Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Hemorrhagic Stroke

What Is It?

A hemorrhagic stroke is bleeding (hemorrhage) that suddenly interferes with the brain's function. This bleeding can occur either within the brain or between the brain and the skull. Hemorrhagic strokes account for about 20% of all strokes, and are divided into categories depending on the site and cause of the bleeding:

• Intracerebral hemorrhage — Bleeding occurs from a broken blood vessel within the brain. Major risk factors include high blood pressure (hypertension), heavy alcohol use, advanced age and the use of cocaine or amphetamines. Additionally a stroke that begins without hemorrhage (a thrombotic or embolic stroke) can lead to intracerebral hemorrhage shortly afterward. This is common for embolic strokes, in which a floating mass within the bloodstream (called an embolus) contains bacteria and inflammatory cells, such as when a person has infective endocarditis. In rare cases, intracerebral hemorrhage may happen because of a leaking arteriovenous malformation, which is a weak-walled blood vessel that is a hybrid between an artery and a vein. This weak blood vessel is present from birth.

• Subarachnoid hemorrhage — Bleeding from a damaged blood vessel causes blood to accumulate at the surface of the brain. Blood fills a portion of the space between the brain and the skull, and it mixes with the cerebrospinal fluid that cushions the brain and spinal cord. As blood flows into the cerebral spinal fluid, it increases pressure on the brain, which causes an immediate headache that can interfere with brain function. In the days immediately following the bleeding, chemical irritation from clotted blood around the brain can cause brain arteries that are near to this area to go into spasm. Artery spasms can damage brain tissue. Most often, a subarachnoid hemorrhage happens because of a burst saccular aneurysm (a sac-like bulge in the wall of an artery), but it also can occur because of leakage from an arteriovenous malformation.