subarachnoid haemorrhage

Bleeding into the subarachnoid space surrounding the brain. It is sudden in onset, with a severe headache followed by vomiting and, often, loss of consciousness. It is usually caused by a burst aneurysm in a cerebral artery or rupture of a developmental anomaly known as an arteriovenous malformation (AVM). Mortality is high, with 30% of patients dying during the first episode and a further 20% dying from a re-bleed; comatose patients or those suffering severe deficit have a poor prognosis. Treatment is by bed-rest, drugs to minimize the likelihood of re-bleeding and, where feasible, surgery to ‘clip’ the aneurysm or repair the AVM.