Carotid arteries are the blood vessels that deliver blood through the neck to the brain. There is one carotid artery on each side of the neck, where its pulsation can be felt with a finger below the jaw bone. Blockages in the carotid artery decrease blood flow to the brain, causing a medical condition known as carotid artery disease. Interruptions in blood flow to the brain (commonly known as stroke) can cause permanent injury. This Cardiology Patient Page describes how blockages resulting from carotid artery disease cause stroke and what you and your doctor can do to prevent it. Stroke, or cerebrovascular accident, is most frequently caused by a sudden stoppage of blood flow to a portion of the brain. Every year in the United States, an estimated 750 000 people become victims of stroke. There are 2 common causes of stroke. First, an irregular heart rhythm, called atrial fibrillation, can cause stroke when small blood clots form as the heart is quivering instead of beating normally. Once a small blood clot is formed, it can be launched by the heart through the carotid arteries, block a blood vessel in the brain, and deprive that part of the brain of blood, resulting in a stroke. The other common cause of stroke is a blockage in the carotid arteries. The carotid arteries carry blood to the brain; like the blood vessels that supply blood to the heart, these arteries can become narrowed or blocked. The blockages are deposits of cholesterol, or atherosclerosis, that narrow the blood flow channel in the carotid arteries (Figure 1). If these cholesterol deposits or blockages break or rupture, small blood clots and cholesterol fragments break off from the plaque, enter the blood flow to the brain, and can get caught in a smaller blood vessel in …