Department of Human Anatomy and Embryology I, School of Medicine, Complutense University of Madrid, Madrid, Spain.
Anat Rec (Hoboken). 2014 May;297(5):955-63. doi: 10.1002/ar.22877. Epub 2014 Jan 24.
Changes in motoneurons innervating laryngeal muscles after section and regeneration of the recurrent laryngeal nerve (RLN) are far from being understood. Here, we report the somatotopic changes within the nucleus ambiguus (Amb) after the nerve injury and relates it to the resulting laryngeal fold impairment. The left RLN of each animal was transected and the stumps were glued together using surgical fibrin glue. After several survival periods (1, 2, 4, 8, 12, 16 weeks; at least six rats at each time point) the posterior cricoarytenoid (PCA) and thyroarytenoid (TA) muscles were injected with fluorescent-conjugated cholera toxin and the motility of the vocal folds evaluated. After section and subsequent repair of the RLN, no movement of the vocal folds could be detected at any of the survival times studied and the somatotopy and the number of labeled motoneurons changed. From 4 wpi award, the somatotopy was significantly disorganized, with the PCA motoneurons being located rostrally relative to their normal location. A rostrocaudal overlap between the two pools of motoneurons supplying the PCA and TA muscles was observed from 2 wpi onwards. Hardly any labeled neurons were found in the contralateral Amb in any of the experimental groups. An injury of the RLN leads to a reinnervation of the denervated motor endplates of PCA and TA. However, misdirected axons sprout and regrowth from the proximal stump to the larynx. As a result, misplaced innervation of muscles results in a lack of functional recovery of the laryngeal folds movement following a RLN injury.
喉返神经（RLN）切断和再生后支配喉肌的运动神经元的变化远未被理解。在这里，我们报告了神经损伤后疑核内的体节变化，并将其与导致的声带褶皱损伤相关联。每只动物的左侧 RLN 均被切断，残端用手术纤维蛋白胶粘合并固定。在几个存活期（1、2、4、8、12、16 周；每个时间点至少有 6 只大鼠）后，后环状软骨肌（PCA）和甲状腺环状软骨肌（TA）被荧光标记霍乱毒素注射，评估声带的运动。RLN 切断后再修复，在研究的任何存活时间都无法检测到声带的运动，而且体节和标记运动神经元的数量发生了变化。从 4 周开始，体节明显紊乱，PCA 运动神经元位于正常位置的前方。从 2 周开始，支配 PCA 和 TA 肌肉的两个运动神经元池之间出现了头尾部重叠。在任何实验组中，几乎没有发现任何标记神经元在对侧疑核中。RLN 损伤导致 PCA 和 TA 的失神经运动终板的再支配。然而，错误导向的轴突从近端残端向喉部发芽和再生。因此，运动神经元的错位支配导致 RLN 损伤后声带褶皱运动缺乏功能恢复。
