Masseteric-facial nerve coaptation – an alternative technique for facial nerve reinnervation

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

BACKGROUND

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.

MATERIAL AND METHODOLOGY

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.

RESULTS

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.

DISCUSSION

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.

Masseteric Nerve Transfer for Facial Paralysis Secondary to Parotid Malignancy: A Retrospective Case Series

Background: The objective outcomes of masseteric nerve transfer in the setting of parotid malignancy are unclear. Objective: To measure objective facial reanimation outcomes of masseteric nerve transfer in patients with parotid malignancy who underwent parotidectomy with facial nerve resection. Materials and Methods: Retrospective review of patients who underwent masseteric nerve transfer for facial paralysis secondary to parotid malignancy was carried out at a tertiary referral hospital from August 2017 to November 2021. Objective facial reanimation outcomes were analyzed using Emotrics. Minimal follow-up of 6 months was required for inclusion. Results: Eight patients (five males) with a median age of 75.5 years (range 53-91) met inclusion criteria. Fifty percent had metastatic squamous cell carcinoma, and 50% had primary parotid malignancy. Five patients underwent concomitant cancer resection with facial nerve reconstruction. Seven patients received postoperative adjuvant radiotherapy. After reinnervation, patients had improved oral commissure excursion (from 1.51 mm ±1.27 to 3.77 mm ±1.81; p < 0.01) and facial symmetry during smile. Conclusion: In this study, masseteric nerve transfer enhanced oral commissure excursion and facial symmetry during smile in patients with parotid malignancy and facial nerve resection.

Dual-Innervated Gracilis Free Functional Muscle Transfers in Facial Palsy Patients: Comparing Long-Term Outcomes between One- versus Two-Stage Procedures

BACKGROUND

 In facial reanimation, dual-innervated gracilis free functional muscle transfers (FFMTs) may have amalgamated increases in tone, excursion, synchroneity, and potentially spontaneity when compared with single innervation. The ideal staging of dual-innervated gracilis FFMTs has not been investigated. We aim to compare objective long-term outcomes following one- and two-stage dual-innervated gracilis FFMTs.

METHODS

 Included were adult patients with facial paralysis who underwent either one- (one-stage group) or two-stage (two-stage group) dual-innervated gracilis FFMT with ≥1 year of postoperative follow-up. Facial measurements were obtained from standardized photographs of patients in repose, closed-mouth smile, and open-mouth smile taken preoperatively, 1 year postoperatively, and 3 years postoperatively. Symmetry was calculated from the absolute difference between the paralyzed and healthy hemiface; a lower value indicates greater symmetry.

RESULTS

 Of 553 facial paralysis patients, 14 were included. Five and nine patients were in the one- and two-stage groups, with mean follow-up time, respectively, being 2.5 and 2.6 years. Within-group analysis of both groups, most paralyzed-side and symmetry measurements significantly improved over time with maintained significance at 3 years postoperatively in closed and open-mouth smile (all p ≤ 0.05). However, only the two-stage group had maintained significance in improvements at 3 years postoperatively in paralyzed-side and symmetry measurements in repose with commissure position (median change [interquartile range, IQR], 7.62 [6.00-10.56] mm), commissure angle (median change [IQR], 8.92 [6.18-13.69] degrees), commissure position symmetry (median change [IQR], -5.18 [-10.48 to -1.80] mm), commissure angle symmetry (median change [IQR], -9.78 [-11.73 to -7.32] degrees), and commissure height deviation (median change [IQR], -5.70 [-7.19 to -1.64] mm; all p ≤ 0.05). In the between-group analysis, all measurements were comparable in repose, closed-mouth smile, and open-mouth smile (all p > 0.05).

CONCLUSION

 Long-term outcomes demonstrate that both one- and two-stage dual-innervated gracilis FFMTs significantly improve excursion, but only two-stage reconstruction significantly improves resting tone.

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

BACKGROUND

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.

MATERLALS AND METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

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.

