Hemorrhagic Stroke occurs when a weakened blood vessel (artery) ruptures or leaks. Hemorrhagic strokes are less common, but they are responsible for about 40 percent of all stroke deaths. Hemorrhagic stroke usually requires surgery to relieve intracranial (within the skull) pressure caused by bleeding. There are two types of hemorrhagic stroke called Intracerebal and Subarachnoid. Intracerebal hemorrhage occurs when a blood vessel inside the brain bursts and leaks blood into surrounding brain tissue. The bleeding causes brain cells to die and the affected part of the brain stops working correctly. High blood pressure and aging blood vessels are the most common causes of this type of stroke. Subarachnoid hemorrhage involves bleeding in the area between the brain and the tissue covering the brain, known as the subarachnoid space. Two types of weakened blood vessels usually cause hemorrhagic stroke: Aneurysms and Arteriovenous Malformations (AVMs). An aneurysm is a ballooning of a weakened region of a blood vessel and AVMs are defects of the circulatory system comprised of snarled tangles of arteries and veins. Intracerebral hemorrhagic stroke can be caused by an AVM while subarachnoid hemorrhagic stroke is most often caused by a burst aneurism.