Subarachnoid Hemorrhage

A subarachnoid hemorrhage bleeds into the area between the brain and the tissues that cover and protect it. SAH is a medical emergency. Your brain is made up of three layers of membranes, or linings, that lie between your skull and your brain tissue. The outermost layer of your brain is called the dura mater, the middle layer is the arachnoid mater, and the layer closest to your brain is the pia mater. SAH occurs when there is bleeding under the arachnoid layer.