Extracranial (Brachiocephalic) Atherosclerosis
Extracranial (brachiocephalic) atherosclerosis is hardening of the arteries that supply the head and neck (carotid and vertebral arteries), causing narrowing and blockage of these vessels. It is similar to hardening of the arteries elsewhere in the body such as the heart or legs. If a vessel becomes completely blocked or even severely narrowed, blood flow to part of the brain can be threatened and a stroke can occur.
The same risk factors that are associated with intracranial atherosclerosis are associated with atherosclerosis elsewhere (such as in the vessels of the heart, causing heart attacks). They include diabetes, high blood pressure, high cholesterol, and smoking. Atherosclerosis of the carotid arteries often causes transient ischemic attacks (TIAs or ministrokes) because pieces of the material that forms the blockage (plaque) and blood clots that form on the plaque break off and are carried into the head where they can block vessels supplying the brain. Typical symptoms include weakness or numbness on one side of the body, inability to speak or understand speech, and changes in vision. If the blockage produced by this material is small and breaks up quickly, a TIA occurs. If there is blockage of a larger vessel or the blockage doesn't break up right away, a stroke follows.
Blockage of the vertebral arteries usually causes symptoms because of decreased blood flow to part of the brain, not because of pieces of plaque and clot breaking off. The symptoms of blockage of these vessels may get better and worse, or they may suddenly appear if a stroke occurs. These symptoms include dizziness, nausea, difficulty with balance or coordination, blurry or double vision, and changes in hearing.