Facial surface electromyography: A systematic review on the state of the art and current perspectives

PURPOSE

Peripheral facial nerve palsy is a severely disabling condition. In current clinical practice, the commonest tools to assess facial palsy are grading scales, digital face image analyses or facial muscle electrophysiology. However, these techniques suffer from subjectivity or invasiveness and cannot be applied as part of a routine clinical assessment. Therefore, novel non-invasive office-based tools are needed. Surface electromyography (sEMG) may potentially fulfill the requirements of objectivity, low examiner-dependence, and minimal invasiveness. The aim of this systematic review is to define the state of the art on the use of sEMG for facial nerve functional assessment.

MATERIALS AND METHODS

Pubmed, Scopus and Web of Science databases were systematically searched. The study protocol was registered on PROSPERO in January 2023. The review was conducted according to the PRISMA guidelines.

RESULTS

After the application of inclusion-exclusion criteria, 15 manuscripts with adequate relevance to this topic were included in the review.

CONCLUSIONS

Facial sEMG represents a potentially useful tool to implement objective quantification of facial nerve function in clinical practice. Given the heterogeneity of methods and analysis in the available studies, sEMG results are hardly comparable. The introduction of methodological guidelines, followed by large prospective studies on well-defined subsets of patients with facial nerve impairment, is advocated.

Pediatric Microsurgery and Free-Tissue Transfer

Advancements in microsurgery, along with increased microsurgical experience in pediatric patients, have made free-tissue transfer a reliable modality for pediatric bone and soft tissue reconstruction today. Free-tissue transfer is most commonly used in children for the coverage of large or complex defects resulting from traumatic, oncologic, or congenital etiologies. While flap success and complication rates between pediatric and adult populations are similar, special considerations must be taken into account within the pediatric population. In this article, we will describe common indications, technical nuances, and clinical considerations for the management of the pediatric free-tissue transfer patient.

Research trends and perspectives on immediate facial reanimation in radical parotidectomy (Review)

For patients diagnosed with advanced malignant parotid tumour, radical parotidectomy with facial nerve sacrifice is part of the treatment. Multiple surgical techniques have been developed to cure facial paralysis in order to restore the function and aesthetics of the face. Despite the large number of publications over time on facial nerve reanimation, a consensus on the timing of the procedure or the donor graft selection has remained to be established. Therefore, the aim of the present study was to conduct a bibliometric analysis to identify and analyse scientific publications on the reconstruction of the facial nerve of patients who underwent radical parotidectomy with facial nerve sacrifice. The analysis on the topic was conducted using the built-in tool of the Scopus database and VOSviewer software. The first 100 most cited articles were separately reviewed to address the aim of the study. No consensus was found regarding the recommended surgical techniques for facial nerve reanimation. The most used donor cranial nerves for transfer included the following: Masseteric branch of the V nerve, contralateral VII nerve with cross-face graft, the XI nerve and the XII nerve. The best timing of surgery is also controversial depending on pre-exiting pathology and degree of nerve degeneration. However, most of the clinical experience suggests facial nerve restoration immediately after the ablative procedure to reduce complications and improve patients' quality of life.

The Selective Trigeminal Nerve Motor Branching Transfer: an Preliminary Clinical Application for Facial Reanimation

OBJECTIVE

To investigate the effectiveness and feasibility of selective trigeminal nerve motor branching in the repair of facial palsy.

MATERIALS AND METHODS

The clinical data of patients with advanced facial palsy from 2016 to 2021 were retrospectively analyzed, including pictures and videos before and 18 months after surgery. The House-Brackmann grading system was used to evaluate facial nerve function before and after repair, and the symmetry scale of oral commissure at rest and Terzis' smile functional evaluation scale were used to qualitatively assess the symmetry of the mouth angle and smile function. The distance of oral commissure movement was assessed to evaluate the dynamic repair effect, and the FaCE facial muscle function scale was used to assess patients' subjective perception before and after surgery.

RESULTS

A total of four patients were included in the study, all of whom showed signs of recovery of facial nerve function within six months. In all four cases, significant improvements were observed in House-Brackmann ratings, the smile function score and the symmetry scale of oral commissure at rest. Compared to the pre-operative period, the four patients demonstrated various degrees of eye-closing function recovery, and a significant improvement in oral commissure movement was observed ( P <0.001). FaCE scores also improved significantly after surgery ( P =0.019).

