Definition

By Mayo Clinic Staff

Subarachnoid hemorrhage is bleeding in the space between your brain and the surrounding membrane (subarachnoid space). Bleeding usually results from the rupture of an abnormal bulge in a blood vessel in your brain (brain aneurysm).

Sometimes an abnormal tangle of blood vessels in your brain (arteriovenous malformation), trauma or other events cause bleeding. A subarachnoid hemorrhage may lead to permanent brain damage or death if not treated.

Aug. 19, 2014