What causes a stroke?

Ischemic strokes are usually caused by blood clots. They make up about 80% of all strokes. Blood clots can be caused by several different kinds of diseases or situations:

  • The most common problem is narrowing of the arteries (major blood vessels coming from the heart) in the neck or head. This is most often caused by the gradual buildup of fat, cholesterol (a waxy substance found in the blood) and/or calcium in the arteries. The arteries can become too narrow or break, allowing blood cells to collect and form blood clots. These blood clots can block the artery where they form, or can move and become trapped in arteries closer to the brain.
  • Another cause of stroke is blood clots in the heart, which can occur as a result of a fast, uneven heartbeat. This is called atrial fibrillation. Atrial fibrillation can cause the blood to flow poorly and form clots that can travel to the brain and cause a stroke.
  • Other causes include the use of certain "street" drugs, injury to the blood vessels of the neck, or health problems, which cause the blood to clot too much.

Transient Ischemic Attack (TIA) - A TIA has the same symptoms as a stroke, but only lasts for a few minutes or a few days. Then symptoms disappear. It does not cause permanent brain damage. A TIA is not a stroke, but it is an important warning signal. It means that the person is in danger of having a stroke. Anyone who experiences stroke symptoms of any length should consult a physician or get emergency medical assistance.

Hemorrhagic strokes make up about 20% of all strokes. There are a number of possible causes:

  • High blood pressure is the leading cause of hemorrhagic strokes. Since high blood pressure often causes no symptoms, many people are not aware they are at risk of having a stroke.
  • Less common causes of hemorrhage include injury, infections, tumors, blood clotting diseases and weaknesses in blood vessels.

next » What are the symptoms of stroke?

Written by: Janice C. May, M.P.A.
Reviewed by: Jeffrey G. Schultze, M.D.
Last Modified: Thursday March 28, 2019 3:33 PM