Masseteric Nerve Research Articles

Gross Anatomy of the Equine Masseter Muscle: Lamination and Intramuscular Course of the N. Massetericus.

The masticatory muscles of the horse are arranged in an asymmetrical pattern. Four individual muscles on the medial side of the mandible are opposed by one muscle (M. masseter) on the lateral side. However, recent studies on various herbivorous mammals indicate that the masseter muscle features a complex stratigraphic structure that might account for a functional diversity resembling an arrangement of several individual muscles. The functional consideration of the multidirectional equine masticatory movements leads to a similar hypothesis. In order to elucidate the detailed anatomy of the equine masseter muscle, eight cadaveric equine heads were dissected. Additional 29 skull specimens were assessed with regard to the masseteric attachment within the Fossa masseterica. A constant arrangement of nine individual muscular layers within the masseteric muscle was determined. The individual layers were clearly separated by tendon plates and their attachment areas at the masseteric fossa of the mandible were arranged in a constant pattern of bony ridges. With similar consistency, the main trunk of the masseteric nerve was found to run from dorsocaudal to ventrorostral: On that course, the nerve penetrated between the muscular layers from medial to lateral at constant positions. The findings of this study serve as a basis for further studies with the aim of developing biomechanical concepts of equine masticatory movement.

Long-term Follow-up of Secondary Reconstruction of Facial Paralysis and Depressive Deformities After Subtotal Temporal Bone Resection.

Subtotal temporal bone resection (STBR) frequently results in facial paralysis and depression, making reconstruction challenging due to significant tissue loss. This study aimed to evaluate the effectiveness of a procedure designed for simultaneous smile and soft tissue reconstruction after STBR. The authors included 3 patients who underwent latissimus dorsi (LD) neuromuscular flap combined with adipose flap transfer after STBR at the Tokyo Medical and Dental University Hospital between 2010 and 2016. Among these patients, 2 had facial vessels unsuitable for anastomosis due to prior neck dissection, and their masseteric nerves were unavailable for neurorrhaphy due to STBR. The thoracodorsal nerve was coaptated to the contralateral facial nerve in all patients and to the ipsilateral masseter nerve in one patient. Follow-up periods ranged from 7 to 13 years, with all patients achieving spontaneous smiles within 12 months post-surgery. Although depressive deformities improved, long-term follow-up revealed buccal muscle bulging due to unstable LD muscle fixation from a zygomatic arch defect caused by STBR. Revision surgeries, including muscle refixation with a tensor fasciae lata graft, muscle reduction, eyebrow lifting, blepharoplasty, and adipose tissue repositioning, were performed as needed. Ultimately, all patients achieved satisfactory facial contours and spontaneous smiles. This study demonstrates that free LD muscle with adipose flap transfer is effective for post-STBR reconstruction. However, detailed surgical planning and multistage reconstruction are often necessary due to the complexities involved.

"Muscle foreshortening after free gracilis transfer for smile: Where, when, why?"

Gracilis free muscle transfer (GFMT) remains the standard for smile restoration in patients with long-standing facial palsy. Resting oral commissure lateralization (ROCL) following GFMT is aesthetically unappealing and can cause functional problems including dysarthria and oral incompetence. The risk factors for ROCL following GFMT are poorly understood. Of all patients who underwent GFMT for smile restoration from 2003 - 2021, patients with subsequent ROCL were identified from a facial nerve database using pre-determined search criteria. Medical records were reviewed to identify potential risk factors for muscle foreshortening. Of 412 patients who underwent successful GFMT since 2003, we identified 41 (10%) patients who subsequently developed ROCL. ROCL rates varied significantly based on gracilis innervation source, with ipsilateral CN VII innervation and dual-innervation (cross-facial nerve graft (CFNG) plus ipsilateral nerve-to-masseter (NTM)) demonstrating the highest foreshortening rates (27.3% and 15.4%, respectively), compared to the lowest rates of foreshortening when gracilis was innervated by CNFG alone (3.2%), p=0.005. Patients with a history of radiation to the surgical field were significantly more likely to develop ROCL (22%) compared to those without a history of radiation (8.6%), p<0.001. Furthermore, the rate of ROCL was significantly higher among patients who underwent concurrent stabilization of the nasolabial fold using a wide band of fascia lata (20.8%) compared to those who did not (6.6%), p<0.001. Herein we report potential risk factors for ROCL following GFMT for smile restoration, including innervation source, radiation history, and concurrent fascia lata static suspension.

