Yamamoto Daisuke, Imai Tomihiro, Tsuda Emiko, Hozuki Takayoshi, Yamauchi Rika, Hisahara Shin, Kawamata Jun, Shimohama Shun
Department of Neurology, Sapporo Medical University School of Medicine, Sapporo, Japan.
Department of Occupational Therapy, Sapporo Medical University School of Health Sciences, Sapporo, Japan.
Clin Neurophysiol. 2016 Feb;127(2):1689-1693. doi: 10.1016/j.clinph.2015.10.037. Epub 2015 Oct 23.
The aim of this study was to evaluate post-tetanic potentiation of muscle twitch in myasthenia gravis (MG).
Post-tetanic potentiation was evaluated by recording the compound muscle action potential (CMAP) of abductor pollicis brevis and movement-related potential (MRP) of the thumb using an accelerometer after tetanic stimulation of the median nerve at the wrist. After baseline recording, tetanic stimulation was delivered to the median nerve at a frequency of 10 Hz for 10s. The CMAP and MRP were successively recorded at baseline and at 5, 10, 30, 60, 90 and 120 s after tetanic stimulation. The chronological changes of CMAPs and MRPs were recorded bilaterally in 11 patients with MG, 9 patients with myopathies (disease controls), and 25 healthy control subjects.
Maximal acceleration of MRP was significantly elevated during 10s after tetanic stimulation without any CMAP changes in all groups. However, statistical analysis detected a significant decrease in post-tetanic potentiation of maximal acceleration of MRP in MG patients only compared to healthy controls, but not in myopathy patients, which may imply impairment of excitation-contraction coupling in MG.
Post-tetanic potentiation of muscle twitch is significantly diminished in MG, suggesting impaired excitation-contraction coupling.
Measurement of post-tetanic potentiation using an accelerometer is a simple and sensitive method to detect impairment of excitation-contraction coupling in MG.
本研究旨在评估重症肌无力（MG）患者肌肉抽搐的强直后增强效应。
通过在腕部对正中神经进行强直刺激后，使用加速度计记录拇短展肌的复合肌肉动作电位（CMAP）和拇指的运动相关电位（MRP），来评估强直后增强效应。在进行基线记录后，以10Hz的频率对正中神经进行10秒的强直刺激。在强直刺激前的基线以及刺激后的5、10、30、60、90和120秒依次记录CMAP和MRP。对11例MG患者、9例肌病患者（疾病对照组）和25名健康对照者双侧记录CMAP和MRP随时间的变化情况。
在所有组中，强直刺激后的10秒内MRP的最大加速度显著升高，而CMAP无任何变化。然而，统计分析发现，仅MG患者与健康对照相比，MRP最大加速度的强直后增强效应显著降低，而肌病患者则无此现象，这可能意味着MG患者存在兴奋 - 收缩偶联功能障碍。
MG患者肌肉抽搐的强直后增强效应显著减弱，提示兴奋 - 收缩偶联功能受损。
使用加速度计测量强直后增强效应是一种检测MG患者兴奋 - 收缩偶联功能障碍的简单且敏感的方法。
