Contribution of intraoperative neuromonitoring to the identification of the external branch of superior laryngeal nerve

Abstract

Objective: We evaluated the contribution of intraoperative neuromonitoring to the visual and functional identification of the external branch of the superior laryngeal nerve.
Material and Methods: The prospectively collected data of patients who underwent thyroid surgery with intraoperative neuromonitoring for external branch of the superior laryngeal nerve exploration were assessed retrospectively. The surface endotracheal tube-based Medtronic NIM3 intraoperative neuromonitoring device was used. The external branch of the superior laryngeal nerve function was evaluated by the cricothyroid muscle twitch. In addition, contribution of external branch of the superior laryngeal nerve to the vocal cord adduction was evaluated using electromyographic records.
Results: The study included data of 126 (female, 103; male, 23) patients undergoing thyroid surgery, with a mean age of 46.2±12.2 years (range, 18-75 years), and 215 neck sides were assessed. Two hundred and one (93.5%) of 215 external branch of the superior laryngeal nerves were identified, of which 60 (27.9%) were identified visually before being stimulated with a monopolar stimulator probe. Eighty-nine (41.4%) external branch of the superior laryngeal nerves were identified visually after being identified with a probe. Although 52 (24.1%) external branch of the superior laryngeal nerves were identified with a probe, they were not visualized. Intraoperative neuromonitoring provided a significant contribution to visual (p<0.001) and functional (p<0.001) identification of external branch of the superior laryngeal nerves. Additionally, positive electromyographic responses were recorded from 160 external branch of the superior laryngeal nerves (74.4%).
Conclusion: Intraoperative neuromonitoring provides an important contribution to visual and functional identification of external branch of the superior laryngeal nerves. We believe that it can not be predicted whether the external branch of the superior laryngeal nerve is at risk or not and the nerve is often invisible; thus, intraoperative neuromonitoring may routinely be used in superior pole dissection. Glottic electromyography response obtained via external branch of the superior laryngeal nerve stimulation provides quantifiable information in addition to the simple visualization of the cricothyroid muscle twitch.

This study was presented at the 7th National Endocrine Surgery Congress, 23-26 April 2015, Antalya, Turkey.

Cite this paper as: Aygün N, Uludağ M, İşgör A. Contribution of intraoperative neuromonitoring to the identification of the external branch of superior laryngeal nerve. Turk J Surg 2017; 33: 169-174.

Ethics committee approval was received for this study from the ethics committee of Şişli Hamidiye Etfal Training and Research Hospital.

Written informed consent was obtained from patients who participated in this study.

Externally peer-reviewed.

Concept - N.A., M.U.; Design - N.A.; Supervision - M.U., A.İ.; Resource - N.A., M.U; Materials - N.A.; Data Collection and/or Processing - N.A.; Analysis and/or Interpretation - N.A., M.U.; Literature Search - N.A., M.U.; Writing Manuscript - N.A., M.U.; Critical Reviews - M.U., A.İ.;

No conflict of interest was declared by the authors.

The authors declared that this study has received no financial support.