Unilateral agenesis of the internal carotid artery presented as transient ischaemic attack: a case report.

Dysgenesis of the internal carotid artery (ICA) is a rare vascular disorder with a variety of different grades (agenesis, aplasia, and hypoplasia). The left internal carotid artery is reported to be affected by dysgenesis three times more often than the right one. Most of the patients with dysgenesis of the internal carotid artery are asymptomatic. We report a case of a patient with right internal carotid artery agenesis presented to our hospital as transient ischaemic attack. CT scans at skull base level with bone settings showed absence of the right carotid canal, consistent with congenital agenesis of the internal carotid artery. MR imaging of the brain revealed signal void of the intracranial portion of right internal carotid artery. Maximum intensity projection reconstruction confirmed the agenesis of the right ICA, with the right middle cerebral artery fed through a dilated posterior communicating artery and the right anterior cerebral artery supplied by the anterior communicating artery (fetal type of collateral flow). In patients with agenesis of the internal carotid artery non-invasive imaging techniques are currently the mainstay of diagnosis.