Nonrecurrent Laryngeal Nerve in the Era of Intraoperative Nerve Monitoring

Nonrecurrent laryngeal nerve (non-RLN) is an anatomical variation increasing the risk of vocal cord palsy. Prediction and early identification of non-RLN may minimize such a risk of injury. This study assessed the effect of intraoperative neuromonitoring (IONM) on the detection of non-RLN. A total of 462 (236 right) nerves in 272 patients were identified and totally exposed, and all intraoperative steps of IONM were sequentially applied on the vagus nerve (VN) and RLN. Right predissection VN stimulation at a distal point did not create a sound signal in three cases (3/236; 1.27%). Proximal dissection of the right VN under IONM guidance established a proximal point, creating a positive signal. The separation point of non-RLN from VN was discovered in all three patients. Non-RLNs were exposed from separation to laryngeal entry. Positive IONM signals were obtained after resection of thyroid lobes, and postoperative period was uneventful in patients with non-RLN. Absence of distal VN signal is a precise predictor of the non-RLN. IONM-guided proximal dissection of the right VN leads to identification of the non-RLN. The prediction of non-RLN by the absence of the VN signal at an early stage of surgery may prevent or minimize the risk of nerve injury.