Laryngeal Nerve Protection Devices in Thyroid Surgery: A Systematic Review and Evidence Synthesis.

Abstract

To synthesize the evidence on the electrophysiologic performance, intraoperative behavior, and clinical impact of monopolar and bipolar handheld probes, stimulating dissecting instruments (SDIs), and attachable ring stimulators (ARS) used for intraoperative neuromonitoring (IONM) of the recurrent laryngeal nerve (RLN), vagus nerve (VN), and external branch of the superior laryngeal nerve (EBSLN) during thyroid and parathyroid surgery. A systematic review was conducted according to PRISMA 2020 with a prospectively registered PROSPERO protocol. PubMed, Embase, Cochrane CENTRAL, and Web of Science were searched from inception to January 28, 2026, for human studies evaluating intermittent or semi-intermittent RLN stimulation systems. Primary outcomes were device-specific stimulation parameters and EMG metrics; secondary outcomes included RLN palsy, mapping characteristics, and device-related complications. Risk of bias was assessed with RoB 2.0, ROBINS-I, and QUADAS-2. Eleven observational studies (7245 patients; 9186 nerves at risk) met inclusion criteria. Across devices, stimulation settings converged on square-wave pulses at 4 Hz, pulse width around 100 μs, activation thresholds of 0.4-0.6 mA, and supramaximal currents of 1-2 mA. Pooled RLN amplitudes were 700-800 μV, VN amplitudes 500-700 μV, and EBSLN amplitudes about 270 μV. No clinically relevant differences in final RLN or VN amplitudes or latencies were observed among device categories once the nerve was exposed. SDIs reduced operative time in one single-center series, while ARS showed amplitudes equivalent to handheld probes in a pilot study. Available evidence suggests comparable EMG performance across devices in open thyroid surgery, whereas evidence for SDIs and ARS remains limited. N/A.