Definition of Subarachnoid hemorrhage

Subarachnoid hemorrhage: A bleeding into the subarachnoid, the space between the arachnoid and the pia mater, the innermost membrane surrounding the central nervous system. Subarachnoid hemorrhage typically occurs when an artery breaks open in the brain, such as from a ruptured aneurysm. This can require emergency neurosurgical procedures.

Source: MedTerms™ Medical Dictionary
http://www.medterms.com/script/main/art.asp?articlekey=12415
Last Editorial Review: 3/19/2012