A stroke occurs when blood flow to the brain is blocked, either by narrowed blood vessels or blood clots or when there is bleeding in the brain. Deprived of nutrients, brain nerve cells begin to die within a few minutes. As a result, stroke can cause vision and sensory loss, problems with walking and talking, or difficulty in thinking clearly. In many cases, the effects of stroke are irreversible.

Some people are more at risk for stroke than others. Chronic health conditions such as high blood pressure and diabetes can increase your risk, as well as lifestyle choices such as smoking cigarettes, being overweight, or drinking excessively. Men, African Americans, and people with a family history of stroke have a higher risk as well. If you have already had a stroke or a transient ischemic attack (referred to as a TIA or "mini-stroke"), you are at highest risk. Warning signs include sudden unexplained numbness or tingling especially on one side), slurred speech, blurred vision, stumbling, or clumsiness.

Preventing Stroke

Experts now believe that stroke is as preventable as heart attack. In addition to primary prevention tactics such as quitting smoking, drinking only in moderation, and exercising, there are medical interventions that can decrease your risk of stroke if you are in a high-risk group. Recent studies, including those supported by the Agency for Health Care Policy and Research (AHCPR), show that if you have conditions known as atrial fibrillation or carotid artery disease, there are interventions that can dramatically lower your risk of stroke.

Atrial Fibrillation

If you have atrial fibrillation, the upper left chamber of your heart beats rapidly and unpredictably, making it hard for all the blood in the chamber to empty. The remaining blood tends to form clots that can travel to any part of your body. If they travel to the brain, these clots can cause a stroke. Treatment with anticoagulants (or blood-thinners) such as warfarin can prevent these clots from forming. Aspirin also is used to reduce the risk of stroke, but the most recent clinical studies have shown that warfarin is superior to aspirin in preventing stroke. Current studies show that treatment with warfarin can prevent over half of the 80,000 strokes that are caused annually by atrial fibrillation.

If you have atrial fibrillation, your health care provider may recommend that you take warfarin. If you do, you need to know:

* Warfarin may increase the risk of bleeding. Careful regular monitoring of blood levels and proper dosage should keep this risk in check. Your health care provider will tell you where to go for monitoring.
* When properly administered, warfarin prevents 20 strokes for every major bleeding complication caused by the medicine.
* Most bleeding incidents are preventable and treatable.
* Certain drugs can interfere with proper anticoagulation. Antibiotics and anticonvulsants (for example, phenobarbital and Tegretol) are examples of drugs that can cause problems. Talk to your physician or pharmacist for more complete information.

Carotid Artery Disease

The carotid arteries run through the neck and supply blood to the brain. When the walls of the carotid arteries are narrowed by fatty deposits known as plaque, small clots in the blood can cut off blood supply to the brain and cause a stroke. A surgical procedure known as a carotid endarterectomy clears arteries of plaque. If you have had a minor stroke or symptoms that suggest you are at high risk for a stroke, and there is evidence of severe blockage in your carotid arteries, your health care provider may suggest you consider carotid endarterectomy as a preventive procedure.

If you are considering this surgery, you should know:

* Certain tests may be required to confirm the diagnosis of carotid artery disease. With angiography, a dye is injected into the artery, followed by an x-ray to check for blockage. Magnetic resonance imaging (MRI) and ultrasonic scans also can test for blockage without entering the arteries.
* Carotid endarterectomy carries some risks. There can be complications if parts of the plaque break away during the procedure and block an artery to the brain or if artery incisions leak.
* Complication rates vary greatly by hospital and surgeon. Ask if your hospital monitors its complication rates for carotid endarterectomy and ask your surgeon how many times he or she has performed the procedure. Evidence shows that surgeons who have performed more procedures have higher success rates.

AHCPR Research

This information is based on research by the Stroke Prevention Patient Outcomes Research Team (PORT) headed by David B. Matchar, MD, of Duke University's Center for Health Policy Research and Education. PORTs are multidisciplinary research studies, sponsored by AHCPR, that are focused on common and costly clinical conditions. PORTs examine the outcomes of treatments provided to typical patients by typical practitioners in typical health care settings.

Like other AHCPR medical effectiveness research studies, PORTs address three core questions about available treatments:

* Are they effective?
* For which patients are they most effective?
* Are they cost-effective?

Printed copies of What You Should Know About Stroke Prevention are available by writing or calling:

AHCPR Publications Clearinghouse
P.O. Box 8547
Silver Spring, MD 20907
800-358-9295 (24 hours a day)

Fax copies of these materials are available by calling AHCPR InstantFAX at (301) 594-2800 using a fax machine with a telephone handset.

AHCPR Publication No. 95-0090
Current as of September 1995

Internet Citation:

What You Should Know About Stroke Prevention. AHCPR Publication No. 95-0090, September 1995. Agency for Health Care Policy and Research, Rockville, MD. http://www.ahrq.gov/consumer/strokcon.htm

Additional Resource:

Stroke Risk Factors and Symptoms from the Brain Attack Coalition and the National Institute of Neurological Disorders and Stroke, National Institutes of Health at: http://www.ninds.nih.gov/health_and_medical/pubs/stroke_bookmark.htm