25 - Vertebral Artery Variation in the United States: A Cadaveric Study

Poster Board Number: 25
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Abstract Body : Introduction

While vertebral artery (VA) variants are uncommon, they may be more prevalent than previously thought. After thorough literature review of numerous cadaveric studies, this has become clear. However, the prevalence of these anomalies in the United States (U.S.) is still unknown. There are no published cadaveric studies examining VA variations on U.S. donors; the majority of studies have occurred overseas, mainly southeastern Asia.

Materials and Methods

To address this gap in the literature, donors from the Ohio University Heritage College of Osteopathic Medicine whole body donation program were dissected in order to expose the VA in its entirety. The VA was then categorized as anatomically normal or variant. Data obtained included: vertebral level of origin, artery origin, vertebral entrance level, diameter at origin and entrance, length from point of origin to entrance in transverse foramen, origin distance from subclavian (L) or common carotid (R) arteries, as well as various demographic data. Data was analyzed using T test, chi-squared, Fishers exact, and FREQ procedure through SAS.

Results

Preliminary data from 35 donors demonstrated that VA variants were present in 20% of the donors. Among those with anomalies, 4 (57.14%) were RVA while 3 (42.86%) were LVA. There was an equal proportion of male (20%) and female (20%) anomalies. Among variants, 1 (2.86%) was categorized as aortic origin, 4 (11.43%) were high entrance, 1 (2.86%) was a double VA, and 1 (2.86%) was aortic origin and high entrance. A RVA level of origin at C7 or T2 were more likely to have an anomaly compared to those with C7-T1, T1, or T1-T2 (28.6% vs. 14.3%) (p=0.012). A LVA level of origin at T1 (60.7%) was more likely to not have an anomaly followed by those with T2 origin (17.9%) and C7-T1, T1-T2 (10.7%) (p=0.034).

Conclusion

There are currently no studies published on VA variance in the U.S. population. Several cadaveric studies report the prevalence in populations overseas being significant. With anomalies being present in 20% of our donors, our data supports their findings and has found similar, if not more significant, results thus far. Greater population sizes are needed to confirm, but it is clear that VA variants are more prevalent in our population than many believe.

Significance

Whether it be in surgery or osteopathic manipulative medicine (OMM), a better understanding of the VA and its anatomical variance can lead to better outcomes in health care. Overall incidence rates of VA injury increase with variants and supports the need for pre-operative imaging. In respect to OMM, there have been case reports of VA dissection following neck manipulation. This study demonstrates the significant variations that may play a factor into the occurrence rate of this tragedy.