The effect of increasing motor end-plate innervation on smile activation in acute and early facial palsy.

While it has been over half a century since primary cross-facial nerve grafting was first described for facial reanimation, the outcome of this procedure, remains inconsistent and provide lesser smile excursion when compared to the likes of the masseteric nerve. However, the latter itself has limitations in terms of the lack of spontaneity and resting tone. While combinations have been attempted more proximally, we ask the question as to whether more distal nerve transfers with vascularized nerve grafts are a better option. In a retrospective review of clinical practice at our institute, 16 consecutive patients had single, double, and finally triple distal nerve transfers, close to the target facial muscle to reinnervate the motor endplates directly, over a 6-year period (2018-23). All patients had the onset of facial palsy within 18 months. Statistical analysis of the comparison between three sub-cohorts was performed using student's t-test and one-way ANOVA, respectively. Qualitatively, masseteric neurotization of a single facial nerve branch translated into smile improvement in 50% of cases, as opposed to all cases of double- and triple-neurotization of the smile muscles. In terms of upper lip elevation, single neurotization showed improvement in 25% of cases, double-neurotization in 40% of cases and triple-neurotization in 100% of cases. Upper lip elevation was also significantly better in those who had a vascularized cross-facial nerve graft (Student's t-test <0.05). In summary, increasing neural input to the motor endplates of smile muscles can significantly improve smile activation, in acute flaccid facial palsies.

Visualization of the Extracranial Branches of the Trigeminal Nerve Using Improved Motion-Sensitized Driven Equilibrium-Prepared 3D Inversion Recovery TSE Sequence.

Visualization of the extracranial trigeminal nerve is crucial to detect nerve pathologic alterations. This study aimed to evaluate visualization of the extracranial trigeminal nerve using 3D inversion recovery TSE with an improved motion-sensitized driven equilibrium (iMSDE) pulse. In this prospective study, 35 subjects underwent imaging of the trigeminal nerve using conventional 3D inversion recovery TSE, 3D inversion recovery TSE with an iMSDE pulse, and contrast-enhanced 3D inversion recovery TSE. The visibility of 7 extracranial branches of the trigeminal nerve, venous/muscle suppression, and identification of the relationship between nerves and lesions were scored on a 5-point scale system. In addition, SNR, nerve-muscle contrast ratio, nerve-venous contrast ratio, nerve-muscle contrast-to-noise ratio, and nerve-venous contrast-to-noise ratio were calculated and compared. Images acquired with iMSDE 3D inversion recovery TSE had significantly higher nerve-muscle contrast ratio, nerve-venous contrast ratio, and nerve-to-venous contrast-to-noise ratio (all P < .001); improved venous/muscle suppression and clearer visualization of the trigeminal nerve branches except the ophthalmic nerve than with conventional 3D inversion recovery TSE (all P < .05). Compared with contrast-enhanced 3D inversion recovery TSE, images acquired with iMSDE 3D inversion recovery TSE had significantly higher SNR, nerve-muscle contrast ratio, and nerve-to-venous contrast-to-noise ratio (all P < .05), and demonstrated comparable diagnostic quality (scores ≥3) of the maxillary nerve, mandibular nerve, inferior alveolar nerve, lingual nerve, and masseteric nerve (P > .05). As for the identification of the relationship between nerves and lesions, iMSDE 3D inversion recovery TSE showed the highest scores among these 3 sequences (all P < .05). The iMSDE 3D inversion recovery TSE is a promising alternative to conventional 3D inversion recovery TSE and contrast-enhanced 3D inversion recovery TSE for visualization of the extracranial branches of trigeminal nerve in clinical practice.

