About 80% of strokes are ischemic, which means they are caused by the interruption of blood flow to the brain due to a blood clot. The buildup of plaque (fatty materials, calcium and scar tissue) is involved in most ischemic strokes narrowing the arteries that supply blood to the brain, interfering with, or blocking the flow of blood. This narrowing is called atherosclerosis. An ischemic stroke is either "thrombotic" or "embolic."
Thrombotic strokes are caused by a blood clot that forms in an artery directly leading to the brain. Embolic strokes occur when a clot develops somewhere else in the body and travels through the blood stream to the brain.
A TIA, or Transient Ischemic Attack which is also known as a "mini-stroke" is caused by a temporary interruption of blood flow to the brain. The symptoms (warning signs) are similar to an ischemic stroke except they go away within a few minutes or hours. Many people can have a TIA without even knowing it. A TIA is an important warning sign that puts you at increased risk of a full-blown stroke.
Last reviewed: August 2008.