Vertebral artery hypoplasia: prevalence and reliability of identifying and grading its severity on magnetic resonance imaging scans.

Objective: The purpose of this study is to examine the inter- and intraexaminer reliability of determining the prevalence of vertebral artery hypoplasia on magnetic resonance imaging (MRI) as well as the reliability of assigning a severity grading of mild, moderate, or marked hypoplasia.

Methods: Two chiropractic radiologists independently evaluated the MR images of 131 adult patients retrospectively for visual vertebral artery hypoplasia. Severity of hypoplastic was graded.