[Perimesencephalic subarachnoid hemorrhage]

Acute, non-traumatic subarachnoid haemorrhage is usually caused by a ruptured aneurysm. This is a serious condition involving high mortality. Perimesencephalic haemorrhage has recently been identified as a clinical subset of subarachnoid haemorrhage. A pattern of haemorrhage predominantly limited to perimesencephalic cisterns on CT is highly predictive of a normal angiogram, and is connected with an excellent prognosis. We describe two patients with perimesencephalic haemorrhage.