If an artery becomes completely blocked (which is called carotid occlusion) or if piece of the blockage breaks off and travels to a smaller vessel where it completely blocks blood flow, a part of the brain may be completely deprived of oxygen, leading to the destruction of brain tissue. This is what happens during the event we call a stroke, or a “brain attack.”  There are nearly half a million strokes each year in the United States, and it’s the third leading cause of death. Stroke claims 140,000 American lives a year — and half of those fatal strokes can be traced to carotid occlusion.