Bilateral motion restored to the paralyzed canine larynx with implantable stimulator

Bilateral stimulation of posterior cricoarytenoid (PCA) muscles offers a physiologic approach to restore ventilation to a normal level in case of bilateral laryngeal paralysis. The objective of this study was to evaluate the long-term efficacy and safety of a new generation stimulator in restoring ventilation and exercise tolerance.

A prospective study of four canines over 8-20 months.

A Genesis XP stimulator and electrodes were implanted and recurrent laryngeal nerves were sectioned and repaired bilaterally. In bimonthly sessions, vocal fold movement resulted from PCA stimulation or induced hypercapnea, was measured endoscopically in the anesthetized animal. Exercise tolerance was measured on a treadmill and swallowing function was examined endoscopically and radiographically.

During the denervation phase, there was minimal ventilatory compromise and near-normal exercise tolerance. PCA stimulation produced only nominal abduction. During the reinnervation phase, synkinetic reinnervation became significant, resulting in a narrowed passive airway and paradoxical glottic closure during hypercapnea. Animals were stridorous and could walk for only 1-2 minutes. Bilateral PCA stimulation increased glottal area, equaling that of a normally innervated animal. Exercise tolerance was also normal. The optimal stimulus paradigm for the synkinetically reinnervated larynx was not different from that for the innervated larynx. Stimulation remained efficacious over the study period. Lead integrity could be maintained by prevention of device migration. There was no evidence of aspiration.

This study demonstrates that ventilatory compromise only occurs following faulty reinnervation. Bilateral PCA stimulation can restore ventilation and exercise tolerance completely without aspiration over the long term.