Investigation of quantitative index for electrophysiology stage in carpal tunnel syndrome

Objective To investigate the quantitative index for the early, middle and late stage in carpal tunnel syndrome (CTS)electromyographically, and to provide the basis for determination of clinical stage. Methods Seventy-four cases in 120 sides with clinical diagnosis of CTS were involved in the study. The electromyography (EMG) in the abductor pollicis brevis,the disal motor latancy(DML) in the median nerve the sensory nerve action potential (SNAP) in the thumb, index and middle finger, the difference of SNAP in the median and ulnar nerve in the ring finger, and its sensory nerve conduction velocity were detected. Then the results were analyzed. Results At the early stage, negative EMG result was found, with the number in DML less than 4.5ms. The amplitude difference of SNAP in the median and ulnar nerve in the ring finger was abnormal(no less than 0.4ms). Of the thumb, index and middle finger, the amplitude in more than 1 finger decreased more than half when compared with that in the contralateral side. At the middle stage, the results of EMG were either positive or negative. The number in DML was no less than 4.5ms. The sensory potential in the 1-3 finger can be detected, but the conduction velocity was decreased(40.0ms). At the late stage, the result in EMG was positive. The DML was markedly lengthened or disappeared. Of 1-4 finger, the sensory potential at least in 1 finger disappeared. Conclusion The staging index between the early and middle stage in CTS is DML, and that between the middle and late stage is whether there is motor or sensation potential.