Ischemic Strokes
Ischemic strokes, which account for about 80 percent of all strokes, are caused by an obstruction in an artery, generally one of the carotid arteries, the major arteries in the neck that carry oxygen-rich blood from the heart to the brain. The path to an ischemic stroke begins when atherosclerosis, in which fatty deposits build up on the inner wall of an artery , develops in one of the carotid arteries (see Arteriosclerosis ). As the fatty deposit grows, it narrows the space through which blood can flow. Atherosclerosis does not actually cause ischemic strokes, but it sets up the conditions that make them likely to occur. The actual obstruction that cuts off blood flow in an ischemic stroke is a blood clot. Often the obstruction develops by a process known as thrombosis , the formation of a clot inside a blood vessel. A clot is likely to form at the site of an atherosclerotic deposit because the deposit causes blood to flow in a turbulent, disorderly fashion. This turbulence can cause