Familial subarachnoid haemorrhage.

Over the nineteen years 1974 to 1992 twenty-four families have been identified in whom more than one member have had a subarachnoid haemorrhage, usually due to rupture of an intracranial aneurysm. These cases usually occurred at an age younger than average, and multiple aneurysms were commonly found on investigation. This series strongly suggests that a congenital arterial defect may predispose to early rupture of these aneurysms.