Prospective randomized study on injury of the external branch of the superior laryngeal nerve during thyroidectomy comparing intraoperative nerve monitoring and a conventional technique

Abstract

Background: The external branch of the superior laryngeal nerve (SLN) is susceptible to injuries during thyroidectomy, causing voice impairment. Intraoperative nerve monitoring may facilitate identification of the nerve, reducing voice impairment.

Methods: A total of 252 patients undergoing thyroidectomy were randomly assigned to group N (the NIM-Response 3.0 system was used) or group C (the conventional technique using the Vari-Stim 3 was used) to identify the external branch of the SLNs. The primary endpoint was the identification rate of the external branch of the SLN. The secondary endpoint was the incidence of postoperative voice impairment.

Results: The visual and the electrostimulatory identification rates of the external branch of the SLN in group N and group C were 48.8% versus 17.8% (p < .001) and 89.2% versus 17.8% (p < .001), respectively. The proportion of female patients who had subjective voice impairment was significantly smaller in group N than in group C.

Conclusion: The use of the NIM-Response 3.0 significantly improved the identification rate of the external branch of the SLN during thyroidectomy, reducing voice impairment.

Keywords: external branch of the superior laryngeal nerve (SLN); intraoperative nerve monitoring; nerve identification; thyroidectomy; voice impairment.