Memory Loss & the Brain

A stroke is a sudden loss of consciousness or other neurological dysfunction caused by loss of blood flow to one or more regions of the brain.

Like all cells in the body, brain cells depend on blood to supply the oxygen and nutrients they need to function. When this supply is cut off or drastically reduced, cells downstream which depend on that supply begin to starve and die. In the brain, this is called a stroke, or sometimes a "brain attack".

One kind of stroke is a hemorrhagic stroke, in which a blood vessel ruptures and bleeds or hemorrhages. It may be caused by injury or aneurysm. Hemorrhagic stroke accounts for about 20% of strokes, and is usually associated with hypertension or high blood pressure. The risk for hemorrhagic stroke in individuals with hypertension can be reduced by treating the hypertension through healthy diet and exercise, reducing or managing stress, limiting caffeine and abstaining from smoking.

A second kind of stroke is an ischemic stroke, in which a small blood clot becomes wedged in one of the tiny blood vessels supplying the brain, blocking the flow of blood. This blood clot may have formed in the brain, or it may have formed elsewhere, broken free, and traveled through the blood stream to reach the brain. The brain is particularly susceptible to such blockages because of the high number of tiny blood vessels in which a blood clot can lodge. Ischaemic stroke is usually associated with arteriosclerosis ("hardening of the arteries") and accounts for about 80% of strokes. Risk for ischaemic stroke is reduced by the same factors that reduce arteriosclerosis -- regular exercise, a diet low in saturated fats, no smoking - as well as by treating any co-existing conditions such as obesity, diabetes and hypertension.

A transient ischemic attack (TIA), often called a "mini-stroke", is a temporary interference with blood flow to the brain. The symptoms may include light-headedness, numbness, loss of balance, fleeting blindness, and problems swallowing or speaking. These symptoms persist for minutes to hours. After the attack, there may be no long-term neurological damage; since TIAs are generally painless, the person may be unaware that a stroke has occurred. TIAs may result from many causes, including decreased heart function, low blood pressure, and overmedication with drugs to treat high blood pressure. Without treatment, about 5% of people experiencing a TIA go on to develop a full-blown stroke within a year.

Stroke is the third leading cause of death in the US. The outcome of a stroke depends on the degree and length of time for which blood flow is reduced. About 70% of stroke patients recover well enough to lead independent lives, but many patients suffer permanent debilitating damage which may include partial paralysis, problems producing and understanding speech, and cognitive deficits. The particular symptoms experienced depend on where the stroke occurred: a stroke which occurs in a blood vessel which normally supplies the part of the brain which oversees speech production can result in deficiencies in speech production, and so on.