Subarachnoid hemorrhage (SAH) is a serious, life-threatening type of stroke caused by bleeding into the space surrounding the brain. A stroke occurs when the brain is deprived of oxygen because of an interruption of its blood supply. SAH can be caused by a ruptured aneurysm. One-third of patients who suffer an SAH will survive with good recovery; one-third will survive with a disability; and one-third will die. Treatment focuses on stopping the bleeding, restoring normal blood flow, relieving the pressure on the brain, and preventing vasospasm.