CONCLUSION

Concurrent selective facial nerve repair with trigeminal branch-facial nerve anastomosis resulted in eye-closing function recovery while improving static and dynamic symmetry, yielding acceptable postoperative results.

Anatomic Analysis of Masseteric-to-zygomatic Nerve Transfer in Rat and Pig Models

Background

Nerve transfer from the masseteric branch of the trigeminal nerve is a widely performed procedure for facial reanimation. Despite achieving powerful muscle force, clinical and aesthetic results leave room for improvement. Preclinical animal models are invaluable to establishing new therapeutic approaches. This anatomical study aimed to establish a masseteric-to-zygomatic nerve transfer model in rats and pigs.

Methods

The masseteric branch of the trigeminal nerve and the zygomatic branch of the facial nerve were dissected in 30 swine and 40 rat hemifaces. Both nerves were mobilized and approximated to achieve an overlap between the nerve ends. Over the course of dissecting both nerves, their anatomy, length, and branching pattern were documented. At the coaptation point, diameters of both nerves were measured, and samples were taken for neuromorphometric analysis.

Results

Anatomic details and landmarks were described. Tension-free coaptation was possible in all rat and pig dissections. In rats, the masseteric branch had an average diameter of 0.36 mm (±0.06), and the zygomatic branch average diameter was 0.46 mm (±0.13). In pigs, the masseteric branch measured 0.52 (±0.16) mm and the zygomatic branch, 0.59 (±0.16) mm. No significant differences were found between the diameters and axon counts of both nerves in pigs. In rats, however, their diameters, axon counts, and fascicular areas were significantly different.

Conclusion

Our study demonstrated the feasibility of direct masseteric-to-zygomatic nerve transfer in rats and pigs and provided general anatomic knowledge of both nerves.

Evidence-Based Practices in Facial Reanimation Surgery

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Describe the causes and preoperative evaluation of facial paralysis. 2. Discuss techniques to restore corneal sensation and eyelid closure, elevation of the upper lip for smile, and depression of the lower lip for lip symmetry. 3. Outline treatment goals, surgical treatment options, timing of repair, and other patient-specific considerations in appropriate technique selection.

SUMMARY

Congenital facial paralysis affects 2.7 per 100,000 children; Bell palsy affects 23 per 100,000 people annually; and even more people are affected when considering all other causes. Conditions that impair facial mimetics impact patients' social functioning and emotional well-being. Dynamic and static reconstructive methods may be used individually or in concert to achieve adequate blink restoration, smile strength and spontaneity, and lower lip depression. Timing of injury and repair, patient characteristics such as age, and cause of facial paralysis are all considered in selecting the most appropriate reconstructive approach. This article describes evidence-based management of facial paralysis.

Histomorphometry of the Sural Nerve for Use as a CFNG in Facial Reanimation Procedures

Facial palsy (FP) is a debilitating nerve pathology. Cross Face Nerve Grafting (CFNG) describes a surgical technique that uses nerve grafts to reanimate the paralyzed face. The sural nerve has been shown to be a reliable nerve graft with little donor side morbidity. Therefore, we aimed to investigate the microanatomy of the sural nerve. Biopsies were obtained from 15 FP patients who underwent CFNG using sural nerve grafts. Histological cross-sections were fixated, stained with PPD, and digitized. Histomorphometry and a validated software-based axon quantification were conducted. The median age of the operated patients was 37 years (5-62 years). There was a significant difference in axonal capacity decrease towards the periphery when comparing proximal vs. distal biopsies (p = 0.047), while the side of nerve harvest showed no significant differences in nerve caliber (proximal p = 0.253, distal p = 0.506) and axonal capacity for proximal and distal biopsies (proximal p = 0.414, distal p = 0.922). Age did not correlate with axonal capacity (proximal: R = -0.201, p = 0.603; distal: R = 0.317, p = 0.292). These novel insights into the microanatomy of the sural nerve may help refine CFNG techniques and individualize FP patient treatment plans, ultimately improving overall patient outcomes.

