喉頭の神経支配に関する研究

第2編 神経切除の声帯筋に及ぼす影響

抄録

Experiments was conducted with 35 grown-up
dogs to resect the superior and inferior laryngeal
nerves on one side, and observations was made for a long period on the figure of the vocal cords. At the same time, histological changes in the intrinsic laryngeal muscles of the animals was thoroughly investigated, and the following conclusions were made.
1. From the experiments in resection in vari- ous parts of the main recurrent nerve, it was lear- ned that, in the various parts resected, no differe- nce was observed in the figure of the vocal cords after the resection. No change was noticed for six months in the position of the vocal cord on the side where the nerve was resected, and remained at all times in the paramedian position. Nor any movement was perceived in the vocal cord or in the arytenoid cartilage.
2. As a histological change in the intrinsic laryngeal muscles of a dog more than three weeks after the resection of the recurrent nerve on one side, very conspicuous atrophy was observed in the thyro-arytenoid muscle on the resected side. The fact has been recognized that the degree of atrophy declined in the order of the posterior crico-aryten- oid muscle, and then the lateral cricoarytenoid muscle. No atrophy was noted in the anterior cricothyroid muscle, while slight atrophy appeared in the traverse part of the arytenoid muscle, not only on the resected side, but also on the side which was not resected.
3. In cases where more than three months had elapsed since the resection of the main recur- rent nerve on one side, a compensatory movement on the normal side of the vocal cord was observed.
4. In a dog whose anterior branch of the recurrent nerve on one side had been resected, the vocal cord on the resected side had taken the par- amedian position at the time of respiration. Ant- erior two-thirds of the glottis were opened spindle- shaped at the time of phonation, showing the form of the vocal cord similar to the clinically so-called "internusparesis" Histologically, atrophy has been observed only in the thyro-arytenoid muscle.
5. In a dog whose inter-mediate branch of the recurrent nerve on one side was resected, the vocal cord on the resected side had taken the paramedian position at the time of respiration. Posterior one- third of the glottis on the resected side did not closed at the time of phonation, showing the form of the vocal cord similar to the clinically so-called
" transversusparesis"Histologically, conspicuous atrophy was seen in the posterior crico-arytenoid muscle alone. Hence, in the case of dogs, this form of vocal cords is considered to be the real "post icusparesis"
6. In a dog whose posterior branch of the recurrent nerve was resected on one side, no intri- nsic laryngeal muscle had showed atrophy. At the time of respiration, the vocal cord on the resected side was situated in the paramedian position, and higher than the opposite side, and therfore appeared to be shorter. So the vocal cord on the normal side looked slackened and paralyzed. At the time of phonation, both vocal cords closed together alm- ost at the median line.
7. In the experiments of resection of both the internal and external branches of the superior lar- yngeal nerve, both vocal cords closed together, at the time of phonation, almost at the median line, and the movement of the arytenoid cartilage was normal. At the time of respiration, however, in the case of resection of the internal branch, slack- ening of the vocal cord on the normal side and of the slowness of movement was observed. In the case of resection of the external branch, slackening of the vocal cord on the resected side and of the movement was seen. Histologically, conspicuous atrophy was observed by the resection of the ext- ernal branch in the anterior crico-thyroid muscle.