CT Brain Interpretation

CT brain interpretation
in emergency department
20
10
CT SCAN BASICS
CT SCAN BASICS: Windowing
With this technique, subtle differences in tissue densities can

be maximized.
CT SCAN BASICS: Systematic Approach
BLOOD = blood
CAN = cisterns
BE = brain
VERY = ventricles
BAD = bone
BLOOD = blood
Ask yourself three questions:
Is blood present?
If so, where is it?
If present, what effect is it having?

BLOOD = blood
Ask yourself three questions:
Is blood present?
If so, where is it?
If present, what effect is it having?

BLOOD = blood
Epidural/Extradural
Hematoma
Lens shaped/biconvex
Does not cross sutures
Classically described with injury

to middle meningeal artery (but
source can be venous)
Low mortality if treated prior to

unconsciousness (< 20%)
https://www.radiologymasterclass.co.uk/
tutorials/ct/ct_brain_anatomy/
ct_brain_anatomy_skull#:~:text=The main
sutures of the,is variably present in adults.
Epidural/Extradural Hematoma
BLOOD = blood
Subdural Hematoma
Typically crescent/falx/sickle - shaped
Crosses sutures but does not cross

midline
most frequently due to trauma
Occasionally due to underlying bleeding

disorder or structural abnormality
Acute subdural is a marker of SEVERE

head injury (mortality approaches 80%)
Chronic subdural usually slow venous

bleed and well tolerated
Subdural Hematoma
BLOOD = blood
Subarachnoid Hemorrhage
Blood in the cisterns/hyperdense material

is seen filling the subarachnoid space
Cause:
Aneurysms (75-80%)
No cause is found in (10-15%)
AVM’s (4-5%)
Vasculitis (<1%)
20% will have associated acute

hydrocephalus
Cistern?
BLOOD = blood
Intraparenchymal Hemorrage
(IPH)
hyperdense collection of blood, often

with surrounding hypodense
oedema.
cause:
Nontraumatic lesions due to

hypertensive disease are typically
seen in elderly patients and occur
most frequently in the basal
ganglia region
Traumatic
BLOOD = blood
Intraventricular Hemorrhage (IVH)
Primary
hypertension
arteriovenous malformations (AVM)
aneurysm (e.g. PICA aneurysms have a tendency

to fill the 4th ventricle, with little basal cistern
blood)
Secondary (more common)
extension from other intracerebral haemorrhages
subarachnoid haemorrhage
trauma (IVH is present in 10% of severe head

trauma)
Hydrocephalus may result regardless of etiology

CAN = cisterns
four key cisterns: (SuCiQudS)

1. Suprasellar
2. Circummesencephalic -around
midbrain
3. Quadrigeminal
4. Sylvian
CAN = cisterns
There are two key questions to ask regarding the four key cisterns
(Circummesencephalic, Suprasellar, Quadrigeminal and Sylvian)
Is there blood (subarachnoid hemorrhage)?
Are the cisterns open/is there high intracranial pressure?
Compression or obliteration of cisterns suggests raised

intracranial pressure (ICP)
Open: hydrocephalus
"Insular ribbon sign"

CAN = cisterns
Evaluate if the circummesencephalic cistern is open or closed
Closure of the circummesencephalic cistern is one of the earliest signs of increased intracranial
pressure (the"canary in the coal mine")
CAN = cisterns
80% of subarachnoid hemorrhages happen somewhere around the circle of willis/suprasellar cistern.
One of the earliest places to see hydrocephalus is on the temporal tips of the suprasellar cistern.
CAN = cisterns
Scrutinize the sylvian cistern for two things:

