke at noon unable to get out of bed
•   Discovered by his mother & brought to
    hospital
Holiday Heart
Monday morning
              Case

• 28 yo woman, 2 days post partum
• Headache, left-sided, nausea, vomiting,
  photophobia, phonophobia, worsening with
  routine activity.
• What else do you want to know?
  What do you want to do?
What do you see?
               Case

• Pt 3 weeks post-partum develps severe
  headache and left leg paresthesias
• Throbbing pain, photophobia, phonophobia,
  nausea, x 4 days
• Worse with valsalva & lying down
Post-Partum Patient
               Case

• 43 yo man works at packing plant
• Developed acute onset of headache and left-
  sided weakness
• One exam, normal power on left, but
  complete sensory loss to all modalities and
  mild neglect
• PMHx; htn, DM
• Ran out of BP meds 2 months earlier
Left sensory loss & neglect



            Thalamic ICH
Acute vertigo, N/V, then coma in
   80 yo hypertensive man




                       Cerebellar
                       hemorrhage
Hypertensive Hemorrhages

 •   Basal ganglia (putamen>caudate)
 •   Thalamus
 •   Pons
 •   Cerebellum
 •   Centrum semiovale
 •   Intraventricular (from basal ganglia)
             Case

• 68 yo RHD woman found wandering at
  work, speaking incoherently.
• PMHx: Htn, gout
• Discontinued BP meds one month ago
Aphasia
              Case

• 70 yo woman developed severe headache &
  confusion
• On examination, has receptive aphasia &
  mild expressive problems
• Right visual field abnormality
  (homonymous hemianopia)
Headache & Confusion
               Case

• 65 yo man with gradual onset of left-sided
  weakness, now has decreased LOC.
?
              Case

• 49 yo woman with known breast cancer
• Presents with complaints of problems
  seeing
• Has L visual field defect
                      ?


Multiple hyperdense
foci




        Edema
                Case

• 65 yo man with colon Ca
• Presents with word finding difficulties and
  headache.
• Onset was acute.
?
  Take-Home Messages

- don’t LP if you think ICP might be up
- Remember to look at more than
  parenchyma: Bones, dura, sinuses, cisterns,
  ventricles, and dural sinuses
- Look for normal anatomy: grey-white
  margin, basal ganglia, insula, internal
  capsule
- Chronic blood is not bright--may be
  isodense, and therefore subtle
Messages about Headache

• If there are focal findings, decreased LOC
  or red flag features: SCAN
• Ask yourself if this could be a dural sinus
  thrombosis
• Do LP query SAH, encephalitis, meningitis
• Do not LP if you’re not sure about the CT
• Do not LP without a CT in a tertiary care
  centre (caveat--some clinical judgement
  here)
 Messages about Stroke

• Compare side to side
• Changes may be present under 3 hours
• Image your TIA patients (sometimes they
  have something else--eg. SDH)
• A normal CT means better prognosis
• Early subtle signs mean more damaged
  tissue, greater risk of hemorrhage
• Time is brain
Tests that sometimes don’t
  happen, but should….
 • If you think there may be a neuro problem, be sure
   to always do these parts of the CNS exam--
   otherwise you may miss the boat:
    •   Look at the discs (don’t be shy about dilating)
    •   Check fields
    •   Look at nasolabial folds & forehead
    •   Look for drift
    •   Check toes
    •   Check for sensory extinction
    •   Walk your patient
I don’t know what the heck this
             is…
now what the heck this
             is…

								
To top