Revisiting the Topographic Anatomy of the Marginal Mandibular Branch of Facial Nerve Relating to the Surgical Approach

The Distribution of the Nerves and Arteries of the Platysma for Clinical Applications

This study aimed to provide anatomical data on the platysma for clinical procedures. The authors obtained 25 specimens from 15 adult Korean cadavers (9 men, 6 women; mean age, 72 years; range, 61-85 years). Lines connecting the gonion with the gnathion (G-GN) and the acromial end (acromial end of the clavicle) with the sternal end (sternal end of the clavicle) were used as references. Modified Sihler staining was used to trace the nerves distributed in the platysma. The superior border values of the platysma were 12.1 ± 2.7 mm, 31.5 ± 5.3 mm, 42.4 ± 5.6 mm, and 61.7 ± 6.4 mm, respectively, for sections 2 through 5 on the G-GN line. The inferior border values of the platysma were 83.6 ± 19.1 mm, 80.1 ± 14.0 mm, 74.8 ± 14.5 mm, 67.2 ± 13.7 mm, and 54.6 ± 7.1 mm, respectively, for the 5 sections on the acromial end of the clavicle-sternal end of the clavicle line. In the hyoid bone, cricoid cartilage, and jugular notch, the mean distance between the bilateral platysma was 14.4 ± 2.2 mm, 22.6 ± 10.6 mm, and 51.1 ± 15.7 mm, respectively. The mean angle at the cervical branch of the facial nerve and the anterior border of the sternocleidomastoid muscle sternal head was 28.7 ± 2.6 degrees and 53.4 ± 7.7 degrees from the G-GN line, respectively. The upper third of the platysma was supplied by branches of the facial artery and submental artery. The middle third was supplied by branches of the occipital artery and received its direct blood supply from branches of the external carotid artery. The lower third was supplied by branches of the transverse cervical artery. The authors hope that the results of this study will be helpful for rejuvenation procedures of the neck.

Delineation and histological examination of the intramuscular innervation of the platysma: Application to botulinum neurotoxin injection

This study aimed to identify the whole innervation pattern of the platysma using the Sihler's staining, and the axonal composition profile of the sensory-motor anastomosis identified by immunofluorescence assays. The findings provide a comprehensive understanding of the neural anatomy of the platysma and facilitate efficient and safe manipulation for neurotoxin injection. Ten fixed and two fresh hemifaces were included in this study. Sihler's staining was used to the study 10 fixed hemifaces and two fresh hemifaces were used for immunofluorescence assays. In all cases, the cervical branch of facial nerve (Cbr) broadly innervated the platysma, and the marginal mandibular branch of facial nerve (MMbr) provided supplementary innervation to the uppermost part of the platysma. The transverse cervical nerve (TCN), great auricular nerve (GAN), and supraclavicular nerve (SCN) were observed in the lower half of the platysma. In 30% of all cases, there was a communicating loop between the Cbr and TCN. In 20% of all the cases, a communicating branch joined between the Cbr and GAN. For successful esthetic rejuvenation procedures, a clinician should consider the Cbr distribution to the overall platysma and additionally innervation by individual nerves (MMbr, GAN, TCN, and SCN) to the middle and lower portions of the platysma muscle.

Essential Surgical Anatomy for Facelift

It is crucial for a facelift surgeon to have a comprehensive understanding of ageing-related changes on the volume, elasticity, and relative position of various facial tissues and layers. These changes lead to an alteration in the surface topography, contour, and ultimately shape of the face. The depressions and sagging of tissues created as a result of ageing then has a bearing on one's perceived age. This article describes the various layers of the face and neck affected by ageing. The fat compartments, superficial musculoaponeurotic system (SMAS), potential facial spaces, facial ligaments, and facial nerve are discussed in detail. Safe and effective execution of facelift requires a thorough understanding of the intricate relationship between the various layers of face and neck, in particular the path of facial nerve, as it negotiates between these layers. The emphasis of this article is on integrating this knowledge to generate practical tips for safe dissection, effective tissue movement, and repositioning during various type of facelift procedures.

