Objective: Laryngeal electromyography (LEMG) of the thyroarytenoid (TA) muscle alone may not be sufficient in all patients to characterize or prove a recurrent laryngeal nerve (RLN) lesion in cases of vocal fold immobility. LEMG of the posterior cricoarytenoid (PCA) muscle may provide additional information.
Study design: Retrospective review.
Method: Between 2008 and 2016, 339 patients in our laryngeal paralysis clinic were examined by transcutaneous needle TA-LEMG and, if tolerated, by PCA-LEMG. LEMGs were rated and compared according to criteria of the European Laryngological Society. Etiology was categorized as iatrogenic, noniatrogenic, or malignancy related.
Results: A total of 282 out of 339 patients had a partial or complete RLN or vagal nerve lesion: 178 iatrogenic, 74 noniatrogenic, and 30 because of nerve involvement by malignancies. Of paralytic vocal folds, 35.7% had normal or near-normal TA innervation, whereas corresponding PCA traces (if present) were pathologic in 94.6%. Comparing pairs of TA and PCA-LEMGs in paralysis of less than 4 months duration showed a predominance of PCA branch injuries in iatrogenic lesions (71.7 %), while in noniatrogenic lesions this was less pronounced (44.4%). In the few malignancy cases, there was an almost even distribution. Synkinetic reinnervation was earlier in iatrogenic RLN lesions.
Conclusion: PCA-LEMG was better in proving an RLN lesion than TA-EMG alone. Our findings suggest etiology-dependent differences in the TA/PCA lesion pattern. To confirm this, larger sample sizes are needed. A preferential damage to PCA innervation in iatrogenic lesions could be relevant for further improvements of intraoperative neuromonitoring.
Level of evidence: 4. Laryngoscope, 128:1152-1156, 2018.
Keywords: EMG; Larynx; PCA; TA; damage pattern; etiology; neuromonitoring; synkinesia; vocal fold paralysis.
© 2017 The American Laryngological, Rhinological and Otological Society, Inc.