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.
- 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