Efficacy of Diagnosing Carpal Tunnel Syndrome Using the Median Nerve Stenosis Rate Measured on Ultrasonographic Sagittal Imagery: Clinical Case-Control Study

BACKGROUND: The purpose of the present study was to evaluate the usefulness of the median nerve stenosis rate (MNSR) measured on sagittal sonographic images of the median nerve in the diagnosis of carpal tunnel syndrome (CTS). METHODS: The study population consisted of 45 hands from 37 patients with idiopathic CTS (CTS group), and 60 hands from 35 asymptomatic healthy subjects (control group). Carpal tunnel syndrome was diagnosed by clinical findings and positive electrophysiological study results. All patients and control subjects underwent ultrasonographic examination. At the carpal tunnel level, the transducer was placed longitudinally to the median nerve, and an image of the longitudinal median nerve was obtained. The minimum median nerve diameter (MND) was measured at the middle part of the capitate level, while the maximum MND was measured at the distal radioulnar joint level. The MNSR was calculated as (1 – minimum MND/maximum MND) × 100 (%). The cross-sectional area of the median nerve was also measured at the level of the pisiform. RESULTS: On longitudinal sonographic images, the MNSR was significantly larger in the CTS group than the control group. When the cut-off value of the MNSR was 26.73%, the sensitivity and specificity were 91.1% and 80%, respectively. The area under the receiver operating characteristic curve was larger for the MNSR than for the cross-sectional area. CONCLUSION: The results suggest that the MNSR proposed in the present study may be useful as an auxiliary method for CTS diagnosis on ultrasonographic examination.