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StrokeSense : Understanding StrokeWhat Is a Stroke?
Sometimes called a "brain attack," a stroke occurs when the blood supply to part of the brain is interrupted, causing the affected area to stop functioning normally. Stroke is most common in people aged 70 and older and is more common in males. It may be caused by either a blockage (ischemic stroke) or a leak (hemorrhagic stroke) in one of the arteries that supply the brain. About one in four people who recover from a stroke will have another stroke within five years. Ischemic stroke, or occlusive stroke, accounts for 80 percent of strokes. It occurs when an artery that supplies the brain with blood gets blocked, suddenly causing the blood flow to dramatically decrease or stop. Some brain tissue in the affected area can die from lack of circulation, a condition known as a brain infarction. Ischemic stroke most often occurs when a blood clot forms in an artery in the brain, a process called cerebral thrombosis. It also can be caused by cerebral embolism, which occurs as a fragment of a blood clot forms in another part of the body, travels through the blood, and lodges in an artery that supplies the brain. Blood clots that lead to cerebral thrombosis and cerebral embolism are more likely to form in an artery that has been damaged by atherosclerosis (hardening of the arteries), a condition in which fatty deposits build up in artery walls. This fatty buildup also can cause the artery to narrow, a process called stenosis, which can also cause ischemic stroke. Cerebral embolism may stem from a complication of heart-rhythm disorders, heart-valve disorders, and recent myocardial infarction, all of which can cause blood clots to form in the heart. A transient ischemic attack (TIA), also known as a "mini-stroke," occurs when part of the brain suddenly fails to function normally. A TIA is caused by a lack of oxygen due to blockage of the brains blood supply. Doctors consider a TIA a full stroke when such symptoms as slurred speech, numbness or weakness on one side of the body, and loss of vision persist for longer than one hour. Most TIAs last for a few minutes, and symptoms go away within one hour. TIAs should be taken seriously and require immediate medical attention, just as strokes do. In fact, about one third of people who experience a TIA will have an acute stroke in the future. Hemorrhagic stroke accounts for 20 percent of all strokes. A hemorrhagic stroke occurs when an artery that supplies the brain bursts and blood leaks into the surrounding tissue, disturbing the blood supply and disrupting the delicate chemical balance that neurons (nerve cells in the brain) need to function. This bleeding is commonly caused by an aneurysma weak or thin spot on an artery wall. The aneurysm can balloon out and later rupture, hemorrhaging (bleeding heavily) into the space surrounding brain cells. Hemorrhaging also can occur when high blood pressure forces the arterial walls to break open. Blood from the ruptured brain arteries can enter the brain (intracerebral hemorrhage) or the areas surrounding the brain (subarachnoid hemorrhage). A subarachnoid hemorrhage is the most deadly of all strokes because it causes extensive damage throughout the brain. Reference "Stroke:
Hope Through Research," National Institute Source of Material: RockHill Communications,
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