New placement of recording electrodes on the thyroid cartilage in intra-operative neuromonitoring during thyroid surgery

Objective: During thyroid surgery, extreme caution is needed not to harm the recurrent laryngeal nerve and to avoid vocal cord palsy. Intra-operative neuromonitoring became increasingly popular as an adjunct to the gold standard of visual identification of the recurrent laryngeal nerve (RLN). Electromyographic (EMG) responses are normally recorded by electrodes attached to the endotracheal tube. Alteration in position can lead to false loss of signal. We developed thyroid cartilage electrodes that can be fixed directly onto the thyroid cartilage. Study design: Prospective clinical cohort Methods: Thyroid surgery with intra-operative neuromonitoring using both endotracheal tube-based electrodes and thyroid cartilage electrodes was performed in 25 patients undergoing thyroid surgery. EMG data were collected and reported as median and interquartile ranges (IQR), and the results were compared with the x Wilcoxon signed-rank test for paired measurements. Results: After stimulating vagal nerve (VN), recurrent laryngeal nerve (RLN) and external branch of the superior laryngeal nerve (EBSLN), significantly higher EMG amplitudes were measured before and after thyroid resection for the thyroid cartilage (TC) electrodes, in all comparisons except for the right VN. At the level of the left EBSLN, median amplitude of 560 mV (IQR 190-1050) before and 785 mV (IQR 405-3670) after resection was noted. At the level of the right EBSLN, median amplitude of 425 mu V (IQR 257-698) before and 668 mV (IQR 310-1425) after resection was noted. Median amplitudes of 760 mV (IQR 440-1180) and 830 mV (IQR 480-1490) were noted at the left RLN, median amplitudes of 695 mV (IQR 405-1592) and 1078 mV (IQR 434-1895) were noted at the right RLN. Conclusion: Thyroid cartilage electrodes appear to be a feasible and reliable alternative for endotracheal electrodes