What is a subarachnoid hemorrhage (SAH)?
Subarachnoid hemorrhage refers to bleeding into the fluid that surrounds the brain. This fluid, known as cerebrospinal fluid (CSF), circulates in the subarachnoid space and serves to cushion the brain against injury. Following rupture of an aneurysm, blood appears in the CSF. The diagnosis can usually be established by CT scanning, but in some cases, a spinal tap (lumbar puncture) is necessary to detect the presence of bloody CSF. SAH can also result from head trauma, cocaine use, or rupture of an arteriovenous malformation.
