Stroke Secondary to Carotid Stenosis

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Overview, Causes, & Risk Factors

Stroke secondary to carotid stenosis occurs when a major portion of one or both carotid arteries (the arteries in the neck that supply blood to the brain) is narrowed or blocked.

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 the artery or a clot (thrombus) may occur at the site of the plaque and also cause obstruction. Blockage of the artery usually develops slowly. Sometimes, however, a piece of atherosclerotic plaque (an embolism) may break off and travel to an artery in the brain causing obstruction far from the initial site where the plaque developed.

Atherosclerotic plaque does not always lead to 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 % 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.