Subarachnoid hemorrhage

Alternative names:

hemorrhage - subarachnoid

Definition:

A disorder involving bleeding between the middle membrane covering of the brain and the brain itself.

Causes, incidence, and risk factors:

Subarachnoid hemorrhage occurs in approximately 1 out of 10,000 people. About 5 to 10% of strokes are caused by subarachnoid hemorrhage. It is most common in people 20 to 60 years old. It is slightly more common in women than men.

Subarachnoid hemorrhage occurs when there is bleeding into the space between the brain and the arachnoid membrane (the middle membrane covering the brain). This may occur from a ruptured cerebral aneurysm or arteriovenous malformation, but some result from unidentified causes. Risks include: disorders associated with aneurysm or weakened blood vessels, including a history of polycystic kidney disease; fibromuscular dysplasia (FMD); aneurysms in other blood vessels; and high blood pressure.

The disorder may cause permanent brain damage from ischemia (loss of blood flow) or from the presence of blood in the tissues of the brain.