Distal middle cerebral artery aneurysm (MCA)
A SAH here may only fill up this cistern with blood.
"Insular ribbon sign"
The insular ribbon is the end organ of the middle cerebral artery - it is the most distal brain perfused by the MCA.
Loss of gray white matter here is the earliest sign of MCA ischemia.
BE = brain
Examine the brain for:
SYMMETRY
Make sure sulci and gyri appear the same on both sides.
Check for effacement of sulci (unilateral or bilateral).
GREY-WHITE DIFFERENTIATION
The earliest sign of a CVA on CT scan is the loss of the grey-white interface on CT scan
Compare one side to the contralateral side.
SHIFT
To evaluate for mass effect, evaluate a mid line structure (septum pellucidum) for shift.
The falx should be in the mid line with ventricles the same on both sides.
HYPER/HYPODENSITY
Blood, calcification and IV contrast are hyperdense (appear lighter) and air, fat and areas of tumor, ischemia are
hypodense (appear darker).
MIDLINE SHIFT AS MEASURED FROM SEPTUM PELLUCIDUM
(ARROW)
CT BRAIN ON LEFT REVEALS MCA CLOT (ARROW); CT BRAIN ON RIGHT 2 DAYS LATER SHOWS HYPODENSE
AREA OF INFARCT (ARROW)
VERY = ventricles/ vessels
CSF is produced in the lateral ventricles --> 3rd ventricle -->
acqueduct of sylvius --> 4th ventricle at approximately 20
cc/hour.
Look for:
Effacement
Shift
Blood
Examine the vessels for signs of clot (hyperdense vessel)

NO GREY-WHITE DIFFERENTIATION OR GYRAL PATTERN SUGGESTS THIS HYDROCEPHALUS IS ACUTE.
THIRD VENTRICULAR HEMORRHAGE THAT HAS WORKED DOWN INTO FOURTH VENTRICLE, OBSTRUCTING
THE AQUADEUCT OF SYLVIUS AND ENLARGING THE TEMPORAL TIPS
BAD = bone
Diagnosing skull fractures can be confusing due to the presence of sutures
in the skull.
Skull fractures are divided into nondepressed (linear) or depressed

fractures.
The presence of intracranial air on a CT scan means that the skull and dura
have been violated at some point.
Non-aerated mastoid air cells suggest basilar skull fracture in petrous ridge.
The maxillary/ethmoid/sphenoid sinuses all should be visible and aerated:

the presence of fluid in any of these sinuses in the setting of trauma should
raise suspicion of a skull fracture.
References:
https://www.downeastem.org/downeastem/2016/11/19/how-to-read-a-head-ct-andrew-perron-md
https://vimeo.com/236506323

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CT brain interpretation

With this technique, subtle differences in tissue densities can

Ask yourself three questions:

If so, where is it?

If present, what effect is it having?

Ask yourself three questions:

If so, where is it?

If present, what effect is it having?

Does not cross sutures

Classically described with injury

Low mortality if treated prior to

Typically crescent/falx/sickle - shaped

Crosses sutures but does not cross

most frequently due to trauma

Occasionally due to underlying bleeding

Acute subdural is a marker of SEVERE

Chronic subdural usually slow venous

Blood in the cisterns/hyperdense material

No cause is found in (10-15%)

20% will have associated acute

hyperdense collection of blood, often

Nontraumatic lesions due to

arteriovenous malformations (AVM)

aneurysm (e.g. PICA aneurysms have a tendency

Secondary (more common)

extension from other intracerebral haemorrhages

trauma (IVH is present in 10% of severe head

Hydrocephalus may result regardless of etiology

four key cisterns: (SuCiQudS)

Is there blood (subarachnoid hemorrhage)?

Are the cisterns open/is there high intracranial pressure?

Compression or obliteration of cisterns suggests raised

"Insular ribbon sign"

Evaluate if the circummesencephalic cistern is open or closed

Scrutinize the sylvian cistern for two things:

Check for effacement of sulci (unilateral or bilateral).

Compare one side to the contralateral side.

Examine the vessels for signs of clot (hyperdense vessel)

Skull fractures are divided into nondepressed (linear) or depressed

The maxillary/ethmoid/sphenoid sinuses all should be visible and aerated:

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