A single motor unit study of spinal cmd brainstem motor neuron in ALS

通过研究经颅磁刺激对肌萎缩性侧索硬化症（ALS）单运动单元随意激活放电特征的影响，探讨脊髓皮质束变性的病理生理机制。用刺激周时间直方图（PSTH）绘制第一背骨间肌（FDI）运动单元放电的发生，并评价运动神经元的兴奋性。为了进行分析，我们开发了新的计算机程序。接下来，我们用同样的分析方法研究了三叉神经电刺激下面神经核的突触功能障碍。FDI肌pths显示，ALS患者16个运动单位中有6个（38%）出现双原发峰（PPs），而多发性硬化症或脑血管疾病患者16个运动单位中只有2个（13%）出现上运动神经元体征。下运动神经元疾病或无上运动神经元征象的ALS患者均无上述异常。这些结果提示典型的ALS具有慢突触或多突触皮质脊髓神经元异常的超兴奋状态。三叉神经电刺激产生三叉神经-面部反射。正常受试者的PSTH表现为早期短兴奋（P1: 10 msec）和后期分散兴奋（P2: 30 msec），持续时间较长。10例ALS患者的P1峰高度同步，潜伏期正常。提示肌萎缩侧索硬化症面神经核存在异常的高兴奋性。这两项结果提示运动神经元的高兴奋状态是肌萎缩侧索硬化症病理生理的一个重要特征。

The pathophysiology of corticospinal tract degeneration in amyotrophic lateral sclerosis (ALS) was investigated by studying the effect of transcranial magnetic stimulation on discharge characteristics of single motor units during voluntary activation. The occurrence of motor unit discharges from first dorsal interosseus muscle (FDI) was plotted in a peristimulus time histogram (PSTH) and evaluated the excitability of the motor neurons. For the analyses, we developed new computer programs. Next, we investigated the synaptic dysfunction of facial nucleus by trigeminal electrical stimulation using the same analysis method.PSTHs from FDI muscle revealed double primary peaks (PPs) in 6 out of 16 motor units (38%) in ALS with upper motor neuron sign as compared to only 2 out of 16 (13%) motor units in multiple sclerosis or cerebrovascular disease with upper motor neuron sign. None of the patients with lower motor neuron diseases or ALS without upper motor neuron sign had these abnormalities. These findings suggest typical ALS has abnormal hyperexcitable state of slow or polysynaptic corticospinal neurons.Trigeminal electrical stimulation produced trigemino-facial reflex. PSTH of the reflex from normal subjects showed an early short excitation (P1 : 10 msec) and a late dispersed one (P2 : 30 msec) with prolonged duration. That from 10 ALS patients revealed highly synchronized P1 peak with normal latency. These findings indicated facial nucleus of ALS had the abnormal hyperexcitability.Both of these findings suggest that the hyperexcitable state of motoneuron is a cardinal feature in the pathopysiology of ALS.