A carotid endarterectomy is a surgical procedure in which a doctor removes fatty deposits from one of the two main arteries in the neck supplying blood to the brain. Carotid artery problems become more common as people age. The disease process that causes the buildup of fat and other material on the artery walls is called atherosclerosis, popularly known as "hardening of the arteries." The fatty deposit is called plaque; the narrowing of the artery is called stenosis. The degree of stenosis is usually expressed as a percentage of the normal diameter of the opening.

Carotid endarterectomies are performed to prevent stroke. Two large clinical trials supported by the National Institute of Neurological Disorders and Stroke (NINDS) have identified specific individuals for whom the surgery is highly beneficial when performed by surgeons and in institutions that can match the standards set in those studies. The surgery has been found highly beneficial for persons who have already had a stroke or experienced the warning signs of a stroke and have a severe stenosis of 70 percent to 99 percent. In this group, surgery reduces the estimated 2-year risk of stroke by more than 80 percent, from greater than 1 in 4 to less than 1 in 10.

In a second trial, the procedure has also been found highly beneficial for persons who are symptom-free but have a severe stenosis of 60 percent to 99 percent. In this group, the surgery reduces the estimated 5-year risk of stroke by more than one-half, from about 1 in 10 to less than 1 in 20.

In 1992, the most recent year for which statistics are available from the National Hospital Discharge Survey, there were about 91,000 carotid endarterectomies performed in the United States. The procedure has a 40-year history. It was first described in the mid-1950s. It began to be used increasingly as a stroke prevention measure in the 1960s and 1970s. Its use peaked in the mid-1980s when more than 100,000 operations were performed each year. At that time, several authorities began to question the trend and the risk-benefit ratio for some groups, and the use of the procedure dropped precipitously. The NINDS-supported North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the NINDS-supported Asymptomatic Carotid Atherosclerosis Study (ACAS) were launched in the mid-1980s to identify the specific groups of people with carotid artery disease who would clearly benefit from the procedure.