Synchronous Regeneration: Key Mechanism for Selective Reinnervation in Bilateral Vocal Fold Paralysis

This study investigates the mechanisms underlying the success of the present selective laryngeal reinnervation technique in bilateral vocal fold paralysis, providing a foundation for future clinical applications.

Seven healthy Beagle dogs underwent selective reinnervation of the left recurrent laryngeal nerve (RLN): the adductor branch was reinnervated with the thyrohyoid branch of the hypoglossal nerve, and the abductor branch with the phrenic nerve root. Preoperative evaluations included laryngoscopy and laryngeal electromyography (LEMG). Postoperative assessments were performed immediately, at 6 weeks, and biweekly until motor unit potentials (MUPs) were detected, up to 24 weeks. Two dogs were euthanized after MUPs were first observed in the posterior cricoarytenoid (PCA) and thyroarytenoid (TA) muscles for double labeling of synaptophysin and acetylcholine receptors (AChR). The remaining five were followed until 24 weeks.

Preoperatively, laryngoscopy showed normal vocal fold motion and LEMG revealed full interference patterns. After surgery, the left vocal fold was fixed with electrical silence on LEMG. MUPs appeared in the PCA and TA muscles starting at 6 weeks. New neuromuscular junctions were confirmed by double labeling. At 24 weeks, three dogs regained normal motion and two showed moderate motion. Full interference patterns were recorded in four dogs. No misdirected potentials were observed on LEMG. Histology showed comparable morphology of transplanted nerves and target muscles.

The present selective laryngeal reinnervation technique successfully promoted synchronous regeneration of neuromuscular junctions, restoring coordinated movement of vocal folds.

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