V to VII Nerve Transfer for Smile Reanimation

Using the wording "facial reanimation," surgeons mean restoring movements to the paralyzed face. According to the condition of mimic muscle, facial palsy can be classified as recent (mimic muscle still alive) and chronic (atrophy of mimic muscle) palsy. The treatment is quite different because in the former group the mimic muscles can be still used so long as a new motor source would be connected to the damaged facial nerve. In the latter group, muscular transplantation is needed to substitute the atrophied mimic muscles of the middle part of the face. In both cases, the neural impulse that makes the muscles (mimic muscle in the former, transplanted muscle in the latter) move come from a new motor nerve. Nowadays, the masseteric nerve is widely used as a new motor source in recent facial reanimation; the same nerve has also a main role in the treatment of both chronic facial palsy where it is used as the new nervous stimulus for the new transplanted muscle and facial paresis where the nervous stimulus coming from the masseteric nerve is used to empower the stimulus coming from the injured facial nerve. The masseteric nerve can be usually connected directly to the facial nerve without the interposition of a nerve graft, with a faster reinnervation. Moreover, the use of the masseteric nerve gives no morbidity to the masticatory functions.

Early Simultaneous Cross Facial Nerve Graft and Masseteric Nerve Transfer for Facial Paralysis after Tumor Resection

We describe a new approach for facial reanimation after skull base tumor resection with known facial nerve sacrifice, involving simultaneous masseter nerve transfer with selective cross facial nerve grafting (CFNG) within days after tumor surgery. This preliminary study compared outcomes of this approach versus a staged procedure involving a masseter nerve "babysitter" performed in a delayed timeline.

Methods

Patients undergoing masseter nerve transfer and CFNG for facial paralysis after skull base tumor resection were consented to participate in video interviews. Facial Clinimetric Evaluation (FaCE) Scale (0-100) patient-reported outcome, eFACE, and Facial Grading Scale scores were compared.

Results

Nine patients had unilateral facial paralysis from resection of a schwannoma (56%), acoustic neuroma (33%), or vascular malformation (11%). Five underwent early simultaneous CFNG and masseter nerve transfer (mean 3.6 days after resection), whereas four underwent two-stage reanimation including a babysitter procedure (mean 218 days after resection). Postoperative FaCE scale and Facial Grading Scale scores were similar in both groups (P > 0.05). Postoperative mean eFACE scores were similar for both groups for smile (early: 71.5 versus delayed: 75.5; P = 0.08), static (76.3 versus 82.1; P = 0.32), and dynamic scores (59.7 versus 64.9; P = 0.19); however, synkinesis scores were inferior in the early group (76.4 versus 91.1; P = 0.04).

Conclusions

Early simultaneous masseter nerve transfer and CFNG provides reanimated movement sooner and in fewer stages than a staged approach in a delayed timeline. The early technique appears to result in similar clinician- and patient-reported outcomes compared with delayed procedures; however, in this preliminary study, the early approach was associated with greater synkinesis, meriting further investigation.

Anatomic and histomorphometric study of the nerve to the vastus lateralis in cadaver for its clinical application in facial reanimation

BACKGROUND

The innervated vastus lateralis flap (IVLF) is a barely used possibility for facial palsy reconstruction because of its thickness compared to the gracilis, latissimus dorsi, and pectoralis minor flaps. The aim of this study is to perform a precise description of the intramuscular distribution of the nerve motor branches and its relationship with the vascular pedicle in order to harvest a segmental muscle flap with the best contractile strength to restore facial reanimation.

METHODS

The study was performed on 16 adult cadaver thighs identifying the vastus lateralis muscle and the distribution and relationships of its neurovascular pedicle and branches. We evaluated where the nerve pierced the muscle and the course of the nerve within it. Transverse segments of the nerve were obtained from the proximal and distal ends of the nerve and stained using anti-ChAT (Choline acetyltransferase) antibodies which are specific of motor neurons.

RESULTS

A nerve for the vastus lateralis from the posterior division of the femoral nerve divided into 2 branches in 56% of cases; the principal branch coursed along the vascular pedicle and pierced the muscle more proximally than the respective vessels, and a minor branch that pierced the muscle 25-60 mm proximally. There were 3 main intramuscular branches. The nerve length (mean 132.65 ± 22.89 mm) allowed to reach the contralateral side of the face in almost all cases (95%). The mean ChAT positive fibers was 351.0 ± 92.4/mm² at the proximal end, and 270.3 ± 87.9/mm² at the distal end (p = 0.49). The number of ChAT negative fibers was higher than ChAT positive in both proximal and distal ends of the nerve.

