The Marginal Mandibular Nerve in Relation to the Inferior Border of the Mandible

Extracapsular dissection with a transparotid facial nerve dissection approach versus partial superficial parotidectomy for benign tumours in the tail of the parotid gland: a single-centre retrospective study of 89 patients

The aims of this study were (1) to evaluate the transparotid facial nerve dissection approach (TFND), in which the intraparotid cervicofacial or temporofacial division is identified first through a superficial lobe incision; and (2) to compare extracapsular dissection with a TFND (ECD-TFND) with partial superficial parotidectomy with a retrograde approach (PSP) for benign tumours in the tail of the parotid gland with respect to surgical outcomes. Eighty-nine patients underwent PSP or ECD-TFND for benign tumours in the tail of the parotid gland: 49 were treated surgically with PSP and 40 with ECD-TFND. The mean ( ± standard deviation) surgical time did not differ significantly between the groups: 64 ± 22.4 min for PSP and 59 ± 19.8 min for ECD-TFND (P = 0.302). There was a significant difference in sialocele: 18 (36.7%) patients in the PSP group and four (10%) in the ECD-TFND group (P = 0.002). There was also a significant difference in facial nerve injuries: temporary paralysis was observed in 13 (26.5%) patients in the PSP group and two (5%) in the ECD-TFND group (P = 0.007). It appears that TFND is a viable and safe approach when performing ECD for benign tumours in the tail of the parotid gland. ECD-TFND should be preferred over PSP for benign tumours in the tail of the parotid gland.

The Anatomic Landmark Approach to Extratemporal Facial Nerve Repair in Facial Trauma

Objective

In this study, we aimed to examine the topical anatomic landmarks of the facial nerve (facial nerve areas) and their application in cases of extratemporal facial nerve injury in maxillofacial trauma.

Materials and methods

We analyzed 25 maxillofacial trauma patients with facial paralysis who underwent facial nerve reanimation surgery at the Ho Chi Minh City National Hospital of Odonto-Stomatology. The characteristics of each trauma case, including the mechanism of injury, the length of the facial injury, and the location/position of injury, were recorded. The association of the injured nerves with the trauma characteristics and the external landmarks of the facial danger zones was analyzed.

Results

The buccal branches had the highest rate of paralysis (22/25 cases), followed by zygomatic branches (15/25), frontal branches (11/25), marginal branches (6/25), and the main trunk (1/25). There were four areas related to the external facial nerve landmarks (facial nerve areas) that helped us find the affected nerves: wounds in Area 1 resulted in frontal branch paralysis in five out of eight cases (62.5%); wounds in Area 2 resulted in zygomatic branch paralysis in 8/13 cases (61.5%) and buccal branch paralysis in 12/12 cases (100%); wounds in Area 3 resulted in marginal branch paralysis in 5/10 cases (50%); and wounds in Area 4 alone resulted in main trunk paralysis in one out of four cases or at least two main branches in three out of four cases.

Conclusion

Extratemporal facial paralysis after facial trauma can be complex and highly variable, leading to difficulty in finding and repairing facial nerves. Thorough clinical examination and evaluation of trauma characteristics can aid in the identification of facial paralysis and repair. Mapping facial wounds using the four anatomic surface landmarks (Areas 1-4 as outlined in this research) helped us anticipate which branches might be traumatized and estimate the position of the distal and proximal endings to repair the nerves in all cases.

Key Anatomical Clarifications for the Marginal Mandibular Branch of the Facial Nerve: Clinical Significance for the Plastic Surgeon

BACKGROUND

The marginal mandibular branch (MMBr) of the facial nerve is the least likely to recover from injury due to infrequent anastomosis with other branches. The MMBr has been described as coursing superior to the inferior border of the mandible. However, studies have reported variations in its location in embalmed and fresh specimens. It has been postulated that the embalming process may effect its anatomic position.

OBJECTIVES

The aim of this study was to re-evalulate the location of the MMBr relative to the inferior border of the mandible in both fresh and embalmed cadavers, and investigate variation in its position with sex, side of the face, and age.

METHODS

Superficial fascial planes were dissected to reveal the MMBr and its anatomic relations. Distance between the most inferior branch of the MMBr and the antegonial notch were measured bilaterally. The most inferior position of the MMBr between the antegonial notch and gonion was measured. Fresh heads were used as a comparison, with an additional measurement taken of the distance between the MMBr and the gonial angle.

RESULTS

The MMBr was located inferior to the border of the mandible (90.3%) more often than above (9.6%). No significant differences were found between fresh and embalmed cadavers, sex, side of body, or age (P > 0.05). No significant difference was found between intact cadavers and fresh heads (P > 0.05).

CONCLUSIONS

This study confirms and describes reliable landmarks for safety zones for the MMBr during plastic and reconstructive surgery of the lower face and upper neck. These data add reliability to studies that have investigated nerve locations in embalmed cadavers.

