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Stroke Causes
Of the 2 main types of stroke, the ischemic stroke occurs 80-85% of the time. With an ischemic stroke, a blood vessel in the brain becomes clogged. With a hemorrhagic stroke, a blood vessel in the brain actually bursts or leaks.
Hemorrhagic strokes tend to be more serious. The distinction between type of stroke can be critical in determining the treatment used.
Ischemic strokes occur when a blood vessel gets so narrow or clogged that not enough blood can get through to keep the brain cells alive.
Plaques (or build-up of cholesterol-containing fatty deposits called arteriosclerosis) in the blood vessel walls can narrow the blood vessels that supply the brain. These plaques build up until the center of the blood vessel is so narrow that little, if any, blood can get past. Many things including high cholesterol and high blood pressure cause plaques. The plaques may occur in small vessels that supply only a very tiny portion of the brain but may also occur in the big blood vessels in the neck (carotids) or in the large arteries to the brain (cerebral arteries).
Ischemic strokes may also be caused by small blood clots or emboli that go through the bloodstream and then get clogged in an artery when the artery narrows. These clots can come from pieces of plaques in the bigger arteries that break off or from the heart.
Hemorrhagic strokes occur when the wall of a blood vessel becomes weak and blood leaks out into the brain.
In addition to having decreased blood flow past the leak, the blood in the brain damages brain cells as it decomposes. If a lot of blood leaks out, it can cause a build-up of pressure in the brain because the brain is enclosed in the skull. There is not room for it to expand, and it can compress and kill important areas of the brain.
Hemorrhagic strokes tend to be more serious than ischemic strokes. Death occurs in 30-50% of people with this type of stroke.