Historical investigations of the functional restoration for recurrent laryngeal nerve paralysis were reviewed and recent studies introduced.
Preliminary experiments are reported in which the Ansa hypoglossi and sternothyroid muscle pedicle were implanted into the denervated posterior cricoarytenoid muscle (abductor), and a new functional combination technique with the selective severance of the abductor branch after neurorrhaphy of the recurrent laryngeal nerve was employed.
The preliminary experiments were carried out on three adults dogs. Under deep intravenously administered anesthesia, the left recurrent laryngeal nerve was transected at the level of the third tracheal ring and each cut end was folded back and tied. After exposing the posterior cricoarytenoid muscle on the left side, the Ansa hypoglossi and sternothyroid mascle pedicle, which was prepared beforehand, was implanted and sutured into the small cut wound of the denervated posterior cricoarytenoid muscle. After three months postoperatively, the abductor on the affected vocal cord was active simultaneously during inspiration and was markingly active during dyspnea in these experimental animals. The results demonstrated that implantation of the Ansa hypoglossi and sternothyroid muscle pedicle into the denervated abductor offer sufficient abductor function.
The new functional combination technique was designed to relieve an inspiratory dyspnea and to maintain a good voice. After 10 months postoperatively, the recovery of satisfactory abductor function during inspiration, dyspnea and deflation of the lung was 67%, and the recovery of satisfactory adductor function during phonation was 89%.
The rapid return of abductor function without special training in all cases suggests that the pedicle nerve muscle grafting technique is the best and that the sternothyroid muscle is available as a substitute for the abductor. The significance of these experimental observations concerning this approach to bilateral vocal cord paralysis is that the operation can be applied to humans quite successfully.