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Aneurysmal Subarachnoid Hemorrhage

KEY FACTS

TERMINOLOGY

• Subarachnoid hemorrhage (SAH) caused by ruptured

aneurysm (aSAH)

○ Saccular aneurysm (SA) > > dissecting aneurysm (DA)

IMAGING

• CT/CTA

○ Hyperdense sulci on NECT

○ Distribution varies with aneurysm location

○ Suprasellar cistern (IC-PCoA, ACoA aneurysms)

○ Sylvian fissure (middle cerebral artery bifurcation)

○ Prepontine, cerebellopontine angle cisterns (posterior

inferior cerebellar artery, blood blister artery bifurcation

SA or vertebral DA)

○ CTA 90-95% positive if aneurysm ≥ 2 mm

• MR/MRA

○ FLAIR hyperintense sulci, cisterns (nonspecific)

○ "Blooms" on T2* GRE 

○ TOF MRA 85-95% sensitive for aneurysms ≥ 3 mm

• DSA

○ Used if CTA negative

○ If endovascular treatment is option

TOP DIFFERENTIAL DIAGNOSES

• Nonaneurysmal SAH

• Pseudo-SAH

• Reversible cerebral vasoconstriction syndrome

CLINICAL ISSUES

• Sudden onset severe headache

○ "Thunderclap/worst headache of life"

• 50% mortality

○ Vasospasm 1-3 weeks post aSAH

• 20% rebleed within 1st 2 weeks

• Treatment: Coil embolization ("coiling") generally > clipping

DIAGNOSTIC CHECKLIST

• Diffuse low-density brain makes normal arteries look

hyperdense, can mimic aSAH

(Left) Axial graphic through

the midbrain depicts

subarachnoid hemorrhage

(SAH) in red throughout the

basal cisterns. Given the

diffuse distribution of SAH

without focal hematoma, the

most likely location of the

ruptured aneurysm is the

ACoA. (Right) Axial NECT scan

in a 63-year-old man found

down in a parking lot shows

diffuse SAH ſt throughout the

basal cisterns. Note the

enlargement of both temporal

horns of the lateral ventricles

﬇ consistent with early

extraventricular obstructive

hydrocephalus.

(Left) Coronal maximal

intensity projection image of

the CTA obtained in the same

patient shows a saccular

aneurysm ﬇ projecting

superiorly from the anterior

communicating artery. (Right)

Coronal shaded surface

display of the DSA obtained in

the same patient nicely

demonstrates the "culprit"

aneurysm ﬇. The lesion was

successfully coiled after this

diagnostic DSA was

performed.

Brain: Pathology-Based Diagnoses: Malformations,

Trauma, and Stroke

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