To investigate the possibility of not damaging the recurrent laryngeal nerve during endoscopic-assisted thyroid surgery. METHODS: Eighty-two patients from December 2004 to June 2006 were resected with endoscopic assistance, using a high-frequency ultrasonic knife as the primary operation to remove the lesion. Subtotal resection should be performed in the thyroid tissue, and total resection should be operated under the posterior thyroid envelope to ensure complete preservation of the thyroid gland, without revealing the laryngeal recurrent nerve intraoperatively. Results: All surgeries were completed successfully, and no serious complications such as hemorrhage or laryngeal nerve occurred. In 1991, the first laparoscopic cholecystectomy was performed in China, and in recent years, with the maturation and promotion of laparoscopic technology, minimally invasive endoscopy has been widely used in various surgical procedures (gastrointestinal tumors, gastric decompression, common bile duct, pancreas, liver, thyroid, etc.). In China, the first lumpectomy of the thyroid gland was performed by Qiu Ming et al. in 2001. Injury to the recurrent laryngeal nerve has always been a major concern in thyroid surgery, and after years of experience in traditional surgery, many measures have been taken to avoid injury to the recurrent laryngeal nerve. Minimally invasive thyroid surgery is a recent procedure. For the protection of the recurrent laryngeal nerve during this procedure, we have formed a fixed pattern of minimally invasive thyroid surgery by drawing on the experience of traditional surgery. （The median age was 24 years old (19-45 years old), with 65 cases of grade II enlargement of the thyroid, 17 cases of grade I enlargement, 32 cases of single adenoma, 50 cases of multiple adenoma, 35 cases of bilateral adenoma, and an average size of 2.1 cm (1.1-3.4 cm) of adenoma suggested by ultrasound. The average size of thyroid adenoma was 2.1 cm (1-3 cm). During the same period, 50 female cases underwent conventional surgery as a control. Minimally invasive surgical method Equipment and instruments: high-frequency ultrasonic knife (Olympus Corporation), Snake 3.5mm endoscope, small pulling structure, and other strippers, separating forceps, and scissors, etc. Surgery method: The operation was performed under general anesthesia with tracheal intubation, with the patient lying flat with the head slightly backward, a transverse cervical line (about 2.0 cm) above the sternocervical vein incision, a symmetrical 1.8-2.0 cm curved incision in the midline, a small circular knife to cut the skin and cervical sphincter, an electric knife to moderately free the upper and lower flaps, a longitudinal incision of about 3.0 cm in the white line, separation of the peri-thyroid gland gap, and a small laparoscope. A small pulling structure was suspended and the peri-thyroidal adhesions were fully freed under the direct view of a 30-degree wide-angle rigid microscope to establish a microscopic view. The middle thyroid vein, the inferior thyroid vessels, isthmus, suspensory ligament, superior pole vessels and thyroid tissue were separated and severed by ultrasonic knife, and subtotal resection ensured that the operation was performed within the thyroid tissue, and total resection ensured that the posterior thyroid envelope was intact, and the laryngeal nerve and parathyroid gland were not exposed during the operation. Results: All 82 endoscopic-assisted thyroid surgeries were completed successfully. The tumor size was (2.10±1.16) cm (0.6 cm-3.6 cm), the average operation time was 42 min (30 min-82 min), the average hospital stay was 3 days, and the average postoperative scar length was 1.9 cm without intraoperative drainage. All 50 cases of conventional surgery were completed successfully. The tumor size was (2.23±1.21)cm (1.0cm-3.9cm), the average operation time was 40min (32min-65min), the average hospital stay was 5 days, the average postoperative scar length was 5.8cm, 22 cases had intraoperative drainage, and the average drainage flow was 35ml. No serious complications such as hemorrhage or laryngeal nerve occurred in both groups. Discussion The laryngeal nerve injury is one of the most common complications of thyroid surgery, and the rate of laryngeal nerve injury during surgery is reported to be 0.4%-3.9% in foreign countries; the incidence is reported to be 0.8%-7.8% in domestic literature. There is no large number of cases of laryngeal nerve injury in lumpectomy thyroid surgery. In recent years, proponents of exposure have reported that the rate of laryngeal nerve injury in the exposed group is significantly lower than that in the non-exposed group, which is statistically significant [7], but opponents believe that the process of exposing the laryngeal nerve also increases the chance of laryngeal nerve injury. The types of laryngeal nerve injuries include severance, ligation, electrocautery, clamping, contusion, and strain injuries. A domestic group of exploratory laryngeal nerve injury cases reported: the laryngeal nerve was suture ligature, scar adhesion compression, severed 43% (28/65), 9% (6/65), 48% (31/65), respectively. Theoretically, lumpectomy thyroid surgery by sternotomy should achieve a lower rate of laryngeal nerve injury than conventional thyroid surgery because of its direct visualization, visual magnification effect, and ultrasonic knife “bloodless” technique, which can avoid ligature-induced injury. The lumpectomy-assisted thyroid surgery is clinically safe and feasible. In recent years, procedures more complex than thyroid, such as gastric cancer, pancreatic tumor, and common bile duct, have achieved positive clinical results, and minimally invasive lumpectomy for these diseases did not have higher complications than conventional surgery. 2004, Miccoli [10] et al. retrospectively analyzed 427 cases of endoscopic-assisted thyroidectomy and noted that endoscopic-assisted thyroidectomy had no difference in operative time and postoperative complications compared with conventional thyroid surgery. conventional thyroid surgery. Our data suggest that there are no complications in endoscopic assisted thyroidectomy by the sternotomy pathway, and the operative time is not significantly (p<0.05) different from that of conventional thyroid surgery, which is longer in the early stage and has been shortened with surgical proficiency compared to conventional surgery. Combined with this group of cases, the authors experienced that in the specific operation, subtotal resection should be performed in the thyroid tissue, and total excision should be operated under the posterior envelope to ensure complete preservation of the thyroid gland, which can avoid damage to the parathyroid glands and the recurrent laryngeal nerve, and intraoperative exposure of the recurrent laryngeal nerve can be unnecessary routinely. Wang Cunchuan [11] et al. also reported that in 147 cases of lumpectomy thyroidectomy, there was no exposure of the recurrent laryngeal nerve and no one case of postoperative recurrent laryngeal nerve injury. In five patients with transient postoperative laryngeal nerve palsy reported by Qiu Ming [12], the tumor diameter was greater than 3 cm, so many authors have listed thyroid tumor diameter less than 3 cm as one of the indications for lumpectomy thyroid surgery. Most lumpectomy thyroid surgeries are performed under general anesthesia, which provides better patient compliance than traditional local anesthesia. For complex thyroid surgery, intraoperative real-time monitoring of the recurrent laryngeal nerve can monitor the nerve function in real time throughout the operation, which can accurately identify the recurrent laryngeal nerve and warn of possible nerve damage, and it is unnecessary to expose the recurrent laryngeal nerve. The lumpectomy of thyroid surgery combined with intraoperative real-time monitoring of the recurrent laryngeal nerve is expected to achieve zero injury to the recurrent laryngeal nerve.