Subarachnoid haemorrhage: epidemiology, natural history, and surgical treatment.

We analysed 360 patients who presented with a proven subarachnoid haemorrhage during the period 1971-78. The most common cause was a cerebral aneurysm (75%), with the anterior communicating artery being the most common site for a ruptured aneurysm. Overall mortality rate before surgical intervention was 28%. During the period of study, 106 Grade 1 patients underwent direct clipping of their aneurysms; this procedure was associated with a 6.6% mortality rate. Delayed surgical intervention was associated with a lower surgical mortality rate.