Effects of carpal tunnel syndrome on intrinsic muscle electromyograms during precision grip

The purpose of this study is to investigate the effects of carpal tunnel syndrome on hand intrinsic muscle activities using surface electromyogram (sEMG) during precision grip. Six CTS patients and six age- and gender-matched healthy volunteers participated in the experiment. The subjects were instructed to stably grip an instrumented apparatus with their thumb and index finger for 80 s. The sEMG signals were recorded from the abductor pollicis brevis (APB) and first dorsal interosseous (FDI). Visual feedback was provided for the first 20-40 s and removed for the remaining 50-70 s during the precision grip. Results showed that the root mean squares (RMS) of sEMG in CTS significantly increased after removing visual feedback. In contrast of the controls, the CTS led to an increase in the RMS without visual feedback. And the median frequency (MF) was lower than the healthy in APB but higher in the left hand FDI on both feedback conditions. However, CTS did not affect the coherence of the two intrinsic muscles- the APB and FDI. There was a weak coherence in both the CTS and control groups. This study revealed that the sensorimotor deficits associated with CTS could alter the intrinsic muscle activities for precision grip.