Great vessels occasionally have an abnormal origin, including: a common origin of the brachiocephalic trunk and the left common carotid artery, the left vertebral artery originating from the aortic arch, and the right subclavian artery originating from the distal portion of the aortic arch and passing behind the esophagus to supply the right arm—as a result, the great vessels form a vascular ring around the trachea and the esophagus, which can potentially produce difficulty swallowing. This configuration is one of the most common aortic arch abnormalities.