Anomalous branch of the internal carotid artery maintains patency distal to a complete occlusion diagnosed by duplex scan.

A 67-year-old man had symptoms of peripheral vascular disease and was noted to have a carotid bruit. Duplex ultrasound examination of the neck demonstrated a short segmental occlusion of the proximal internal carotid artery (ICA) with antegrade flow distal to the occlusion maintained by an anomalous branch of the ICA. Angiography confirmed the findings and suggested that the branch was from the distribution of the occipital artery. The ICA findings were surgically proved, and endarterectomy was successfully performed without complication. This case reinforces the usefulness of duplex ultrasonography of the carotid arteries and is a rare situation in which a completely occluded ICA can be repaired with a good clinical outcome.