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Clinical Overview

Reviewed by Brian R. Robinson, MD

A stroke is a "brain attack” (like a “heart attack”) caused either by bleeding in the brain or a loss of blood flow to the brain. Stroke is extremely dangerous and requires immediate emergency medical treatment.

When blood flow in the brain is blocked or disrupted, the brain cells fed by the blocked blood supply begin to die. This leads to severely impaired brain function, and can result in serious brain damage or even death, if the damage is severe enough.

There are two major kinds of stroke.

Ischemic stroke occurs when something blocks a blood vessel that supplies the brain. It is estimated that up to 80% of strokes are ischemic strokes. There are three main types of ischemic strokes. Embolic strokes occur when a small blockage, called an embolus, travels to a blood vessel in the brain and becomes lodged there, choking off blood flow. Thrombotic stroke occurs when a blood clot forms in the brain itself, and becomes large enough to stop blood flow to an area of the brain. Ischematic stroke results from stenosis when arteries narrow as a result of the buildup of fatty plaque (made of cholesterol and other fatty substances) in the brain.

Hemorrhagic stroke is the result of bleeding in or around the brain. When there is bleeding in the brain, the blood surrounds brain cells, known as neurons, which are normally fed not via the blood directly, but through a thin membrane. When blood surrounds neurons, they cannot work properly. Also, the abnormal bleeding results in insufficient blood flow to other areas, which results in the “starvation” of other neurons. There are two main causes for this type of stroke. The first is the rupture of plaque-filled arteries in the brain, and the second is brain aneurysm, a bulbous stretch of artery caused by a weakening or strain of the arterial wall.

Risk factors for stroke include:

• aging
• family history of stroke
• High blood pressure
• Heart disease
• diabetes
• high cholesterol (LDL over 130, or HDL under 35), or a lifestyle that will lead to high cholesterol
• head and neck injuries
• recent viral or bacterial infection
• sickle cell anemia
• smoking
• high alcohol intake (more than 1-2 drinks a day)
• Drug abuse (cocaine, marijuana, amphetamines, heroin, and anabolic steroids)
• High intake of caffeine, L-asparaginase, or pseudoephedrine (in over-the-counter decongestants)

Additionally, stroke occurs more often in men and people of African American heritage. Stroke is frequently a recurrent problem. There is a much higher risk of stroke in people who have already suffered one.

Last updated: Jan-01-00

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