Deep masseteric triangular area to define masseter neurovascular bundle: A cadaveric study

IntroductionFacial reanimation procedures are used in the treatment of the disorder that impairs mimetic function and jeopardizes physical and psychological health, and one of the most important instruments of these techniques is the masseteric neurovascular bundle (NVB) and proper identification at the mandibular notch level. In the current study, a triangular area (deep masseteric triangle, DMT) on the lateral surface of the masseter muscle that was identified to help reliable determination of the masseteric NVB at the mandibular notch level. Material and methods40 parotideomasseteric region dissections were performed in 10 female and 10 male donated cadavers. Structures lateral to the masseter muscle were removed. The edge length of the masseter muscle on the zygomatic arch side was measured. After the edges of the DMT were measured, the masseteric NVB was found by dissection and its distance (depth) from the skin line was measured. ResultsThe mean lengths of the superior, posterior, and anterior margins were 17.3 (±4.5) mm, 25.9 (±6.2) mm, and 26.3 (±6.5) mm, respectively. The total length of the upper edge of the masseteric muscle attached to the zygomatic arch averaged 52.7 (±5.2) mm. The masseteric neurovascular bundle was detected at a depth of approximately 17 mm from the skin of the parotideamasseteric region. DiscussionThe visualization of the DMT can be used as an important landmark for access to branch-free part of the masseteric nerve. Moreover, an specific approach for masseteric NVB localization can be established by drawing a line between the mandibular angle and the midpoint of the upper edge of the DMT. This technique can greatly improve the accuracy of both masseteric nerve harvesting and masseteric nerve block procedures.

Masseteric Atrophy Following Masseteric Nerve Transfer: Radiographic Findings of Asymmetry in the Paralyzed Face?

To characterize the effect of facial reanimation using masseteric nerve transfer on the masseter muscle itself, examining whether there is any demonstrable atrophy postoperatively. Electronic medical records of adult patients who underwent facial reanimation using masseteric nerve transfer at our institution over a 15-year period were reviewed. To account for the impact of postoperative radiation, randomly selected patients who underwent radical parotidectomy without nerve transfer and received postoperative radiation served as controls in a 1:1 fashion against those who underwent masseteric nerve transfer with postoperative radiation. Twenty patients were identified who underwent masseteric nerve transfer and had sufficient pre- and postoperative imaging to assess masseter volume (mean age 58.2, 60% female). Of the four patients who did not receive postoperative radiation, each demonstrated masseteric atrophy on the side of their nerve transfer, with a mean reduction in masseter volume of 20.6%. The remaining 16 patients were included in the case-control analysis accounting for radiation. When compared with controls, those in the study group were found to have a statistically significant difference in atrophy (p = 0.0047) and total volume loss (p = 0.0002). The overall reduction in masseter volume in the study group was significantly higher compared with the control group, at 41.7% and 16.6%, respectively (p = 0.0001). Facial reanimation utilizing masseteric nerve transfer appears to result in atrophy of the denervated masseter when compared with the contralateral muscle. This volume deficit may lead to further facial asymmetry for patients undergoing comprehensive reanimation surgery. 3 Laryngoscope, 134:4514-4520, 2024.

Anatomical Identification and Possibilities of Transfer of the Masseteric Nerve for Facial Reanimation

The masseteric nerve (MN) is often used as a donor nerve for facial reanimation. In addition to already established techniques, MN transfer is rapidly gaining importance, mainly due to the single-stage approach of the procedure and its reconstructive potential. This anatomical study and the associated questionnaire study aimed to evaluate the established methods for identification of the MN and its suitability for direct nerve transfer as well as to assess the importance of MN transfer in the daily clinical routine. Bilateral dissection of 25 fresh-frozen head specimens (n=50; 13 female, 12 male) was performed with accompanying measurement of the MN. In a questionnaire study conducted at established centres for facial surgery in German-speaking countries, clinical experience data of MN transfer was collected using the SurveyMonkey software. The data obtained was statistically analysed using Microsoft Excel and presented in numerical tables and boxplots. Using anatomical landmarks such as the zygomatic arch and the mandibular notch for orientation, the MN was found in 100% of cases. Its average length from the emerging point below the zygomatic arch towards its entry into the masseter muscle was measured to be 22 mm and was the length available for nerve transposition. Tension-free coaptation of the MN with the zygomatic branch was possible in 94% of cases. The questionnaire showed that the MN is considered an important donor nerve for motor nerve transfers and that MN transfer is now largely established as a standard procedure. In accordance with previously published studies, the MN was reliably found at the height of the mandibular notch and, in the vast majority of cases, was suitable for tension-free coaptation with the zygomatic branch. Differences to the existing literature, however, can be seen in the length of the nerve available for nerve transposition and the frequency of its division into several branches before entering the masseter muscle. In German-speaking countries, Cross-Face Nerve Grafting (CFNG) is still the preferred method for facial reanimation surgery. However, MN transfer is also well established by now, both as an alternative and a supplement to other techniques, possibly due to its low donor site morbidity and short time to regeneration.

