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. The side of hypoplasia and sex of the patient were recorded. The process was repeated after I month. Descriptive statistics were calculated for prevalence, severity, and sex distribution of hypoplasia. The K statistic was calculated for the reliability of detecting and grading the hypoplasia. Results: Interexaminer reliability was substantial for both readings (kappa = 0.68, 83% agreement for the first reading; kappa = 0.75, 86% agreement for the second reading). Interexaminer reliability for grading the severity of asymmetry was substantial (kappa = 0.73, 83% agreement for the first read; kappa = 0.69, 81% agreement for the second reading). Intraexaminer reliability readings provided a kappa of 0.71 (substantial) and 83% agreement for examiner 1. Examiner 2 had a kappa of 0.85 (almost perfect) with 92% agreement. Overall, 57 (43.5%) of the 131 patients demonstrated hypoplasia. Hypoplasia was more common in women (49%) than men (35.8%). Seven arteries demonstrated severe hypoplasia. Six of these 7 patients were women. Conclusions: Vertebral artery hypoplasia is common and can be reliably diagnosed and categorized on cervical MRI scans. Vertebral artery hypoplasia was more common in women than men in this group of patients. (J Manipulative Physiol Ther 2010;33:207-211)