CONCLUSION

We propose the IVLF as a one-step surgical flap for facial paralysis reanimation due to the constant neurovascular pattern and lengthy pedicle. The amount of motor fibers in several segments of the nerve is appropriate to produce a powerful contraction for dynamic reconstruction.

Assessing the Efficacy of Anastomosis between Ansa Cervicalis and Facial Nerve for Patients with Concomitant Facial Palsy and Peripheral Neuropathy

Background: For decades, patients with facial asymmetry have experienced social interaction difficulties, leading them to seek treatment in the hope of restoring facial symmetry and quality of life. Researchers evaluated numerous surgical techniques, but achieving results remains a significant hurdle. Specifically, anastomosis between the ansa cervicalis (AC) and facial nerve (FN) can hinder the patient's physical appearance. Objective: Our study goal was to examine the efficiency of anastomosis between AC and FN for facial motor function recovery even in the presence of peripheral neuropathy. Materials and Methods: Four patients diagnosed with facial palsy grade VI on the House & Brackmann Scale (HB) after vestibular schwannoma (VS) resection (Koos grade IV) via the retrosigmoid approach underwent AC and FN anastomosis. Outcomes were related to tumor grade, previous therapy, and the time between postoperative facial palsy and anastomosis. Images and neurophysiological data were evaluated. Results: After vs. resection, all four patients demonstrated HB grade VI facial palsy for an average of 17 months. During the follow-up program, lasting between 6 and 36 months, two patients were evaluated as having HB grade III facial palsy; the other two patients were diagnosed with grade IV HB facial palsy. None of the patients developed tongue atrophy, speech disorder, or masticatordys function. Conclusions: Anastomosis between the AC and FN is a safe and effective treatment for facial paralysis after cerebellopontine tumor resection. Nerve reanimation may be feasible even for patients with peripheral polyneuropathy. This study also offers a new option for patients with a progression-free status.

Masseteric-to-facial nerve transfer for treatment of pediatric facial paralysis: An initial report

OBJECTIVES

The indications and outcomes of masseteric-to-facial nerve transfer in pediatric patients with short-term facial paralysis is incompletely understood as compared to its use in adult patients. This report aims to retrospectively quantify outcomes with both clinician-based measurements and objective facial analysis software.

METHODS

Retrospective case series at a single institution. The Sunnybrook Facial Grading System was used for clinician-based measurements and Emotrics software for objective measurements.

RESULTS

Four pediatric patients underwent masseteric-to-facial nerve transfers from 2016 to 2018. The mean patient age at the time of surgery was 4.5 years (range = 2-7) and the mean time from paralysis onset to surgical intervention was 12.9 months (range = 10.0-16.2). The mean follow-up was 18.3 months (range = 14.5-23.6). With regards to the Sunnybrook resting nasolabial fold symmetry, 3 of the 4 patients improved from 2 (absent nasolabial fold) to 1 (less pronounced nasolabial fold). Per the Emotrics analysis, the pre- and post-operative mean absolute differences for commissure excursion between the normal functioning and paralyzed sides were 11.8 mm and 6.7 mm, respectively (p = 0.04).

CONCLUSION

The masseteric-to-facial nerve transfer technique leads to an objective improvement in dynamic smile function in select pediatric patients.

Multiple Model Evaluation of the Masseteric-to-Facial Nerve Transfer for Reanimation of the Paralyzed Face and Quick Prognostic Prediction

