Morphological and physiological investigation of the neuromuscular junction in the recurrent laryngeal nerve palsy

本研究的目的是阐明喉返神经（RLN）损伤后的错误神经再支配1。观察了豚鼠单侧RLN冻伤后环杓后肌（PCA）运动神经元的变性、再生过程和重组。大多数轴突在3 d内退化，7 d后再生发芽并形成生长锥。2 ~ 6个月时，PCA内运动神经元数量逐渐增加，再生神经元所占面积逐渐扩大。在对照组PCA运动神经元区外发现再生的PCA运动神经元。冻伤后，即使神经突受损但基底膜未受影响，靶特异性再生也不完全。观察猫单侧RLN神经缝合或冻伤后声带运动、喉内肌肌电图及PCA运动神经元的重组。在神经缝合的病例中，受损侧的声带被固定在旁正中位置，即使在9个月后，声带肌和PCA的活动模式也与正常侧不同。在对照组的PCA运动神经元区之外存在许多再生的PCA运动神经元。这些结果提示患侧声带功能障碍是由喉内肌神经再支配方向错误引起的。冻伤患者4个月后声带运动及肌电图恢复正常，在正常PCA运动神经元区外发现少量再生运动神经元。这表明，喉内肌的功能实际上是正常的，虽然有轻微的错误方向的再神经支配发生。

The purpose of this investigation was to clarify misdirected reinnervation after injury of the recurrent laryngeal nerve(RLN).1. Degeneration and regeneration processes, and reorganization of the motoneurons reinnervating the posterior cricoarytenoid muscle(PCA) after freezing injury of the unilateral RLN of the guinea-pig were observed. Most axons degenerated within 3 days and regenerative sprouting with growth cones was observed after 7 days. From between 2 to 6 months, the number of the motoneuron in the PCA gradually increased and the area occupied by regenerated neurons gradually expanded. Regenerated PCA motoneurons were found outside the PCA motoneuron area of the control. Target specific regeneration was incomplete even after freezing injury in which neurites were damaged but the basal lamina was not affected.2. The movement of the vocal fold, electromyogram of the internal laryngeal muscles and reorganization of the PCA motoneurons were observed after neurorrhaphy or freezing injury of the unilateral RLN of the cat. In neurorrhaphy cases, the vocal fold on the damaged side was fixed in the paramedian position and the activity pattern of the vocalis muscle and PCA differed from those of the normal side even after 9 months. Many regenerated PCA motoneurons existed outside the PCA motoneuron area of the control. These results suggested that the dysfunction of the vocal fold in the affected side was caused by misdirected reinnervation in the internal laryngeal muscles. In freezing injury cases, movement of the vocal fold and electromyogram returned to normal after 4 months, and a few regenerated motoneurons were found outside the normal PCA motoneuron area. It is suggested that the functions of the internal laryngeal muscles were practically normal, although a slightly misdirected reinnervation occurred.