Electrophysiologic evaluation of local steroid injection in carpal tunnel syndrome.

Extensive sensory and motor nerve conduction studies were performed in a series of patients with electrophysiologically proven, idiopathic carpal tunnel syndrome who were treated by a single steroid injection (40 mg of triamcinolone acetonide). Electrophysiologic studies, which included evaluation of median, ulnar, and radial orthodromic sensory action potentials, median and ulnar motor action potentials, and electromyography of two intrinsic muscles of the hand, were done before and at 45 days and six months after the treatment. By the end of the follow-up period, the symptoms had remitted completely in 11 hands (35%), 18 (58%) benefitted from partial relief, and two did not improve. In addition to the relief of symptoms, abnormalities of motor nerve conduction improved in 65% of cases, and abnormalities of sensory nerve conduction improved in 73% of all the individual digital branches of the median nerve examined. Recovery of function of the median nerve continued for a long period, even after the pharmacologic effect of the steroid agent had presumably ceased.