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Stroke

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Stroke

Definition:

A stroke is an interruption of the blood supply to any part of the brain. A stroke is sometimes called a "brain attack."

Alternative Names:

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Cerebrovascular disease; CVA; Cerebral infarction; Cerebral hemorrhage 

Causes, incidence, and risk factors:

Every 45 seconds, someone in the United States has a stroke. A stroke can happen when:

• A blood vessel carrying blood to the brain is blocked by a blood clot. This is called an ischemic stroke.
• A blood vessel breaks open, causing blood to leak into the brain. This is a hemmorhagic stroke.

If blood flow is stopped for longer than a few seconds, the brain cannot get blood and oxygen. Brain cells can die, causing permanent damage.

ISCHEMIC STROKE

This is the most common type of stroke. Usually this type of stroke results from clogged arteries, a condition called atherosclerosis. (See stroke secondary to atherosclerosis.) Fatty deposits and blood platelets collect on the wall of the arteries, forming a sticky substance called plaque. Over time, the plaque builds up. Often, the plaque causes the blood to flow abnormally, which can cause the blood to clot. There are two types of clots:

• A clot that stays in place in the brain is called a cerebral thrombus.
• A clot that breaks loose and moves through the bloodstream to the brain is called an cerebral embolism.  

Another important cause of cerebral embolisms is a type of  arrhythmia   called atrial fibrillation. Other causes of ischemic stroke include endocarditis   and the use of a mechanical heart valve. A clot can form on the artificial valve, break off, and travel to the brain. For this reason, those with mechanical heart valves must take blood thinners.