Electrophysiological and clinical comparison of recurrent laryngeal nerve stimulated by different type of electrostimulator probes

Background and Aim; Intraoperative recurrent laryngeal nerve monitoring is often used to prevent recurrent laryngeal nerve injury, neural mapping and evaluation of nerve functions during thyroidectomy. According to our knowledge ,there is no study showing superiority between bipolar and monopolar stimulator probes used in neuromonitoring in the literature. In this study, we aimed to evaluate the superiority of two different types of probes. Material and Method: Twenty-one patients with total thyroidectomy and hemithyroidectomy indications and who had no previous neck surgery with normal pre-operative vocal cord examination were included in the study. During operation, amplitude and latency values obtained with both bipolar and monopolar stimulator probes from 10 anatomical points (vagal nerve, recurrent laringeal nerve inferior portion, recurrent laryngeal nerve superior portion, external branch of superior laryngeal nerve (EBSLN)) were recorded both sheath intact and dissected in a prospective database and examined retrospectively. Results: The difference of the monopolar probe amplitudes at 4 points out of 20 points was significantly higher than the bipolar porbe (p <0.05). At one point, bipolar probe latency values were higher (p = 0.038). On the right side of the EBSLN values, the bipolar probe amplitude values were significantly higher (p = 0.024). On the left side, the latency values of the monopolar probe were longer (p = 0,000). No statistically significant difference was found between the amplitudes and latency values at 13 points on the other remaining sides. When the sheaths were dissected, the amplitude values were significantly higher than the intact values, and when the pre- and post-resection values were compared, there was a decrease in the amplitudes compared to pre-resection values. In the measurements between the superior and inferior of the recurrent nerve, the majority of the latens values were longer in the inferior side of reccurent nerve, indicating that this system works properly. Conclusion: Considering the monopolar probe amplitude data, it is more suitable for neural mapping at certain points, and the differences between the two probes are generally found to be statistically insignificant. The monopolar probe allows for wider use because it allows modification with surgical instruments. For a constant view, there is a need for multi-centered studies involving more patients.