Functional Electrical Stimulation of the Bilaterally Paralyzed Human Larynx

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Bilateral vocal fold paralysis (BVFP) is a serious and often life-threatening condition. Approximately 7,000 patients are stricken by this paralysis each year in the United States. A much larger number are susceptible in less medically advanced countries (e.g. India and China, > 80,000). The recurrent laryngeal nerve carries motor fibers that innervate both the abductor (posterior cricoarytenoid, PCA) muscle and the adductor muscles of the vocal folds. If the nerves are injured on both sides, regeneration usually occurs but the reinnervation by inspiratory and reflex glottic closure motoneurons becomes partially crisscrossed between these antagonistic muscles. The larynx remains paralyzed or nonfunctional in view of the synkinetic nature of the reinnervation. Partial laser resection of the vocal fold (cordotomy) is the standard of care for BVFP to improve ventilation. However, it only mildly increases airflow through the mouth, damages the voice, and compromises swallowing through aspiration. A more natural approach is to restore vocal fold opening through electrical stimulation of the PCA muscle with an implantable laryngeal pacemaker. Further, synkinetically reinnervated muscles are particularly responsive to electrical stimulation. A clinical trial of unilateral laryngeal pacing was conducted by the PI in 1996. In this study, it was found that ventilation with pacing was marginally greater than with cordotomy, and there was no deterioration of voice quality or swallowing function. Recently, a more advanced implantable pulse generator (EonCTM) has become available commercially. It has a multi-programmable feature that allows independent stimulation of the PCA muscles on both sides. In a preliminary study in the canine, the PCA muscles were bilaterally activated through a pair of implanted stimulation electrodes. Ventilation and exercise performance was restored to a normal level without any aspiration in these animals. In this clinical research proposal, the primary goal will be to compare bilateral laryngeal pacing to cordotomy with respect to ventilation and voice outcomes. In the pacing patients, we will also compare the impact of bilateral versus unilateral stimulation on these outcome measures. Laryngeal reanimation with functional electrical stimulation should provide a superior treatment approach for BVFP.