Congenital absence of the internal carotid artery

We report three cases of congenital absence of an internal carotid artery ( ICA), diagnosed incidentally by digital subtraction angiography. The analys is of the cases is based on the classification of segmental ICA agenesis pr oposed by Lasjaunias and Berenstein. Usually the patients with this rare va scular anomaly are asymptomatic; some may have symptoms related to cerebrov ascular insufficiency, compression by enlarged intracranial collateral vess els, or complications associated with cerebral aneurysms. Diagnosis of cong enital absence of ICA is made by skull base computed tomography (CT) scan, CT and magnetic resonance angiography, and conventional or digital subtract ion angiography.