Aneurysmal subarachnoid hemorrhage

A subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space that exists between the arachnoid and pia membranes that surround the brain.

SAH may result from trauma or occur spontaneously from a ruptured cerebral aneurysm or less commonly from an arteriovenous malformation. SAH comprises 1–7% of all strokes. Incidence is estimated to be about 9 per 100,000 per year. Patients with SAH tend to be younger than those with other types of stroke, but the incidence increases with age. SAH is a medical emergency and can lead to death or severe disability. Up to one-half are fatal, many even before the patient reaches the hospital. Symptoms include rapid onset of a severe headache (often called a “thunderclap headache”), nausea, confusion, altered consciousness, seizure, visual disturbances, cardiac arrhythmias, and focal neurological deficits such as hemiparesis, sensory loss, or aphasia. About one-third of...