Synkinetic reinnervation of the posterior cricoarytenoid muscle after recurrent laryngeal- or vagal nerve lesions

Introduction: after higher-grade lesions of the recurrent laryngeal (RLN) or vagal nerve in most cases a random reinnervation of nerve fibers into the abductor and adductor muscles of the larynx occurs. This is generally accepted as the main reason for the persistance of many vocal fold paresis. Especially in iatrogenic RLN lesions initial damage is partial and often unevenly distributed, affecting the posterior cricoarytenoid muscle (PCA) more than the thyroarytenoid muscle (TA). We wanted to know the innervation status of vocal fold paresis with persistent immobility. Methods: EMG-data of 96 vocal folds with immobility longer than 6 months was evaluated retrospectively (96 PCA-EMG's with corresponding ipsilateral TA-EMG's in 80 cases). Results: In 70 of 96 cases PCA-EMG showed a strongly diminished voluntary activity (interference pattern strongly decreased, single fiber pattern or no voluntary activity). In 26 cases voluntary activity was only mildly diminished. However all those cases showed a strong synkinesis. There were no cases with normal physiologic PCA-EMG pattern. In TA the damage was variable, in most cases less severe (only 27 cases with strongly diminished voluntary activity, of 53 cases with mildly diminished interference only 21 had relevant signs of synkinesis, in 6 cases synkinesis had not been evaluated). Conclusions: In all persistent RLN paresis in this study there was electrophysiologic evidence of a severe lesion either in form of a strongly diminished innervation or a pathologic synkinetic reinnervation. In most cases however there seem to be sufficient motor units present to support future dynamic therapeutic concepts such as laryngeal pacing. Publication History Publication Date: 23 April 2019 (online) © 2019. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial-License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/). Georg Thieme Verlag KG Stuttgart · New York