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Fibers of the facial muscles occasionally extend, cross the midline, and connect to surrounding structures on the contralateral side, perhaps enabling the mouth to make more delicate movements and generate more facial expressions. This case report describes a variant in which the extended fibers of the mentalis crossed the midline and indicates the relationship of these fibers to the surrounding structures. Some of the deepest fibers of the mentalis descended inferomedially and crossed transversely just below the chin prominence to attach to the periosteum of the mandible on the contralateral side. The variation presented in this study shed light on the interactions of the mentalis with the surrounding muscles.

Background Botulinum toxin type A (BTA) injection is a widely-used procedure to correct cosmetic problems caused by muscular hyperactivity. "Cobblestone chin" refers to the appearance of remarkable chin creases caused by mentalis contraction. Aims The aim of this case report is to raise the awareness of paradoxical bulging after BTA injection in mentalis. Patient/methods A 26-year-old female asked for cosmetic correction of the "cobblestone chin". BTA injection was performed routinely to the mentalis muscle. However, on the second day after injection, an unusual paradoxical bulging at chin was presented. Results We speculated that the imbalanced relaxation of mentalis caused by improper injection and uneven diffusion of BTA is responsible for the bulging. After a supplementary injection of BTA in the remaining hyperactive muscle fibers based on the ultrasound examination, the bulging was relieved and chin contour improved significantly. Conclusion Injection of BTA in mentalis should cover the whole thickness of the muscle to prevent imbalanced paralysis and paradoxical chin bulging, especially in severe mentalis hyperactivity cases.

OBJECTIVE The purpose of this study is to determine if different facial muscle groups demonstrate different responses to facial nerve stimulation, the results of which could potentially improve intraoperative facial nerve monitoring (IOFNM). METHODS IOFNM data were prospectively collected from patients undergoing cochlear implantation. At different stages of nerve exposure, three sites were stimulated using a monopolar pulse. Peak electromyography (EMG) amplitude (μV) in four muscle groups innervated by four different branches of the facial nerve (frontalis-temporal, inferior orbicularis oculi-zygomatic, superior oribularis oris-buccal, and mentalis-marginal mandibular) were recorded. RESULTS A total of 279 peak EMG amplitudes were recorded in 93 patients. At all three stimulating sites, the zygomatic branch mean peak EMG amplitudes were statistically greater than those of the temporal, buccal, and marginal mandibular branches (P

The mentalis muscle is now considered key structures when performing procedures for rejuvenating the lower face. The aim of this study was to determine the anatomical morphology and location of the mentalis muscle and thereby provide anatomical information for facilitating clinical procedures designed to rejuvenate the lower face. Forty-four adult hemifaces from five Thai cadavers and 21 Korean cadavers were dissected to identify the locations of the mentalis muscle. Sixty-six hemifaces from 33 healthy young Korean subjects were included in an ultrasonographic study. The depth of the mentalis muscle below the skin surface, the thickness of the mentalis muscle, and the distance from the bone to the mentalis muscle were measured at the two points that were 5 mm lateral to the most-prominent point of the chin. The mentalis muscle was classified into two types based to its shape: in type A (86.4%, 38 of the 44 cases) it was dome shaped in three dimensions, while in type B (13.6%, 6 of the 44 cases) it was flat. The mentalis muscle was present mostly at the area 5–10 mm from the midsagittal line and 20–30 mm from a horizontal line connecting the mouth corners. The mentalis muscle was present between depths of 6.7 to 10.7 mm below the skin. This new information about the location of the mentalis muscle may help when identifying the most effective and safe botulinum toxin injection points and depths during esthetic procedures for weakened facial rhytides on the lower face.

A 17-month-old boy was evaluated for a midline mass on his chin. The mass was anchored to the mentalis muscle with a stalk-like structure. The pathological diagnosis of the mass was rhabdomyomatous mesenchymal hamartoma. This is the first report of rhabdomyomatous mesenchymal hamartoma presenting as a midline chin mass in Korean pediatric patients.

Botulinum toxin for the inferior third of the face can help address several areas such as marionette lines, masseter hypertrophy, perioral lines, correction of gummy smile, mentalis muscle strain, facial asymmetries, and improvement of platysmal bands.

