Perimesencephalic Haemorrhage

Perimesencephalic haemorrhage is a distinct type of subarachnoid haemorrhage 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 ischaemia are rare and the prognosis is excellent. The other 5% of cases are due to a vertebrobasilar aneurysm and the prognosis is worse.
References:
1. Van der Schaaf IC, et al. Venous Drainage in Perimesencephalic Hemorrhage. Stroke 2004;35:1614-1618
2. Birgitta K, et al. Perimesencephalic Hemorrhage: Exclusion of Vertebrobasilar Aneurysms With CT Angiography. Stroke 1999;30:1103-1109
Credit: Dr Donna D'Souza
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