[Segmental agenesis of the cervical internal carotid artery with collateral blood supply from the ascending pharyngeal artery and intercavernous anastomosis: a clinical case and literature review].

The article presents a clinical case of segmental agenesis of the cervical ICA with collateral blood supply to the ICA territory through the intercavernous anastomosis and ascending pharyngeal artery with the branching primitive stapedial artery - the aberrant ICA variant. A feature of the case is a unique combination of the intercavernous anastomosis and the aberrant ICA, which provide collateral blood flow in cervical ICA agenesis. In the world literature, there are no reports of similar combinations. The discussion provides information on the stages of circle of Willis formation and presents a literature review of cases of intercavernous anastomoses associated with ICA agenesis.