Effects of Nerve-Muscle Pedicle on Immobile Rat Vocal Folds in the Presence of Partial Innervation

Abstract

Objectives: We investigated whether implantation of an ansa cervicalis nerve (ACN)–muscle pedicle into the thyroarytenoid (TA) muscle is efficacious in the presence of partial recurrent laryngeal nerve (RLN) innervation. Methods: We studied a total of 36 rats. Twelve of the rats served as positive and negative control animals. In the remaining 24 rats, the left RLN was transected, a 1-mm piece of nerve was removed, and the stumps were abutted in silicone tubes (STs), inducing partial RLN regeneration. Twelve of the ST-treated rats underwent this procedure alone, and the other 12 rats had a nerve-muscle pedicle (NMP) implanted into the left TA muscle 5 weeks after ST treatment. At 15 weeks, reinnervation was assessed by histologic evaluation of the TA muscle and by electromyography with stimulation of the RLNs and ACNs. Results: The muscle area, the number of nerve terminals, the number of acetylcholine receptors, and the ratio of nerve terminals to acetylcholine receptors were significantly greater (p < 0.05) in the NMP group than in the ST group. Electromyography elicited TA muscle compound action potentials upon stimulation of the RLNs and ACNs. Conclusions: In rats, NMP implantation is efficacious for reducing atrophic changes in the TA muscle in the presence of partial RLN innervation.