Objective To investigate the clinical significance of visual identification and intraoperative neuromonitoring of recurrent laryngeal nerve (RLN) during thyroidectomy. Methods Totally 1 664 patients underwent thyroidectomy with RLN protection from January 2009 to December 2009 were included in this study, in which 1 447 cases were protected by visual identification only, and 217 complex thyroidectomy cases were protected by visual identification and intraoperative monitoring. Results By the “multisites, three steps” RLN exposure method, 1 417 cases （85.16%） were successfully recognized and the recognition time was (3.57±1.26) min. The recognition time in the rest 30 complex cases (2.07%) without intraoperative neuromonitoring was (17.02±5.48) min. By this method, the temporary RLN injury occurred in 23 cases (1.54%) and 15 cases (65.22%) recovered within 2 weeks. In patients undewent intraoperative neuromonitoring, the recognition rate was 100% (217/217) and recognition time was (2.18±0.67) min. The temporary RLN injury occurred in 4 cases (1.84%) and 3 cases (75.00%) recovered within 2 weeks. All temporary RLN injuries recovered within 1 month and no persistent RLN injury occurred. Conclusions Conventional visual identification can reduce the RLN injury, but not meet the needs of the RLN protection during complex thyroidectomy. The combination of visual identification and intraoperative neuromonitoring can further improve the recognition rate and shorten the recovery time of vocal cord dyskinesia.
ObjectiveTo research the relevancy between the amplitudes of EMG signal of recurrent laryngeal nerve (RLN) during thyroidectemy with the movement of vocal cords after operation by applying the intraoperative neuromonitoring (IONM) and verify the proper warning criterion. MethodsFrom April 2013 to October 2013, 130 patients (214 nerves at risk) underwent complex thyroidectomy with the application of IONM. According to the degree of amplitude changing on different sites of RLN (proximal site and distal site) before closing incision, all the patients were divided into 10 groups. Every patient's vocal cords movement after operation by laryngoscopy and simulated the neural function in real time were compared. ResultsSeven patients got abnormal movement of vocal cords, the corresponding amplitudes of the EMG signal of RLN were in the range between 0 to 50%, 1 case from Group 6 (40%≤Rp/Rd<50%), 1 case from Group 8 (20%≤Rp/Rd<30%), 1 case from Group 9 (10%≤Rp/Rd<20%), 4 cases from Group 10 (0≤Rp/Rd<10%), and there's no permanent RLN palsy. ConclusionThe final amplitude of RLN decrease below 50%R1 would probably lead to vocal cords' abnormal movement, and when it decrease below 30%R1, the possibility of abnormal movement would increase; 50% decrease of EMG amplitude can be used as a warning criterion to prevent nerve function damage.
ObjectiveTo introduce the advances of intraoperative neuromonitoring (IONM) during thyroid or parathyroid surgery. MethodsThe literatures about IONM during thyroid or parathyroid surgery in recent years at home and abroad were collected and reviewed. ResultsIONM is improved from invasive to noninvasive:endotracheal intubation with electrode on its surface. Standardized procedures of IONM is developed. Intermittent monitoring is replaced by continuous monitoring. The monitoring of external branch of superior laryngeal nerve is also a supplement to laryngeal recurrent nerve. With the aid of IONM, non-recurrent laryngeal nerve could be identified easily, also injury spot, and damage degree. We could speculate probable damage mechanisms and prevent irreversible nerve damage through IONM. ConclusionsIONM could be an effective technique to reduce the risk of recurrent laryngeal nerve injury during thyroid or parathyroid surgery, especially in complex surgery and reoperations, which could predict the postoperative function of laryngeal recurrent nerve, and help to avoid severe postoperative complications.
ObjectiveTo explore optimal current intensity for neural monitoring of vagus nerve and recurrent laryngeal nerve during the thyroid and parathyroid surgery, so that we can judge function, location, identify, and protect the nerve more effectively and more quickly. MethodA total of 100 patients who underwent thyroid or parathyroid operations by the same surgeon in West China Hospital, meanwhile accepted intraoperative neuromonitoring (IONM), and 186 nerves at risk were enrolled in this study. According to the standardized process of nerve monitoring, we stimulated the vagus nerve with the current strength of 1-5 mA, and respectively stimulated laryngeal recurrent nerve with 1-3 mA indirectly and directly, and recorded the amplitude of electromyographic signal, and changes of heart rate and blood pressure during the process. The purpose was seeking the optimum current strength for each stage of IONM. ResultsIn 186 vagus nerves being tested, when monitoring the vagus nerve outside the carotid sheath, 109 vagus nerves (58.6%) sent out signals and got stable electromyography and warning tone with 1 mA, 164 (88.2%) vagus nerves had signals with 2 mA, 177 (95.2%) vagus nerves had signals with 3 mA, 182 (97.8%) vagus nerves had signals with 5 mA. Before and after the vagus nerve stimulation, heart rate and blood pressure of patients had no significant change. When directly monitoring the vagus nerve with 1 mA, V1 signals had no response in 2 vagus nerves (1.1%), V2 signals had no response in 9 vagus nerves (4.8%). But if the current intensity of stimulation was 2 mA or 3 mA, all patients got stable electromyographic signals. When searching for the laryngeal recurrent nerve, 92 (49.5%) got signals with 1 mA, 171 (91.9%) got signals with 2 mA, 184 (98.9%) got signals with 3 mA. When identifying laryngeal recurrent nerve and others, if the intensity of current was more than 2 mA, the current might conduct around and produce illusion. However, if the intensity of stimulation current was 1 mA, there's no electromyographic signal when we put the probe onto the tissue close to the laryngeal recurrent nerve. During identification of branches of laryngeal recurrent nerve with current strength of 1 mA, each electromyographic signal could be obtained. The chief branch into the throat produced the highest amplitude. The esophagus and trachea branch emg amplitude value was similar, equalling to 1/3-1/4 of the amplitude value in chief branch. ConclusionsWe suggest using current intensity of 5 mA on the surface of the carotid sheath to monitor the vagus nerve indirectly and obtain V1 signal, as an alternative to opening the carotid sheath. If fail, dissecting the carotid sheath, and using current intensity of 3 mA to monitor the vagus nerve directly; 3 mA is the optimal current intensity to search for the laryngeal recurrent nerve, and 1 mA is the optimal current intensity to identify the laryngeal recurrent nerve and its branches of esophagus and trachea, blood vessels, and so on.