Ascending pharyngeal artery collateral circulation simulating internal carotid artery hypoplasia

Complete occlusion of the cervical segment of the internal carotid artery may result in a collateral circuit between an enlarged ascending pharyngeal artery and the intracranial segment of the internal carotid artery. This anastomosis may simulate a severely stenotic or hypoplastic internal carotid artery. Differentiation between these entities is particularly important if carotid endarterectomy for relief of stenosis is contemplated.