New Backstrap Vagus Electrode for Continuous Intraoperative Neuromonitoring in Thyroid Surgery

Introduction. Continuous intraoperative neuromonitoring (CIONM) via vagal nerve stimulation allows real-time surveillance of the recurrent laryngeal nerve during thyroid surgery. However, for effective CIONM, subtle changes in recurrent laryngeal nerve conductivity have to be detected. A newly developed stimulation electrode that provides stable nerve stimulation and safe application is presented. Methods. For electrode validation, current distribution was simulated with the finite element method. Mechanical characteristics were assessed through bench testing. Clinical evaluation was initiated with 11 thyroid surgeries. Results. Experimental and clinical results led to the development of a tripolar gold/polyimide electrode mounted onto a backstrap-shaped silicone body. It facilitated rapid electrode implantation and extraction (median implantation time 4 +/- 19 seconds). Peak extraction force was 570 mN. Median supramaximal stimulation currents were 2.00 +/- 0.95 mA and resulted in reliable electromyogram responses (median 3.1 +/- 3.0 mV). No intraoperative electrode dislocations occurred, and no postoperative nerve palsy was observed. Conclusion. The new backstrap vagal stimulation electrode meets the requirements for reliable CIONM.