Protection of the Marginal Mandibular Branches of the Facial Nerves by Different Surgical Procedures in Comprehensive Cervical Lymphadenectomy for Locally Advanced Oral and Oropharyngeal Cancer: A Multicenter Experience

Abstract Background and objective: Tumor treatment has been progressive. Targeted therapy and immunotherapy have contributed in the surgical success of several patients with advanced oral and oropharyngeal cancer. Surgery is the primary treatment for oral and oropharyngeal cancer, and cervical lymphadenectomy is crucial in surgery. Evidence has shown that submandibular glands can be preserved in cervical lymphadenectomy for early stage oral and oropharyngeal cancer; however, the removal of the submandibular glands is inevitable in cervical lymphadenectomy for locally advanced oral and oropharyngeal cancer. Nowadays, with individualized and precise treatment, the anatomy and protection of the marginal mandibular branches of the facial nerves have received increasing attention. In this study, according to the different characteristics of patients and cervical lymph node metastasis of oral and oropharyngeal cancer, the marginal mandibular branches of facial nerves were treated by different surgical procedures, and the safety and protective effects of different surgical procedures were investigated.Methods: From January 2014 to June 2021, 197 patients with oral and oropharyngeal cancer satisfying the inclusion criteria were selected from the Head and Neck Department of Shenzhen Otolaryngology Research Institute/Shenzhen Longgang Otolaryngology Hospital, Head and Neck Department of Gannan Medical University Affiliated Cancer Hospital, Department of Oral and Maxillofacial Surgery of the First Hospital of Qiqihar in Heilongjiang Province, and Department of Otorhinolaryngology-Head and Neck Surgery of First Affiliated Hospital of Gannan Medical University. All patients underwent radical surgery by comprehensive cervical lymphadenectomy or radical surgery plus repair and reconstruction. During the operation, the marginal mandibular branches of the facial nerves were treated and the submandibular glands were removed. According to the different characteristics of patients and cervical metastatic lymph nodes, three different surgical procedures were used to treat the marginal mandibular branches of the facial nerve: finding and exposing the marginal mandibular branches of the facial nerves at the mandibular angles of the platysma flaps, finding and exposing the marginal mandibular branches of facial nerves at the intersections of the distal ends of facial arteries and veins with the mandible, and not exposing the marginal mandibular branches of the facial nerves. The anatomical position, injury, and complications of the marginal mandibular branches of the facial nerves were observed.Results: The marginal mandibular branches of the facial nerves penetrated from the front or lower ends of the parotid glands. They were constantly located between the deep surface of the platysma and the superficial layer of the deep fascia cervicalis, and on the plane of the lower mandible. They crossed the superficial surface of the posterior facial veins, mandibular angles, and anterior facial veins from back to front and entered the deep surface of deltoid muscles at the distal ends of facial arteries and veins. Among the 197 oral and oropharyngeal cancer patients undergoing comprehensive cervical lymphadenectomy with excision of the submandibular glands, the marginal mandibular branches of the facial nerves were found and exposed at the mandibular angles of the platysma flaps in 102 patients (102/197, 51.78%); the marginal mandibular branches of facial nerves were found and exposed at the intersections of the distal ends of the facial arteries and veins with the mandibles in 64 patients (64/197, 32.49%); the marginal mandibular branches of facial nerves were not exposed in 31 patients (31/197, 15.73%); the two methods for finding the marginal mandibular branches of the facial nerves both successfully found the marginal mandibular branches. Among the 197 patients with oral and oropharyngeal cancer, four patients (4/197, 2.03%) had permanent injury of the marginal mandibular branches of the facial nerves. Among them, one patient (1/102,0.98%) had injury of the marginal mandibular branches of the facial nerves found and exposed at the mandibular angles of platysma flaps; one patient (1/64, 1.56%) had injury of the marginal mandibular branches of the facial nerves found and exposed at the intersections of the distal ends of the facial arteries and veins with the mandible; the marginal mandibular branches of the facial nerves were not found and exposed in two patients (2/31, 6.45%), and the differences were not statistically significant (P>0.05). Temporary injury occurred in seven patients (7/197, 3.55%). Among them, two patients (2/102, 1.96%) had injury of the marginal mandibular branches of the facial nerves found and exposed at the mandibular angles of platysma flaps; two patients (2/64, 3.13%) had injury of the marginal mandibular branches of the facial nerves found and exposed at the intersections of the distal ends of facial arteries and veins with the mandible; and the marginal mandibular branches of facial nerves were not found and exposed in three patients (3/31, 9.68%). The differences were not statistically significant (P>0.05). The patients were followed up for 6 to 90 months after surgery, and the functions were restored in all patients with temporary injury of the marginal mandibular branches of the facial nerves.Conclusion: The three different surgical procedures were all safe and effective in treating the marginal mandibular branches of the facial nerves. Finding and exposing the marginal mandibular branches of the facial nerves at the mandibular angles of the platysma flaps was suitable for those with larger and more lymph nodes in region Ib. Finding and exposing the marginal mandibular branches of the facial nerves at the intersections of the distal ends of facial arteries and veins with the mandible was suitable for those with larger and more lymph nodes in region IIa. Not exposing the marginal mandibular branches of the facial nerves was suitable for those without obvious lymph nodes in region Ib or region IIa. Intraoperatively, we should choose an appropriate method in dealing with the marginal mandibular branches of the facial nerves according to the different characteristics of patients and cervical metastatic lymph nodes as well as the proficiency of surgeons.