Left Common Carotid Artery Agenesis With Independent Origins of the External and Internal Carotid Arteries From the Aortic Arch: A Rare Case in a Patient With Ankylosing Spondylitis.

The agenesis of the left common carotid artery, with independent origins of the external and internal carotid arteries from the aortic arch, is a well-described but extremely rare congenital anomaly. We present a case of agenesis of the left common carotid artery with the independent origin of the left internal and left external arteries from the arch of the aorta in a patient with ankylosing spondylitis which was depicted by CT angiogram and magnetic resonance angiography. The diagnosis of this anatomical variant especially before interventional procedures is of great importance, as it could complicate the catheterization of these arteries.