Facial palsy reconstruction.

The facial nerve stimulates the muscles of facial expression and the parasympathetic nerves of the face. Consequently, facial nerve paralysis can lead to facial asymmetry, deformation, and functional impairment. Facial nerve palsy is most commonly idiopathic, as with Bell palsy, but it can also result from a tumor or trauma. In this article, we discuss traumatic facial nerve injury. To identify the cause of the injury, it is important to first determine its location. The location and extent of the damage inform the treatment method, with options including primary repair, nerve graft, cross-face nerve graft, nerve crossover, and muscle transfer. Intracranial proximal facial nerve injuries present a challenge to surgical approaches due to the complexity of the temporal bone. Surgical intervention in these cases requires a collaborative approach between neurosurgery and otolaryngology, and nerve repair or grafting is difficult. This article describes the treatment of peripheral facial nerve injury. Primary repair generally offers the best prognosis. If primary repair is not feasible within 6 months of injury, nerve grafting should be attempted, and if more than 12 months have elapsed, functional muscle transfer should be performed. If the affected nerve cannot be utilized at that time, the contralateral facial nerve, ipsilateral masseter nerve, or hypoglossal nerve can serve as the donor nerve. Other accompanying symptoms, such as lagophthalmos or midface ptosis, must also be considered for the successful treatment of facial nerve injury.

Novel Method of Dual-innervated Free Gracilis Muscle Transfer for Facial Reanimation: A Case Series.

Dynamic facial reanimation is the gold standard treatment for a paralyzed face. The use of the cross-face nerve graft (CFNG) in combination with the masseteric nerve to innervate the free gracilis muscle has been reported to provide both spontaneity and strong neural input. We report a case series of dual innervation, using a novel method where the branch to masseter is coapted to the side of the CFNG. Eight patients received free gracilis muscle transfer using the new dual innervation method between September 2014 and December 2017. The CFNG, which was performed nine months prior, was sutured in an end-to-end fashion to the obturator nerve. A nerve graft was coapted to the ipsilateral masseteric nerve and then sutured in an end-to-side fashion to the CFNG proximal to its coaptation to the obturator nerve. All patients recovered smile function with and without teeth clenching around the same time period. Smiles without teeth clenching appeared later in two of eight patients and earlier in one of eight patients, being noted at an average of 8.25 months of follow-up versus 7.6 months. The estimate of true attainment is limited by the spacing of follow-up dates. Average follow-up time was 36.07 months (range: 10-71.5). FACE-Gram software smile analysis with and without biting demonstrated similar excursion on average (7.64 mm versus 8.6 mm respectively, P = 0.93), both of which are significantly improved from preoperation. This novel method of a dual-innervated free gracilis muscle transfer offers a viable technique that achieves a symmetric, strong, and emotional smile.

Optimizing Facial Function in Patients With High-Risk Recurrent Pleomorphic Adenoma and a History of Facial Nerve Injury.

Parotid pleomorphic adenoma (PA) patients present significant diagnostic and surgical challenges rendering them high risk for facial nerve injury. Recurrent PA patients often present with history of facial nerve injury or previous reanimations making salvage of the facial nerve or previous reanimations significantly more complex. The study aim is to share our experience with this high risk for facial nerve injury population and review the literature. Adult patients with recurrent PA and history of facial nerve injury with at least 3 months of follow-up were analyzed for demographics, facial palsy history, previous head and neck surgeries, previous facial paralysis reconstruction, preoperative imaging, surgical approach, and postoperative outcomes. Four female patients were identified with an average age of 62 years. All patients underwent an initial protective dissection of the facial nerve or previous reanimation reconstruction by the facial nerve reconstructive team followed by the extirpative team. The average number of previous head and neck surgeries was 5, the number of recurrences was 2, and follow-up was 20 months. Half had prior dynamic facial reanimation. Two patients underwent complete preextirpative dissection of the facial nerve resulting in neuropraxia, which recovered completely after an average of 143 days. A third patient presented with 2 recurrences, both during and after reanimation with a dually innervated free functional muscle transfer. The reconstruction was salvaged, and motion was achieved. A fourth patient presented with benign preoperative findings, but intraoperative findings confirmed malignancy, necessitating facial nerve sacrifice, followed by immediate intratemporal grafting of the facial nerve and masseteric nerve transfer. Motion appeared 139 days postoperatively. A multidisciplinary effort should be implemented in this high risk for facial nerve injury population with the primary goal of protecting the facial nerve or any previous reanimation procedures, yet with preparedness to apply any reconstructive strategy based on intraoperative findings.

