Relationship between Vertebral Artery Hypoplasia and Posterior Circulation Ischemia.

Vertebral artery hypoplasia (VAH) is a common congenital anatomical variation. In previous reports, it was unclear whether VAH was an independent risk factor for posterior circulation ischemia. The purpose of this study was to evaluate the impact of VAH on posterior circulation ischemia.Subjects were patients with acute ischemic stroke who underwent brain magnetic resonance imaging (MRI) and carotid ultrasonography. Diagnostic criteria for VAH were as follows: (1) Vertebral artery (VA) diameter less than 2.5 mm; (2) VA diameter less than 3.0 mm and a difference in length equal to or greater than 1:1.7; (3) VA diameter less than 3.0 mm, peak systolic velocity less than 40 cm/second, and resistance index value greater than .75. The patients were categorized by the location of the ischemic stroke on MRI as follows: lesion in posterior circulation (P group), lesion in anterior circulation (A group), and multiple lesions in both the anterior and posterior circulations (AP group).We evaluated 129 consecutive patients. VAH was seen in 39, and VA occlusion was found in 15. The prevalence of VAH in the P group (44.4%) was significantly higher than that in the A + AP group (24.7%, P = .034). Multivariate regression analysis showed that large-artery atherosclerosis (odds ratio, 6.3; 95% confidence interval [CI], 1.3-30.1), posterior circulation ischemia (odds ratio, 12.0; 95% CI, 2.8-51.2), and VAH (odds ratio, 4.2; 95% CI, 1.2-15.0) were independent factors related to VA occlusion.VAH was an independent factor related to VA occlusion. Therefore, VAH likely plays a role in posterior circulation ischemia.