Facial nerve: A review of the anatomical, surgical landmarks and its iatrogenic injuries

Facial nerve iatrogenic injuries are serious and can negatively affect the quality of life of the patients. Due to the properties of the nerve, the complications are devastating involving the aesthetic appearance and the function of the face. Moreover, the multiple branches of the nerve increase the risk of an iatrogenic injury making the detailed knowledge of the anatomical correlations around them critical. In this review, a meticulous analysis was performed including the surgical procedures posing the greater risk of an iatrogenic injury as well as the full description of all the reported anatomical landmarks involving the extracranial course of the facial nerve.

Conservative Neck Rejuvenation

In the field of facial rejuvenation, among the recurrent topics, one of the most discussed is the return to less invasive techniques. Lower face rejuvenation is best achieved acting on the platysma muscle. Many techniques are used and usually include platysma section, redundancy reduction, and redraping. Platysma plication is also used especially in secondary cases because of the increased risk of nerve injury due to possible anatomical damage caused by previous operations. A technique that preserves the deep planes based on a new plication method is proposed (conservative neck rejuvenation). In this technique, the dissection plane is only subcutaneous to reduce the risk of nerve injuries. An effective neck contouring is possible using a simpler technique with very good results and a lower rate of morbidity.

Cadaveric Study of Topographic Anatomy of Temporal and Marginal Mandibular Branches of the Facial Nerve in Relation to Temporomandibular Joint Surgery

PURPOSE

Detailed anatomy of the facial nerve, including the variations among different ethnic groups, is essential to prevent an iatrogenic injury. The purpose of the study was to document topographic anatomy of temporal and marginal mandibular (MM) branches of the facial nerve in relation to temporomandibular joint (TMJ) surgery. The specific aim was to demonstrate detailed course of temporal and MM nerves, their surgical implications, and to compare the results obtained with the previous studies.

METHODS

The investigators implemented a prospective cadaveric study. A dissection was carried out on 52 facial halves. The facial nerve was dissected according to the instructions described in the Cunningham^'s dissection manual. Anatomic landmarks were selected as determined by Al-Kayat and Bramley, and results obtained were compared with previous published articles.

RESULTS

The study sample was composed of 52 facial halves (males, n = 35; females, n = 17). The number of branches of temporal nerve varied in dissected facial halves from 3 (n = 37 [70%]), 2 (n = 14 [26%]), to 1 (n = 1 [2%]). The distance between the lowest concavity of the bony external auditory meatus to the point at which the facial nerve bifurcates (distance B) was considerably less in the study population (1.79 cm) when compared with the reported literature (2.3 cm). There was no significant influence of gender and cephalic index on distances measured. There was 1 branch in 15% of the dissected facial halves (1 in 52) and 2 branches in 85% (44 of 52). The MM nerve was seen coursing below the inferior border of the mandible, and in 44 (85%), the nerve was present above the inferior border of mandible all along the course.

CONCLUSIONS

The topographic anatomy of the temporal and MM nerves is the same as reported in the literature. The only considerable difference was found in distance B; hence, surgical procedures involving the distance B require special consideration.

Evaluation of the course of the marginal mandibular branch of the facial nerve: a fresh cadaveric study

The aim of this study was to determine the course of marginal mandibular nerve (MMN) in relation to the inferior border of the mandible from the gonion until its terminal insertion to the depressor anguli oris, relating the position to a palpable anatomical landmark with emphasis on the depth of the nerve in relation to platysma and the deep cervical fascia. Twelve fresh adult cadavers were dissected and the mandibular base was contoured using needles with 5mm gaps, starting from the mandibular angle to the muscular termination point of the nerve bilaterally. The distance between the MMN and the mandibular base and total length of the nerve was measured bilaterally. The highest levels of MMN were measured 6.9mm and 6.5mm above, and the lowest levels were measured 4mm and 3mm below the mandibular base on right and left sides, respectively. The mean (SD) total length of the nerve until the muscular termination point was calculated 33.57 (3.41) mm on the right and 33.51 (4.88) mm on the left side. Previous publications that we had read all fell short of defining the schematic pathway of the nerve, as the described landmarks were of a combination of bone and soft tissue, which are not always clinically reliable. We have overcome this difficulty by standardising the inferior border of the mandible as a point in order to trace the marginal mandibular branch pathway. It originates along the gonion and ends at the second premolar tooth area.

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.

Novel Surface Anatomic Landmarks of the Jowl to Guide Treatment with ATX-101

Supplemental Digital Content is available in the text.

Facial appearance is critical to physical attractiveness, and maintaining a youthful face and neck is a major motivation for individuals seeking facial cosmetic procedures. A strong mandibular border without prominent jowls is one sign of a youthful face as jowling occurs with age, contributing to squaring of the face and loss of jawline definition. Excess jowl fat has traditionally been reduced with surgical liposuction when jowling is caused by fat flow across the mandible. The approval of ATX-101 (deoxycholic acid injection) for submental fat reduction provides a minimally invasive technique that may also be suitable for jowl fat reduction. The author has developed novel facial markings that consistently isolate the jowl fat area of concern at the mandible for treatment with ATX-101. The current work refreshes physicians on important jowl anatomical structures, defines the facial markings that consistently isolate the jowl, and describes an injection technique to safely treat excess jowl fat with ATX-101.

