Increased detection of non-recurrent inferior laryngeal nerve (NRLN) during thyroid surgery using systematic intraoperative neuromonitoring (IONM)

BACKGROUND: Non-recurrent inferior laryngeal nerve (NRLN) is a rare anatomical variant with a reported incidence of 0.6-1.3 %. It carries a higher risk of palsy during thyroid surgery. Its detection is mandatory in order to avoid such complication. METHODS: Systematic intraoperative neuromonitoring (IONM) was carried out for 806 consecutive nerve at risk (NAR) patients in two centers (Lille and Varese). In 402 patients surgery to the right side was performed with IONM. The IONM of the inferior laryngeal nerve (ILN) was conducted as recommended by international guidelines (V1/R1/V2/R2). RESULTS: A NRLN was detected in 11 of 402 NAR (2.7 %). In the first center (Lille) the incidence of NRLN was 6.0 % (7/117). No loss of signal (LOS) was reported in this group of patients. Postoperative laryngoscopy was normal in all patients with NRLN. CONCLUSIONS: The true incidence of NRLN may be higher than expected. Neurophysiology helps the surgeon to better understand the anatomy and function of nervous structures. Intraoperative neuromonitoring is a useful tool that should be systematically implemented in thyroid surgery to better understand the anatomy and physiology of the inferior laryngeal nerve. Its use may allow the surgeon to decrease the incidence of nerve palsy especially in case of NRLN. The IONM adjunct does not add significantly to the costs for thyroid surgery.