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

本研究的目的是澄清喉返神经(RLN)损伤后误导的神经再支配。本实验观察了豚鼠一侧RLN冷冻损伤后，支配环鳗后肌(PCA)的运动神经元的退行性变、再生过程及神经元的重组。大部分轴突在3d内变性，7d后可见再生萌发，并有生长锥体。2~6个月后，PCA内运动神经元数量逐渐增多，再生神经元所占面积逐渐扩大。对照组在PCA运动神经元区外可见再生的PCA运动神经元。结论：1.冷冻损伤后，神经突起受损，但基底板未受影响，靶区特异性再生仍不完全。在猫一侧喉返神经吻合或冷冻损伤后，观察声带运动、喉内肌肌电和PCA运动神经元的重组。神经缝合术中，损伤侧声带固定于旁正中位置，术后9个月声带肌和PCA的活动模式与健侧不同。对照组的PCA运动神经元区外有大量再生的PCA运动神经元。这些结果表明，患侧声带功能障碍是由于喉内肌神经支配方向错误所致。冻伤后4个月，声带运动和肌电恢复正常，在正常的PCA运动神经元区外可见少量再生运动神经元。结果表明，喉内肌的功能基本正常，尽管有轻微错位的神经支配。

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.