Lower Facial Nerve Nomenclature Clarification: Cervical Branch Controls Smile-Associated Lower Lip Depression and Dental Display.

OBJECTIVE: In head and neck ablative surgery, traditional teaching is that the key facial nerve branch to preserve along the plane of the lower border of the mandible is the marginal mandibular branch (MMb), which is considered to control all lower lip musculature. The depressor labii inferioris (DLI) is the muscle responsible for pleasing lower lip displacement and lower dental display during natural emotive smiling. STUDY DESIGN: To understand the structure/function relationships of the distal lower facial nerve branches and lower lip musculature. SETTING: In vivo extensive facial nerve dissections under general anesthesia. METHODS: Intraoperative mapping was performed in 60 cases, using branch stimulation and simultaneous movement videography. RESULTS: In nearly all cases, the MMb innervated the depressor anguli oris, lower orbicularis oris, and mentalis muscles. The nerve branches controlling DLI function were identified 2 ± 0.5 cm below the angle of the mandible, originating from a cervical branch, separately and inferior to MMb. In half of the cases, we identified at least 2 independent branches activating the DLI, both within the cervical region. CONCLUSION: An appreciation of this anatomical finding may help prevent lower lip weakness following neck surgery. Avoiding the functional and cosmetic consequences that accompany loss of DLI function would have a significant impact on the burden of potentially preventable sequelae that the head and neck surgical patient frequently carries.

A modified method for minimizing damage to the marginal mandibular branch (MMB) during partial superficial parotidectomy(PSP): A retrospective study.

The aim of this study was to compare modified partial superficial parotidectomy (MPSP) with conventional partial superficial parotidectomy (CPSP) in a retrograde approach, and to determine whether MPSP can reduce the risk of injury to the MMB of the facial nerve and the rate of postoperative facial palsy. Patients with benign parotid gland tumors of the superficial lobe were included retrospectively in two groups: one group was treated with CPSP; the other group was treated with MPSP, in which the MMB was dissected in an anterograde direction or not dissected. The patients' sex and age, location of tumor, size of tumor (maximum tumor diameter), histopathological distribution, operative time, and incidence of postoperative facial nerve weakness were compared. There was no significant difference in operative time between the two groups (p = 0.913). There was a significant difference (p = 0.008) in postoperative facial nerve weakness, with temporary facial nerve weakness observed in 19 and five patients in the CPSP and MPSP groups, respectively. Furthermore, there was a significant difference (p = 0.009) in MMB weakness, with temporary MMB weakness observed in 15 and three patients in the CPSP and MPSP groups, respectively. There was no significant difference (p = 0.564) in the weakness of other branches between the two groups. All cases of paresis scored ≤3 on the House-Brackmann scale, and all cases of temporary facial nerve weakness resolved within 6 months of surgery. No patient developed permanent paralysis. Within the limitations of the study, it seems that modified partial superficial parotidectomy (MPSP) should be preferred over conventional partial superficial parotidectomy (CPSP) whenever appropriate.

Peripheral facial nerve schwannoma at the inferior mandibular margin: a case report.

Schwannomas commonly occur in the head and neck region as acoustic neuromas. Facial nerve schwannomas are rare and usually occur in the temporal region. A 57-year-old woman presented with a mass at the right mandibular margin. Magnetic resonance imaging revealed a schwannoma located immediately caudal to the mental foramen. We were initially uncertain whether it arose from the trigeminal nerve or the facial nerve. Excision was performed under general anesthesia. The mass was encapsulated and easily detached from the surrounding tissue. The nerve of origin was identified proximal to the tumor. A facial nerve origin was confirmed as the muscles supplied by the marginal mandibular branch of the facial nerve moved on nerve stimulation. Nerve fibers were not found distal to the tumor, possibly because they had been cut during excision. We believe that this is the first report of a schwannoma arising from the peripheral facial nerve.

Indications for partial parotidectomy using retrograde dissection of the marginal mandibular branch of the facial nerve for benign tumours of the parotid gland.

The aims of this study were to evaluate the efficacy of partial parotidectomy using retrograde dissection of the marginal mandibular branch of the facial nerve for benign tumours of the parotid gland and to establish the indications for its use. We examined 106 consecutive patients with previously untreated benign tumours in the lower portion of the parotid gland who were treated by parotidectomy. The first group (anterograde group, n=52) consisted of those who had standard anterograde parotidectomy. The remaining patients, who underwent retrograde parotidectomy, were further divided into two groups: those in whom the upper edge of the tumour was located below the mastoid tip (below mastoid group, n=46) or those in whom it was above the mastoid tip (above mastoid group, n=8). The operating time was significantly shorter in the below mastoid group (141.2, 127.5, and 98.1minutes, respectively) as was intraoperative blood loss (41.1, 53.0, and 24.4ml, respectively), compared with the other two groups. There was a higher incidence of facial nerve dysfunction in the above mastoid group postoperatively (4/8) than in the other two groups. The results suggested that the presence of a tumour of any size located below the mastoid tip is a good indication for parotidectomy using retrograde dissection of the marginal mandibular branch of the facial nerve.

Preserving the marginal mandibular branch of the facial nerve during submandibular region surgery: a cadaveric safety study.

