Sharma K R, Kent-Braun J A, Majumdar S, Huang Y, Mynhier M, Weiner M W, Miller R G
Department of Neurology, University of California at San Francisco, USA.
Neurology. 1995 Apr;45(4):733-40. doi: 10.1212/wnl.45.4.733.
We investigated the mechanisms of muscle fatigue in ALS. In the muscles of ALS patients and healthy control subjects, we examined (1) fatigue using measurements of muscle force, (2) energy metabolism using phosphorus-31 magnetic resonance spectroscopy, and (3) activation using neurophysiologic measures and MRI. During 25 minutes of intermittent isometric exercise of the tibialis anterior muscle, both maximum voluntary and tetanic force declined more in patients than in controls, indicating greater fatigability in ALS. There was a similar decline of voluntary and tetanic force, suggesting that much of the fatigue was not central. Evoked compound muscle action potential amplitudes were preserved during exercise in both groups, indicating no failure of neuromuscular transmission; this result suggests that the source of fatigue was not at the neuromuscular junction or within the muscle membrane. In spite of greater fatigability, changes during exercise in energy metabolites and proton signal intensity tended to be less in ALS patients compared with controls, suggesting impaired muscular activation. We conclude that the greater muscle fatigue in ALS patients results from activation impairment, due in part to alterations distal to the muscle membrane.
我们研究了肌萎缩侧索硬化症（ALS）中肌肉疲劳的机制。在ALS患者和健康对照者的肌肉中，我们进行了以下检查：（1）通过测量肌肉力量来检测疲劳；（2）使用磷-31磁共振波谱法检测能量代谢；（3）使用神经生理学测量方法和磁共振成像检测激活情况。在胫骨前肌进行25分钟的间歇性等长运动期间，患者的最大自主收缩力和强直收缩力下降幅度均大于对照组，表明ALS患者的疲劳程度更高。自主收缩力和强直收缩力有类似程度的下降，这表明大部分疲劳并非源于中枢。两组在运动期间诱发的复合肌肉动作电位幅度均保持不变，表明神经肌肉传递未出现故障；这一结果表明疲劳的根源不在神经肌肉接头或肌膜内。尽管疲劳程度更高，但与对照组相比，ALS患者在运动期间能量代谢物和质子信号强度的变化往往较小，提示肌肉激活受损。我们得出结论，ALS患者更严重的肌肉疲劳是由激活受损导致的，部分原因是肌膜远端的改变。
