Laryngeal reinnervation

In the past, numerous experiments have been performed to attempt reinnervation of the paralyzed larynx. None have been consistently successful. Two experiments were performed in this study, one to restore abduction of a paralyzed vocal cord and one to restore adduction. To paralyze the vocal cord, the recurrent laryngeal nerve was sectioned in all dogs in both experiments. The first experiment was to restore abduction and was performed as follows. An intralaryngeal dissection was performed to separately identify the abductor and adductor branches of the recurrent laryngeal nerve. The adductor branch was sectioned and ligated. Next the phrenic nerve was identified and sectioned. In the dog, the phrenic nerve will not reach the abductor branch of the recurrent laryngeal nerve, so it was sutured to the main trunk of the recurrent laryngeal nerve. Since the adductor branch was severed, regenerating fibers from the phrenic nerve could only grow into the abductor branch and thus to the posterior cricoarytenoid muscle. This experiment produced excellent return of abduction synchronous with inspiration. The second experiment was to restore adduction and was performed as follows. Intralaryngeal dissection was again done to identify the abductor and adductor branches of the recurrent laryngeal nerve. In addition, the motor branch of the superior laryngeal nerve was identified and transected as it entered the cricothyroid muscle. This branch was then anastomosed to the adductor branch of the recurrent laryngeal nerve. The results of this experiment led to chronic adduction of the vocal cord throughout the respiratory cycle. Suggestions for future research include anastomosis of the ansa cervicalis to the abductor branch of the recurrent laryngeal nerve and anastomosis of the main trunk of the vagus nerve to either the abductor or adductor branches of the recurrent laryngeal nerve.