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Vertebral Artery Anomalies at the Craniovertebral Junction in the US Population

O'Donnell, Courtney M., MD*; Child, Zachary A., MD*; Nguyen, Quynh, MHS, PA-C*; Anderson, Paul A., MD; Lee, Michael J., MD*

doi: 10.1097/BRS.0000000000000447

Study Design. Retrospective review.

Objective. To evaluate the prevalence of anatomical variations of the vertebral artery at the craniovertebral junction and the posterior arch of the atlas in the US population.

Summary of Background Data. Recent studies from Asia have reported a 5% to 10% prevalence of a persistent first intersegmental vertebral artery and 1% to 2% prevalence of a fenestrated artery. These anomalous vertebral artery courses lie directly over the starting point for atlas lateral mass screw insertion. The relatively high reported prevalence of these anomalies suggests that routine preoperative computed tomographic angiogram be considered prior to upper cervical fixation. We have not observed this anomaly as commonly as reported.

Methods. The authors analyzed the records of 975 patients from a level I trauma center and adjacent university hospital who underwent computed tomographic angiography to evaluate the incidence of anomalous variations in the third segment of the vertebral artery. These results were compared with similar studies performed in Korea and Japan.

Results. The mean age of the patients was 52.9 years. The ethnic distribution of the patients was as follows: 69.3% of the patients were Caucasian, 11% Asian, 10.8% African American, and 6% Hispanic. The prevalence of a persistent intersegmental artery was 0.01% (1/975); a fenestrated vertebral artery was 0.01% (1/975); and origin of a posterior inferior cerebellar artery was 0.4% (4/975). The incidence of these anomalies was significantly lower than those previously published from Korea and Japan.

Conclusion. Vertebral artery course anomalies in the upper cervical spine were rare (0.42%) in our patient population. This finding contrasts with recent published reports from Asia, citing as high as a 10% rate of vertebral artery presence over the starting point for C1 lateral mass screw insertion. On the basis of the infrequent occurrence of this anomaly, we do not recommend routine computed tomographic angiography when planning upper cervical instrumentation.

Level of Evidence: N/A

We retrospectively reviewed 975 computed tomographic angiograms from a level I trauma center and found the incidence of vertebral artery anomalies at the V3 segment to be 0.42% in our patient population. This finding contrasts with published reports from Asia, citing as high as 10% rate of vertebral artery anomalies.

*Department of Sports and Orthopaedic Surgery, University of Washington, Seattle; and

Department of Sports and Orthopaedic Surgery, University of Wisconsin, Madison.

Address correspondence and reprint requests to Courtney M. O'Donnell, MD, Department of Orthopaedics and Sports Medicine, Harborview Medical Center, Box 359798, 325 9th Ave, Seattle, WA 98104; E-mail:

Acknowledgment date: February 13, 2014. Revision date: April 29, 2014. Acceptance date: May 21, 2014.

The manuscript submitted does not contain information about medical device(s)/drug(s).

No funds were received in support of this work.

Relevant financial activities outside the submitted work: consultancy, royalties, stock/stock options and other.

© 2014 by Lippincott Williams & Wilkins