Recent Developments of Intraoperative Neuromonitoring in Thyroidectomy

Area of Science:

• Neurosurgery
• Otolaryngology
• Surgical Technology

Background:

• Intraoperative neuromonitorization (IONM) using surface electrode-based endotracheal tubes (ETT) is standard for thyroidectomy, with intermittent (I-IONM) and continuous (C-IONM) approaches.
• Current ETT-based IONM faces limitations due to inadequate electrode contact with vocal cords, prompting investigation into alternative recording methods.
• Continuous IONM typically requires direct vagus nerve stimulation, which involves invasive nerve dissection and probe placement.

Purpose of the Study:

• To explore novel electrode configurations and continuous monitoring techniques to overcome limitations of current IONM in thyroidectomy.
• To evaluate the efficacy of alternative recording electrodes and the newly developed laryngeal adductor reflex continuous IONM (LAR-CIONM).

Main Methods:

• Investigation of various recording electrodes, including needle and surface electrodes applied to the thyroarytenoid muscle, posterior cricoarytenoid muscle (PCA), tracheal cartilage, or skin.
• Implementation of laryngeal adductor reflex continuous IONM (LAR-CIONM), a non-probe method utilizing the vocal cord adduction reflex.
• Comparison of EMG amplitudes and stability across different electrode types and monitoring methods, assessing their response to tracheal manipulation.

Main Results:

• Needle electrodes yield higher EMG amplitudes than ETT electrodes, despite being more invasive.
• Adhesive surface electrodes provide safe EMG recordings with lower amplitudes than ETT electrodes but are less affected by tracheal manipulations.
• LAR-CIONM demonstrates a novel approach to continuous monitoring by tracking the vocal cord response to a stimulus, bypassing the need for direct vagus nerve stimulation.

Conclusions:

• Alternative electrodes offer potential improvements in IONM accuracy and reliability during thyroidectomy.
• LAR-CIONM presents a promising, less invasive alternative for continuous neuromonitorization, enhancing vocal cord protection.
• Ongoing research into advanced electrode technologies and reflex-based monitoring is crucial for refining IONM in thyroid surgery.