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

Area of Science:

• Neurosurgery
• Otolaryngology
• Endocrinology

Background:

• Intraoperative neuromonitoring (IONM) is crucial for preserving laryngeal nerve function during thyroid and parathyroid surgery.
• Various devices, including handheld probes, stimulating dissecting instruments (SDIs), and attachable ring stimulators (ARS), are used for IONM of the recurrent laryngeal nerve (RLN), vagus nerve (VN), and external branch of the superior laryngeal nerve (EBSLN).

Purpose of the Study:

• To synthesize evidence on the electrophysiologic performance, intraoperative behavior, and clinical impact of different IONM devices for laryngeal nerves during thyroid surgery.
• To compare monopolar and bipolar handheld probes, SDIs, and ARS in terms of stimulation parameters, EMG metrics, and clinical outcomes.

Main Methods:

• A systematic review adhering to PRISMA 2020 guidelines was performed.
• Searches were conducted in PubMed, Embase, Cochrane CENTRAL, and Web of Science for human studies on RLN stimulation systems.
• Risk of bias was assessed using RoB 2.0, ROBINS-I, and QUADAS-2.

Main Results:

• Eleven observational studies including 7245 patients and 9186 nerves were analyzed.
• Stimulation parameters converged across devices: 4 Hz, ~100 μs pulse width, 0.4-0.6 mA activation threshold, and 1-2 mA supramaximal current.
• Pooled nerve amplitudes were observed for RLN (700-800 μV), VN (500-700 μV), and EBSLN (~270 μV), with no significant differences among device categories once the nerve was exposed.

Conclusions:

• Electrophysiologic performance appears comparable across different IONM devices in open thyroid surgery.
• Evidence regarding the specific utility and impact of SDIs and ARS is currently limited.
• Further research is needed to fully elucidate the role of newer devices like SDIs and ARS in laryngeal nerve monitoring.