What Is an Ischemic Stroke?
An ischemic
stroke is a type of stroke that occurs when not enough essential oxygen- and nutrient- rich blood is able to get to certain parts of the brain for a long enough period of time that brain tissue is damaged and eventually dies (known medically as a brain infarction). Ischemic strokes account for approximately 80 percent of all strokes. The second main type of stroke -- hemorrhagic stroke -- accounts for the other 20 percent of strokes.
An ischemic stroke occurs because a blood vessel in the brain or neck becomes severely narrowed or blocked. There are a several ways in which a blood vessel in the brain may become severely narrowed or blocked. The two most common are an embolism and thrombosis. An embolism occurs when a blood clot or other tissue from another part of the body (such as the heart) moves through the blood into to the neck or brain.
In thrombosis, a blood clot (known as a thrombus) forms within a blood vessel of the brain or neck. Unlike an embolism, with thrombosis, the blood clot does not break free.
A third way that a blood vessel can become narrowed or blocked involves stenosis. Stenosis is severe narrowing of an artery in or leading to the brain. Stenosis is most often caused by a
plaque buildup.
(Click Stroke Causes to learn about specific causes for narrowing or blocked arteries.)
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