Cryptogenic spontaneous subarachnoid haemorrhage

Patients with spontaneous primary subarachnoid haemorrhage (SAH) in whom initial diagnostic investigation, including cerebral four-vessel angiography, does not reveal a cause, present a difficult problem. In a series of 95 patients a cause became apparent in about 10% of cases during the first three weeks, predominantly missed aneurysms. After three weeks the clinical evolution was benign. Cryptogenic SAH seems to be a disease of its own, but in the individual case the possibility of missed aneurysm or later of no re-bleed aneurysm always remains.