Ultrasonography in severe carpal tunnel syndrome

INTRODUCTION: In up to 30% of patients with carpal tunnel syndrome (CTS), the cross-sectional area (CSA) of the median nerve may not be enlarged. We hypothesize that this could be the result of secondary atrophy of the nerve in severe CTS. The aim of this study was to measure the ultrasonographic CSA of the median nerve at the wrist in patients with severe CTS. METHODS: In 14 consecutive patients with clinically and electrophysiologically defined severe CTS, the CSA of the median nerve was measured and compared with that of control subjects. RESULTS: CSA of the median nerve exceeded the upper limit of normal in the majority of patients with severe CTS. CONCLUSIONS: Atrophy of the median nerve in severe CTS does not explain negative ultrasonographic test results. Instead, the CSA of the median nerve is enlarged in most patients with severe CTS.