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What Is a Stroke?

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Updated November 13, 2011

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

If you have had a stroke, you have suffered damage to a portion of your brain tissue because of an interruption in the blood flow to a part of your brain. Strokes nearly always produce some degree of permanent impairment, which can range from barely noticeable to catastrophic. The type and severity of this impairment is determined by which part of the brain is damaged, and how much brain tissue is lost.

What Causes Strokes?

There are two general kinds of vascular problems that cause stroke. Ischemic strokes occur when blood flow is interrupted by a blockage in one of the blood vessels that supply the brain. Hemorrhagic strokes are caused by the rupture of a blood vessel, leading to bleeding in or around the brain.

Ischemic Strokes

Ischemic strokes can have one of two causes: thrombosis or embolism.

Thrombotic strokes occur when a blood clot forms within one of the arteries that supply the brain, blocking the flow of blood to the brain. These clots form at the site of plaques, which are caused by atherosclerosis in the artery.

This is the same atherosclerosis that produces coronary artery disease (CAD) and peripheral artery disease (PAD), so the same risk factors that lead to CAD and PAD also lead to strokes. These include elevated cholesterol levels, smoking, diabetes, and especially hypertension. Risk reduction is important not only to prevent heart attacks and PAD, but also stroke.

Embolic strokes occur when a blood clot travels from somewhere else in the body, through the vascular system, and lodges in a brain artery. There, it blocks blood flow to a portion of the brain.

There are several potential sources for the blood clots that cause embolic stroke. The most common are a number of heart problems that lead to the formation of blood clots - especially atrial fibrillation, heart valve disease, infectious endocarditis, and dilated cardiomyopathy.

There are several less common causes of embolic stroke, including air that is inadvertently introduced into the bloodstream during medical procedures, cardiac myxoma, and deep venous thrombosis. This latter condition can only produce stroke if there is also an abnormal opening in the heart that allows the clot to travel from the veins to the arterial side of the circulation, such as atrial septal defect or patent foramen ovale.

If you have any of these conditions, you should talk to your doctor about whether you should be taking blood thinners to prevent embolic strokes.

Hemorrhagic Strokes

Hemmorhagic strokes are most often caused by the rupture of a brain aneurysm, or an arteriovenous malformation. Hemorrhagic strokes more often occur in the presence of significant hypertension. In contrast to ischemic strokes (which are usually painless), hemorrhagic strokes are often accompanied by a sudden, severe headache.

Bleeding into or around the brain can cause several distinct clinical syndromes, including:

What Are the Symptoms of Stroke?

The symptoms of stroke are extremely variable, and depend on the part of the brain that is damaged, and the extent of the damage that is done. The symptoms usually come on either quite suddenly, or, when the stroke occurs during sleep, are noticed immediately upon waking up in the morning.

How Is Stroke Treated?

If you think you may be having a stroke - that is, if you notice the appearance of any of the symptoms that might be caused by a stroke - it is critical for you to receive medical care immediately. A rapid diagnosis and quick, aggressive treatment can greatly limit the amount of permanent disability you will have. But brain tissue dies rapidly when it is deprived of oxygen, so minutes count. In fact, the biggest key to avoiding permanent disability from a stroke (or even a worse outcome) is seeking medical care immediately.

Recovering From a Stroke

If you have had a stroke, the right medical care and the right rehabilitation can make all the difference in your ability to lead a happy and productive life.

Sources:

Adams, HP Jr, del Zoppo, G, Alberts, MJ, et al. Guidelines for the early management of adults with ischemic stroke: a guideline from the American Heart Association/American Stroke Association Stroke Council, Clinical Cardiology Council, Cardiovascular Radiology and Intervention Council, and the Atherosclerotic Peripheral Vascular Disease and Quality of Care Outcomes in Research Interdisciplinary Working Groups. Stroke 2007; 38:1655.

Broderick, J, Connolly, S, Feldmann, E, et al. Guidelines for the management of spontaneous intracerebral hemorrhage in adults: 2007 update: a guideline from the American Heart Association/American Stroke Association Stroke Council, High Blood Pressure Research Council, and the Quality of Care and Outcomes in Research Interdisciplinary Working Group. Stroke 2007; 38:2001.

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