Background: The number of TOETVA surgeries has increased worldwide but the anatomical passage of trocars is not clearly defined. We aimed to define detailed surgical anatomical passage of the trocars in cadavers. The incisions in oral vestibule, anatomical pathways of trocars, affected mimetic muscles, neurovascular relations of trocars and histological correlation of surgical anatomy were investigated. Methods: Four cadavers and 6 six patient oral vestibules were used. The locations of optimised vestibular incisions were measured photogrammetrically. Initial steps of TOETVA surgery were performed on cadavers according to those optimal incisions. TOETVA preformed cadavers dissected to determine anatomical passages of the trocars. Afterwards, flap of lower lip and chin were zoned by software appropriate to the trocars routes. Histological analyses of the zones were made in correlation with dissections. Results: Mimetic muscles associated with median (MT) and lateral trocars (LT) are orbicularis oris, mentalis, depressor anguli oris, depressor labii inferioris and platysma muscles. Trocars affect mimetic muscles in the perioral, chin and submental regions in different ways. The risk of mental nerve injury by MT is low. LT pass through the DLI muscle. The transmission of LT to the subplatysmal plane in the submental regions can be in two different ways. The arterial injury risk is higher with LT than the MT. Conclusions: The surgical anatomy of the perioral, chin and submental regions for the initial TOETVA steps has been defined. Detailed surgical anatomical passages of the MT and LT were determined. Anatomical pattern to reach subplatysmal plane are presented. Mimetic muscles effected by trocars were determined. Endocrine surgeons should know the anatomical passage of TOETVA trocars. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

Because of the soft-tissue envelope and the dimensional complexity of the muscular contraction of the mentalis muscle, the projection and shape of the chin is not determined by only the bony projection. In a subset of patients with a seemingly underprojected chin, a hyperactive, high-riding mentalis muscle contributes to a blunted chin contour.To evaluate the use of onabotulinumtoxinA (botulinum toxin A) for improving chin aesthetics in patients with an underprojected bony chin and a high-riding hyperactive mentalis muscle.This case series and photographic analysis included 11 patients presenting with an underprojected bony chin and a high-riding hyperactive mentalis muscle at a private facial plastic surgery practice from August 25, 2006, to November 10, 2012. Data were analyzed from November 13, 2012, to April 9, 2013.Injection with 12 to 15 U of onabotulinumtoxinA into the mentalis muscle.Photographic analysis of the vertical and horizontal positions of the pogonion relative to fixed facial points before and after injection. A patient satisfaction scale was also used to assess improvement in overall chin aesthetic.Eleven patients (3 men and 8 women; mean [SD] age, 46.3 [16.4] years) participated in the study, including 2 who had undergone prior chin implantation. The vertical position of the pogonion was more inferior after injection in 10 of 11 patients (mean [SD] vertical position, 1.36 [0.18] preinjection and 1.44 [0.18] postinjection; P = .005). Although the horizontal position of the pogonion changed in all patients, this change was not statistically significant (mean [SD] horizontal position, 0.11 [0.13] preinjection and 0.14 [0.13] postinjection; P = .32). All patients experienced improvement in their overall chin aesthetic and a subjective decrease in chin tension. Chin contour was improved, with soft-tissue volume overall displaced more inferiorly with a rounded rather than blunted appearance. No adverse effects were reported after injection.OnabotulinumtoxinA is effective at improving chin aesthetics by altering the position of the pogonion. In this first photographic analysis to date of the influence of onabotulinumtoxinA treatment, patients demonstrated a measurable change in the position of the pogonion, in addition to improvements to the chin contour on profile. This nonsurgical mentoplasty may be used as an independent procedure or as an adjunct to optimize traditional chin augmentation in carefully selected patients.4.

Purpose To investigate the relationship between mentalis muscle activity and mandibular symphysis morphology in patients with Class I or II skeletal patterns. Materials and methods 123 female Thai patients (17 years old+) participated in the present study. Subject pretreatment lateral cephalometric radiographs were examined. All subjects were diagnosed as having a skeletal normal bite. Subjects were grouped according to their sagittal skeletal pattern (ANB angle) into Class I (ANB 2–6) or Class II (ANB > 6). For each skeletal type, the subjects were divided into 2 groups, normal mentalis muscle activity (control group) and hyperactivity (experimental group). The skeletal Class I group comprised 37 subjects with mentalis muscle hyperactivity and 31 subjects with normal activity, while the skeletal Class II group comprised 30 hyperactive and 25 normal activity subjects. Eight cephalometric variables (angular, linear, and proportional measurements) were measured to evaluate mandibular symphysis morphology. The data were statistically analyzed using the Mann–Whitney U test or Independent-Sample t-test based on the normality of the data. Results In the skeletal Class I type, the experimental group revealed a trend of narrower alveolar symphysis width and greater symphysis height compared to the control group, but this was not significant. However, in the skeletal Class II type, the experimental group demonstrated significantly narrower alveolar symphysis width and significantly greater symphysis height compared to the control group (p Conclusion An increase in mandibular symphysis height and decrease in alveolar symphysis width may relate to mentalis muscle hyperactivity, and such relationship is more obvious in patients with Class II skeletal pattern.

