Magnetic Resonance Imaging–Measured Cross-Sectional Area of the Median Nerve

PURPOSE: The size of the median nerve may serve as a useful parameter to predict carpal tunnel syndrome (CTS) in a subset of patients. The purpose of this study was to evaluate magnetic resonance imaging–based measurements of median nerve cross-sectional area (CSA) to examine trends between patient subgroups and CSA that may assist in predicting the individuals who are most likely to develop CTS symptoms. METHODS: A retrospective chart review of 1,273 wrist magnetic resonance images was performed, and the images were analyzed to evaluate the median nerve CSA at the level of the pisiform and the hook of hamate. The age, sex, height, weight, and body mass index (BMI) of the patients were collected from their medical records. RESULTS: The median nerve size correlated with patient BMI. Additionally, patients with CTS had larger median nerves at the hook of hamate and pisiform than those without CTS. When subdividing patients on the basis of BMI, obese patients with CTS had larger median nerve CSA at the pisiform than those without CTS. CONCLUSIONS: This study demonstrated that increased BMI is associated with increased median nerve CSA at the hook of hamate and pisiform in patients with or without CTS. Additionally, patients with CTS had larger median nerve CSA than those without CTS. Measurements at these locations may help predict individuals who are likely to experience median nerve impingement. TYPE OF STUDY/LEVEL OF EVIDENCE: Prognostic III.