Can early postoperative ultrasound replace routinary flexible laryngoscopy after neuromonitoring-assisted thyroid surgery?

Ultrasound (US) has been proposed to assess vocal cord motility after thyroid surgery since early post-operative flexible laryngoscopy (FL) is not readily available in all centers. We aimed to verify if FL can be avoided in intraoperative neuromonitoring (IONM)-assisted thyroid surgery followed by early US vocal cord motility evaluation. Two hundred and thirty-four patients who underwent IONM-assisted thyroidectomy were included. When total thyroidectomy (TT) was planned, the surgical procedure was stopped in case of loss of signal (LOS) or significant signal reduction (SSR) after the dissection of the first lobe. US vocal cord motility evaluation and FL were performed in all patients on postoperative day 1. Among 377 nerves at risk (91 thyroid lobectomies and 143 TT), post-operative FL showed 9 unilateral vocal cord palsies and 4 unilateral hypomotilities. IONM results showed 15 LOS and 10 SSR. US vocal cord motility evaluation confirmed unilateral vocal cord palsy in 8 cases and correctly identified normal post-operative vocal cord motility in 13 patients with altered IONM results. FL was able to diagnose 4 unilateral vocal cord hypomotilities in patients with normal IONM results and US evaluation. Overall accuracy was 91.4% for IONM and 96.5% for US, respectively. Early postoperative US evaluation after IONM-assisted thyroid surgery improves the overall accuracy of IONM alone in assessing laryngeal function after thyroid surgery. Nonetheless, IONM results and post-operative US do not replace FL, which remains the gold standard for early detection of laryngeal motility changes also in asymptomatic patients.