Application And Evaluation Of Monitoring Technique Of External Branch Of Superior Laryngeal Nerve In Thyroid Surgery

Purpose In thyroid surgery,the superior larylaryngeal nerve(SLN)is sometimes damaged.The anatomical difference of the external branch of the superior laryngeal nerve is often difficult to identify during the operation.After the injury of the external branch of the superior laryngeal nerve,cricothyroid muscle dysfunction can be caused,resulting in pitch reduction,change of tone,relaxation of vocal cords,inability to produce high pitch and other symptoms.The clinical symptoms are relatively hidden,with great differences,and it is difficult to diagnose.Abnormal activity of vocal cords are inobvious in laryngoscope.Intraoperative nerve monitoring(IONM),as an adjunctive means of golden standard,has been widely recognized to identify and locate the recurrent laryngeal nerve(RLN)in thyroid surgery.In contrast to the conventional anatomy of the recurrent laryngeal nerve,many surgeons do not routinely expose and identify the external branches of the superior laryngeal nerve during thyroid or parathyroid surgery.Relevant literatures have shown that IONM is beneficial to identify and locate EBSLN,evaluate its integrity and function,and contribute to voice protection after thyroidectomy or parathyroidectomy.In this study,a retrospective comprehensive control experiment was conducted to analyze the application effect of superior laryngeal nerve monitoring technology in open thyroid surgery.Methods This study retrospectively analyzed 350 cases of open thyroid surgery in our hospital,including 181 cases in the monitoring group using intraoperative monitoring of the external branch of the superior laryngeal nerve and 169 cases in the non-monitoring group without intraoperative monitoring of the external branch of the superior laryngeal nerve.This stydy compared the indicators below between monitoring group and non-monitoring group patients,such as EBSLN damage probability,preoperative and postoperative voice disorders index scale version Jane(VHI-10)score,operation time,blood loss,postoperative 1 day operation drainage,postoperative extubation time,postoperative hospital stay and other indicators,and compared electromyographic signal S1,S2 of external branch of the superior laryngeal nerve among monitoring group patients during the operations.The results(1)There was no significant difference(P > 0.05)of preoperative VHI-10 score between the monitoring group and non-monitoring group in all patients,and postoperative VHI-10 score of both groups was higher than that before operation.There was no statistically significant difference in the patients of monitoring group(P > 0.05),and there was statistically significant difference in the patients of non-monitoring group.Compared to the monitoring group,VHI-10 score increased significantly in the non-monitoring group after surgery.(2)The operation time and drainage volume of the monitoring group were less than that of the nonmonitoring group on the first day after surgery,and the differences between the two groups were statistically significant(P < 0.05).(3)Intraoperative blood loss in the experimental group was less than that in the non-monitoring group,and the difference between the two groups was statistically significant(P < 0.05),except for patients in the unilateral total thyroidectomy group.There were only 2 patients in the monitoring group who underwent unilateral total thyroidectomy,and the sample size was small,so more samples were needed for experimental study.(4)Postoperative extubation time were the same between non-monitoring group and monitoring group undergone all unilateral thyroid resection + most unilateral thyroid resection + unilateral central cervical lymph node dissection.In patients of unilateral total resection of thyroid and unilateral total resection of thyroid + most unilateral thyroid resection,postoperative extubation time of the monitoring group was less than the that of non-monitoring group,but the difference had no statistical significance(P > 0.05).Postoperative extubation time of the remaining experimental group was less than that of the nonmonitoring group,and the difference was statistically significant(P < 0.05).(5)Among the patients undergoing unilateral total thyroidectomy + unilateral majority thyroidectomy + unilateral central cervical lymph node dissection,unilateral total thyroidectomy and unilateral total thyroidectomy + unilateral majority thyroidectomy,the postoperative hospital stay of the monitoring group was less than that of the nonmonitoring group,but P > 0.05,that means there was no significant difference between the two groups.The postoperative hospital stay of the remaining monitoring group was less than that of the non-monitoring group,and there was significant difference between the two groups.Conclusion Intraoperative nerve monitoring technology is an effective auxiliary means to identify the external branches of the superior laryngeal nerve.It can help surgeons identify and locate EBSLN during the operation and evaluate its integrity and function.In most patients,intraoperative stimulation of EBSLN will produce the recorded waveform amplitude,providing quantifiable information basis for functional evaluation of EBSLN.In open thyroid surgery,laryngeal nerve on the monitoring technology can reduce the risk of EBSLN injury in thyroid surgery,and reduce the probability of early pronunciation change after thyroidectomy,be conducive to the protection of the patients with postoperative voice,reduce the proportion of subjective voice disorders,and reduce the operation time,in the operation flow,intraoperative blood loss,postoperative drainage tube and postoperative extubation time such confinement.Due to the small sample size of part of this experiment,the studies on intraoperative blood loss,duration of drainage tube extubation and postoperative hospital stay need to be further verified by more samples.