The usefulness of ultrasonography to diagnose the early stage of carpal tunnel syndrome in proximal to the carpal tunnel inlet: A prospective study

This study aimed to investigate the relationship between the change of median nerve cross-sectional area (CSA) and the severity of carpal tunnel syndrome (CTS) determined by electrodiagnostic study based on the area immediately proximal to the carpal tunnel inlet (IPCTI). From December 2016 to August 2017, 34 patients (8 men and 26 women; mean age, 61.68 years ± 11.83; range, 28–80 years) with CTS symptoms were recruited. Electrodiagnostic study was performed in all patients to categorize the severity of CTS according to Bland classification. The CSA of median nerve and carpal tunnel at IPCTI, and carpal tunnel inlet/outlet level was measured by one physician. The Kruskal-Wallis test was used for comparing the CSA of the median nerve and carpal tunnel among CTS severity groups divided by electrodiagnostic study. The Dunn procedure was used for post-hoc comparison. At IPCTI and the carpal tunnel inlet level, the CSA of the median nerve was statistically larger depending on the severity of CTS (P < .01, P < .01). In the post-hoc comparison, only the CSA measured at the IPCTI level could differentiate normal reference values from mild CTS indicating the early stage (P < .05). Measuring the CSA of median nerve in IPCTI level is the most sensitive method to diagnose the early stage CTS.