Nerve Conduction Study of Electrophysiologically Defined Severe Carpal Tunnel Syndrome Before and After Surgical Release

ABSTRACT

BACKGROUND: A nerve conduction study (NCS) is a useful method to diagnose and evaluate the therapeutic effect of carpal tunnel syndrome (CTS). Severe CTS often shows evidence of axonal injury, which may lead to incomplete recovery of symptoms or NCS abnormalities. To evaluate the degree of NCS recovery after decompression in patients with severe CTS, we studied NCS before and after surgical release in severe CTS with electrophysiological evidence of axonal injury. METHODS: We analyzed the NCS changes in 17 patients (21 hands) with severe CTS just before and 1 year after CTS release. The severe CTS was electrophysiologically defined with the following criteria; 1) prolonged median sensory and motor distal latencies, 2) either an absent SNAP or low amplitude/absent thenar CMAP, and 3) abnormal needle EMG findings. The patients averaged 53.3 years of age and all were females. RESULTS: The mean interval between the first and second NCS was 20.5 months and post-operation symptoms were free in 8 hands, markedly (>50%) improved in 11 hands, and symptoms remained (< 50%) in 2 hands. In 13 hands, SNAPs were not elicitable before surgery, but all were obtainable after surgery. One patient who had no CMAP did not show recovery after surgery. The mean median sensory latency, SNAP amplitude, and sensory NCV over the finger-wrist segment improved significantly (P < 0.05). The mean median motor latency and CMAP amplitude also improved significantly (P < 0.05). The parameters of NCS, however, showed incomplete and subnormal recovery after decompression except for sensory latency, amplitudes of SNAP and CMAP which recovered to the normal range. CONCLUSIONS: After CTS release even with electrophysiologically defined severe CTS patients, there were significant improvements of clinical symptoms and electrophysiological parameters. However, only some parameters(median sensory latency, SNAP amplitude and CMAP amplitude) were restored to the normal range.