Carpal tunnel syndrome as an expression of muscular dysfunction in the neck.

Carpal tunnel syndrome (CTS) may be a consequence of increased forearm flexor activity secondary to muscle dysfunction in the neck. Eighteen CTS patients, with an average duration of symptoms of 10 months, were studied. Standardized nerve-conduction studies were administered before and after treatment. Surface-EMG techniques measured sternomastoid and cervical paraspinal muscle activity and flexor and extensor muscle activity during head movement. Both sets of neck muscles were found to be asymmetrical when compared side to side. Reduction of the sternomastoid asymmetry decreased forearm flexor EMG activity. Significant decreases in all nerve conduction measures were noted for every subject. Over half reported a loss of symptoms with post hoc analysis suggesting this may be related to the sternomastoid median frequency. It is suggested that increased flexor and/or extensor motor activity is an expression of dysfunctional sternomastoid activity. Possible mechanisms of dysfunction including the tonic neck reflex are discussed.