Median nerve ultrasound as a screening tool in carpal tunnel syndrome: correlation of cross-sectional area measures with electrodiagnostic abnormality.

INTRODUCTION

Sonographically measured median nerve cross-sectional area (CSA) at the wrist is increased in patients with carpal tunnel syndrome (CTS). Ultrasound of the median nerve may be useful in screening for electrodiagnostic (EDx) abnormalities.

METHODS

EDx studies were performed on all participants. Sonographic evaluation of median nerve CSA at the wrist and in the forearm was performed by a physician blinded to the EDx results. Multivariate and receiver operating characteristic (ROC) analysis were used to assess the data.

RESULTS

Fifty control wrists and 192 symptomatic wrists were analyzed. Sensitivity of ultrasound in excluding EDx abnormality was 99% for CSA of 9 mm(2) and 97% for a wrist-forearm ratio (WFR) of 1.4. There was no clinically significant correlation between ultrasound parameters and EDx severity.

CONCLUSIONS

Median nerve ultrasound is a highly sensitive screening tool for EDx abnormality, but it cannot determine severity. This may lead to changes in the current standards for evaluating CTS.