Double inter-internal carotid artery communication through intercavernous anastomosis and posterior communicating artery associated with multiple intracranial artery segmental agenesis/aplasia.

Segmental internal carotid artery (ICA) and basilar artery (BA) agenesis/aplasia are rare vascular anomalies. We report an extremely rare case of combined ICA, BA, and A1 segmental absence presenting with double inter-ICA collateral communication through the intercavernous anastomosis and posterior communicating arteries. The patient presented with diplopia and transient ischemic attack. The pathogenesis of the anatomic anomalies and clinical symptoms are discussed.