Novel model to assess laryngeal function, innervation, and reinnervation.

Objectives: Laryngeal paralysis remains an unsolved problem, and the behavior of the laryngeal muscles following injury to the native innervation appears to be a function of denervation and reinnervation. The aim of the present study was to develop a reliable, accurate, and multifaceted animal model for study of laryngeal function, innervation, and reinnervation. Methods: A spontaneous-breathing anesthesia technique, suspension laryngoscopy, endoscopic evaluation of the rat larynx, and transoral injection of a retrograde neuronal tracer, hydroxystilbamidine (FluoroGold), were developed. We submitted 14 rats to the developed technique to map the brain stem projections of the superior laryngeal nerve and the recurrent laryngeal nerve and to determine the feasibility and accuracy of the endoscopic injection technique. Results: This endoscopic technique provided full evaluation of the rat larynx. We performed transoral endoscopic injection of FluoroGold and transcervical application of the tracer to transected superior laryngeal and recurrent laryngeal nerves in 14 different rats and successfully created a neural projection map for the superior laryngeal nerve, the recurrent laryngeal nerve, and the cervical ganglia. Conclusions: A reliable, accurate model for the characterization of laryngeal function, routes of innervation, and sources of spontaneous reinnervation following recurrent laryngeal nerve resection has been developed. This stable and reproducible model can serve as a dependable tool in future investigations of laryngeal nerve injury and recovery.