Surface EMG signal alterations in Carpal Tunnel syndrome: a pilot study.

Carpal Tunnel syndrome (CTS) is one of the most common compartmental syndromes and nerve conduction studies are widely considered as the standard to diagnose the pathology. The purpose of this pilot study was to investigate whether multichannel surface electromyography can detect muscle alterations in patients diagnosed with severe CTS. Surface EMG signals were recorded at 10, 20, 30, and 80% MVC from the flexor and abductor pollicis brevis muscles of five patients with CTS and five control subjects. Subjects with severe CTS showed different interference patterns, lower signal amplitude, lower neuromuscular efficiency, and lower myoelectric manifestations of fatigue with respect to the control group. At submaximal levels, action potentials recorded from the flexor and abductor pollicis brevis muscles of the CTS group were characterized by lower conduction velocity and lower mean spectral frequency than the healthy group. These findings support, among others, the hypothesis of a selective loss of fast motor units (type II fiber) associated with CTS.