Quantitative Measurement of Laryngeal Electromyography Using Motor Unit Action Potential in Unilateral Vocal Cord Paralysis

ABSTRACT

BACKGROUND AND OBJECTIVES: Laryngeal electromyography (LEMG) is valuable to evaluate the innervation status of the laryngeal muscles and the prognosis of vocal fold paralysis (VFP). However, there is a lack of agreement on quantitative interpretation of LEMG. The aim of this study is to measure the motor unit action potentials (MUAP) quantitatively in order to find cut-off values of amplitude, duration, phase for unilateral vocal fold paralysis patients. MATERIALS AND METHOD: Retrospective chart review was performed for the unilateral VFP patients who underwent LEMG from March 2016 to May 2018. Patient's demography, cause of VFP, vocal cord mobility, and LEMG finding were analyzed. The difference between normal and paralyzed vocal folds and cut-off values of duration, amplitude, and phase in MUAP were evaluated. RESULTS: Thirty-six patients were enrolled in this study. Paralyzed vocal fold had significantly longer duration (p=0.021), lower amplitude (p=0.000), and smaller phase (p=0.012) than the normal. The cut-off values of duration, amplitude, and phase in MUAP for unilateral VFP were 5.15 ms, 68.35 µV, and 1.85 respectively. CONCLUSION: An analysis of MUAP successfully provided quantitative differences between normal and paralyzed vocal folds. But, additional research is needed to get more available cut-off value which is helpful to evaluate the status of laryngeal innervations.