Transcript Document 7249444

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:
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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?
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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?
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Hygroma
Blood
Tumor
Air
Things between skull & brain
that shouldn’t be there
Hygroma
Subdural
hematoma
Meningioma
Epidural hematoma
Pneumocephaly
General Principles
• Look at the brain:
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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 of
caudate lateral ventricle
lentiform
Internal
capsule
(post.
limb)
Insular ribbon
Sylvian
fissure
thalamus
3rd
Pineal glan
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
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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 cells
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 cistern
Normal CT
Insular ribbon
Sylvian fissure
Anterior horn
of left lateral
ventricle
Caudate
Lentiform
Posterior limb
of internal
capsule
Thalamus
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?
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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!
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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
hemorrhage
Epidural
hematoma
Intracerebral
hemorrhage
Obliteration of
ant horn of R
lateral ventricle
assault
Midline shift
66 yo man with subacute onset
of language difficulty
Hypodense mas
Edema
Midline shift
wet
Ring enhancing
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 cortica
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 chronic
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
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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 leftsided 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
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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.
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Case
• 49 yo woman with known breast cancer
• Presents with complaints of problems
seeing
• Has L visual field defect
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Multiple hyperdense
foci
Edema
Case
• 65 yo man with colon Ca
• Presents with word finding difficulties and
headache.
• Onset was acute.
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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:
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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…