any structural anomaly of the left or right common carotid arteries which extend headward on each side of the anterior neck and deliver oxygenated nutrient filled blood from the heart to the head, neck and brain; the left originates in the arch of the aorta over the heart; the right originates in the brachiocephalic trunk, the largest branch from the arch of the aorta; each common carotid artery divides into an external and an internal carotid artery