In patients who are prone to plaque build-up,one of the affected areas of the bifurcation is the carotid bulb, the upper most part of the common carotid artery just before it divides. The other location is the start of the internal carotid artery. So a vicious cycle begins. Consequently, there are even more things for the red cells to bump into, which further increases turbulence. More plaque, more turbulence, more plaque, and so on.
Trouble comes from two directions.
First, the build-up physically narrows the channel and may start diminishing flow. Second, not only does fatty plaque accumulate on the walls of the arteries, but small clots may start accumulating on damaged sections of the wall and on the plaque itself. If they get dislodged by turbulently flowing blood, they go directly into the internal carotid artery and on to the brain. When the plaque build-up in the artery narrows the channel significantly, flow diminishes to a serious degree and, depending upon clinical circumstances, steps may be taken to eliminate the narrowing surgically. Such surgery is not to be taken lightly but is lifesaving in many circumstances.