Common carotid artery deep cervical artery and the descending branch of the occipital artery; the vertebral artery takes the place of the internal carotid artery within the cranium. The right common carotid may rise above the level of the upper border of the sternoclavicular joint; this variation occurs in about 12 percent of cases. In other cases, the artery on the right side may arise as a separate branch from the arch of the aorta, or in conjunction with the left carotid. The left common carotid varies in its origin more than the right. In the majority of abnormal cases it arises with
Carotid endarterectomy (CTA) or invasive angiography. Revascularization of symptomatic stenoses has a much higher therapeutic index compared to asymptomatic lesions. The North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the European Carotid Surgery Trial (ECST) are both large randomized class 1 studies which have helped define current indications for carotid endarterectomy in symptomatic patients. The NASCET found that for every six patients treated, one major stroke would be prevented at two years (i.e. a number needed to treat (NNT) of six) for symptomatic patients with a 70–99% stenosis, where percent stenosis was defined as: Symptomatic patients with less severe carotid occlusion (50–69%)