Stroke
Definition of a stroke:
A stroke is an interruption of the blood supply to any part of the brain, resulting in damaged brain tissue.
Causes, incidence, and risk factors of stroke:
Stroke accounts for 1 out of every 15 deaths in the United States. It is the 3rd leading cause of death in most developed countries, and the leading cause of disability in adults. The risk doubles with each decade after age 35.
Most strokes are due to blood clots that block blood flow. Bleeding into the brain occurs if a blood vessel ruptures or if there is a significant injury.
BLOOD CLOTS
A common cause of stroke is atherosclerosis. (See stroke secondary to atherosclerosis.) Fatty deposits and blood platelets collect on the wall of the arteries, forming plaques. Over time, the plaques slowly begin to block the flow of blood. The plaque itself may block the artery enough to cause a stroke.
Often, the plaque causes the blood to flow abnormally, which leads to a blood clot. A clot can stay at the site of narrowing and prevent blood flow to all of the smaller arteries it supplies. (This type of clot, which doesn't travel, is called a thrombus.) In other cases, the clot can travel and wedge into a smaller vessel. (A clot that travels is called an embolism.)
Strokes caused by embolism are most commonly caused by heart disorders. An embolism may originate in a major blood vessel as it branches off the heart. A clot can also form elsewhere in the body for any number of reasons, and then travel to the brain, causing a stroke.
Stroke
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