The trajectory of the medial fibers of depressor anguli oris muscle that pass deep to the depressor labii inferioris muscle (dDAO) and the anatomic relationship have not yet been examined. The aim of this study was to clarify the arrangement of the dDAO and its relationships with the surrounding structures. The dDAOs were investigated in 40 hemifaces from Korean cadavers. The dDAOs were observed in 18 of the 40 specimens (45%). The anatomic relationships of the dDAO were classified into the following 4 categories according to their connection with the incisivus labii inferioris muscle (ILI): (1) connected to the ILI and attached to the inferior border of the mandible lateral to the mentalis muscle (14 specimens, 35%), (2) connected to the ILI and intermingled with the lateral lower fibers of the mentalis muscle (2 specimens, 5%), (3) connected to the ILI but neither attached to the mandible nor intermingled with the mentalis muscle (1 specimen, 2.5%), and (4) not connected to the ILI but intermingled with the mentalis muscle (1 specimen, 2.5%). Therefore, in 17 specimens, the dDAOs were connected to the ILI (42.5%), in 14 specimens, they were attached to the inferior border of the mandible (35%), and, in 3 specimens, they were intermingled with the mentalis muscle (7.5%). The new anatomic data regarding the dDAO will contribute toward the understanding of movements of the mouth and lower face, which will be helpful when designing effective botulinum toxin type A therapies and performing various types of facial surgery.

Background/Objectives: Although the electromyographic (EMG) activity of the perioral muscles, including the orbicularis oris and mentalis muscles, has been described in individuals with lip incompetence during lip sealing, blood flow through these muscles remains to be elucidated. The purpose of this study was to examine the blood flow associated with EMG activity in the perioral muscles using laser speckle imaging in individuals with lip incompetence. Subjects/Methods: Blood flow and EMG activity of the superior and inferior orbicularis oris and mentalis muscles were measured with the lips in contact (C condition) and apart (O condition) in lip incompetence (experimental) and control subjects ( n = 15 in each group; mean age: 29.5 years). The change ratios of blood flow and EMG activity in the C condition versus O condition (C/O ratios) were calculated and plotted in a scattergram. The Mann–Whitney U -test, Wilcoxon signed-rank test, discriminant analysis using the Mahalanobis generalized distance, and Spearman correlation were used for statistical analysis. Results: In the experimental group, blood flow and EMG activity in all muscles were significantly greater in the C condition than in the O condition. The plots of C/O ratios in the experimental group showed a distinct and wide distribution and were significantly different than those in the control group. In both groups, a significant positive correlation was observed between blood flow and EMG activity in the mentalis muscle. Conclusions/Implications: The present findings suggest that observing blood flow in the mentalis muscle is an effective and easily performed method of evaluating lip incompetence.

Purpose: The aim of the present study was to record the electromyographic (EMG) activity of the mentalis muscle (Ment) during various jaw functions in healthy young subjects.Methods: Twelve healthy males were enrolled for the study. A portable EMG recording device was used to record the EMG activity from the Ment, anterior belly of the digastric muscle (Dig), and the masseter (Mm) muscles. The EMG activities of these muscles were recorded during maximal voluntary clenching (MVC), maximal voluntary jaw opening (MVO), and the masticatory process. The EMG activity of Ment was compared with the EMG activities of Dig and Mm during various jaw functions.Results: (1) The EMG activities of Ment and Dig were significantly greater during MVO than during MVC (P

The mentalis muscle (MT) is the only elevator of the lower lip and the chin, and it provides the major vertical support for the lower lip. However, there are few reports on the relationship between the MT and its surrounding muscles. The aim of this study was to clarify the morphology of the MT, especially in relation to the orbicularis oris muscle and the incisivus labii inferioris muscle (ILI), thereby providing data to understand the function of the MT in relation to the surrounding muscles. The MT was examined in 40 specimens of embalmed adult Korean cadavers. The medial fibers of both MTs descended anteromedially and crossed together, forming a dome-shaped chin prominence in all specimens. The lateral fibers of the MT descended inferomedially in 38 specimens (95%) and inferolaterally in 2 specimens (5%). The upper fibers of the MT were short and ran horizontally, whereas the lower fibers were long and descended inferomedially or vertically. The upper fibers of the MT were intermingled with the inferior margin of the orbicularis oris muscle in all specimens. The originating muscle fibers of the ILI were intermingled with the upper lateral MT in all specimens. Some of the ILI fibers extended inferomedially to the middle or lower portion of the MT in 22 specimens (55%). The results of this study constitute new anatomical knowledge regarding the MT and will be useful to surgeons performing various surgical procedures of the chin area.

