Cerebrovascular AccidentsJeetendra Bhandari

Normal CT

Index:• T temporal lobe• P pituitary gland • Dor sel dorsum sellae• Pe petrous bone• C cerebellar hemisphere • V vermis• IV fourth ventricle

Index:• Syl fissure Sylvian fissure

Index:• LV lateral ventricle• Th thalamus• Int capsule internal

capsule• III third ventricle

Index:• CP choroid plexus • LV lateral ventricle

Index:• CR corona radiata• O occipital lobe

Major intracranial arteries

Index:

• ACA anterior cerebral artery

• ACommA anterior communicating artery

• AICA anterior inferior cerebellar artery

• bas art basilar artery

• CarotidA carotid artery

• MCA middle cerebral artery

• PCA posterior cerebral artery

• PCommA posterior communicating artery

• PICA posterior inferior cerebellar artery

• SCA superior cerebellar artery

• VertA vertebral artery

Stroke

• Defined as a sudden, focal neurological deterioration due to a disturbance in the blood supply to the brain

• Causes includes:• Cerebral infarction, which may be due to in situ thrombus or embolus from

the proximal artery or heart

• Intracerebral hemorrhage

• Subarachnoid hemorrhage

• Acute management of thromboembolic infarct is to destroy clot with thrombolysis, but is contraindicated in the presence of hemorrhage –therefore CT is the best first test

Outcome of CT performed in Stroke

• Presence of hemorrhage rule out thrombolysis treatment

• Stroke mimics are conditions that present like stroke, such as a subdural hematoma or brain tumor

• Normal scan either means the patient is not having a stroke or is at the very early stages of a stroke before the CT becomes abnormal and therefore thrombolysis can be carried out

• Then there are the early signs of a stroke seen on CT. The dense artery sign is high density clot visualized within a major intracranial artery.

Dense artery sign. Unenhanced CT showing acute thrombus in the right middle cerebral artery (arrow). Early sign seen on CT.

(Right) Initial CT scan a few hours after the onset of symptoms showing low attenuation in the posterior cerebral artery territory with swelling causing effacement of the local sulci (arrow). (left)CT scan a month later showing low attenuation gliotic change in the same territory and atrophy causing localized expansion of the lateral ventricle and widening of the sulci (arrow).

Intracerebral hemorrhage

• Acute hemorrhage seen on CT as high attenuation, frequently causing a mass effect

• Initial high density lessens over time, leaving a low density area indistinguishable from an infarct

• MRI can be useful in the follow-up of intracerebral hemorrhages to exclude underlying vascular malformation or occult metastasis, which may be obscured by the presence of blood

• If no cause identified, formal cerebral angiography may be required to exclude a subtle vascular anomaly

Acute parenchymal hemorrhage. CT scan showing the hematoma as a high density area with local mass effect (H) in the left frontal lobe

Subarachnoid Hemorrhage

• Spontaneous due to a ruptured intracranial aneurysm or vascular malformation.

• CT best initial investigation to diagnose a subarachnoid hemorrhage and to demonstrate the site of bleeding

• Recognized by high density blood outside the brain in the sulci, Sylvian fissures and basal cisterns

• CT prevent the need for lumbar puncture and CSF examination, but sensitivity of CT decreases with time after a hemorrhage and a normal examination does not exclude the diagnosis

Subarachnoid hemorrhage. High density subarachnoid blood can be seen in the basal cisterns outlining the brain stem (long arrow), the Sylvian fissures (short arrow) and within the fourth ventricle (curved arrow).(Normal on top left)

Reference

• Rockall, Andrea, Hatrick, Andrew, Armstrong, Peter, Wastie, Martin. Diagnostic Imaging, 7th ed.

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