VASCULAR/INTERVENTIONAL Bilateral Absence of the Common Carotid Arteries with Separate Origins of the Internal and External Carotid Arteries Detected by CT Angiography: Case Report Emilio P. Supsupin Jr. MD, Jeanie M. Choi MD, Eliana E. Bonfante-Mejia MD, Clark W. Sitton MD, and Leo Hochhauser MD ABSTRACT We report a rare case of bilateral absence of the CCAs with separate origins of the ICAs and ECAs, detected by CTA. INTRODUCTION We report a rare case of bilateral absence of the CCAs with separate origins of the ICAs and ECAs. To our knowledge, this is the first CTA depiction of this variant vas- cular anatomy. CASE REPORTS A 25-year-old man had undergone cervical spinal fusion. Concern for injury to the left VA following screw placement prompted a CTA, revealing this interesting anatomy. Imaging Findings CTA demonstrated absence of both CCAs with independent origins of the ICAs and ECAs on each side, individually ascending into the neck as separate vessels. The right ECA and ICA separately emanated from the IA proximal to the right subclavian ar- tery origin. On the left, the ECA directly originated from the aortic arch, whereas the left ICA and left VA arose from a single vessel trunk off of the arch (Figs 1–3). DISCUSSION We found 2 reported cases of bilateral ab- sence of the CCAs in the literature. The first, described in 1784 by Malacarne, in- volved a double aortic arch with indepen- dent origins of the ICAs and ECAs from each of these arches (quoted by T.A. Lie). 1 The only other case, in 1978, described ex- clusive origins of the bilateral ICAs and ECAs with a single arch on conventional angiography. 2 Agenesis of both CCAs is shared by our case. However, an added feature involving a common origin of the left ICA and left VA makes our case unique. Neither of the previous reports de- scribed this additional variant. A common origin of the left ICA and left VA was once observed, but not in this setting. 3 From an embryologic standpoint, persistence of the ductus caroticus with involution of the third aortic arch is the most commonly ac- cepted mechanism for the absence of the CCAs. 2 This is the opposite of the normal formation of the aortic arch, in which the ductus caroticus is obliterated and the third aortic arch persists, forming the CCA and proximal ICA (Fig 4). 4 Except for a double aortic arch on 1, the 2 previously reported cases of bilateral CCA agenesis were not known to have as- sociated congenital abnormalities. Associ- ABBREVIATION KEY CCA = common carotid artery CTA = CT angiography ECA = external carotid artery IA = innominate artery ICA = internal carotid artery VA = vertebral artery Received September 1, 2011; accepted after revision October 2. From the Department of Diagnostic and Interventional Imaging, University of Texas Houston Medical School, Houston, Texas. Please address correspondence to Emilio P. Supsupin, Jr., MD, Univer- sity of Texas Houston, Diagnostic and Interventional Imaging, 6431 Fannin St, Houston, TX 77030; e-mail: Emilio.P.Supsupin@uth. tmc.edu http://dx.doi.org/10.3174/ng.1120024 44 | Neurographics 02:44 – 46 March 2012 www.neurographics.com