Increased Detection of Non-recurrent Inferior Laryngeal Nerve (NRLN) During Thyroid Surgery Using Systematic Intraoperative Neuromonitoring (IONM)
PURPOSE The nonrecurrent laryngeal nerve (NRLN) is a rare anatomical variant but associated with high risk of nerve injury during thyroid and parathyroid operations. Therefore, intraoperative detection and verification of NRLN are necessary. METHOD A total of 390 consecutive patients who underwent thyroid and parathyroid operations (310 RLNs dissected on the right side and 293 nerves on the left side) were enrolled. Electrically evoked electromyography was recorded from the vocalis muscles via an endotracheal tube with glottis surface recording electrodes. At an early stage of operation, vagal nerve was routinely stimulated at the level of inferior thyroid pole to ensure normal path of RLN. If there is a negative response from lower position but positive response from upper vagal stimulation, it indicates the occurrence of a NRLN, and we localize its separation point and path. RESULTS Four right NRLNs (1.3%) without preoperative recognition were successfully detected at an early stage of operation. Three patients were operated on for thyroid disease, one for parathyroid adenoma and all were associated with right aberrant subclavian artery. All NRLNs were localized and identified precisely with intraoperative neuromonitoring. Functional integrity of all nerves was confirmed by the intraoperative neuromonitoring and postoperative laryngeal examination. CONCLUSIONS Vagal stimulation at the early stage of operation is a simple, useful, and reliable procedure to detect and identify the NRLN.