Agenesis of the ICA with a Contralateral Cavernous-Supraclinoid Anastomotic Vessel

Congenital agenesis of an ICA is exceptionally rare. Survival requires remodeling of the intracranial vasculature, with several classic vascular patterns and anastomoses having been recognized in the literature. We present a patient with ICA agenesis who exhibited a distinctive anastomotic vessel extending from the contralateral cavernous carotid artery directly to the supraclinoid ICA on the affected side, a finding only documented in a handful of patients with this already rare condition.