Anatomy of the facial nerve branching patterns, the marginal mandibular branch and its extraparotid ramification in relation to the lateral palpebral line

Prognostic Value of Electroneuronography in Severe Cases of Facial Palsy

OBJECTIVE

To examine the prognostic value of electroneuronography (ENoG) in predicting functional recovery in severe cases of acute facial palsy.

METHODS

Patients with severe degrees of facial palsy (initial House-Brackmann [HB] grades IV to VI) with available electrodiagnostic studies conducted 2-4 weeks after symptom onset were reviewed retrospectively. The patients were categorized into "good recovery" and "poor recovery" groups, with the former showing mild to no dysfunction (HB I to III) and the latter exhibiting moderate to severe dysfunction (HB IV to VI) on follow-up evaluation, 2 months after onset. ENoG amplitudes in four facial muscles (frontalis, nasalis, orbicularis oculi, and orbicularis oris), as well as age, sex, affected side, disease etiology, comorbidities, and laboratory findings, were compared between the two groups.

RESULTS

Thirty-seven patients were included. Twenty-nine of the patients showed "good recovery," and eight showed "poor recovery" at 2 months after symptom onset. Univariate analysis yielded no significant difference in age, sex, affected side, disease etiology, comorbidities, and laboratory findings between the two groups. Preserved ENoG amplitudes (individual, average, and trimmed means) were significantly higher in the good recovery group than in the poor recovery group (p<0.005). Sex (p=0.038) and the ENoG of the nasalis muscle, acquired 2-4 weeks from symptom onset (p=0.004), showed significant differences in multivariate regression analysis.

CONCLUSION

This study suggests that the female sex and lower ENoG of the nasalis muscle, acquired 2-4 weeks from symptom onset, have negative prognostic value for the 2-month functional outcome of severe facial palsy cases.

Extratemporal facial nerve branching patterns: systematic review of 1497 cases

Objective

The aim of this systematic review was to analyse the complex anatomy of the extratemporal portion of the facial nerve with an accurate description of the branching patterns based on the Davis classification.

Method

Medline, ScienceDirect and the Cochrane Library databases as well as other sources were searched by two independent reviewers.

Results

Analysis of 21 studies with a total of 1497 cases showed that type III is the most common branching pattern accounting for 26.8 per cent of cases. The type I pattern, previously considered as the normal anatomy in most textbooks, was the fourth most common branching pattern at 16.3 per cent. The majority of specimens (96.4 per cent) were found to have a bifurcated main trunk, and only 3.2 per cent were found with a trifurcated main trunk.

Conclusion

Surgeons should be aware of anatomical variations in the course of the facial nerve. An early identification of the branching pattern during surgery reduces the risk for iatrogenic facial nerve injury.

Surgical Anatomy of the Marginal Mandibular Nerve: A Systematic Review and Meta-Analysis

The high number of marginal mandibular nerve (MMN) anatomical variants have a well-known clinical significance due to the risk of nerve injury in several surgical procedures. The aim of this study was to find and systematize the available anatomical data concerning this nerve. The PubMed and Scopus databases were investigated in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. All studies reporting extractable data on the origin, course, splitting, anastomosis and relationship of the MMN with the mandible or the facial vessels were included. We included 28 studies analyzing 1861 halves. The MMN had one (PP = 35% 95% CI:18-54%), two (PP =35% 95% CI:18-54%), three (PP = 18% 95% CI:0-35%), or four branches (PP = 2% 95% CI:0-8%). Anastomosis with the great auricular nerve, transverse cervical nerve, mental nerve, and other branches of the facial nerve were defined. The origin of the MMN in relation to the parotid and the mandible was variable. The MMN nearly always crossed the anterior facial vein laterally (PP = 38% 95% CI:9-72% if single, PP = 57% 95% CI:22-90% when multiple); its relation with other vessels was less constant. At least one branch of the MMN was found below the inferior border of the mandible (IBM), with a PP of 39% (95% CI:30-50%). The MMN has high anatomical variability and it is more often represented by one or two branches; its origin is frequently described at the parotid apex and above the IBM, although in its course at least one branch often runs below the IBM. Its most frequent anastomosis is with the buccal branch of the facial nerve. Clin. Anat., 33:739-750, 2020. © 2019 Wiley Periodicals, Inc.

Patterns and surgical significance of facial nerve branching within the parotid gland in 43 cases

PURPOSE

Different patterns of facial nerve branching within the parotid gland were detected, and these anatomical variations may affect the treatment approaches and outcomes of surgery. The aim of this study was to identify the patterns of facial nerve branching with the parotid gland and their importance in surgical procedures.

MATERIALS AND METHODS

A total of 43 patients undergoing surgical treatments of parotid lesions were included in this study. Each patient's demographic data and type of operation were recorded. In addition, the courses of the facial nerve within the gland were classified into six types according to their branching patterns and communication.

RESULTS

In all of the patients, the facial nerve consisted of one trunk separated into two divisions. Branching type III was the most common variety found (30.2 %) followed by type II (23.2 %), while type V represented the least frequent pattern (4.6 %).

CONCLUSION

It is essential for surgeons to become familiar with the different types of nerve morphologies in order to avoid morbidity and preserve the facial nerve during surgery. Variations and anastomosis can explain the different consequences of facial nerve injury that may occur after parotid surgery.