Comparison of Outcomes of Facial Reanimation Between the Use of Cross-facial Nerve Graft and the Masseteric Nerve as the Donor Nerve for Reinnervation of Gracilis Muscle Flap Transfer.

In patients with facial paralysis, the free functional gracilis muscle transfer is preferred for facial reanimation. The choice of an adequate motor nerve to innervate the transplanted gracilis muscle is one of the procedure's key components. We present a comparative study between cross-facial nerve graft (CFNG) and masseteric nerve as donor nerves for reinnervated gracilis flap transfer in patients with complete facial paralysis. Retrospective analysis was performed on all patients with complete facial paralysis who had a free functional gracilis muscle transfer for facial reanimation between January 2014 and December 2021. Only those who received gracilis transfer reinnervated by either CFNG or masseteric nerve were included in this study. The smile excursion and lip angle were measured for evaluating the outcomes postoperatively. The inclusion criteria were met by a total of 21 free functional gracilis muscle transfers, of which 11 were innervated by CFNG and 10 by the masseteric nerve. Both surgical procedures resulted in a highly considerable smile excursion of the reanimated side and postoperative improvement of static or dynamic lip angle. Masseteric nerve coaptation led to greater smile excursion and more significant improvement of dynamic lip angle than CFNG. For patients who have complete facial paralysis, face reanimation can be successfully accomplished by free gracilis transfer reinnervated by the CFNG or the masseteric nerve. In particular, the masseteric nerve is a reliable choice for dynamic smile reanimation.

Three-dimensional evaluation of symmetry in facial palsy reanimation using stereophotogrammetric devices: A series of 15 cases

Facial palsy can severely compromise quality of life, significantly altering the harmony and symmetry of the face, which can be restored by surgical rehabilitation. The aim of the study was the quantification of facial symmetry following facial reanimation.Fifteen consecutive adult patients were surgically treated through triple innervation for reanimation of flaccid unilateral facial paralysis (contralateral facial nerve, masseteric nerve, and hypoglossal nerve) and fascia lata graft for definition of the nasolabial sulcus. In the preoperative stage and at least 11 months after the surgical treatment, three-dimensional facial images were recorded through stereophotogrammetry in a neutral (rest) position, and with Mona Lisa and full-denture (maximum) smiles. Labial commissure inclination relative to the interpupillary axis, and a surface assessment of local facial asymmetry at rest and while smiling were obtained for the upper, middle, and lower facial thirds.The angle between the interpupillary axis and the labial commissure significantly improved in post-surgical acquisitions, regaining symmetry at rest (t-test; p < 0.001). Facial symmetry increased significantly when passing from pre-to postsurgical facial scans, from the lower to the upper facial third, and from the full smile to the rest position (ANOVA; p < 0.001). After treatment, the full smile recovered more symmetry than the other two expressions. In summary, surgical treatment significantly reduced facial asymmetry, but this reduction differed significantly among the various animations and facial thirds.The results of this study confirmed clinical findings of significant static and dynamic improvements in facial symmetry after triple innervation reanimation surgery.

Simultaneous Reconstruction of Smiling Eye Using V-Shaped Long Latissimus Dorsi Muscle Transfer in Patients with Flaccid Facial Paralysis.