Communicating Branches of the Facial Nerve: Descriptions and Clinical Considerations

BACKGROUND

Major branching patterns of the facial nerve have been extensively studied because damage to branches of the nerve is associated with complications ranging from weakness to paralysis. However, communicating branches of the facial nerve have received far less attention despite being hypothesized as a means of motor recovery following facial nerve injury.

OBJECTIVES

The aim of this study was to characterize the frequency of communicating branches of the facial nerve to provide clarity on their anatomy and clinical correlations.

METHODS

Bilateral facial dissections were completed on cadaveric donors (n = 20) to characterize the frequency and location of communicating branches across terminal branches of the facial nerve. Statistical analyses were employed to analyze differences between the location of communications by side and whether the communicating branches were more likely to occur on the left or right side (P < 0.05).

RESULTS

Communicating branches were identified among all terminal branches of the facial nerve and their frequencies reported. The highest frequencies of communicating branches were identified between the buccal-to-marginal mandibular and zygomatic-to-buccal branches, at 67.5% (27 comm/40 hemifaces). The second highest frequency was identified between the temporal-to-zygomatic branches in 62.5% (25/40) of donors. The marginal mandibular-to-cervical branches had communicating branches at a frequency of 55% (22/40). Location or sidedness of communicating branches did not significantly differ.

CONCLUSIONS

Our characterization more accurately defines generalizable areas in which communicating branches are located. These locations of branches, described in relation to nearby landmarks, are fundamental for clinical and surgical settings to improve procedural awareness.

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.

High-resolution ultrasound of the marginal mandibular branch of the facial nerve: Normal appearance and pathological findings in a postsurgical case series

BACKGROUND

The aim of this study was to validate high-resolution ultrasound (US) as an imaging modality able to map the normal marginal mandibular nerve (MMN) and recognize its abnormalities in the postoperative setting.

METHODS

The ability of US to recognize the MMN was first tested by injecting latex under US guidance on three fresh frozen cadavers. Then, a standardized scanning protocol was established on 20 healthy volunteers based on appropriate landmarks. Finally, a postsurgical series of three patients with MMN abnormalities were examined with US.

RESULTS

In the cadaveric study, US-guided latex injection provided identification of the MMN. In healthy volunteers, US was able to recognize the MMN for a segment of 3.4 ± 1.2 cm in length. Pathologic abnormalities of the MMN were detected and characterized in three patients.

CONCLUSIONS

High-resolution US is a valuable diagnostic tool to identify the MMN and might have potential for detecting its pathologic changes.

Marginal Mandibular Nerve Mapping Prior to Nonablative Radiofrequency Skin Tightening

BACKGROUND

Aging skin and increased skin laxity is a prevalent concern of patients. Nonsurgical treatments, such as radiofrequency, are increasing in popularity due to decreased pain, downtime, and scarring. ThermiRF (Thermi, Irving, TX) is a subdermal radiofrequency treatment for tightening skin. When applying radiofrequency treatments to the neck, it is important to avoid ablating the marginal mandibular nerve and causing nerve trauma.

OBJECTIVES

The purpose of this study was to locate and record the position of the marginal mandibular nerve in 72 patients undergoing subdermal radiofrequency skin tightening, to determine how often the nerve correlates to its textbook anatomic position.

METHODS

Marginal mandibular nerves were located with a nerve stimulator and marked with the subject in both upright and recumbent positions. Photographs were taken and the nerve position in relation to the mandible was recorded.

RESULTS

The marginal mandibular nerve was in its correct anatomic position above the mandible in 18% of patients. Nerve position did not shift between the upright and recumbent positions. Only 10% of patients had left-right nerve symmetry.

CONCLUSIONS

To avoid nerve injuries, nerve mapping prior to nonablative radiofrequency treatment is recommended. The marginal mandibular nerve is not always in its correct anatomic position or symmetric to the opposing side. Its location cannot be assumed from the textbook anatomic position or from a single-side mapping.

LEVEL OF EVIDENCE: 4

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.