Management of the marginal mandibular nerve during and after neck dissection

PURPOSE OF REVIEW

Marginal mandibular nerve palsy (MMNP) is often an understated complication after neck dissection. This article reviews literature regarding anatomic landmarks that help define marginal mandibular nerve (MMN) during neck dissection, oncologic safety of surgical maneuvers, implications of MMNP, and reconstructive options.

RECENT FINDINGS

A thorough knowledge of anatomy of the nerve can aid in its preservation. Course, branching pattern and communications of MMN are extremely variable. The Hayes Martin method classically described to preserve the nerve may not be oncologically safe in patients with prefacial nodal involvement. MMNP significantly affects quality of life after neck dissection. Cause, timing, and degree of neural damage play an important role in determining diagnostic and therapeutic options to correct the deformity resulting from MMNP. Owing to treatment-related factors, functionality of local structures may be compromised, which limits available reconstructive options for the surgeon. This should favor a shift of management option toward more conservative procedures in patients treated for head and neck cancer.

SUMMARY

When oncologically safe, the MMN must always be preserved. The patient perceived deformity resulting from MMNP is significantly higher than clinician-detected rate. In select patients who are affected by significant smile asymmetry, multiple dynamic and static corrective procedures can be offered.

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.

Intraoperative monitoring of marginal mandibular nerve during neck dissection

BACKGROUND

The purpose of this study was to assess the efficacy of intraoperative nerve integrity monitoring (NIM) to prevent marginal mandibular nerve injuries during neck dissection.

METHODS

This prospective study compared 36 patients undergoing NIM-assisted neck dissection from July 2014 to March 2015 to a cohort of 35 patients subjected to neck dissection over an identical period of time before the technique was introduced. We also assessed possible correlations between marginal mandibular nerve injuries and other factors, such as anthropometric measurements, presence of clinical neck metastases, type of neck dissection, and site of primary tumor.

RESULTS

The incidence of marginal mandibular nerve paralyses was significantly lower among the group of patients undergoing NIM-assisted neck dissection (P = .021). There was no significant difference in the duration of the procedure, and the technique resulted in a limited increase of cost. No other factor seemed to influence the onset of marginal mandibular nerve palsy.

CONCLUSION

In our opinion, NIM is a valuable aid for preventing marginal mandibular nerve injuries during neck dissection.

[Anatomic study of the submental artery relationships for submental flap raising]

INTRODUCTION

Submental flap is useful for intra-oral reconstructions and reconstructions of the lower two thirds of the face. Dissection is delicate because of a difficult exposure under the lower rim of the mandible, numerous collateral arterial branches and the proximity of the marginal branch of the facial nerve. The aim of our work was to propose anatomical landmarks in order to facilitate the submental flap raising.

MATERIAL AND METHOD

Ten bodies preserved in Biomet liquid were dissected bilaterally. The anatomic relationships between the marginal branch of the facial nerve and the mandible, the relationships of the submental artery, the amount and the location of its collateral branches were measured by means of a caliper.

RESULTS

The highest marginal branch observed was located 0.5 cm above the mandibular lower rim, while the lower one was located 0.6cm below this rim. The mean length measured between the facial artery at its crossing over the mandibular rim at the level of the pre-angular notch and the origin of the submental artery was 1.5cm. The average number of collateral branches was 3.6.

DISCUSSION

A skin incision made directly under the mandibular lower rim, as mentioned by some authors, may endanger the mandibular marginal branch of the facial nerve. Three positions of the submental artery in relation to the sub-maxillary gland are reported. The collateral branches are intended for gland, muscle, skin and bone. It is necessary to pay particular attention to the sub-lingual artery, an artery of big diameter that arises at 2.8cm on average from its origin and plunges towards the mouth's floor. It must not be followed at risk of clamping the thin pedicle destined to the digastric muscle. It is important to preserve the fat tissue around the submental pedicle in order to avoid venous congestion of the flap.

Relationship between facial nerve damage and transbuccal trocar placement: an anatomical cohort study

The surgical treatment of ramus and mandibular angle fractures is typically performed by intraoral and transbuccal approaches. As these approaches may result in nerve damage, this anatomical study was performed to establish the relationship between the transbuccal trocar position and the likelihood of inducing facial nerve damage. Twenty dissections of the parotid regions were performed after a simulation of surgical approaches aimed at addressing mandibular condylar and angle fractures. Two trocar tubes, ramic and angular, were inserted and left in position throughout the dissection. This procedure allowed the qualitative relationship between the various tube positions and facial nerve damage to be analyzed. The potential risk of contact between the ramic trocar and the facial nerve branches was 90%, while the angular trocar was in contact in 45% of cases. There was no contact with the trunk, cervicofacial division, or temporofacial division of the facial nerve. The contacts occurred at the level of secondary division branches, particularly pronounced for superior and inferior buccal branches, despite the absence of macroscopically visible trauma. Based on these findings, it is proposed that trocars should be used in procedures aimed at addressing subcondylar or angle fractures of the mandible.