Laryngeal synkinesis: its significance to the laryngologist.

Basic research and surgical cases have shown that the injured recurrent laryngeal nerve (RLN) may regenerate axons to the larynx that inappropriately innervate both vocal cord adductors and abductors. Innervation of vocal cord adductor muscles by those axons that depolarize during inspiration is particularly devastating to laryngeal function, since it produces medial vocal cord movement during inspiration. Many patients thought to have clinical bilateral vocal cord paralysis can be found to have synkinesis on at least one side. This will make the glottic airway smaller, particularly during inspiration, than would true paralysis of all the intrinsic laryngeal muscles. Patients with bilateral vocal cord paralysis should undergo laryngeal electromyography. If inspiratory innervation of the adductor muscles is present, simple reinnervation of the posterior cricoarytenoid muscle will fail. The adductor muscles also must be denervated by transection of the adductor division of the regenerated RLN.