Various neurovascular free muscle transfers for smile reconstruction in patients with facial paralysis have been reported. However, these methods focused on perioral smiling rather than eye smiling. Although the lower eyelid does not contribute significantly to eyelid closure, dynamic reanimation of the upward movement of the lower eyelid with bulging of the malar region during smiling is important in smile reconstruction. The authors present a novel procedure for smiling eye and perioral smiling. The V-shaped latissimus dorsi muscle flap containing the descending branch (DB) of the thoracodorsal nerve (TDN) was used. Muscle A (15 to 17 cm), which is located along the main trunk of the DB, is much longer than muscle B (10 to 12 cm), which is along the branch of DB. A distal stump of the TDN involved in muscle B was prepared. The true trunk and distal stump of the TDN were sutured to the contralateral facial and ipsilateral masseteric nerves, respectively. The central region of muscle A was positioned at the lateral part of the lower eyelid; the distal end of long muscle A was affixed to the temporal region, which enabled periocular movements and narrowing of the palpebral fissures alongside perioral smiling when muscle A contracted. Nine patients with complete flaccid facial paralysis were treated. All patients attained muscle contraction induced by the ipsilateral masseteric and contralateral facial nerves. The smiling eye appearance was observed in 7 of 9 patients. This procedure simultaneously improves paralytic ectropion at rest and aids eyelid closure and enables early voluntary smile and a later spontaneous smile.

Evaluation of Long-Term Surgical and Patient-Reported Outcomes after Pediatric Facial Reanimation.

Outcomes of pediatric facial reanimation beyond 10 years are not known. This cross-sectional study evaluated long-term surgical and patient-reported outcomes of adults who underwent smile reconstruction as children with either a cross-face nerve graft (CFNG) or masseter nerve transfer at least 10 years previously. Commissure excursion was quantified with FACE-Gram software at 3 time points: preoperatively, early postoperatively within 2 years, and at long-term follow-up. Patient-reported outcomes were evaluated with validated questionnaires (Facial Clinimetric Evaluation Scale, FACE-Q 1.0) and thematic analysis of semistructured interviews. Results are reported as median (interquartile range [IQR]). A total of 42 patients were included (26 women and 16 men). Median long-term follow-up was 19.3 years (IQR, 8.8 years) for CFNG and 17.6 years (IQR, 5.8 years) for masseter nerve transfer. For both groups, commissure excursion increased significantly from preoperative to early postoperative time points and remained stable at long-term follow-up (P < 0.0001). Commissure excursion at long-term follow-up between the 2 groups was not significantly different (CFNG, 5.0 mm [IQR, 9.4 mm]; masseter nerve transfer, 8.4 mm [IQR, 4.1 mm]); P > 0.05). For patient-reported outcomes, median Facial Clinimetric Evaluation Scale score was 72 of 100, and 95% of respondents agreed with the statement "I am pleased with the result" on the FACE-Q 1.0. Overall quality of life was rated at 7 of 10 or greater by 97% of participants, and all participants would recommend the surgery to other children. Pediatric facial reanimation with CFNG or masseter nerve transfer reliably improves commissure excursion with longevity beyond 10 years. Adult patients report overall high satisfaction and social functioning.

The masseteric nerve for facial reanimation: Macroscopic and histomorphometric characteristics in 106 human cadavers and comparison of axonal ratio with recipient nerves

Peripheral facial palsy causes severe impairments. Sufficient axonal load is critical for adequate functional outcomes in reanimation procedures. The aim of our study was to attain a better understanding of the anatomy of the masseteric nerve as a donor, in order to optimize neurotization procedures.Biopsies were obtained from 106 hemifaces of fresh frozen human cadavers. Histological cross-sections were fixed, stained with PPD, and digitized. Histomorphometry and a validated software-based axon quantification were conducted. Of the 154 evaluated branches, 74 specimens were of the main trunk (MT), 40 of the anterior branch (AB), and 38 of the descending branch (DB), while two halves of one cadaver featured an additional branch.The MT showed a diameter of 1.4 ± 0.41 mm (n = 74) with 2213 ± 957 axons (n = 55). The AB diameter was 0.9 ± 0.33 mm (n = 40) with 725 ± 714 axons (n = 30). The DB diameter was 1.15 ± 0.34 mm (n = 380) with 1562 ± 926 axons (n = 30). The DB demonstrated a high axonal capacity — valuable for nerve transfers or muscle transplants.Our findings should facilitate a balanced selection of axonal load, and are potentially helpful in achieving more predictable results while preserving masseter muscle function.

