The Application Of Intraoperative Neromonitoring Of Recurrent Laryngeal Nerve During Thyroid Surgery

The causes of recurrent laryngeal nerve injury include transection, clamping, stretching, electro-thermal, ischemia, suction, etc. But the actual causes of recurrent laryngeal nerve injury, especially in those with visual integrity, are still not well understood. Recurrent laryngeal nerve injury caused hoarseness, seriously affected the quality of life, and raise to one of the leading causes of medical dispute. The rates of temporary recurrent laryngeal nerve injury to initial thyroid surgery, reoperatively surgery and more than 2 times cutting surgery are 2.1%, 3.8%, and 9.5% respectively; the corresponding rates of permanent recurrent laryngeal nerve injury are 1.0%, 1.5%, and 4.8% separately. The incidence of postoperative vocal cord paralysis was 6.6% by laryngoscopic examination , which revealed visual identification of intraoperative nerve continuity, only 1.1% in patients were diagnosed as nerve injury. The intraoperative monitoring can help clinical beginners to recognise 85% of the recurrent laryngeal nerve smoothly, increase the identification rate from 90% to 99.3%.The weakened EMG hints recurrent laryngeal nerve injury. Analyze the operation procedure before and after the signal change, explored along the nerves, "injury points"can help operators find out the causes to the nerve injury to avoid permanent nerve injury. Randomized clinical trials show that the monitoring during thyroid surgery can reduce the rate of temporary recurrent laryngeal nerve injury, especially obviously in high-risk groups.In complex thyroid surgery including thyroid cancer has been predicted preoperatively to violate, compress or adhesion with the recurrent laryngeal nerve and neural variation such as non recurrent laryngeal nerve may exist, it is extremely difficult and significantly risky to expose the recurrent laryngeal nerve. The occurrence of non recurrent laryngeal nerve is associated with embryonic development of aortic arch anomalies, especially closely related with the lack of brachiocephalic trunk and abnormal right subclavian artery (ARSA). Non recurrent laryngeal nerve loses the normal course as hooking around the blood vessel, branches from the vagus nerve, directly lateropuls or rampages around the inferior thyroid artery into the throat, is a rare anatomic variation of the recurrent laryngeal nerve with the incidence of 0.5%, very difficult to preoperatively predict and intraoperatively visual identify, the high risk factor to vocal cord paralysis after thyroid surgery with injury rate of 12.9%. For non-recurrent laryngeal nerve poses special risks to the thyroid surgery, turn to be an independent risk factor for hoarse voice. Surgeon tried various options such as preoperative neck enhanced CT, angiography, esophagoscopy, barium meal examination, magnetic resonance, even cervical ultrasound to test the existence of the vascular malformation to speculate non recurrent laryngeal nerve. Although the methods above can predict non recurrent laryngeal nerve, but they need a rich imaging experience, can not routinely evolve, neither replicated. The application of the " indirect vagus nerve monitoring method " during thyroid surgery can not only recognize non recurrent laryngeal nerve in high accuracy, but also implement non recurrent laryngeal nerve function monitoring to ensure the integrity of nerve function, which need no special expert imaging skills, and facilitate to promote in clinical surgery doctors.Objective:This paper aims to use the recurrent laryngeal nerve being motor nerve, dominanting vocal cord muscles, with the principles of electrical excitability. Apply the intraoperative neuromonitoring technology to reduce the injury risk of recurrent laryngeal nerve by establishing a standardized monitoring methodology, standarding indicator parameters and improving the specificity. Apply the"indirect vagus nerve monitoring methods" to identify and protect the non recurrent laryngeal nerve. Explore a new method to reduce the non recurrence laryngeal nerve injury.Data and method: 279 patients who underwent complex thyroid surgery with the recurrent laryngeal nerve monitoring were studied retrospectively, including six cases of non recurrent laryngeal nerve monitoring, from March 2009 to January 2010 patients attendance at division of thyroid in the 3rd hospital affiliated to Jilin University. 