Chang Ming-Hong, Liu Lu-Han, Lee Yi-Chung, Hsieh Peiyuan F
Section of Neurology, Taichung Veterans General Hospital, Taichung, and Department of Neurology, Chung-Shan Medical University, Taichung, Taiwan.
J Clin Neurophysiol. 2008 Jun;25(3):161-6. doi: 10.1097/WNP.0b013e3181775981.
The objective of this study was to determine the cause of median forearm motor conduction velocity (FMCV) slowing in patients with carpal tunnel syndrome, due to either focal conduction abnormality over wrist or retrograde conduction slowing, and to decide whether the slowing is related to severity of compression or not. Fifty carpal tunnel syndrome patients confirmed by conventional nerve conduction study with abnormal electromyography of the abductor pollicis brevis muscle were group 1, and 100 with normal electromyography, group 2. One hundred volunteers served as controls. In addition to conventional nerve conduction study of median and ulnar nerves, palmar stimulations for median mixed and motor nerves were also performed to calculate wrist-palm mixed nerve conduction time and motor conduction velocity (W-P MCV). For group 1, group 2, and control subjects, respectively, W-P MCV were 19.73+/-7.65 (mean+/-SD), 32.7+/-6.83, and 52.75+/-6.4 m/s, whereas median FMCV were 48.63+/-8.32, 54.42+/-2.11, and 57.86+/-4.24 m/s. There was a significant reduction in the W-P MCV (62.6%, P<0.00001) and a decrease in the median FMCV (15.95%, P<0.00001) in group 1, and 38% reduction in W-P MCV (P<0.00001) and 5.9% decrease in median FMCV (P<0.00001) in group 2 when compared with controls, but ulnar FMCV and sensory nerve conduction study results did not, suggesting the reduction of median W-P MCV is not parallel with that of median FMCV in both patients groups. Furthermore, there is a poor correlation of median FMCV and W-P MCV in patient groups, implying conduction blockage of the large myelinating fibers at the wrist, leaving only slower axons to be measured, is not the likely cause of reduction of FMCV. In addition, the reduction of compound muscle action potential amplitude of abductor pollicis brevis muscle, conduction block at wrist and weak correlation of median FMCV and compound muscle action potential amplitude of abductor pollicis brevis exclusively occurred in group 1. Therefore, the retrograde conduction slowing really occurs among patients with carpal tunnel syndrome-markedly in those with abnormal electromyography and mildly in those with only demyelination. This finding counters conventional wisdom that nerve function changes only in segments distal to injured sites.
本研究的目的是确定腕管综合征患者前臂正中运动传导速度（FMCV）减慢的原因，是由于腕部局灶性传导异常还是逆行传导减慢，并确定这种减慢是否与压迫的严重程度相关。通过常规神经传导研究及拇短展肌肌电图异常确诊的50例腕管综合征患者为第1组，100例肌电图正常的患者为第2组。100名志愿者作为对照。除了对正中神经和尺神经进行常规神经传导研究外，还对正中混合神经和运动神经进行掌部刺激，以计算腕-掌混合神经传导时间和运动传导速度（W-P MCV）。第1组、第2组和对照组的W-P MCV分别为19.73±7.65（均值±标准差）、32.7±6.83和52.75±6.4 m/s，而正中FMCV分别为48.63±8.32、54.42±2.11和57.86±4.24 m/s。与对照组相比，第1组的W-P MCV显著降低（62.6%，P<0.00001），正中FMCV降低（15.95%，P<0.00001）；第2组的W-P MCV降低38%（P<0.00001），正中FMCV降低5.9%（P<0.00001），但尺神经FMCV和感觉神经传导研究结果无变化，这表明两组患者正中W-P MCV的降低与正中FMCV的降低不平行。此外，患者组正中FMCV与W-P MCV的相关性较差，这意味着腕部大髓鞘纤维的传导阻滞，仅留下较慢的轴突可供测量，不太可能是FMCV降低的原因。此外，拇短展肌复合肌肉动作电位幅度的降低、腕部传导阻滞以及正中FMCV与拇短展肌复合肌肉动作电位幅度的弱相关性仅在第1组中出现。因此，逆行传导减慢确实发生在腕管综合征患者中——在肌电图异常的患者中明显，在仅有脱髓鞘的患者中轻微。这一发现与传统观点相反，即神经功能仅在损伤部位远端的节段发生变化。
