Carotid artery stenosis  is the narrowing of the carotid arteries. These are the main arteries in the neck that supply blood to the brain. Carotid artery stenosis, also called carotid artery disease, is a major risk factor for ischemic stroke. (This is the most common form of stroke and is usually caused by a blood clot plugging an artery.)

The narrowing is usually caused by plaque in a blood vessel. Plaque forms when cholesterol, fat and other substances build up in the inner lining of an artery. This process is called atherosclerosis.

Carotid artery stenosis may or may not cause symptoms. A doctor may hear an abnormal sound called a bruit when listening to the artery with a stethoscope. The stenosis can be easily detected with an ultrasound probe placed on the side of the neck near the carotid arteries. This is called carotid ultrasonography .

Depending on the degree of stenosis and the patient's overall condition, carotid artery stenosis can usually be treated with surgery. The procedure is called carotid endarterectomy. It removes the plaque that caused the carotid artery to narrow. Carotid endarterectomy has proven to benefit patients with arteries stenosed (narrowed) by 70 percent or more. For people with arteries narrowed less than 50 percent, anti-clotting medicine is usually prescribed to reduce the risk of ischemic stroke. Examples of these drugs are antiplatelet agents and anticoagulants.