Influence of Vertebral Artery Dominance on Basilar Artery Occlusions

Introduction: Basilar artery occlusions (BAO) are severe posterior circulation strokes with high morbidity. They can arise from multiple mechanisms, including in-situ atherosclerosis, dissection, or cardiogenic embolism. While treatments depend on the underlying cause, advancements such as endovascular treatment (EVT) for embolic occlusions have significantly improved outcomes. However, factors predisposing patients for BAO, including anatomical variance, remain understudied.

Methods: A single-center retrospective study analyzed patients with primary BAO treated with EVT between 2016 and 2023. Patients were excluded if they experienced prior documented BAO. Clinical and radiological data was reviewed for pre-occlusion factors and anatomical variations. Incidence of vertebral artery dominance (VAD) was compared against the general population with Chi-square. Multinomial logistic regression analysis was conducted to assess the association of VAD and aortic arch type with occlusion location and vertebral artery (VA) dissection, controlling for occlusion mechanism.

Results: Of the 110 patients with BAO (age 67.5+/-16.3 years; 64.5% male), 64.5% of patients had occlusions of embolic origin, 22.7% of atherosclerotic/stenotic origin, and 12.7% of undefined origin. Sixteen (14.5%) patients had VA dissections. Patients with BAO demonstrated significantly higher rates of right VAD (28.2% vs 22.4%) and codominant VAs (45.4% vs. 31.1%) compared to the general population (p < 0.001). Aortic arch variance was noted in 15 cases (12 bovine arch, 2 aberrant left vertebral arteries, 1 aberrant right subclavian artery). On multivariate analysis, left VAD was significantly associated with vertebral artery dissection (p=0.036).

Conclusion : Patients with right VAD or VA codominance may have a greater risk of BAO. Assessing anatomical and morphological variance may be relevant to identifying at-risk patients.