Subarachnoid hemorrhage (SAH) The brain is covered by three layers of membranes. From outside in they are: dura, arachnoid, and pia. The spaces between these layers and brain contain fluid and blood vessels. SAH means bleeding (or hemorrhage in medical terms) in the area/space between the brain and the arachnoid membrane. This area is called the subarachnoid space. Causes of Subarachnoid hemorrhage Ø     ...