Structural Versus Functional Perspectives on Vertebral Artery Dominance

We read with great interest the recent study by Zhai and Hacking examining the association between vertebral artery (VA) origin variation and vertebral artery dominance (VAD) [1]. The authors are to be congratulated for demonstrating a significant relationship between aortic origin of the left VA and increased contralateral (right-sided) dominance. Their findings provide important structural evidence that congenital vascular variants may influence vertebrobasilar asymmetry. The proposed mechanism—namely that a longer and more tortuous pre-foraminal segment of an aortic-origin left VA may increase vascular resistance and shift dominance contralaterally—is anatomically plausible. However, we would like to expand the discussion by considering whether diameter-based criteria alone sufficiently characterise vascular dominance. Although a ≥ 0.3 mm luminal difference is widely used to define VAD, vascular dominance in physiological terms relates primarily to blood flow rather than calibre alone. Previous work has demonstrated that vertebral artery asymmetry may influence basilar artery curvature and posterior circulation infarction patterns, underscoring the hemodynamic dimension of dominance beyond structural size differences [2]. Given that CT angiography datasets permit detailed geometric analysis, future studies could incorporate measurements such as V1-segment length, curvature indices and take-off angles to better quantify geometric contributors to resistance. Computational fluid dynamics modelling or phase-contrast MR techniques may further clarify whether contralateral enlargement represents adaptive remodelling secondary to altered flow or reflects developmentally predetermined asymmetry. Flow-dependent arterial remodelling has been well described in experimental vascular physiology, suggesting that structural differences may represent downstream effects of sustained hemodynamic forces [3]. From an embryologic perspective, persistence of a non-seventh cervical intersegmental artery in cases of aortic-origin left VA may establish asymmetric flow conditions early in vascular development. Such developmental coupling between origin variation and dominance could partially explain the consistent shift towards right-sided dominance observed in this cohort. Systematic anatomical reviews have highlighted the complexity and variability of vertebral artery development, supporting the need for integrative structural and functional analyses [4]. Overall, this study provides a valuable foundation for understanding the interaction between vertebral artery origin and dominance. Incorporating flow-sensitive and geometry-based metrics in future investigations may refine our conceptualization of VAD as a dynamic vascular phenotype rather than a purely diameter-defined observation. Peng Xu: writing – original draft. Yuting Fu: writing – original draft, writing – review and editing. The authors declare no conflicts of interest. The authors have nothing to report.