BACKGROUND: The marginal mandibular branch of the facial nerve is vulnerable to iatrogenic injuries during surgeries involving the submandibular region. This leads to significant post-operative morbidity. Studies assessing accurate anatomical landmarks of the marginal mandibular branch are sparse in South Asian countries. Present study was conducted to assess the relationship between the marginal mandibular branch and the inferior border of the body of mandible. METHODS: Twenty-two preserved cadavers of Sri Lankan nationality were selected. Cadavers were positioned dorsal decubitus with necks in extension. The maximum perpendicular distance between the inferior/caudal most ramus of the marginal mandibular branch and the inferior border of the body of the mandible was recorded on both hemi faces. RESULTS: Recorded maximum distance was 17.65 mm on left side and 10.80 mm on right side. Mean maximum distance, was 7.12 ± 2.97 mm. There was no statistically significant difference in the maximum deviation on left (7.84 ± 3.41 mm) and right sides (6.44 ± 2.37 mm). CONCLUSION: Course of the marginal mandibular nerve is complex. If the distance of the incision in the posterior submandibular approach is less than 2 cm from the inferior border of the mandible, there is a high probability of damaging the inferior ramus of the marginal mandibular branch of the facial nerve.

Neurovascular structures of the mandibular angle and condyle: a comprehensive anatomical review.

BACKGROUND: Various surgical interventions including esthetic surgery, salivary gland excision, and open reduction of fracture have been performed in the area around the mandibular angle and condyle. This study aimed to comprehensively review the anatomy of the neurovascular structures on the angle and condyle with recent anatomic and clinical research. METHODS AND RESULTS: We provide detailed information about the branching and distributing patterns of the neurovascular structures at the mandibular angle and condyle, with reported data of measurements and proportions from previous anatomical and clinical research. Our report should serve to help practitioners gain a better understanding of the area in order or reduce potential complications during local procedures. Reckless manipulation during mandibular angle reduction could mutilate arterial branches, not only from the facial artery, but also from the external carotid artery. The transverse facial artery and superficial temporal artery could be damaged during approach and incision in the condylar area. The marginal mandibular branch of the facial nerve can be easily damaged during submandibular gland excision or facial rejuvenation treatment. The main trunk of the facial nerve and its upper and lower distinct divisions have been damaged during parotidectomy, rhytidectomy, and open reductions of condylar fractures. CONCLUSION: By revisiting the information in the present study, surgeons will be able to more accurately prevent procedure-related complications, such as iatrogenic vascular accidents on the mandibular angle and condyle, complete and partial facial palsy, gustatory sweating (Frey syndrome), and traumatic neuroma after parotidectomy.

Avaliação da Função Nervo Marginal Mandibular após Acessos Risdon / Assessment of the Marginal Mandibular Nerve Function after Risdon Approach

O conhecimento detalhado da anatomia do nervo facial e de seus ramos, em especial o ramo marginal mandibular, é de fundamental relevância em cirurgias para tratamento de fraturas mandibulares com uso do acesso cirúrgico Risdon, evitando-se possíveis lesões. O objetivo deste trabalho é o de avaliar a função do ramo marginal mandibular após tratamento cirúrgico dessas fraturas, utilizando-se o acesso tipo Risdon. Foi avaliada a função do nervo marginal mandibular de 44 pacientes com fraturas de corpo e ângulo mandibulares, utilizando exame visual com base na escala de classificação do nervo facial House-Brackmann, no pré-operatório e pós-operatório (24h). Os pacientes que apresentaram algum grau de disfunção em 24 h foram reavaliados em 01 semana, 01 mês e 03 meses de pós-operatório. Do total avaliado, treze (29,55%) apresentaram algum grau de disfunção no 1º DPO, e trinta e um pacientes (70,45%) apresentaram normalidade na função, sendo o gênero feminino mais acometido (71,43%). Após 03 meses, 91% dos pacientes apresentaram grau I (normal) e 9%, grau II (disfunção branda). Assim, pode-se concluir que a maioria dos pacientes avaliados apresentou normalidade na função do nervo marginal mandibular em todos os tempos pós-operatórios, sendo a disfunção branda a mais encontrada, demonstrando segurança nos acessos Risdon realizados.

Detailed knowledge of the anatomy of the facial nerve and its branches, especially the marginal mandibular one is of fundamental importance in surgical treatment of mandibular fractures by making use of the Risdon surgical approach. The aim of this study is to evaluate the function of the marginal mandibular branch of facial nerve after surgical treatment these fractures by access Risdon. 44 patients with fractures of the mandibular body and angle, and the marginal mandibular nerve function being analyzed through visual inspection based on the rating scale in House-Brackmann facial nerve, in the preoperative and postoperatively (24 hours). Patients who had some degree of dysfunction within 24 hours were reassessed during 01 week, 01 month and 03 months postoperatively. Thirteen (29.55%) had some degree of dysfunction in a PO and thirty one (70.45%) patients had normal function, being females the most affected ones (71.43%). After 03 months, 91% of patients had grade I (normal) and 9% had grade II (mild dysfunction). It can be concluded that the majority of patients showed normal function of the marginal mandibular nerve at all times postoperatively demonstrating safety in the Risdon approaches performed.