Subarachnoid Hemorrhage and Aneurysms Overview

Subarachnoid Hemorrhage

Overview: The subarachnoid spaces (SASs) are cerebrospinal

fluid (CSF)-filled spaces between the arachnoid (on the

outside) and the pia (on the inside). Focal expansions of the

SASs at the base of the brain and around the brainstem,

tentorial incisura, and foramen magnum form the brain

cisterns.

The SASs are anatomically unique, as they surround the entire

brain, spinal cord, and spinal nerve roots and contain all the

major brain arteries and cortical veins.

Acute extravasation of blood into the CSF spaces between the

arachnoid membrane and pia can be caused by arterial leaks