Internal Carotid Artery Agenesis: A Rare Entity.

Congenital absence of the internal carotid artery (ICA) is an extremely rare entity that occurs due to insult during the embryonic development of the ICA. Various intracranial collateral pathways develop to compensate for the ICA agenesis. Patients can present with aneurysmal subarachnoid hemorrhage, stroke-like symptoms, or other neurological symptoms due to compression of brain structures from enlarged collateral pathways/aneurysms.