A right-sided aortic arch (RA) with an abnormal origin of the left vertebral artery (VA) from the left common carotid artery (CCA) is extremely rare. RA with left VA-CCA has an interesting embryologic mechanism based on which transverse foramen (TF) of the cervical vertebra the VA entered into.
A 55-year-old asymptomatic man was referred to us with a diagnosis of RA. Computed tomography showed RA with the aberrant left subclavian artery (SCA) arising from Kommerell diverticulum and the left VA originating from the left CCA (A). The supra-aortic vessels arose in the following order: left CCA, right CCA, right SCA, and aberrant left SCA (B). The right VA entered the C6 TF. The left VA entered the C5 TF (C). He had been observed because the size of his Kommerell diverticulum was 26 mm. The patient gave consent to publish his data and images.
Discussion
The anomalous origin of the supra-aortic vessels is due to the aberrant development of the embryonic vasculature. In normal embryologic development, the right SCA develops from the right dorsal aorta. During this process, the caudal part of the dorsal aorta regresses just before the confluence with the left dorsal aorta. The right seventh cervical intersegmental artery (CIA) becomes the right SCA.
The VA is usually a branch of the ipsilateral CIA. In a study, total prevalence of variation in the origin of the left VA was 6.0%. The most prevalent variation in the left VA origin was direct aortic origin proximal to the left SCA in 4.1%.1 The left VA arising from the CCA is extremely rare.
The TF entrance level indicates which CIA persists. A left VA that does not originate from the SCA will never enter the C6 TF.2 Here, the left VA entered the C5 TF. Therefore, it is thought to develop from the persistent left fifth CIA and involution of the ipsilateral middle dorsal aorta between the persistent fifth and the seventh CIA (D).
Acknowledgments
We thank Kiyokuni Matsuo and Naoyuki Inagaki for radiologic assistance.
Footnotes
Author conflict of interest: none.
The editors and reviewers of this article have no relevant financial relationships to disclose per the Journal policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest.
References
- 1.Uchino A., Saito N., Takahashi M., Okada Y., Kozawa E., Nishi N. Variations in the origin of the vertebral artery and its level of entry into the transverse foramen diagnosed by CT angiography. Neuroradiology. 2013;55:585–594. doi: 10.1007/s00234-013-1142-0. [DOI] [PubMed] [Google Scholar]
- 2.Meila D., Tysiac M., Petersen M., Thesien O., Wetter A., Mangold A. Origin and course of the extracranial vertebral artery: CTA findings and embryologic considerations. Clin Neuroradiol. 2012;22:327–333. doi: 10.1007/s00062-012-0171-0. [DOI] [PubMed] [Google Scholar]