54 male cases, 225 female cases (male to female ratio, 1:4.1). Age ranged 19 ~ 72 (46.21±8.71) years old. 220 cases of thyroid papillary carcinoma, 3 cases of medullary thyroid cancer, cancer accounted for 79.9℅, 130 cases of malignant tumors with lymph node metastasis (46.6℅); 53 cases of nodular goiter, thyroiditis and 3 patients, 39 cases of thyroid disease with thyroiditis, benign disease 20.1℅. Reoperation in 136 cases (accounting for 48.7℅), 143 cases of initial surgery (accounting for 51.3℅).6 patients with non recurrent laryngeal nerve, 1 male case ,5 female cases ,aged 20 to 51 years old. The average age is 38.83 years old. They were admitted to hospital due to medical examination found thyroid nodule. No complain of palpitation, shortness of breath, polyphagia, irritability, hoarseness, difficulty in swallowing or breathing.Apply intraoperative neuromonitoring, which includes"The cross shape recurrent laryngeal nerve localization" methodBefore recurrent laryngeal nerve dissection, stimulate the connective tissue below the lower pole of the thyroid with 2mA current, detect perpendicular to the direction of tracheal to rapid position recurrent laryngeal nerve; detect parallel to the direction of tracheal to exclude the coexistence of non recurrent laryngeal nerve. There will be 97% of the patients whose recurrent laryngeal nerve can explore the EMG signal. Then, separating the connective tissue in the strongest signal point could quickly reveal the recurrent laryngeal nerve.The "multi-sites, Trilogy" recurrent laryngeal nerve exposure method RLN revealed below by the lower pole of thyroid gland, in the dorsal of the lower pole, under the inferior thyroid artery, and the place recurrent laryngeal nerve enter into larynx (0.5cm below the angle of the thyroid cartilage) and others, called"multi-sites".And "Find, identify, protect," called "trilogy".The"point cut tumor with continuous monitoring of the recurrent laryngeal nerve"methodDangerous operations lead to intraoperative recurrent laryngeal nerve injury easily. Compare the change between EMG before and after each step, even "continuous monitoring" When it is necessary, assessment of nerve function integrity by EMG in the premise of " point cut tumor ", which help analyze the mechanism or step of nerve injury in a timely manner to lift and repair nerve damage."4-step procedure of inraoperative recurrent laryngeal nerve monitoring" Result:1. Among the 279 patients who underwent complex thyroid surgery with the recurrent laryngeal nerve monitoring, from March 2009 to January 2010 patients attendance at division of thyroid in the 3rd hospital affiliated to Jilin University, 6 cases of non recurrent laryngeal nerve were monitored and protected successfully, Courser ofⅡA type, located on the right. The junction with vagus nerve were revealed by retrograde.2.Non recurrent laryngeal nerves transverse into the throat from the branch point of the vagus equivalent to the thyroid isthmus plane. Application of intraoperative nerve monitoring confirmed,The EMG exist at the branching point in the vagus nerve, and the proximal part of the branching point (the level of upper pole of the thyroid) , but disapeare in the 5mm or 10mm distal part of the branching point (the level of lower pole of the thyroid) .Summary of 6 cases NRLN monitoring experience, when the vagus nerve signals is undetectable at the level of the inferior thyroid pole, surgeons should detect the vagus nerve at the level of the upper thyroid pole. If signal produced, operators can infer the existence of NRLN. The 6 patients with NRLN underwent intraoperative neuromonitoring, laryngoscopy showed vocal cord movement normal postoperatively, no tone or sound changes happened by clinical observation.Conclusion:1. No EMG in the distal part of the branching point of vagus nerve may be related to which the vagus nerve was mixed nerve (including somatic motor, somatic sensory, visceral motor and visceral sensory nerve, etc.) and losing of the typical antegrade or retrograde stimulus conduction. 2. When the vagus nerve signal is undetectable at the level of the inferior thyroid pole, surgeons should detect the vagus nerve at the level of the upper thyroid pole. 3. surgeons could predict NRLN ,when the vagus nerve signals is undetectable at the level of the inferior thyroid pole, but detectable at the level of the upper thyroid pole.4. The"indirect Vagus nerve monitoring method" is a simple method which could diagnose of non recurrent laryngeal nerve accurately and reliablely, before operating the recurrent laryngeal nerve, does not require extensive dissection, and easy to be promoted among the surgeons.5. There is no longer need to do various imaging studies to exclude a variety of preoperative vascular anomalies for the patients using"indirect vagus nerve monitoring method". This method makes specially sense in patients without vascular abnormality associated symptoms, or the corresponding preoperative imaging examination, found non recurrence laryngeal nerve intraoperativly.