Evaluation of the Incidence of Thyroidectomy-induced Recurrent Laryngeal Nerve Injuries and Their Risk Factors Using Acoustic Analysis: An Observational Study

Abstract Background: Thyroidectomy is one of the most common operations performed, with recurrent laryngeal nerve injury (RLNI), both complete and incomplete, being one of the most serious potential complications. In this study, we used acoustic analysis of jitter, shimmer, noise-to-harmonic ratio (NHR), and maximum phonation time (MPT) as an objective method of diagnosing RLNI. Materials and Methods: We evaluated the mean values of jitter, shimmer, NHR, and MPT in patients undergoing thyroidectomy. These values, in addition to laryngoscopy, were measured preoperatively, at 1 week post operatively, and at 3 months postoperatively. Results: The values of jitter, shimmer, NHR, and MPT were all raised in the first postoperative follow up; however, jitter, shimmer, and NHR were significantly raised ( P < 0.001) in patients whose recurrent laryngeal nerve (RLN) was not identified intraoperatively in comparison to those where it was identified. All of these parameters returned to near-normal levels at 3 months postoperatively. Conclusion: Identification of the RLN intraoperatively during thyroidectomy significantly decreased the incidence of its injury both completely and incompletely. The use of acoustic analysis is an objective way of measuring incomplete injury of the RLN postoperatively.