Functional Electrical Stimulation of the Bilaterally Paralyzed Human Larynx

Despite recent advances in medicine, rehabilitation of the paralyzed larynx remains a complex clinical problem. Based on national health statistics, it is anticipated approximately 7,000 patients will be diagnosed with BVFP in the United States each year. BVFP is a serious and often life-threatening clinical condition. The recurrent laryngeal nerve (RLN) carries motor fibers that innervate both the abductor muscle (posterior cricoarytenoid muscle) and adductor muscles of the vocal folds. Damage to the nerve compromises both of these functions and arrests the vocal folds in a near-closed position. With BVFP, voice tends to be functional, but airway compromise is often severe enough to warrant tracheotomy to relieve inspiratory stridor and dyspnea. If spontaneous recovery does not occur within one year, it is likely that the patient's vocal folds will be chronically paralyzed. In such instances, long-term tracheostomy can be considered. Unfortunately, permanent tracheostomy is associated with complications such as tracheal stenosis, chronic infection, and psycho-social impairment. For this reason, laryngeal surgery is usually recommended to enlarge the airway and restore breathing through the mouth. Procedures such as arytenoidectomy, cordotomy, or repeated Botox injections, regarded as the standard of care for enlarging the airway, also have inherent complications. Specifically, they impair voice and compromise airway protection during swallowing. The limitations associated with these current treatments have prompted investigation into a more physiologic, dynamic approach to rehabilitation: reanimation of the paralyzed PCA muscle by functional electrical stimulation (FES). Ideally, stimulation should be applied during the inspiratory phase of respiration to abduct the vocal folds. This has been termed "laryngeal pacing". During non-inspiratory phases, stimulation would cease, and the vocal folds would passively relax to the midline to allow for normal voice production and airway protection. Previously, our clinical trial of unilateral pacing demonstrated a significantly greater return of ventilation without any compromise of voice or swallowing. However, the level of ventilation was only marginally better than that associated with cordotomy. In the current project, we will investigate the safety of a novel intervention (laryngeal pacing) for BVFP (Aim 1). The overarching hypothesis is that neuromuscular activation of the PCA muscles bilaterally reestablishes bilateral glottal opening and ventilation through the mouth without alteration of voice or swallowing, compared to a sham-operated control (Aim 2). The ventilation from bilateral pacing should be significantly greater than from unilateral pacing and allow the patient to engage in a normal pre-paralysis activity level (Aim 3).