Brian Liebowitz, age 16, of Fargo, N.D.,.for his question:
WHAT CAUSES A STROKE?
A "stroke" is a sudden brain disturbance caused by an interruption of the blood supply. It results from disease of the blood vessels that supply the brain or cerebrum. This condition is usually termed a "cerebrovascular disease."
There are three general types of stroke: cerebral hemorrhage, cerebral thrombosis and cerebral embolism.
Cerebral hemorrhage is caused by ruptures of a cerebral blood vessel with bleeding into the brain (intracerebral hemorrhage) or under its covering membranes.
Cerebral thrombosis stems from obstruction of a cerebral blood vessel when a blood clot forms within its walls. The clot may be caused by abnormal thickening of the blood, damage to the vessel wall from arteriosclerosis or hardening of the arteries, atherosclerosis or fatty deposits in the vessel walls, inflammation of the arteries ("arteritis") or inflammation of the veins ("phlebitis").
If the blood supply is completely stopped or falls below one fourth of its normal level, softening of the brain, called "cerebral infarction" can result. Infarction causes permanent brain damage.
A cerebral embolism is obstruction of a cerebral artery by a blood clot or a foreign body which usually has migrated from another part of the body's circulation. An example of this is a blood clot breaking off from a damaged heart and being transported to a main artery of the brain.
The clots commonly fragment and lodge in the left middle cerebral artery, which in right handers supplies the speech areas of the brain. This artery also supplies the nerve cells controlling movement of the right side of the body, particularly the right arm and leg.
In the United States, stroke is the third most common cause of death after heart disease and cancer, and it is the most common disabler.
More than 2 million Americans and Canadians are disabled by stroke. Fortunately, thanks to control of hypertension, the incidence is decreasing.
Chronological age and physical age are not the same because some people age more rapidly than others. Nor is age a disease, although diseases increase with advancing age. Some 80 year olds are strikingly free of arteriosclerosis.
The peak incidence of stroke, however, is reached after age 50 and continues through the 70s. Men have a higher incidence in the earlier decades than women.
What are the common symptoms of a stroke? When the blood supply to part of the brain is suddenly interrupted, there will be a corresponding loss of the functions controlled by that part of the brain.
Depending on location, this may include loss of speech ("aphasia") or slurred speech, confusion, paralysis of one side of the body ("hemiplegia"), paralysis of one side of the face, paralysis of movement of the eyes with squint, unequal pupils, staggering and loss of coordination ("ataxia"), loss of sensation to parts of the body, headache, nausea and loss of consciousness.