Utility of the cutaneous silent period in the evaluation of carpal tunnel syndrome

Objective: This study investigates the utility of the cutaneous silent period (CuSP) in evaluating patients with carpal tunnel syndrome (CTS). Methods: The authors measured the CuSP from the abductor pollicis brevis muscle in 135 hands of patients with idiopathic CTS and 30 hands of age- and gender-matched controls. The patient group was further divided into subgroups according to the Canterbury scale. The differences in parameters between the patient subgroups and control group were analysed. A predetermined analysis looked at the possible correlation between the CuSP and symptom severity as measured by the Boston-Questionnaire. Results: The mean CuSP latencies in the patient group (72.4 ± 16.1. ms) was significantly longer than the control group (64.6 ± 13.4. ms; P=0.014), although there was no difference in the duration of the CuSP between groups. The duration and latency of the CuSP correlated to a higher severity on the Canterbury scale (r=0.273, P<0.001 and r=-0.164, P=0.036, respectively). However, the CuSP parameters did not correlate with the Boston-Questionnaire scores. Conclusions: Although patients with CTS had significantly prolonged CuSP latency, the CuSP did not correlate with the clinical symptoms scale. Significance: The CuSP is a useful ancillary test to evaluate Aδ fibre function; however, it is not a reliable tool to quantify clinical severity.