Laryngeal Nerves Monitoring in Thyroid Surgery

In recent years, intraoperative neural monitoring (IONM) has gained widespread acceptance as an adjunct to the gold standard of visual nerve identification and it can be used to identify both the recurrent laryngeal nerve (RLN) and external branch of the superior laryngeal nerve (EBSLN). At present, three types of IONM are performed: RLN intermittent neuromonitoring (i-IONM); RLN continuous neuromonitoring (c-IONM); neuromonitoring of the EBSLN. i-IONM remains the most employed method for confirming visual RLN identification as well as for neural mapping to identify the nerve before it is exposed in the surgical field. i-IONM allows for prognostication of postoperative nerve function and for modifying the surgical plan – i.e., postponing surgical treatment of the contralateral side (staged thyroidectomy) – if during the procedure loss of signal occurs. On the other hand, c-IONM allows for detection of severe combined events warning the surgeon about an impending nerve injury, and allows for modification of surgical maneuvers with a potential of preventing unilateral RLN injury. EBSLN may be at risk during dissection of the superior thyroid vessels. Therefore, intraoperative stimulation of the EBSLN with or without nerve monitoring can improve the visual identification rate and functional preservation of the nerve and voice following thyroidectomy.