Subarachnoid Haemorrhage

SAH affects 6-9 people per 100,000 of the population per year and constitutes about 6% of first strokes. An apparent decrease from older published figures is attributed to a higher rate of CT scanning, excluding other haemorrhagic causes. Approximately 85% of patients bleed from intracranial arterial aneurysms, 10% from a non-aneurysmal peri-mesencephalic haemorrhage and 5% from other vascular abnormalities including arteriovenous malformation, vasculitis and abnormal blood vessels associated with tumour.. SAH represents only 6% of cases of stroke but it is relatively far more important, as it tends to affect younger people, of whom about half die in that episode. The mean age is 50 years: most patients are under 60 years. Women have a higher risk than men: relative risk 1.6. Patients of Afro-Caribbean descent have a higher risk than white Europeans: relative risk 2.1:1 Incidence is significantly higher in Finland and Japan. Spontaneous SAH is usually due to aneurysmal rupture but traumatic brain injury is a more common cause of blood in the subarachnoid space. Subarachnoid blood can be detected on CT scanning in as many as 60% of people with traumatic brain injury .