Re: Variations in the origin of the vertebral artery and its level of entry into the transverse foramen diagnosed by CT angiography

Abstract

Dear Sir,We read with interest and pleasure the recently publishedarticle: “Variations in the origin of the vertebral artery and itslevel of entry into the transverse foramen diagnosed by CTangiography” by Uchino et al. [1]. Unfortunately, the authorsforgot to mention or ignored our previously published work:“Origin and course of the extracranial vertebral artery: CTAfindings and embryologic considerations” [2]. This paperdeals exactly with the variations of the origin and course ofthe extracranial vertebral artery as described by Uchino andcolleagues and demonstrates clearly the relationship to thelevel of entrance into the transverse foramen. We were ableto demonstrate that the level of entrance into the transverseforamen indicates which metameric artery or arteries in caseof duplication persist. Additionally, we illustrated the varia-tions in modified schematic figures and a matrix for thevertebro-basilar system adapted from Lasjaunias et al. [3].Uchino et al. found that 0.2 % of left vertebral arteries arosefrom the aortic arch distal to the left subclavian artery andentered the seventh transverse foramen. They state that theirstudy is the first to report its prevalence. However, we previ-ously showed in our large CTA study the frequency of thisvariationtobe0.56%,whichisquitesimilar.Furthermore,theauthorsdealwiththeduplicatedoriginofthevertebralarteries.They stated that all patients in literature (including otherworks but not ours) demonstrate left vertebral arteries ofnormaloriginandofaorticarchoriginthatfusetogether.Theybelieve that the duplicate origin of the left vertebral arteryforms if both the seventh and sixth segmental arteries persist.This is a generalization that does not fit always. We showedonecasewithbilateralduplicationofthevertebralarteries.Onthe left side, both vertebral arteries originated from the aorticarchwiththedistalsegmententeringthetransverseforamenatthe level of C5, corresponding to the sixth metameric orsegmental artery and the proximal segment entering at thelevel of C4, corresponding to the fifth segmental artery, re-spectively. In our opinion, variations of the vertebral arterysystem can occur nearly at any level. The basic principles ofmetameric distribution should be mastered to understand andrecognize these variations.