Does Variation of the Vertebral Artery (VA) Origin Affect Vertebral Artery Dominance? A Retrospective, Single Centre Cohort Study.

INTRODUCTION: The vertebral arteries (VA), usually arising from the subclavian arteries, supply the posterior circulation of the brain. Anatomical variations in VA origin occur in up to 5.8% of cases, most commonly with direct aortic origin of the left VA. As paired vessels, the sizes of VAs are often mismatched, a phenomenon known as VA dominance. This results in unequal haemodynamic stress, which has been associated with increased risks of atherosclerosis, posterior circulation strokes and vertebrobasilar dissection. Despite their recognised clinical significance, limited studies have examined the relationship between VA origin and dominance. To address this gap, we conducted a retrospective study of CT angiography of the head and neck to assess whether variations in VA origin are associated with VA dominance.

METHODS: This study included 287 patients who underwent CT head and neck angiograms at the Princess Alexandra Hospital between 08/09/24 and 09/11/24.

RESULTS: Anatomical origin of the VAs were identified in 264 (92.0%) patients. Aortic origin of the left VA was observed in 22 (7.7%) patients, while a single patient (0.3%) exhibited a right-sided aberrant VA origin. Among patients with anatomical origin of the VA, 42.0% (n = 111) were co-dominant, 39.0% (n = 103) had left VAD and 18.9% (n = 50) had right VAD. In contrast, patients with an aortic origin of the left VA showed a shift towards contralateral dominance, with 59.1% (n = 13) demonstrating right VAD, 31.8% (n = 7) co-dominance, and only 9.1% (n = 2) left VAD. (p < 0.05).

CONCLUSION: Aortic origin of the left VA is strongly correlated with right VA dominance.