Background: Carpal tunnel syndrome (CTS) diagnosis has traditionally relied on electrodiagnosis (EDX) to confirm the diagnosis and to assess severity. Ultrasound has shown potential in measuring median nerve cross-sectional area (CSA) for CTS diagnosis, and magnetic resonance imaging (MRI) can be used for wrist soft-tissue evaluation. This study explored the correlation between CTS diagnosis and median nerve CSA measured on MRI at different wrist levels. Methods: A retrospective review of an electronic medical record database identified patients who underwent both wrist MRI and EDX within a 90-day interval between January 2000 and December 2022. Median nerve CSA was measured on axial T2-weighted images at 3 levels: proximal to the carpal tunnel inlet (the distal radioulnar joint DRUJ), the inlet, and the outlet. Continuous variables are presented as means ± standard deviations. A logistic regression model was constructed to evaluate the diagnostic accuracy of median nerve CSA, at the 3 anatomical levels, in identifying CTS. Empirical cut point estimation determined optimal cutoffs and corresponding areas under the receiver operating characteristic curve (AUCs). Results: Sixty-eight patients (76 wrists; mean age, 51.4 ± 14.2 years; male-to-female ratio, 26 to 50; 59 White patients, 8 Hispanic patients, and 1 Asian patient) were included. The mean median nerve CSA in the EDX-negative group compared with the EDX-positive group was 10.6 ± 3.4 versus 11.7 ± 4.0 mm 2 (p = 0.248) at the DRUJ level, 11.1 ± 3.1 versus 14.4 ± 5.1 mm 2 (p = 0.007) at the inlet level, and 9.8 ± 2.4 versus 11.0 ± 5.2 mm 2 (p = 0.833) at the outlet level. The inlet CSA cutoff for CTS was 11.3 mm 2 (AUC = 0.67), with a sensitivity of 74% and a specificity of 60%. Conclusions: MRI-based measurements of median nerve CSA, particularly at the inlet level, suggest that relying solely on CSA measurements may not be an optimal diagnostic strategy for CTS in patients with equivocal clinical symptoms. Even with MRI and highly standardized measurement protocols, only poor-to-fair diagnostic accuracy was achieved. This study raises questions about the diagnosis of CTS based on CSA measurements. Level of Evidence: Diagnostic Level III . See Instructions for Authors for a complete description of levels of evidence.
Liu et al. (Tue,) studied this question.