Intra-surgical optimized identification of masseteric nerve for central facial nerve neurorrhaphy: A retrospective study

It is the aim of the study to provide a detailed intraoperative assessment of the masseteric nerve and the facial branch of the smiling muscles complex through the same superficial musculoaponeurotic system (SMAS) incision.This observational retrospective study aimed to define the straightest and safest surgical route to identify the facial nerve for the smiling muscles complex and the masseteric nerve, using distance from the tragus and zygomatic arch as anatomical landmarks.30 patients were included in the study. The mean distance from the tragus to the masseteric nerve was 40.03 mm, the mean distance from the zygomatic arch was 12.24 mm, and the mean depth from the SMAS was 10.84 mm. Data were consistent, with little variation. The distance from the zygoma was found to be higher in male patients. There was a positive correlation between the depth to the nerve and the distance from the zygoma, but no correlation between body mass index and the other parameters studied.Within the limitations of the study it seems that the proposed standardized direct approach to the masseteric nerve is a reproducible technique that may be used to increase the safety of the procedure, reduce the operating time, and decrease the amount of dissection and related postoperative scarring, thereby fostering positive results.

Masseteric Nerve Transfer for Facial reanimation: Meta-analysis study

Masseteric Nerve Transfer for Facial reanimation: Meta-analysis study

Age-related outcomes of facial reanimation surgery using gracilis free functional muscle transfer innervated by the masseteric nerve: A retrospective cohort study

The free functional muscle gracilis transfer is an established approach in facial reanimation surgery; however, the significance of its neurotization and the patient's age is still inconclusive. Several donor nerves are available for facial reanimation using the free functional gracilis muscle transfer. This retrospective cohort study investigates whether the masseteric nerve is an equally reliable donor nerve in both older and younger patients. We included 46 patients (13-71 years, male and female) who underwent nerve-to-masseter (NTM)-driven free functional muscle transfer (FFMT) between January 2008 and December 2019. Patients were distributed into three cohorts according to their age at surgery. We assessed the facial symmetry before and after surgery using the pupillo-modiolar angle. Commissure height and excursion deviation were measured with the Emotrics software. Patient-reported outcome measurements were taken using the Facial Clinimetric Examination (FaCE) scale. All patients had successful flap innervation, except for one patient in the middle-aged cohort (31-51 years). The postoperative facial symmetry at rest, smiling, and laughing was analyzed with the pupillo-modiolar angle and the Emotrics software and showed similar results between all cohorts. The FaCE scale showed similar scores for the middle-aged (31-51 years) cohort and the senior cohort (52-71 years). The social function score in the senior cohort was higher than in the middle-aged cohort, without statistical significance. One patient in the middle-aged (31-51 years) cohort and the senior cohort (52-71 years), respectively, underwent emergency revision due to impaired flap perfusion and could be salvaged. NTM-driven FFMT for facial reanimation is a safe and reliable procedure across all age groups of patients.

Extra- and intramuscular innervation of the masseter: Implications for facial reanimation

Irreversible facial paralysis results in significant functional impairment. The motor nerve to the masseter is a reconstructive option, but despite its clinical importance, there are few parametric anatomic studies of the masseteric nerve. The purpose of this study was to investigate the extra- and intramuscular innervation of the masseter in 3D to determine the relationship of the nerve to the muscle heads and identify landmarks to aid identification. The nerve was dissected throughout its entire course in eight formalin-embalmed cadaveric specimens (mean age 84.9±12.2 years). The nerve was digitized at 1-2mm intervals using a MicroScribe™ digitizer and modeled in 3D in Autodesk® Maya®. Two or three extramuscular nerves were found to enter the deep head (DH) of the masseter: one main "primary" nerve (n=8) and one (n=4) or two (n=4) smaller primary nerve(s). The main primary nerve supplied both the deep and superficial heads, whereas the smaller primary nerve(s) only supplied the DH. Surgical landmarks for masseter nerve localization were quantified. Comprehensive mapping of the innervation of the masseter muscle throughout its volume revealed neural partitioning that could provide a basis for safety planning for muscle flaps and donor nerve identification and explain why masseter functional loss is not incurred by donor nerve sacrifice. Quantified landmarks correlate to previous studies and support the constant anatomy of this nerve. Our results provide a basis to optimize surgical approaches for donor nerve and muscle flap surgery.