What causes a stroke?

Stroke is a cardiovascular disease that affects the blood vessels supplying blood to the brain. It is also called brain attack.

A stroke occurs when a blood vessel bringing oxygen and nutrients to the brain bursts or is clogged by a blood clot or some other particle. Because of this rupture or blockage, part of the brain doesn't get the flow of blood it needs. Deprived of oxygen. nerve cells in the affected area of the brain can't function and die within minutes. And when nerve cells can't function, the part of the body controlled by these cells can't function either. The devastating effects of stroke are often permanent because dead brain cells aren't replaced.

There are four main types of stroke: two caused by blood clots, and two by hemorrhage. Cerebral thrombosis and cerebral embolism, both caused by clots, are by far the most common, accounting for about 70-80 percent of all strokes. Cerebral and subarachnoid hemorrhages are caused by ruptured blood vessels. They have a much higher fatality rate than strokes caused by clots. Warning Signals of Stroke

If you notice one or more of these signals, don't wait. Get immediate medical attention. The faster you call an ambulance and get to the hospital, the greater your chance of limiting brain injury.

• Sudden weakness or numbness of the face, arm or leg on one side of the body.
• Sudden dimness or loss of vision, particularly in one eye.
• Loss of speech, or trouble talking or understanding speech.
• Sudden severe headaches with no apparent cause.
• Unexplained dizziness, unsteadiness or sudden falls, especially along with any of the previous signals.

About l0% of strokes are preceded by "temporary strokes" (transient ischemic attacks or TIAs) days, weeks or even months before a major stroke. The usual symptoms are like those of a full-fledged stroke, except that the symptoms of a TIA last 24 hours or less. TIAs are extremely important warning signs for stroke and shouldn't be ignored. People who have had TIAs are about 10 times more likely to have a stroke than people of the same age and sex who haven't had a TIA.