Intra-operative vagal neuromonitoring predicts non-recurrent laryngeal nerves: technical notes and review of the recent literature

Abstract Background During thyroid surgery, extreme caution must be taken not to harm the recurrent laryngeal nerve to avoid vocal cord palsy. A non-recurrent laryngeal nerve (NRLN) is a rare anatomical variation that is extremely vulnerable during thyroid surgery. Methods Description of two NRLN during thyroid surgery discovered early by using continuous intra-operative vagal nerve neuromonitoring and review of the literature. Results During thyroid surgery, we use continuous intra-operative vagal nerve neuromonitoring starting with checking vagal nerve signals. It is essential to start stimulation in the most proximal portion of the carotid sheath. An absent pre-dissection signal on the right vagal nerve with a positive signal on the left vagal nerve indicates a non-recurrent course of the right laryngeal nerve. Post-operatively computed tomography scan (CT-scan) was performed and showed an associated extra-anatomical course of the subclavian artery also known as an arteria lusoria. Conclusion The NRLN is an important surgical challenge because unilateral palsy can lead to permanent hoarseness. This anomaly emphasizes the importance of a thorough surgical dissection and the use of intra-operative vagal nerve neuromonitoring. Our method of continuous intra-operative vagal nerve monitoring makes it possible to predict a non-recurrent laryngeal nerve in an early stage during surgery.