Endoscopic Anatomy And Clinical Study Of Superior Laryngeal Nerve And Superior Laryngeal Artery

Background and Objectives: Hypopharyngeal squamous cell carcinoma(HSCC)is a common type of tumor in the head and neck.Transoral surgery(TOS)is a very important treatment method for the early stage HSCC,because it can decrease operative trauma and preserve the function of the larynx as much as possible.The intraoperative bleeding and postoperative decrease in swallowing function affect the promotion of TOS.The internal branch of the superior laryngeal nerve(ib SLN)and the superior laryngeal artery(SLA)are the most important innervation nerve and blood supply vessel.There are few studies on the anatomy of the two from an endoscopic perspective.In this study,firstly,we prepared an isolated larynx,then perform endoscopic dissection of ib SLN and SLA on the isolated larynx,and we analyze and summarize the anatomical characteristics of the two outside the larynx and inside the larynx under endoscopy.Secondly,we applied the anatomical concept of endoscopy to the TOS of HSCC,conducted relevant clinical research to understand the clinical benefits of appropriately managing the ib SLN and SLA during the TOS of HSCC.Methods: 1.Anatomical research: Preparation of isolated larynx with 8 cadaveric heads,which arteriovenous system were poured with colored latex,the anatomical range is: the boundary on both sides are the outer sides of the carotid sheath,the upper boundary is the upper edge of the hyoid bone,and the dorsal side is the retropharyngeal space behind the esophagus.Then,detached the internal and external carotid arteries above the carotid bifurcation behind the origin point of lingual artery.We observed the anatomical characteristics of the SLA,ib SLN,and cervical artery during the process.By conducting endoscopic dissection of the isolated larynx and analyzing anatomical data,we observed the entry position of the SLA and ib SLN under the endoscopic view,as well as the branching innervation of ib SLN and SLA in the larynx and their anatomical relationship.2.Clinical research:We observed the effect of preserving the ib SLN during the TOS of HSCC.29 patients who underwent TOS of HSCC were randomly divided into two groups.Patients in Group A underwent actively dissect and preserve of ib SLN nerve during the TOS,while patients in Group B underwent routine TOS.Both groups underwent Water Swallowing Test(WST)and M.D.Anderson Dysphagia Inventory(MDADI)before and after surgery,and executed regular follow-up after surgery.We also included 23 patients for a single arm observational study to observe the effects on the preventive managing of SLA during the TOS of HSCC.Through the anatomy and preventive ligation of SLA during TOS,we observed the branches and course of SLA,and recorded the amount of intraoperative bleeding and the time of surgery,and observed its impact on postoperative bleeding by follow-up.Results: 1.We successfully prepared the isolated larynx.Among 8cadaveric heads(16 sides),the Superior thyroid artery(STA)originated from multiple sources,with 10 sides originating from the external carotid artery(ECA),3 sides originating from the carotid bifurcation(CB),2sides originating from the common carotid artery(CCA),and 1 side originating from the arterial trunk.Except for one side originating from the arterial trunk,all other SLA originate from STA.The SLA of 7 cases(14 sides)entered the larynx through the thyrohyoid membrane,and 1case(2 sides)entered the larynx through the thyroid foramen.The average outer diameter of the CCA is 7.06 ± 0.76 mm,the average outer diameter of the ICA is 5.49 ± 0.69 mm,the average outer diameter of the ECA is 4.90 ± 0.71 mm,the average outer diameter of the STA is 1.87 ±0.25 mm,and the average outer diameter of the SLA is 1.04 ± 0.12 mm.In addition,the outer diameter ratio and correlation between each branch artery and the mother artery were analyzed.The distance from the CB to the origin point of the STA from the ECA is about 5.6 ± 3.89 mm,the distance from the origin of the STA to the origin of the SLA is about 8.17± 3.12 mm,and the distance from the origin of the SLA to its entry into the larynx is 14.7 ± 3.9mm.The diameter of the main ib SLN is about1.56 ± 0.19 mm,and only one side of ib SLN is divided into two branches before entering the larynx.Regarding the routing relationship between ib SLN and SLA outside the larynx,the directions of the two are basically the same,mostly from the outer lower to the upper inner,and the direction of the two is related to their starting points.2.Regarding the endoscopic anatomy of isolated larynx,we summarized the pattern of the ib SLN entering the larynx,and found that it enters the larynx at the posterior one-third of the lateral wall of the pyriform sinus.The ib SLN usually divide to three branches,distributed in supraglottic and pyriform sinus.And SLA have 2 to 6 branches,providing blood to the supraglottic region.We have defined the types of branches of SLA as three types: "tree root","丰-like",and "two main branches",most of which branch in the "tree root" type.Furthermore,we define three types of relationships between the ib SLN and the SLA according to the relationship of them when entry into the larynx: Type I:the ib SLN and the SLA enter the larynx through thyrohyoid membrane at the same point;Type II: the SLA and ib SLN enter the larynx through thyrohyoid membrane at different points.Type III: the ib SLN enter the larynx through the thyrohyoid membrane,and the SLA enter the larynx through the thyroid foramen.For the first two types,SLA is often located below the anterior part of ib SLN,and the distance between the two does not exceed one-third of the upper edge of thyroid cartilage in pyriform sinus.3.Clinical study of protection of ib SLN during TOS of HSCC:There were no differences in age,gender,TNM staging,pathological diagnosis,preoperative swallowing function,MDADI score,surgical time,and intraoperative bleeding between the two groups of patients(P>0.05).After surgery,the WST was performed to evaluate swallowing function.The Group A had a higher proportion of patients with normal swallowing function on the 1st day(P=0.035),5th day(P=0.039),and 7th day(P=0.033)after surgery compared to the control group.On the 14 th day after surgery,the MDADI scores of Group A are higher than those in the Group B in three dimensions: overall(P=0.021),functional(P=0.017),and physiological(P=0.034),except for the emotional dimension(P=0.070).The median time for postoperative soft food intake,normal oral diet,and gastric tube removal in Group A was 2 days,5 days,and 6days respectively,which were earlier than those in Group B(P<0.001).4.Clinical study of protection of SLA during TOS of HSCC: the SLA of 23 patients were located and preprocessed during TOS of HSCC.The average surgical duration is 44.8 ± 12.7 minutes,and the average intraoperative bleeding volume is approximately 25.2 ± 9.0ml.All patients did not experience postoperative bleeding within one week after surgery.2 patients found that SLA entered the larynx through the thyroid foramen,and more than three branches of SLA were located during TOS in 16 patients.Conclusion: The preparation of the isolated larynx is of great significance for understanding the anatomical characteristics of cervical blood vessels and nerves;ib SLN can be explored at one-third of the upper edge of the thyroid cartilage on the lateral wall of the pyriform fossa,and SLA can be found in the anterior lower part of ib SLN during TOS;Anatomy and preservation of ib SLN,dissecting and pretreatment SLA during TOS of HSCC can accelerate the recovery of postoperative swallowing function and reduce the risk of intraoperative and postoperative bleeding.