Utility of laryngeal electromyography for establishing prognosis and individualized treatment after laryngeal neuropathies.

ABSTRACT

Laryngeal electromyography (LEMG) is a technique used to characterize neuropathic injuries to the recurrent laryngeal nerve (RLN) and superior laryngeal nerve (SLN). The RLN and SLN innervate the laryngeal muscles to produce vocal fold (VF) motion and elongation, respectively. VF motion deficiencies can affect voice, swallowing, and breathing, which can greatly affect a patient's quality of life. Neuropathy-related VF motion deficiencies most often result from surgical interventions to the skull base, neck, or chest likely due to the circuitous route of the RLN. LEMG is ideally conducted by an electromyographer and an otolaryngologist using a team-approach. LEMG is a powerful diagnostic tool to better characterize the extent of neuropathic injury and thus clarify the prognosis for VF motion recovery. This updated review discusses current techniques to improve the positive and negative predictive values of LEMG using laryngeal synkinesis and quantitative LEMG. Synkinesis can be diagnosed by comparing motor unit potential amplitude during vocalization and sniff maneuvers when recording within adductor muscles. Quantitative turns analysis can measure motor unit recruitment to avoid subjective descriptions of reduced depolarization during vocalization, and normal values are >400 turns/s. By integrating qualitative, quantitative, and synkinetic data, a robust prognosis can help clinicians determine if VF weakness will recover. Based on LEMG interpretation, patient-centered treatment can be developed to include watchful waiting, temporary VF augmentation, or definitive medialization procedures and laryngeal reinnervation.