Bilateral Internal Carotid Artery Agenesis in a Patient With a Family History of Intracranial Pathology

Agenesis of the internal carotid artery (ICA) is a rare congenital malformation that is often asymptomatic until the fourth or fifth decade. ICA agenesis is associated with several intracranial pathologies, the most reported being intracranial aneurysms, thought to be attributable to the increased flow in the collateral vessels supplying the anterior circulation. The cause of ICA agenesis is largely unknown and has not been consistently associated with any genetic mutations or syndromes. We present the case of a 37-year-old female who was incidentally found to have bilateral agenesis of the ICA system. Patient history revealed that the patient's father and 12 of his 14 siblings died from either ruptured brain aneurysms or cerebrovascular accidents before the age of 50 years. Presenting symptoms included right eye pain radiating to her right posterior neck, a 2-month history of diplopia, and associated nausea and vomiting. Differential diagnoses included immunoglobulin G4-related disease, sarcoidosis, lymphoma, and vasculitis. Absent internal carotids were attributed to congenital agenesis vs hypoplasia. The patient was seen by neurology and initiated on prednisone 80 mg by mouth once daily with a 2-week taper to treat systemic inflammation. The patient was deemed stable for discharge after a 2-day hospital admission and was scheduled for follow-up appointments with genetics, neurology, rheumatology, and ophthalmology. Bilateral ICA agenesis is a rare occurrence, with only 33 cases documented in a case report and literature review published in 2016. Because of the otherwise normal anatomy of the patient and the pervasive intracranial pathology seen in late adulthood in her family, we propose the likelihood of an inheritable form of bilateral ICA agenesis vs vascular disease or familial aneurysms.