Association between vertebral artery hypoplasia and vertebral artery aneurysms: A case-control study.

BACKGROUND: The aim of this retrospective case-control study is to determine the association of vertebral artery hypoplasia (VAH) and other anatomical variants with saccular vertebral artery posterior inferior cerebellar artery (VA-PICA) aneurysms.

METHODS: The prevalence of VAH, vertebral artery (VA) atresia, VA aplasia, and PICA aplasia was analyzed using CT angiography in 64 patients with VA-PICA aneurysms (43 ruptured and 21 unruptured) and compared to 128 age- and sex-matched controls. Logistic regression was performed to identify independent risk factors for aneurysm formation.

RESULTS: Univariate analysis showed patients with VA-PICA aneurysms had significantly higher incidence of VAH (53% vs. 17%; odds ratio [OR] 4.8; 95% confidence interval [CI] 2.4-9.4; p < 0.0001) and VA aplasia (14% vs. 1%; OR 20.8; 95% CI 2.5-168.0; p = 0.004) compared with controls. Multivariate analysis identified VAH (odds ratio, 3.6; 95% CI 1.8-7.3; p < 0.0001) as an independent strong risk factor for VA-PICA aneurysm formation. VA-PICA aneurysms are detected significantly more often in the dominant VA, which is contralateral to VAH. Other anatomical variants are not related to aneurysm formation.

CONCLUSIONS: VAH and VA aplasia are potential risk factors for VA-PICA aneurysms. Altered hemodynamics caused VAH may result in intracranial aneurysm formation. Additional research should clarify the pathophysiological association of VAH, VA aplasia, or vascular occlusion with arteriosclerosis and intracranial aneurysm formation.