Perimesencephalic subarachnoid hemorrhage

Case contributed by Oscar Gutierrez
Diagnosis certain

Presentation

A Patient with a history of obesity. She came to the emergency department for sudden onset headache, with nausea and vomiting.

Patient Data

Age: 60 years
Gender: Female

A Hyperdensity surrounding the pons, midbrain and basal cisterns, which corresponds to acute subarachnoid hemorrhage.

CTA rules out the presence of aneurysms.

Fetal origin of rigth posterior cerebral artery.

Case Discussion

The CT findings are consistent with Perimesenchephalic subarachnoid hemorrhage.

Perimesenchephalic subarachnoid hemorrhage represents 5-10% of all SAHs. Most have a normal CTA (as in this case), so the etiology is thought to be bleeding of venous origin.

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