The American Heart Association spends more on stroke-related research and stroke-related programs than any other non-profit organization, second only to the federal government. In November 1998 the AHA made the decision to rename its Stroke Division. It is now the American Stroke Association — a division of the AHA.

What is a stroke?

A stroke is a cardiovascular disease that affects the blood vessels supplying blood to the brain.

What causes a stroke?

A stroke occurs when a blood vessel bring 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 blood flow 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 or other particles and two by bleeding or hemorrhage. Cerebral thrombosis and cerebral embolism are by far the most common, accounting for about 70-80 percent of all strokes. They're caused by clots or particles that plug an artery bringing blood to part of the brain. Cerebral and subarachnoid hemorrhages are caused by ruptured blood vessels. They have a much higher fatality rate than strokes caused by clots.

One identifying feature of cerebral thrombosis is that they often occur at night or first thing in the morning, when blood pressure is low. Another is that very often they're preceded by a transient ischemic attack, also called a TIA or "mini-stroke."

In a recent New York Times article — Absence of Urgency: A Deadly Problem When Strokes Occur — it was reported that there is a three-hour window after a patient begins to have symptoms in which TPA, a tissue plasminogen activator which breaks up blood clots and the first drug to win (in 1996) approval from the Food and Drug Administration for treating ischemic stroke, is safe and effective. After three hours, there is a risk of brain hemorrhage.

Unfortunately, some people delay going to the hospital, said the Times, by mistakenly calling their primary care doctors first and by waiting for the call back. Others do not bother to call 911; rather, they have a family member drive them to the hospital. But studies show that stroke patients who travel to the hospital by ambulance arrive sooner and are treated faster than those who travel by personal car.

The American Stroke Association says these are the warning signs of a stroke:

1. Sudden numbness or weakness of the face, arm or leg, especially on one side of the body.
2. Sudden confusion, trouble speaking or understanding.
3. Sudden trouble seeing in one or both eyes.
4. Sudden trouble walking, dizziness, loss of balance or coordination.
5. Sudden, severe headache with no known cause.