Efficacy of Intraoperative Neuromonitoring in Reoperation for Recurrent Thyroid Cancer Patients

BACKGROUND: The use of intraoperative neuromonitoring (IONM) in thyroid surgery to preserve recurrent laryngeal nerve (RLN) function has been widely accepted. We aimed to evaluate the usefulness of IONM in reoperation for recurrent thyroid cancer patients to help identify the RLN and prevent vocal cord palsy (VCP). METHODS: We analyzed 121 consecutive patients (with IONM group, 48 patients; without IONM group, 73 patients) who underwent reoperation for recurrent thyroid cancer after total thyroidectomy from January 2009 to March 2019 in our institution without VCP due to previous operations. Data including age, sex, number of previous operations, histologic subtype of the malignancy at the initial operation, operation time, RLNs at risk, difficulty of RLN identification, surgical procedure, VCP, and other postoperative complications were reviewed. Vocal cord movement evaluations were performed preoperatively and at 2 weeks postoperatively to evaluate RLN function. In patients with VCP, additional evaluations were performed. VCP exceeding 12 months after surgery was considered permanent VCP. RESULTS: VCP was observed in six (12.5%) and 16 (21.9%) patients with and without IONM (P=0.189). Transient and permanent VCP were found in three (6.3%) and three (6.3%) patients with IONM (P=0.098 and P=0.982, respectively) versus in 12 (16.4%) and four (5.5%) patients without IONM. CONCLUSION: The incidence of transient VCP seems to be lower in reoperations with IONM; however, there was no statistical significances. Further study will be needed to ascertain the efficacy of IONM in reoperation for recurrent thyroid cancer patients.