Sonography in carpal tunnel syndrome with normal nerve conduction studies.

INTRODUCTION

We assessed the yield of high-resolution ultrasonography (HRUS) in patients with clinically definite carpal tunnel syndrome (CTS) and normal nerve conduction studies (NCS).

METHODS

This blinded, prospective, cross-sectional study involved 35 patients (60 hands) with clinically definite CTS and normal NCS, and 20 controls (40 hands). Cross-sectional area (CSAs) of the median nerve at the level of the pisiform bone and flexor retinaculum thickness (FRT) were measured.

RESULTS

CSA was abnormal in 48.6% of patients (confidence interval 32.0-65.2%, P = 0.95). FRT was increased in only 34.3% (18.3-49.7%), but was independently abnormal in 2 patients. CSA abnormalities correlated with positive provocative tests and sensory loss. The HRUS changes were mild.

CONCLUSIONS

HRUS confirms clinically diagnosed CTS in about half of the patients with normal NCS.