Stroke secondary to carotid stenosis

Definition:

A group of brain disorders involving loss of brain functions caused by obstruction of the carotid arteries (most often related to atherosclerosis).

Causes, incidence, and risk factors:

Stroke secondary to atherosclerosis affects about 2 out of 1,000 people, or approximately 50% of all who have strokes. Strokes secondary to carotid stenosis form only a small percentage of these strokes. Stroke secondary to carotid stenosis occurs when atherosclerotic plaque narrows a major portion of one or both carotid arteries (the arteries in the neck that supply blood to the brain).

Atherosclerosis (hardening of the arteries) is a condition where fatty deposits occur in the inner lining of the arteries, and atherosclerotic plaque (a mass consisting of fatty deposits and blood platelets) develops. The plaque may obstruct (occlude) the artery, or a clot (thrombus) may occur at the site of the plaque. The occlusion of the artery usually develops slowly. Atherosclerotic plaque does not necessarily cause stroke. There are many small blood vessels around the carotid arteries. If blood flow gradually decreases, these small connections will increase in size and "by-pass" the obstructed area (collateral circulation). If there is enough collateral circulation, even a totally blocked artery may not cause neurologic deficits. A second safety mechanism is that the arteries are large enough that 70 to 75% of the blood vessel can be occluded, and there will still be adequate blood flow to the brain.

Stroke secondary to carotid stenosis is most common in older people, and often, there is underlying atherosclerotic heart disease and/or diabetes mellitus.

Risks are the same as for stroke secondary to atherosclerosis.