What is a stroke?
Strokes are the third leading cause of death in the U.S. Each year, about 795,000 Americans suffer a new or recurrent stroke while more than 137,000 people die as a result of a stoke. Over 60% of stroke deaths occur in women. Strokes are also associated with long-term disability among survivors, and 25% of those who survive their first stroke will have another within 5 years.
Stroke occurs when the blood supply to a part of the brain is suddenly blocked or diminished, which alters the body function controlled by that area of the brain. This is often referred to as a "brain attack." If any part of the body - including the brain - is without a source of fresh blood and oxygen, the cells will be injured or may die. Although some cell injury is reversible, the death of brain cells is permanent, usually leaving lasting disability.
There are two main types of stroke:
- Ischemic – caused by a blockage of arteries supplying blood to the brain; account for 87% of strokes; can occur from a blood clot in a narrow artery (thrombotic stroke) or a clot that breaks off in a blood vessel somewhere in the body and travels to the brain (embolic stroke)
- Hemorrhagic – caused by rupture of a blood vessel, resulting in bleeding in and around the brain; can occur from the inside by aneurysms or from the outside from head injury. Aneurysms are often caused by congenital defects or high blood pressure (hypertension). Hemorrhagic strokes are the most severe and are often fatal.