Subarachnoid Hemorrhage Information

The term subarachnoid hemorrhage (SAH) refers to extravasation of blood into the subarachnoid space between the pial and arachnoid membranes. SAH constitutes half of all spontaneous atraumatic intracranial hemorrhages; the other half consists of bleeding that occurs within the brain parenchyma. Subarachnoid hemorrhage occurs in various clinical contexts, the most common being head trauma. However, the familiar use of the term SAH refers to nontraumatic (or spontaneous) hemorrhage, which usually occurs in the setting of a ruptured cerebral aneurysm or arteriovenous malformation (AVM).