Vertebral Artery Dominance in Patients with Embolic Basilar Artery Occlusion: Insights Toward Embolus Trajectory

Purpose: Embolic basilar artery occlusion (eBAO) is less common than anterior circulation stroke. The anatomic basis for this discrepancy is not understood. Vertebral artery dominance (VAD) correlates with blood flow to the basilar artery. We hypothesized that left VAD is less common in eBAO, as the right vertebral artery is the more proximal to the heart in typical aortic arch anatomy. Methods: This retrospective single-center, case-control study identified cases of eBAO. Right, left, and co-dominant (RVAD, LVAD, and CVAD) prevalence was calculated in standardized fashion by CTA. To estimate the VAD prevalence in asymptomatic patients, a systematic review and metanalysis was performed. The pooled estimate of VAD prevalence in the asymptomatic group was compared to the eBAO cohort using χ ² test. Results: In total, 72 eBAO were identified in the institutional cohort, and prevalence of LVAD, RVAD, and CVAD was 23.6%, 33.3%, and 43.1% respectively. Systematic review included eight studies and 1813 asymptomatic patients. Mean VAD prevalence in the asymptomatic population was LVAD 47.0% (39.0-55.1%), RVAD 26.9% (22.7–31.5%), and CVAD 25.9% (18.8–34.7%). VAD proportions differed significantly in the eBAO group (p < .001), with lower proportion of LVAD (OR 0.37, CI 0.20–0.67, p < .001), higher proportion of CVAD (OR 1.89, CI 1.13–3.13, p = .01) but no difference in RVAD (1.39, CI 0.81–2.35, p = .22). Conclusion: LVAD is significantly less common in patients with eBAO compared to asymptomatic patients. Non-LVAD anatomy (RVAD and CVAD) may represent a novel anatomic risk factor for eBAO. This finding could influence techniques for endovascular thrombectomy.