Plaque forms when high cholesterol, high blood pressure and smoking damages the endothelium, or smooth inner lining, of a carotid artery, states WebMD. As white blood cells attempt to stop irritants from moving deeper into the artery wall, they combine with cholesterol and other irritants to form debris-filled masses.
The progressive buildup of plaque leads to hardened, narrowed arteries in a process known as atherosclerosis, according to WebMD. Atherosclerosis typically begins in early adulthood, but symptoms manifest during middle age when plaque deposits grow large enough to create dangerous blockages in the arteries. However, plaque that starts inside the artery wall may never extend far enough to obstruct the blood vessel or cause health problems.
Atherosclerosis increases the risk of developing carotid artery disease, which affects arteries in the neck that enable blood flow between the heart and the brain, notes VascularWeb from the Society for Vascular Surgery. When a plaque deposit ruptures, the immune system triggers an influx of platelets to form protective blood clots. The resulting clots can block off a carotid artery and deprive the brain of blood and oxygen. If a piece of plaque dislodges and passes through the bloodstream, it may block an artery in the brain and cause a stroke. During the early stages of symptomatic atherosclerosis, doctors may advise patients to change their diets, quit smoking, start an exercise regiment or learn weight management techniques.