The Yucatan Minipig: A Reliable Model for Studying Unilateral Vocal Fold Paralysis

Objectives/Hypothesis: Given the complex pathology underlying unilateral vocal fold paralysis (UVFP), there has been limited systematic exploration of curative treatments in humans. Central to the investigation of experimental therapies includes establishing a reliable and analogous large animal model. The study goal was to create a standardized porcine model of UVFP by establishing characteristic pathophysiology and functional outcomes. Methods: Four female Yucatan minipigs underwent transection of the right recurrent laryngeal nerve (R-RLN). Measurements of acoustic vocalization data, bilateral nerve conduction studies, and laryngeal adductor pressure (LAP) were obtained prior to transection (baseline) and 7 weeks after transection. Laryngeal adductor muscle complex volume was analyzed via 3D ultrasound. Histological analysis with myofiber diameter measurement of bilateral thyroarytenoid muscles was conducted at study conclusion. Results: Stimulation of the R-RLN 7 weeks after transection demonstrated reduction of motor unit action potentials. In addition, there was a statistically significant reduction in LAP compared to preinjury when stimulating the R-RLN. Voice analysis notably revealed decreased intensity and frequency ranges at 7 weeks postinjury, and statistically lower average intensity and frequency of glottic phonations. Denervated right-sided laryngeal muscle volume was statistically lower compared to noninjured side. Morphological changes consistent with denervation, including smaller myofibril diameters and decreased nerve-to-muscle contact, were observed in right thyroarytenoid muscle and associated neuromuscular junctions. Conclusions: Given that our porcine model yielded histopathological and functional changes consistent with human UVFP, it has potential to serve as a viable model for systematic and controlled studies of potential treatments for UVFP. Level of evidence: NA.