Neuromonitored Thyroid Surgery: Optimal Stimulation Based on Intraoperative EMG Response Features

Area of Science:

• Neurosurgery
• Electrophysiology

Background:

• Neuromonitoring during thyroid surgery is crucial for preserving recurrent laryngeal, vagus, and external branch of superior laryngeal nerves.
• Different stimulators are used for intraoperative nerve monitoring, each with unique electrophysiologic response characteristics.

Purpose of the Study:

• To compare the normative electrophysiologic electromyography (EMG) response characteristics of key nerves.
• To evaluate evoked responses using various stimulators employed in neuromonitored thyroid surgery.

Main Methods:

• A prospective crossover study involving 11 patients undergoing thyroid surgery.
• EMG responses were recorded using endotracheal tube surface electrodes.
• Stimulation was performed with monopolar (Prass standard, ball tip), bipolar, and dissecting instruments.

Main Results:

• Monopolar (Prass standard) stimulators showed shorter latency when nerves were not covered by fascia.
• Pooled mean latency and threshold increased significantly when nerves were covered by fascia.
• Monopolar and bipolar electrodes demonstrated higher depolarization rates; monopolar electrodes had limited response at a distance.

Conclusions:

• Monopolar stimulators are more sensitive for neural mapping, while bipolar instruments offer greater specificity.
• Dissecting instruments present a viable alternative, combining monopolar features with enhanced specificity.