The global (permanent and transient) injury rate of the Recurrent Laryngeal Nerve (RLN) during thyroidectomy is up to 13%. However, that rate increases if all patients receive a postoperative laryngoscopy. Permanent RLN injury occurs in 1-2% of thyroidectomies in “experienced hands” (whatever that means). Important to note that these injuries may be present in an anatomically normal RLN. Additionally, intraoperatively, only 10-14% of injured nerves are identified as damaged by the surgeon. RLN injury is associated with important negative consequences to the patient, with voice changes being the most common reason for litigation after thyroid surgery. Airway obstruction with the need of a tracheotomy (in case of a bilateral injury) and swallowing difficulties are other consequences of nerve damage. So, I believe all efforts should be made to reduce the risk of RLN injury. This includes using every kind of technology that can help us find and preserve the nerve function.
Intraoperative nerve monitoring (IONM) is a useful tool that can help us map the nerve, find it, and preserve its function till the end of surgery. Its standard use is still debatable because some works found no statistical difference compared to visualization alone (VA). Surgeons must not forget that visual identification of the RLN is the gold standard, but many works showed IONM plus VA has advantages compared to VA. That is why I am systematically using IONM during all thyroidectomies. Is it necessary? Am I adding morbidity by using IONM?
In January 2025, a retrospective analysis from the USA (Johns Hopkins, Baltimore, Maryland) reported the use of IONM in 44265 patients who underwent thyroidectomy between January 2016 and December 2022. The common indications were goiter and single nodule/neoplasm. The use of IONM increased during the study period (62.5% in 2016 to 75.9% in 2022). The overall rate of RLN injury was 6%. However, it is important to highlight that the use of IONM was associated with decreased odds of RLN injury. Cancer patients had low odds of injury. Hypocalcemia and cervical hematoma were not influenced by the IONM. Dr Madison Hearn et al. state that “although IONM use is widespread, further research is needed to identify patients who would benefit the most from this technology”. In my opinion, there may be patients for whom the use of IONM should be standard of care (large goiters, reoperations, substernal goiters, cancer patients), but if IONM can reduce the injury rate of the RLN, this technology should be proposed to all patients. Saving one nerve out of 100 nerves at risk will not have statistical significance but will have an important clinical significance.
Returning to my previous question. Am I adding morbidity by using IONM? No important morbidity is associated with the use of IONM. I routinely use intermittent IONM (I-IONM) and have already changed the initial proposed surgery because of nerve monitoring. IONM can protect surgeons and patients from major complications by postponing contralateral lobe dissection in case of loss of signal (LOS) during first lobe dissection. I do not perform vagus nerve dissection because it is possible to stimulate the vagus without seeing it. However, it is paramount to follow the sequence (L1)-V1-R1-R2-V2-(L2) to assure a correct and reliable IONM. It is well known that some surgeons obtain neither a V1 nor a V2, especially during endoscopic thyroidectomies. This is not a correct procedure and puts the patient at risk of RLN injury. Always keep in mind: V1 and V2 are crucial and are the only way to assure a good prediction of normal postoperative nerve function.
In conclusion, I believe IONM is becoming a standard of care during thyroidectomy. If you have it, learn how to use it. If you have it, use it with all patients. If you use it, use it correctly. Safety always comes first.
Link to article:
Dr. Carlos Eduardo Costa Almeida
General Surgeon
Comments