Excitability properties at the motor point of the abductor digiti minimi (ADM) muscle were measured using an accelerometer placed on the little finger tip in 31 healthy subjects, and the results were compared with those at the wrist level of the ulnar nerve. ADM motor point stimulation allowed us to demonstrate a significantly shorter strength-duration time constant and smaller threshold changes in deporalizing and hyperpolarizing threshold electrotonus than those at wrist stimulation. At the wrist, hyperpolarizing threshold electrotonus correlated with age (smaller threshold changes), while other excitability indices did not show age-dependent changes at both sites. There were no significant gender differences at these sites. The differences between the wrist and ADM motor point suggest that there are smaller persistent sodium currents and greater inward and outward rectification at the ADM point compared with the wrist. Motor point excitability testing can provide new insights into the pathophysiology of distal motor axons in various peripheral neuropathies and motor disorders.

中文翻译：

---

人类尺神经远端运动轴突的兴奋性

使用放置在 31 名健康受试者小指尖上的加速度计测量小指外展 (ADM) 肌肉运动点的兴奋性特性，并将结果与​​尺神经腕部水平的结果进行比较。与腕部刺激相比，ADM 运动点刺激使我们能够在去极化和超极化阈值electrotonus 中证明明显更短的强度持续时间常数和更小的阈值变化。在腕部，超极化阈值electrotonus 与年龄相关（较小的阈值变化），而其他兴奋性指数在两个部位均未显示年龄依赖性变化。这些站点没有显着的性别差异。腕关节和 ADM 运动点之间的差异表明，与腕关节相比，ADM 点存在更小的持续钠电流和更大的向内和向外整流。运动点兴奋性测试可以为各种周围神经病和运动障碍中远端运动轴突的病理生理学提供新的见解。