The Anatomy And Protection Of The External Branch Of The Superior Laryngeal Nerve In Thyroid Surgery

Objective:The classification of the external branch of the superior laryngeal nerve(EBSLN)are generally classified according to the relationship of the nerve to the superior thyroid artery,or the superior pole of the thyroid.This study was carried out to investigate the location of the EBSLN,and the close relationship between the EBSLN and the superior thyroid artery,the superior pole of the thyroid,cricothyroid artery,the inferior pharyngeal constrictors.Based on this we explore the clinical guidance of the classification of the EBSLN,and find a more effective surgical method to protect the EBSLN.Methods:Retrospective analysis of 80 patients(110 sides)who underwent thyroid surgery in the Department of Otorhinolaryngology Head and Neck Surgery,Fourth Hospital of Hebei Medical University from October 2018 to February 2019,the EBSLN was routinely identified during thyroid surgery.The EBSLN was classified according to the classification of Cernea,Friedman and the shortest distance between the EBSLN and the superior thyroid vessels into glandular point.Results:1.According to the Friedman classification method,there were 31 sides(about 28.2%)for type Ⅰ,64 sides(about 58.2%)for type Ⅱ,and 15 sides(about 13.6%)for type Ⅲ.2.According to the Cernea classification method,there were 13 sides(about 11.8%)for type Ⅰ,57 sides(about 51.8%)for type Ⅱa,and 40 sides(about 36.4%)for type Ⅱb.3.In the treatment of the superior pole of the thyroid,according to the number of upper vascular disconnections,there were 63 sides that require secondary disconnection and 47 sides that require three times.The number of upper vascular disconnections was related to the location of the tumor and the size of the thyroid gland.According to the shortest distance between the EBSLN and the superior thyroid vessels insert gland point:the first blood vessel: there were 35 sides(31.8%)for type of safe,60 sides(54.6%)for type of danger,and 15 sides(13.6%)for type of vulnerability.The second blood vessel: there were 30 sides(27.3%)for type of safe,55 sides(50.0%)for type of danger,and 25 sides(31.8%)for type of vulnerability.The third blood vessel: there were 17 sides(36.2%)for type of safe,25 sides(53.2%)for type of danger,and 5 sides(10.6%)for type of vulnerability.The classification of upper vascular disconnection was related to factors such as tumor location,thyroid size and patient height.4.According to the relationship between the EBSLN and the cricothyroid artery: there were 15 sides(13.6%)located above the cricothyroid artery,17 sides(15.5%)parallel to the cricothyroid artery,and 78 sides(70.9%)located below the cricothyroid artery.Conclusions:1.The cernea classification has less practical guidance for surgery.2.Full opening of the cricothyroid space is the key to thyroid surgery.Separating the space from the Angle of the cricothyroid artery and the superior pole is a reliable method for finding the EBSLN.3.The key of the protection of the EBSLN is the manage of the superior pole of the thyroid.And the key of the manage of the superior pole is the treatment of the superior thyroid vessels.Single manage of the superior thyroid vessels is the key to protecting the EBSLN during surgery.The treatment of the superior thyroid vessels is not at the upper pole level,but on the point of the superior thyroid vessels into the gland.The shortest distance between the EBSLN and the point determines the degree of vulnerability of the EBSLN.