Anatomical Study And Clinical Application Of Extracranial Segment Of Facial Nerve

Part Ⅰ Anatomical Study of Extracranial Segment of Facial Nerve Objective: The facial nerve is closely related to the parotid gland,and the study of the anatomical characteristics of the facial nerve is essential to reduce the damage to the facial nerve during parotid tumor surgery.The purpose of this study is to grasp the anatomical characteristics of the facial nerve and each branch,including the number of branches,the anterior length of branches,the transverse diameter of branches and the general pattern of travel,so as to provide a reliable theoretical basis for clinical application.Methods: Twenty-five cranial specimens(50 sides)were selected for the study,14 male specimens and 11 female specimens.After the fine dissection of the facial nerve,vernier calipers were used to measure the important structures,mainly to obtain a series of data such as the number of facial nerve and each branch,transverse diameter,length before branching,etc.The transverse diameter and length before re-branching of the facial nerve in different genders were compared and analyzed.The specific locations of the upper and lower buccal branches were searched for according to the fixed body surface markings of the parotid ducts,and the relationship between the two locations was explored,and the distances,distribution patterns and potential connections between the parotid ducts and the upper and lower buccal branches were recorded.The data were compiled and the results were statistically analyzed with the help of SPSS26.0 software system.Result:(1)Among the general facial nerve trunk types,the two-branch type is most common with the temporal and cervical facial trunks being predominant,the temporal trunk being divided into the temporal,zygomatic and superior buccal branches.The cervical facial trunk includes the three-branch type of the inferior buccal branch,the mandibular rim branch and the cervical branch,but there are also two facial trunks in which the mandibular rim branch and the cervical branch share a common stem,with four sides having no inferior buccal branch.(2)The temporal and zygomatic branches were fixed in position,with branches of(2.4 ± 0.7)and(2.2 ± 0.8),and transverse diameters of(1.2 ± 0.1)mm and(1.9 ± 0.1)mm,respectively,while the branches of the mandibular rim branch had(1.8 ± 0.8)and transverse diameters of(1.4 ± 0.3)mm,and the branches of the cervical branch had(1.3 ± 0.5).(3)There was no statistically significant difference in the transverse meridian and pre-rebranching length of the common trunk and branches of the facial nerve by comparing different sexes(P > 0.05).(4)The buccal branch typology was two buccal branch type and three buccal branch type,two buccal branch type including one upper buccal branch and one lower buccal branch type and two upper buccal branch types.The three-branch type includes two upper buccal branches and one lower buccal branch type and one upper buccal branch and two lower buccal branches type,among which the two upper buccal branches and one lower buccal branch type are the most common.(5)In the classification of three buccal branches,the distance between the first upper buccal branch and parotid duct is(9.78±2.62)mm,the distance between the second upper buccal branch and parotid duct is(18.12±3.03)mm,and the distance between the lower buccal branch and parotid duct is(10.78 2.96)mm.The distances from the upper and lower buccal branches of the two buccal branches to the parotid duct are(13.66±3.35)mm and(9.98±2.02)mm respectively.Conclusions:(1)Among the types of facial nerve branches,the temporal branch is the most,the cervical branch is the least,the transverse diameter of the facial nerve trunk is the thickest,the transverse neck of the cervical branch is the thinnest,the length of the upper buccal branch before re-branching is the longest,and the mandibular marginal branch is the shortest.(2)There was no significant difference in the length before the transverse meridian and rebranching of the common trunk and branches of the facial nerve in males compared with females.(3)The buccal branches are closely related to the parotid duct,and the distance between the upper and lower buccal branches along the anterior margin of parotid gland is about 1cm.Through the relationship between their positions and distances,the parotid duct can provide a good reference standard for clinical surgery.Part Ⅱ Application of Anterograde Anatomy of Facial Nerve in Benign Tumors of Parotid GlandObjective: Anatomy of facial nerve is a key step in parotid tumor resection.Based on the anatomical characteristics of facial nerve,this study adopts anterograde anatomy from trunk to branch to explore the safety,effectiveness and clinical application value of this anatomical method in parotid benign tumor surgery,so as to improve the success rate of surgery and the quality of life of patients.Methods: Forty-nine patients with tumors located in the superficial lobe of the parotid gland and ≤3 cm in diameter were collected from the Department of Maxillofacial Surgery,Department of Stomatology,The First Affiliated Hospital of Bengbu Medical College, from January 2020 to September 2021,and were preoperatively diagnosed with benign parotid tumors.After designing a "V"-shaped incision,the facial nerve was gently dissected along the general trunk of the facial nerve,and the auricular nerve and parotid ducts were protected,while the mass and 0.5-1.0 cm of normal tissue around the parotid gland were excised.A bioprosthetic membrane was placed on the surface of the parotid gland to prevent the occurrence of gustatory sweating syndrome,and patients were regularly followed up and observed through objective and subjective evaluation indexes after surgery.Result:(1)All patients successfully resected the diseased tissue and part of parotid tissue by anterograde dissection,and the scope and length of all incisions did not extend.The pathological results showed that all patients were benign tumors of parotid gland.(2)Two patients showed symptoms of facial palsy with temporary lower lip tilt after surgery,and the facial nerve function score was grade II.Patients were instructed to take regulating nutritional nerve drugs,and the H-B facial palsy score was performed again on two patients at about 6 months,and the patients recovered to normal,and the remaining patients had no damage to the facial nerve.(3)All 49 patients had the greater auricular nerve preserved,but all had temporary periauricular numbness after surgery.(4).No tumor recurrence was observed during the observation period of 6-12 months after surgery.Conclusions: The paralleling dissection method along the common facial nerve trunk has clear anatomical landmarks,smooth path,complete tumor resection,low postoperative facial nerve injury,and good clinical results,which is a good choice for facial nerve dissection in parotid tumor resection.