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Your brain needs a constant supply of oxygen-rich blood to nourish its 100 billion nerve cells. When this supply is reduced or shut off completely, starving brain cells die within minutes. That is why stroke is sometimes called a "brain attack".

Blood flow to the brain can be cut off in two ways:

• A clot blocks the flow of blood to the brain. If the clot forms inside the brain, the stroke is thrombotic. About 40 percent to 50 percent of all strokes fall into this category. If the clot forms in another part of the body then breaks loose and travels to the brain, it can cause an embolic stroke. Nearly 20 percent of all strokes are embolic.

• When blood vessel within the brain bursts or leaks, the result is a hemorrhagic stroke. Such strokes are often linked to high blood pressure. The force of high blood pressure can weaken blood vessel walls and eventually cause them to burst. Hemorrhagic strokes also may result from a burst or ruptured aneurysm -- a sac formed on an artery wall either as a result of age or genetic predisposition.

You may think that strokes happen only to older people, physically inactive people and men who are under job stress. In fact, 28 percent of people who have strokes are under age 65 and many are women.

External Resources: American Stroke Association, 7272 Greenville, Dallas TX 75231, 1-800-242-8721 www.amht.org The National Institute of Neurological Disorders and Stroke National Institutes of Health, PO Box 5801 Bethesda, MD 20824 1-800-352-9424

This article was published on 1999-06-08
This article was reviewed on 2003-02-03