Internal carotid artery agenesis: correlation by conventional and digital subtraction angiography, and by computed tomography.

A case is presented of agenesis of the right internal carotid artery in a fifteen-year-old female with an unrelated seizure disorder. Conventional angiography revealed an absent right internal carotid artery, supply to the right anterior cerebral artery from the left internal carotid artery, and supply to the right middle cerebral artery by anastomosis through the vertebral basilar system. The congenital nature of the anomaly was confirmed by intravenous digital subtraction angiography, which revealed no portion or remnant of the right internal carotid artery to be present, and by computerized tomography of the base of the skull, which demonstrated no bony carotid canal on the right side. This is the first reported case of internal carotid artery agenesis to be elucidated by intravenous digital subtraction angiography. A brief discussion concerning the congenital nature of this anomaly is presented, including the role of angiography and computed tomography in establishing the diagnosis of this condition.