Importance: Intraoperative neuromonitoring (IONM) may prevent bilateral vocal cord palsy after thyroidectomy by prompting the surgeon to abort planned total thyroidectomy in case of loss of signal from the recurrent laryngeal nerve (RLN) on the first side. The International Nerve Monitoring Study Group recommends stimulation in the sequence V1 (predissection vagus nerve), R1 (predissection RLN), R2 (postdissection RLN), V2 (postdissection vagus nerve). Objectives: To investigate sensitivity of V2 stimulation for identification of postoperative vocal cord palsy vs R2 stimulation only. Design, Setting, and Participants: This retrospective cross-sectional study included patients undergoing thyroidectomy from February 2024 to October 2025, using IONM with stimulation in the sequence of V1, R1, R2, V2. The findings were compared with previous cohort of 1159 nerves at risk (NARs) for which vagal nerve stimulation was performed selectively. The study was performed at an academic tertiary referral center for thyroid surgery. Consecutive patients planned for thyroidectomy were included. Inclusion criteria were thyroidectomy performed using intermittent IONM with postoperative laryngoscopy. Exclusion criteria were preoperative vocal cord palsy, deliberate or inadvertent RLN section, or no postoperative laryngoscopy performed. Exposures: V2 stimulation. Main Outcomes and Measures: The primary outcome measure was vocal mobility on the first postoperative day. The sensitivity, specificity, negative predictive value, and positive predictive value of the 2 strategies were compared. Results: Among 240 patients (mean SD age, 50 15 years; 188 78.3% female patients), 43 of 353 NARs (12.2%) had loss of signal (33 9.3% persistent). Of these, 9 (27.3%) had V2 loss of signal, with no preceding loss of signal or electrophysiological events on the RLN. Six patients planned for total thyroidectomy had change in operative plan to lobectomy only, including 2 patients with unexpected V2 loss of signal. Impaired vocal mobility was present in 7 of 9 cases with intact R2 and absent V2 response (77.8%). The sensitivity of R2 and V2 stimulation for postoperative vocal cord palsy was 57.9% and 100%, respectively. Among the earlier cohort undergoing selective vagal nerve stimulation, the sensitivity of IONM for impaired vocal cord mobility was 83.3%. Conclusion and Relevance: The findings of this cross-sectional study suggest that IONM without systematic V2 stimulation has inferior sensitivity to systematic V2 stimulation. Systematic V2 stimulation should be considered criterion standard to minimize risk of bilateral vocal cord palsy after total thyroidectomy.
Berg et al. (2026) studied this question.