Preoperative Localization of the Carotid Bifurcation for Cervical Carotid Exposure Using the Mastoid-Hyoid Line

Background and Importance:

The location of the carotid bifurcation (CB) is highly variable, which makes precise exposure of the cervical carotid artery difficult, especially in transverse incisions. The method for preoperative localization of the CB is not well established. We used the distance from the mastoid-hyoid (M-H) line to the CB, measured preoperatively with computed tomography angiography, to localize the location of the transverse skin incision. We describe and evaluate the accuracy of a method for preoperative localization of the CB for cervical carotid exposure.

Methods:

The researchers retrospectively evaluated 16 patients with aneurysms arising from the internal carotid artery (ICA) who had received cervical carotid exposure using the localization method of incision and were retrospectively evaluated from February 2018 to November 2019. The method of measurement and localization of the skin incision are described, and two illustrative cases are demonstrated.

Results:

Saccular aneurysms of the ophthalmic (C2) segment and communicating (C1) segment of the ICA were found in 8 and 8 patients, respectively. Nine patients had left-sided exposure, and 7 patients had right-sided exposure. The mean distance from the M-H line to the CB was 2.1 cm (range 0.5–3.5 cm). The accuracy of this method was 93.8%. No paralysis of the depressor anguli oris or the depressor labii inferioris was found postoperatively.

Conclusion:

The distance from the M-H line to the CB can be used to estimate transverse skin incisions for cervical carotid exposure.

The "Segmental SMAS Model": A Didactic Concept of Face and Neck Lift Anatomy

Profound understanding of the surgical anatomy of the face and neck is the key to successful face lift surgery. The "Segmental SMAS Model" presented herein is the result of a decade-long effort in teaching fellows a logical and coherent anatomic model of face lift anatomy. The superficial musculo-aponeurotic system (SMAS) consists of segments with distinct surgical characteristics. These are determined by the presence of a deep gliding plane and/or adhesion through fibrous insertions. In this article, we define SMAS segments that are profoundly heterogeneous in their behavior and have surgical implications on the maneuvers required for a deep plane face lift. The present model introduces several novel interpretations of the surgical anatomy of the face and neck lift procedure and hopes to convey a better understanding of face lift anatomy to training surgeons.

Morbidity of marginal mandibular nerve post vascularized submental lymph node flap transplantation

BACKGROUND

This study investigated the morbidity of the marginal mandibular nerve (MMN) post vascularized submental lymph node (VSLN) harvest.

METHODS

The VSLN with sacrifying or preserving the medial platysma was retrospectively classified as group I or II. Midline deviation and horizontal tilt were subjectively evaluated. Horizontal, vertical, and "area distribution" of the lower lip excursions of the surgical site were objectively compared with the nonsurgical site.

RESULTS

Seventeen patients in group I and 12 patients in group II were included. At a median follow-up of 48.6 ± 16.8 months in group I and 14.8 ± 7.5 months in group II, no MMN palsy was found in both groups. Median midline deviation and horizontal tilt were 4.53 ± 0.52 and 5 ± 0 in group I and 4.67 ± 0.65 and 5 ± 0 in group II, respectively (P = .419 and 1.000). Median horizontal, vertical and area of distribution of lower lip excursions were 97.5 ± 12.3%, 98.8 ± 14.4% and 87.2 ± 14.7% in group I, and 99.3 ± 15.1%, 95.8 ± 8.2% and 84.2 ± 14.2% in group II, respectively (P = .679, .948 and .711).

CONCLUSION

The VSLN flap was a safe procedure with minimal MMN morbidity.

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.

Versatility of the Berger-Tenenhaus Approach for Mandibular Fractures

INTRODUCTION

Mandibular fractures between the angle and condyle can be difficult to access and treat. The authors sought to evaluate a small transcutaneous incision between the marginal mandibular and buccal nerve branches (Berger-Tenenhaus incision) to treat these fractures.

METHODS

Ten cadaveric hemi-faces were dissected. Surrounding facial nerve branches were identified and measured in relation to the discussed incision. Our clinical experience with the approach for mandibular angle, ramus, subcondylar, and condylar fractures was reviewed. Operative technique and postoperative outcomes were examined.

