Basilar artery aneurysm with aplasia of internal carotid artery: A case presentation

• We have recently encountered a patient with basilar trunk aneurysm and aplasia of internal carotid artery. • Basilar artery aneurysm was not observed past magnetic resonance imaging scan. • We conducted stent-assisted coil embolization to prevent rebleeding. Aplasia of the internal carotid artery (ICA) is rare. Patients with ICA aplasia are complicated with intercranial aneurysms due to hemodynamic factors more often than others, although they are asymptomatic. Clinical presentation We herein report a case of subarachnoid hemorrhaging due to a ruptured basilar artery (BA) aneurysm associated with congenital left ICA aplasia treated with endovascular therapy. The patient had been diagnosed with congenital ICA aplasia 15 years earlier; however, no aneurysm had been found at that time. Hemodynamic factors associated with ICA aplasia may lead to de novo aneurysm formation. And also, wall share stress may lead to aneurysm formation.