Can Ultrasonography of Median Nerve Differentiate between Mild, Moderate and Severe Carpal Tunnel Syndrome? (P5.108)

OBJECTIVE: Determine whether cross sectional area (CSA) of the median nerve at the carpal tunnel inlet, measured by high resolution ultrasonography (US) can differentiate between electrophysiologically defined mild, moderate and severe carpal tunnel syndrome (CTS). Background: Several studies have indicated that CSA of the median nerve at the carpal tunnel inlet measured by US has high sensitivity and specificity for diagnosis of CTS; CSA of more than 0.10 cm2 is generally considered as the criterion. However, there have been questions raised regarding its sensitivity in mild and severe CTS. METHODS: This is a retrospective analysis of patients confirmed to have CTS by electrodiagnostic studies; a simple grading was used to classify CTS into mild (abnormal sensory conduction only), moderate (abnormal sensory and motor conduction) or severe (additional presence of denervation of abductor pollicic brevis). US measurement of CSA of median nerve at distal wrist crease was performed using 18 M Hz probe. RESULTS: 30 Patients with mild CTS showed mean CSA of 0.11cm2 with STD of .019 with sensitivity of 73.3 %. Among 75 patients with moderate CTS, mean CSA was .15 cm2 with STD of .03 and sensitivity of 92% . Among 35 patients with severe CTS mean CSA was .188 cm2 with STD .05. and sensitivity of 100 % CONCLUSIONS: US measurement of CSA of median nerve has high sensitivity in moderate and severe CTS. CSA values of .2 cm2 or more indicate severe CTS (76%). CSA 0f more than .15 cm2 is not seen in mild CTS and indicates moderate or severe CTS.