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Perimesencephalic subarachnoid hemorrhage

Case contributed by Laughlin Dawes
Diagnosis almost certain

Note: This case has been tagged as "legacy" as it no longer meets image preparation and/or other case publication guidelines.

Perimesencephalic subarachnoid hemorrhage. 

Case Discussion

Perimesencephalic hemorrhage is a distinct type of subarachnoid hemorrhage confined to the basal cisterns around the midbrain (typically the interpeduncular and prepontine cisterns). 95% of cases have a normal cerebral angiogram and the source of bleeding is not identified; the cause is thought to be a venous bleed. In these cases rebleeding and ischemia are rare and the prognosis is excellent. The other 5% of cases are due to a vertebrobasilar aneurysm and the prognosis is worse.

Credit: Dr Donna D'Souza. 

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