When not fatal, stroke can leave brain functions impaired. About 500,000 people suffer strokes each year. A major cause of stroke is arteriosclerosis, or hardening, of the carotid arteries that supply blood to the brain. As we age, a plaque of fat, calcium deposits and blood clotting material can form on the inner lining of the arteries, impeding the flow of blood to the brain. Stroke occurs when a piece of this plaque breaks off and lodges in a smaller blood vessel, shutting off the flow of blood to that part of the brain.
Stroke also can happen when the carotid itself is completely blocked.
A person whose artery is 70 percent blocked or more has four times the risk of stroke as a person with lesser blockage. Severe blockages can be surgically removed. Currently, doctors use cerebral angiography as the final step in assessing the blockage to determine whether surgery is needed. This method involves inserting a catheter in the leg and following the arteries up into the head. There, a dye is released into the blood that can be seen on x-rays.