Carotid artery stenosis refers to atherosclerotic narrowing of the extracranial carotid arteries. It typically refers to the internal carotid arteries or the common and internal carotid arteries. A "clinically important" degree of stenosis is defined as the percentage of stenosis that corresponds to a substantially increased risk for stroke. However, because stroke risk depends on more than just the degree of stenosis, it is difficult to set a lower...