Objective: To study the laryngeal electromyography (LEMG) behaviors of recurrent laryngeal nerve (RLN) paralysis at different time and severity level.
Method: Eighty-seven cases with RLN paralysis were divided into seven groups according to their paralysis time. Their LEMG behaviors were investigated, and compared with normal.
Result: (1) Fibrillation potentials and positive sharp wave could be found in injuries thyroarytenoid muscles(TA), posterior cricoarytenoid muscles(PCA), lateral cricoarytenoid muscles(LCA) as early as five days after the onset of paralysis. The denervation potentials increased, and reinnervation potentials appeared from two weeks to three months after the onset. The former became less and the latter increased from 3 months, and the denervation potentials vanished after three years. (2) The recruitment patterns of paralyzed muscles were weak and even there was no interference patterns in them. The amplitude and turns significantly decreased compared with normal control, and the decrease of the turns was more significant. The recruitment potentials of other normal laryngeal muscles increased right after the onset of disease. (3) Evoked potentials (EP) of most paralyzed laryngeal muscles vanished only in some patients, in others there were small and weak EPs, which had a longer latent period and small amplitude.
Conclusion: LEMG is important for the diagnosis and differentiation of RLN paralysis. The denervation potentials and reinnervation potentials are important marks of RLN injury, and closely correlated with the degree and time of RLN injury. The abnormal EP of paralyzed laryngeal muscles could suggest the degree of injury.