Left common carotid artery agenesis with bovine origin of the left internal carotid artery.

The absence of the left common carotid artery, with separate origins of the external carotid and internal carotid arteries from the aortic arc is a well-described but extremely rare congenital anomaly. We present a unique case of agenesis of left common carotid artery depicted at MR angiography where the left internal carotid artery had a bovine origin (from the brachiocephalic trunk) and the left external carotid artery arose from the aortic arc. In addition, it is important to diagnose this anatomical variant especially prior to interventional procedures, as it could hinder the catheterization of these arteries.