Diagnostic utility of anteroposterior measurements of the median nerve on sagittal ultrasonographic images and their correlation with clinical findings in carpal tunnel syndrome.

Abstract

To investigate the efficacy of sagittal ultrasonography of the median nerve in diagnosing carpal tunnel syndrome (CTS). Seventy-six hands with idiopathic CTS and 80 hands of asymptomatic subjects were included. All patients with CTS underwent ultrasonographic examination, electrodiagnostic testing, and CTS-6 assessment. In the sagittal ultrasonographic examination, the maximum and minimum median nerve diameters (MNDs) were measured at the proximal and distal ends of the carpal tunnel, respectively. The median nerve stenosis rate (MNSR) was computed as (1 - minimum MND/maximum MND) × 100 (%). The cross-sectional area (CSA) of the median nerve at the level of the pisiform was measured. In the sagittal ultrasonographic examination, the mean maximum MNDs were 0.252 cm and 0.202 cm, mean minimum MNDs were 0.145 cm and 0.165 cm, and mean MNSRs were 41.83% and 17.35% in the CTS and control groups, respectively; the mean maximum MND and MNSR were considerably larger in the CTS group. The maximum MND and MNSR were correlated with the electrodiagnostic testing results and CTS-6 score. The MNSR with a cut-off value of 34.0% had a higher sensitivity and specificity than the CSA in diagnosing CTS. Sagittal ultrasonographic examination is useful in diagnosing CTS.