An anomalous adventure of type I proatlantal artery.

Abstract

A 68-year-old man presented for vascular review after two carotid territory transient ischemic attacks with left-sided weakness. His medical history included transient ischemic attacks, smoking, and hypercholesterolemia. Carotid duplex ultrasound revealed slow resistive flow in the right common carotid artery and trickle flow in the right internal carotid artery (ICA) with low-velocity flow in the distal right ICA. Computed tomography angiography showed a short proximal occlusion of the right ICA (A). The left vertebral artery was dominant with a hypoplastic right vertebral artery, with refilling of the distal vessel by the anomalous vessel (B). At the junction of C3 and C4, a branch of the right ICA traversed anteromedially in a cranial direction, reaching the suboccipitoatlantal space, passing through a large variant of the hypoglossal canal. It then passed caudally to connect to the vertebral artery (C/Cover and D). Despite proximal right ICA occlusion, because of persistent flow in the distal ICA from the anomalous vessel, right carotid endarterectomy was able to be performed with restoration of flow from common carotid artery to ICA. The patient’s consent was obtained. In clinical practice with ligation, clamping, or endarterectomies, an understanding of these anomalies minimizes chances of decreasing circulation where ischemia may ensue. Surgeons performing carotid endarterectomy should familiarize themselves with these anomalies.1 Type I proatlantal intersegmental arteries are a remnant of carotid vertebrobasilar embryologic anastomosis originating from the ICA passing through the foramen magnum.2 The literature highlights the distinction between the hypoglossal artery and proatlantal intersegmental artery by its passage through the hypoglossal canal and foramen magnum, respectively, and its origin at skull base and C2.3 It is clinically important that vascular anomalies be appreciated beforehand, particularly in vascular intervention of the neck, brain, and chest.