Download HEAD TRAUMA

EVERYTHING A MEDICAL
STUDENT SHOULD KNOW
ABOUT A CT SCAN OF THE
HEAD
By Thanh Binh Nguyen
Neuroradiologist
Ottawa Hospital
Last updated July 2007
What is a CAT scan?
 CAT scan stands for
Computed Assisted
Tomography
 Cross sectional
images are obtained
by multiple
measurements of
the x-rays
attenuation from
several projections.
What are we measuring?
 The attenuation
coefficient reflects the
reduction in the x-ray
intensity by the material
relative to water.
 The Hounsfield Unit is
the scale used.
(HUwater=0, HUbone >500,
HUlung=-500)
CT and radiation
 Effective dose takes into account which
tissue has absorbed what radiation
dose (expressed in Sievert)
 We can decrease the effective dose in
CT by reducing the tube current but
image noise will be increased
Radiation and risk of cancer


1.
2.
3.
Lifetime risk of developing fatal cancer
from radiation exposure in a
population is 0.005% per
milliSievert(mSv)
Exposure from
mSV
Natural background
3 /yr
CT head
2
CT spine
10
STROKE
Canadian Stroke Facts*
 40,000-50,000 new
stroke’s /year
 65% of survivors
have disability
 4th leading cause of
death
 Longest length-ofstay for any
diagnosis (37 d)
 Leading cause of




transfer to long term
care
Leading cause of neuro
disability in adults
Cost >$2.7 billion/year
$27,500 / acute stroke
$46,000-$122,000 /
patient for chronic care
*Canadian Heart and Stroke
Foundation
Stroke
 denotes a persistent loss of neurologic
function with sudden onset
 diverse etiologies...
Ischaemic Cerebrovascular Stroke
Venous Congestion / Stroke
Hemorrhagic Stroke
Anatomy
Arterial Territories
 Anterior Cerebral
 Middle Cerebral
 Posterior Cerebral
 Basilar
 Superior Cerebellar
 Anterior Inferior
Cerebellar
 Posterior Inferior
Cerebellar
Supratentorial Territories
From Osborne, A: Neuroradiology
Left PCA
MCA
ACA
Anterior choroidal infarct
Watershed (between ACA and MCA)
Ischaemic CV Stroke
 Thromboembolic most common
 Hemodynamic
 Atherosclerotic
 Dissection
 Vasospasm
 Hypotensive /asphyxia (watershed)
 Migraine
 Vasculitis
 Thrombotic: hypercoagulable states
Hemorrhagic Stroke
 Primary Intracerebral bleed
Hypertensive
 Amyloid angiopathy
 Arteriovenous malformations
 Neoplasms
 Trauma

 Subarachnoid hemorrhage
Aneurysm
 AVM’s
 Trauma

Hypertensive
Hemorrhage
Classically involves
the deep nucleii
Amyloid angiopathy
Hyperdense vessel
sign
Hyperdense vessel
sign & loss of
gray/white
junction...
Left insular ribbon sign & effacement of sulci
NEOPLASM
APPROACH TO BRAIN
TUMOR
 Intra-axial(from the brain) versus Extra-axial




(from the meninges or skull)
Location (supratentorial vs infratentorial)
Age of patient
Imaging characteristics
Could you this be something other than
neoplasm (infarction, abscess, etc…)? CT
with contrast or MRI is often needed.
EDEMA
 Vasogenic edema:
 Involves
white matter primarily with sparing
of gray matter
 Seen with brain tumors, abscess
 Cytotoxic edema
 Involves
both white matter and gray matter
 Seen with infarction
BRAIN TUMORS
 Extraaxial: meningioma
 Intraaxial:
 Primary
Glial tumors: low grade to high grade
astrocytoma (glioblastoma multiforme)
 Non glial tumor (lymphoma,
hemangioblastoma, etc…)

 Metastasis
(lung, breast, colon, etc…)
Unenhanced CT of the head shows a mass in
the left frontal lobe with vasogenic edema
Ring enhancing
lesion (GBM)
Vasogenic
edema
GLIOMAS
 Astrocytomas
 85% of cerebral gliomas
 Young to middle-aged adults (20-50 years)
 Varying degree of malignancy. Highest grade is
glioblastoma multiforme which presents as a mass
with ill-defined margins, variable enhancement
and extensive vasogenic edema.
 Oligodendrogliomas
 Young, middle-aged adult
 Solid, well-defined mass with calcification
 70 year old gentleman complaining of
dizziness and off balance for one week
with associated nausea and vomiting.
He also had attack of left facial
numbness and left arm numbness for a
week. Cerebellar exam showed
nystagmus of lateral gaze and left-sided
incoordination
C-
C+
Left tonsillar herniation
C-
C+
C-
C+
Hyperdense cerebellar mass seen on plain CT scan
which enhances homogeneously and causes
compression of the 4th ventricle and hydrocephalus
C-
C+
DIAGNOSIS
 BURKITT LYMPHOMA
Ct scan of the head with contrast in
patient with renal cell carcinoma
Enhancing nodule at
corticomedullary
junction
Vasogenic edema:
involves whiter matter
more than gray
matter
DIAGNOSIS
 METASTASES
 Hematogenous
seeding to
corticomedullary junction
 Usually in MCA territory
 Usually the degree of edema is out of
proportion to the size of the lesion
Ct scan of the head without contrast
Hyperdense
mass
Enhances
homgeneously
and appears
extraaxial
Thickening of
the adjacent
bone
(hyperostosis)
DIAGNOSIS
 MENINGIOMA
INFECTION
INTRACRANIAL INFECTION
 Intraaxial:
 Encephalitis
 Cerebritis
 Abscess
 Extraaxial:
 Subdural empyema
 Epidural abscess
 Meningitis
CEREBRAL INFECTION
 Encephalitis: generalized and difuse
infection of the brain. Often of viral
origin (ex.herpes simplex)
 Cerebritis: localized but poorly
demarcated area of parenchymal
softening.
 Abscess: follows cerebritis. Occurs
when a central zone of necrosis
becomes encapsulated.
MODE OF SPREAD
 Hematogenous spread: could reach the
corticomedullary junction or
leptomeninges.
 Direct extension: ex.sinusitis leading to
epidural abscess or subdural
empyemas
 Spread along the nerves (ex.herpes
encephalitis along the trigeminal nerve)
ABSCESS (could look similar to
metastatic lesion on CT)
Ring
enhancing
lesion
Vasogenic
edema
SUBDURAL EMPYEMA (C-)
SUBDURAL EMPYEMA (C+)
TUBERCULOSIS
Basal
leptomeningitis
(seeding of the
subarachnoid
space)
TUBERCULOSIS
Multiple
tuberculomas
seen on MRI
exam with
contrast
THE END