To study the electroneurographic facial muscle pattern in Bell's palsy over time, electroneurographic recordings in the frontalis, orbicularis oculi, nasalis, and mentalis muscle regions were performed early (mean, day 11) and 1 and 3 months after the onset of the condition in 30 consecutive patients. The correlation between facial muscle electroneurographic recordings over time was also calculated. An additional aim was to assess whether further prognostic information could be obtained by electroneurographic recordings in more than one facial region. The recovery pattern was similar in all 4 facial regions. Initially, the correlation between the facial recordings was weak (r = 0.20-0.27), but it was improved at follow-up examinations (r = 0.33-0.65). Favorable outcome in 23 of 24 patients (96%) could have been predicted by the initial nasalis and/or mentalis recordings. The gap between patients with favorable outcome and patients with unfavorable outcome increased when the average electroneurography values were calculated from 1, 2, and 4 muscle recordings (4%, 8%, and 15%, respectively). Our results indicate that in Bell's palsy, electroneurographic examination of more than one facial muscle region may add prognostic information and that the degree of degeneration is initially different in the nerve branches.

A 61-year-old female presented with a rare case of hemifacial spasm (HFS) resulting from facial nerve compression near the internal acoustic meatus. She underwent a first surgery for microvascular decompression at the root entry zone of the facial nerve, but this did not achieve resolution of the HFS. During the second surgery, the meatal loop of the anterior inferior cerebellar artery (AICA) was found to be the offending artery near the internal acoustic meatus. When the AICA was dissected and separated from the facial nerve, abnormal muscle responses of the mentalis muscle due to electrical stimulation of the zygomatic branch of the facial nerve were abolished. Following surgery the patient was completely free of the HFS.

The authors have studied the hand-mouth reflex of Babkin on 422 newborns. 413 out of 422 newborns were considered normal. We have found responses not yet published such as accentuation of inferior limb flexion, trunk flexion, upper limb adduction, contraction of the mentalis muscle, contraction of the orbicular of the lips, extension of the inferior limb, extension of the pododactiles and cry. We obtained the same responses by pressing the infraclavicular space just near the esternal bone. We compared statistically: a) responses to the stimulus on the palm of the hand and on the new reflexogenous zone; b) responses presented by term and preterm newborns; c) responses of newborns less than 12 hours of age and more than 24 hours of age.

The lip is an organ consisting mostly of muscle similar to the tongue. While the tongue is known as a muscular hydrostat, it is unclear whether the lip is also. In this paper the muscular hydrostat issue was explored from the anatomical and functional point of view using high‐resolution static MRI (hr‐MRI; 0.125 mm/pixel) and tagged‐cineMRI (t‐MRI). A 3‐D reconstruction of the lips and its muscles was obtained from hr‐MRI during sustained vowels /i/ and /u/. The muscular geometry of the orbicularis oris, mentalis, and depressor labii inferior muscles were superimposed onto the principal strains that depicts compression and expansion of the internal tissue obtained from t‐MRI. It is shown that (1) orbicularis oris muscle shape can predict both the borderline of glabrous and hairy skin and the manner in which the lips are protruded; (2) the lips volume is almost identical for both speech tasks; and (3) direction and intensity of compression of orbicularis oris and mentalis muscle bundles imply the role of these muscles in the protrusion appearance. These results indicate that the muscular architecture and volume preserving characteristics of the lips are consistent with a muscular hydrostat. [This work was supported by NIH (USA) and NiCT (Japan).]

• Extension of neuromuscular pedicles and direct nerve implants was investigated in ten rabbits. All rabbits underwent facial nerve resection bilaterally. In five rabbits a neuromuscular pedicle, based on the ansa cervicalis nerve, was implanted into the denervated mentalis muscle unilaterally. On the opposite side, reinnervation was attempted using a neuromuscular pedicle with an interposed nerve graft. In the other five rabbits, reinnervation was attempted using a direct nerve implant on one side and a direct nerve implant extended with a nerve graft on the opposite side. Evoked electromyographic muscle tension and histologic studies were used to evaluate reinnervation. Functional neuromuscular units were consistently produced with neuromuscular pedicles, direct nerve implants, and extended direct nerve implants, while extended neuromuscular pedicles failed to produce detectable reinnervation. ( Arch Otolaryngol Head Neck Surg 1989;115:217-223)

Fifty mentalis muscles were examined on 25 adult human cadavers with edentulous mandibles. The following observations were made: 1. 1. The right and left mentalis muscles were symmetrically placed on either side of the midline of the edentulous mandible, and they were found to be apart by a mean distance of 12 mm. 2. 2. The mean width of the mentalis muscle at the origin was approximately 5 mm. 3. 3. The medial fibers of the mentalis muscle crossed the midline to join the mentalis muscle of the opposite side. The most superficial fibers of the mentalis muscle coursed upward to join the obicularis oris. 4. 4. Sixty-seven per cent (20 of 30) of the muscles examined originated on the crest of the bone of the residual ridge. Twenty-seven per cent (8 of 30) of the muscles examined originated between the crest of the bone of the residual ridge and the fornix of the labial vestibule. 5. 5. Twenty-one of 30 (70 per cent) mentalis muscles examined in Group B had origins which correlated with elevations on the mucous membrane surface as recorded in modeling compound.