Flexor carpi radialis motoneuron pool in subjects with chronic carpal tunnel syndrome are more excitable than matched control subjects.

We compared excitability of the flexor carpi radialis (FCR) motoneuron pool in subjects with and without carpal tunnel syndrome (CTS). The study involved 11 subjects with chronic idiopathic CTS and 11 asymptomatic subjects as controls. The H-reflex and M-response of FCR muscle were obtained by stimulating the median nerve in the cubital fossa in the presence of an isometric background contraction using surface stimulating and recording electrodes. There was a significantly higher H-reflex latency and amplitude and Hmax/Mmax in CTS subjects (P<0.05). Latency and amplitude of the M-response remained unaffected in CTS group. The results support the hypothesis that central hypersensitivity does occur in chronic CTS. Therefore even in the presence of pathology in peripheral structures central mechanisms should be considered by clinicians.