Best diagnostic criterion in high-resolution ultrasonography for carpal tunnel syndrome

High-resolution ultrasonography (HRUS) has been used to diagnose carpal tunnel syndrome (CTS) in recent years. However, the best diagnostic criterion and optimal cut-off value for HRUS remain controversial.

This study enrolled 37 patients with idiopathic CTS (61 CTS hands) and 20 healthy subjects (40 normal hands). The subjects underwent nerve conduction studies along with HRUS. Several ultrasonographic measurements with good reliability were compared, including the median nerve cross-sectional areas (CSA) at the pisiform and hook of hamate levels; the flattening ratios (FR) at the pisiform, hook of hamate, and distal radioulnar joint levels; retinacular bowing (RB); and the longitudinal compression sign (LCS). Receiver operating characteristic (ROC) curves were plotted for the optimal cut-off values as well as the sensitivity and specificity.

There was a significant increase in the median nerve CSA at the pisiform and hook of hamate levels, RB, and LCS, but the FR was decreased at the hook of hamate level. The ROC curves demonstrated that the median nerve CSA at the pisiform level was most predictive of CTS; the optimal cut-off value was > or = 9.875 mm2, yielding 82% sensitivity and 87.5% specificity.

CTS can be diagnosed by HRUS. The most useful diagnostic criterion is a median nerve CSA of > or = 9.875 mm2 at the pisiform level.