Chang Ming-Hong, Lee Yee-Chung, Hsieh Peiyuan F
Section of Neurology, Taichung Veterans General Hospital, Taichung, Taiwan.
J Clin Neurophysiol. 2008 Dec;25(6):373-7. doi: 10.1097/WNP.0b013e31818e7930.
The decrease of forearm median motor conduction velocity (CV) in carpal tunnel syndrome (CTS) is a common electrodiagnostic finding in clinical practice and is possibly secondary to either conduction block at wrist or retrograde conduction slowing (RCS). This study is attempted to confirm the existence of RCS and to explore why this controversy occurs for a long time. Eighty CTS patients and controls were recruited. In addition to conventional electrodiagnosis, subjects received further electrodiagnostic protocol. First, a recording electrode was placed over the wrist and then at elbow with palm stimulation to calculate indirect forearm mixed nerve CV (forearm-mix CV) that represented real measurement of nerve fibers through the carpal tunnel. Then, direct measurement of forearm-mix CV was performed with recording at the elbow and stimulation at the wrist. CTS patients had markedly prolonged distal motor and sensory latencies and significantly prolonged wrist-palm sensory and motor conduction. There was a significant decrease in forearm median motor CV; however, there was no difference in ulnar distal motor latency and forearm motor CV. The mild decrease of forearm median motor CV was not proportional to the marked reduction of W-P MCV and there was no demonstrated conduction block at wrist, implying the reduction of forearm median motor CV is unlikely due to conduction blockage or slowing of the large myelinating fibers at the wrist and RCS really occurs over the forearm median nerve. In addition, the direct Forearm-mix CV was similar in CTS and controls; however, there was a significant decrease in indirect forearm-mix CV only in the CTS. Moreover, the difference between direct and indirect forearm-mix CV was significantly greater and poor consistency of direct and indirect forearm-mix CV in CTS, suggesting that direct and indirect forearm-mix CV represent CV from quite different nerve fibers. Therefore, we conclude that RCS really does occur in CTS and the direct forearm-mix CV reflects the CV of nerve fibers without damage in CTS. The misinterpretation and measurement of different components of forearm-mix CV results in the existence of this controversy till now.
腕管综合征（CTS）患者前臂正中神经运动传导速度（CV）降低是临床实践中常见的电诊断结果，可能继发于腕部传导阻滞或逆行传导减慢（RCS）。本研究旨在证实RCS的存在，并探讨这一争议长期存在的原因。招募了80例CTS患者和对照组。除了常规电诊断外，受试者还接受了进一步的电诊断方案。首先，将记录电极置于腕部上方，然后置于肘部，进行手掌刺激，以计算间接前臂混合神经CV（前臂混合CV），该值代表通过腕管的神经纤维的实际测量值。然后，在肘部记录，腕部刺激，直接测量前臂混合CV。CTS患者的远端运动和感觉潜伏期明显延长，腕部至手掌的感觉和运动传导明显延长。前臂正中运动CV显著降低；然而，尺神经远端运动潜伏期和前臂运动CV没有差异。前臂正中运动CV的轻度降低与腕部至手掌运动CV的显著降低不成比例，且腕部未显示传导阻滞，这意味着前臂正中运动CV的降低不太可能是由于腕部大髓鞘纤维的传导阻滞或减慢，RCS确实发生在前臂正中神经上。此外，CTS患者和对照组的直接前臂混合CV相似；然而，仅CTS患者的间接前臂混合CV显著降低。此外，CTS患者直接和间接前臂混合CV之间的差异显著更大，且直接和间接前臂混合CV的一致性较差，这表明直接和间接前臂混合CV代表来自截然不同神经纤维的CV。因此，我们得出结论，RCS确实发生在CTS中，直接前臂混合CV反映了CTS中未受损神经纤维的CV。前臂混合CV不同成分的错误解读和测量导致了这一争议至今仍然存在。