RESULTS

The incision is located in a safe interval between neighboring facial nerve branches. Marginal mandibular nerve branches maintained a consistent distance beneath the incision along its length (median distances of 0.95-cm (SD ± 0.5), 1.05-cm (SD ± 0.5), and 1.00-cm (SD ± 0.8) posterior to anterior, respectively). Buccal nerve branches increased in distance and ascended away from the incision line (median distances of 0.75-cm (SD ± 0.9), 1.4-cm (SD ± 0.8), and 1.45-cm (SD ± 0.9) respectively posterior to anterior). No nerves were injured. In our clinical experience, all postoperative patients (n = 9) have had successful fracture reduction with restoration of occlusion, intact facial nerve function and an acceptable cosmetic result.

CONCLUSIONS

The Berger-Tenenhaus incision can safely and efficiently be used to treat difficult to access mandible fractures between the angle and condyle.

LEVEL OF EVIDENCE

VI.

Contemporary Concepts of Primary Dynamic Facial Nerve Reconstruction in the Oncologic Patient

Transection of the facial nerve and its branches during extensive ablative procedures in the oncologic patient causes loss of control of facial mimetic muscles with severe functional and aesthetic sequelae. In such patients with advanced tumorous disease, copious comorbidities, and poor prognosis, rehabilitation of the facial nerve has long been considered of secondary priority. However, recent advances in primary facial nerve reconstruction after extensive resection demonstrated encouraging results focusing on rapid and reliable restoration of facial functions. The authors summarize 3 innovative approaches of primary dynamic facial nerve reconstruction by using vascularized nerve grafts, dual innervation concepts, and intra-facial nerve transfers.

Novel Expanded Safe Zone for Reduction of Submental Fullness with ATX-101 Injection

ATX-101 (deoxycholic acid injection; Kybella) provides an approved nonsurgical treatment option for reduction of submental fullness caused by submental fat. Current one-size-fits-all recommendations for the use of ATX-101 limit treatment to a central area, which may not provide complete resolution of submental fat for some patients. An expanded safe zone is described, allowing for individualized, comprehensive treatment of submental fat with ATX-101 according to each patient’s anatomy and desired outcomes.

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.

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.

Platysma Motor Nerve Transfer for Restoring Marginal Mandibular Nerve Function

BACKGROUND

Injuries of the marginal mandibular nerve (MMN) of the facial nerve result in paralysis of the lower lip muscle depressors and an asymmetrical smile. Nerve reconstruction, when possible, is the method of choice; however, in cases of long nerve gaps or delayed nerve reconstruction, conventional nerve repairs may be difficult to perform or may provide suboptimal outcomes. Herein, we investigate the anatomical technical feasibility of transfer of the platysma motor nerve (PMN) to the MMN for restoration of lower lip function, and we present a clinical case where this nerve transfer was successfully performed.

METHODS

Ten adult fresh cadavers were dissected. Measurements included the number of MMN and PMN branches, the maximal length of dissection of the PMN from the parotid, and the distance from the anterior border of the parotid to the facial artery. The PMN reach for direct coaptation to the MMN at the level of the crossing with the facial artery was assessed. We performed histomorphometric analysis of the MMN and PMN branches.

RESULTS

The anatomy of the MMN and PMN was consistent in all dissections, with an average number of subbranches of 1.5 for the MMN and 1.2 for the PMN. The average maximal length of dissection of the PMN was 46.5 mm, and in every case, tension-free coaptation with the MMN was possible. Histomorphometric analysis demonstrated that the MMN contained an average of 3,866 myelinated fiber counts per millimeter, and the PMN contained 5,025. After a 3-year follow-up of the clinical case, complete recovery of MMN function was observed, without the need of central relearning and without functional or aesthetic impairment resulting from denervation of the platysma muscle.

CONCLUSIONS

PMN to MMN transfer is an anatomically feasible procedure for reconstruction of isolated MMN injuries. In our patient, by direct nerve coaptation, a faster and full recovery of lower lip muscle depressors was achieved without the need of central relearning because of the synergistic functions of the PMN and MMN functions and minimal donor-site morbidity.