R426 – Muscle-Nerve-Muscle Neurotization of the Rat Larynx

Abstract

Problem The ability to reliably restore physiologic movement to a paralyzed vocal fold is not yet in hand. Muscle-nerve-muscle (M-N-M) neurotization is a process whereby axons sprouting from within an innervated muscle are directed toward a denervated muscle via a neural conduit. Given the paired laryngeal musculature, M-N-M neurotization holds promise for restoring physiologic vocal fold movement in cases of unilateral paralysis. This study is aimed at exploring the effectiveness of M-N-M neurotization in a rat model. Methods Twelve Sprague-Dawley rats were divided equally into Control and M-N-M groups. The left recurrent laryngeal nerve was transected in both groups, and in the M-N-M group a nerve graft was interposed between the innervated right thyroarytenoid (TA) muscle and the denervated left TA muscle via bilateral laryngeal windows. Vocal fold mobility was serially documented pre- and post-operatively by video-assisted endoscopy. The rats will be sacrificed at 6 weeks and immunohistochemistry used to quantify percent nerve-motor endplate contact in the left TA muscles. Myelinated axons per cross-section of the nerve graft will be counted. Results The initial surgical and endoscopic procedures were successful in all rats. Immunohistochemical data, endoscopic findings, and axon counts in the M-N-M grafts will be presented as measures of reinnervation, with comparisons between groups for percent nerve-motor endplate contact and endoscopy data. Conclusion M-N-M grafts can be performed in a rat laryngeal model and the degree of successful neurotization can be determined by this analysis paradigm. Significance This study contributes new data toward the eventual goal of restoring movement to the paralyzed vocal fold. Support This project is supported by the University of Michigan's Program for Neurology Research and Discovery and the Department of Otolaryngology - Head and Neck Surgery.