Laryngeal EMG: Preferential damage of the posterior cricoarytenoid muscle branches especially in iatrogenic recurrent laryngeal nerve lesions.

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.