Facial paralysis is negatively associated with functional, aesthetic, and psychosocial consequences. The masseteric-to-facial nerve transfer (MFNT) has many advantages in facial reanimation. The aim is to evaluate the effectiveness of our MFNT technique and define the potential factors predictive of outcome. The authors conducted a retrospective review of 20 consecutive patients who underwent MFNT using the temporofacial trunk of facial nerve. Videotapes and images were documented and evaluated according to Facial Nerve Grading Scale 2.0 (FNGS2.0) and Sunnybrook Facial Grading System (FGS). The quality-of-life was obtained using the Facial Clinimetric Evaluation (FaCE) Scale. Moreover, Facial Asymmetry Index (FAI), quantitative measurement of the width of palpebral fissure, deviation of the philtrum, and angles or excursions of the oral commissure were applied to explore the effect of the transfer metrically. Multivariable logistic regression models and Cox regression were prepared to predict the effect of MFNT by preoperative clinical features. The patients showed favorable outcomes graded by FNGS2.0, and experienced significantly improved scores in static and dynamic symmetry with slightly elevated scores in synkinesis evaluated by the Sunnybrook FGS. The score of FaCE Scale increased in all domains after reanimation. The quantitative indices indicated the symmetry restoration of the middle and lower face after MFNT. Regression analysis revealed that younger patients with severe facial paralysis are preferable to receive MFNT early for faster and better recovery, especially for traumatic causes. The findings demonstrate that MFNT is an effective technique for facial reanimation, and case screening based on clinical characteristics could be useful for surgical recommendation.

Seminal Studies in Facial Reanimation Surgery: Consensus and Controversies in the Top 50 Most Cited Articles

ABSTRACT

Facial paralysis can impair one's ability to form facial expressions that are congruent with internal emotion. This hinders communication and the cognitive processing of emotional experience. Facial reanimation surgery, which aims to restore full facial expressivity is a relatively recent undertaking which is still evolving. Due in large part to published techniques, refinements, and clinical outcomes in the scientific literature, consensus on best practice is gradually emerging, whereas controversies still exist.Taking stock of how the discipline reached its current state can help delineate areas of agreement and debate, and more clearly reveal a path forward. To do this, the authors have analyzed the 50 seminal publications pertaining to facial reanimation surgery. In longstanding cases, the free gracilis transfer emerges as a clear muscle of choice but the nerve selection remains controversial with prevailing philosophies advocating cross facial nerve grafts (with or without the support of an ipsilateral motor donor) or an ipsilateral motor donor only, of which the hypoglossal and nerve to masseter predominate. The alternative orthodoxy has refined the approach popularized by Gillies in 1934 and does not require the deployment of microsurgical principles. Although this citation analysis does not tell the whole story, surgeons with an interest in facial reanimation will find that this is a good place to start.

Microanatomy of the Frontal Branch of the Facial Nerve: The Role of Nerve Caliber and Axonal Capacity

BACKGROUND

A commonly seen issue in facial palsy patients is brow ptosis caused by paralysis of the frontalis muscle powered by the frontal branch of the facial nerve. Predominantly, static methods are used for correction. Functional restoration concepts include the transfer of the deep temporal branch of the trigeminal nerve and cross-facial nerve grafts. Both techniques can neurotize the original mimic muscles in early cases or power muscle transplants in late cases. Because axonal capacity is particularly important in cross-facial nerve graft procedures, the authors investigated the microanatomical features of the frontal branch to provide the basis for its potential use and to ease intraoperative donor nerve selection.

METHODS

Nerve biopsy specimens from 106 fresh-frozen cadaver facial halves were obtained. Histologic processing and digitalization were followed by nerve morphometric analysis and semiautomated axon quantification.

RESULTS

The frontal branch showed a median of three fascicles (n = 100; range, one to nine fascicles). A mean axonal capacity of 1191 ± 668 axons (range, 186 to 3539 axons; n = 88) and an average cross-sectional diameter of 1.01 ± 0.26 mm (range, 0.43 to 1.74 mm; n = 67) were noted. In the linear regression model, diameter and axonal capacity demonstrated a positive relation (n = 57; r2 = 0.32; p < 0.001). Based on that equation, a nerve measuring 1 mm is expected to carry 1339 axons.

CONCLUSION

The authors' analysis on the microanatomy of the frontal branch could promote clinical use of cross-facial nerve graft procedures in frontalis muscle neurotization and free muscle transplantations.

End-to-Trunk Masseteric to Facial Nerve Transfer With Selective Neurectomy for Facial Reanimation

OBJECTIVE

To examine functional outcomes following end-to-trunk masseteric to facial nerve transfer in patients with chronic flaccid facial paralysis.

DESIGN

Retrospective chart review.

SETTING

Tertiary-care private practice setting.

PARTICIPANTS

Patients with complete unilateral facial paralysis of less than 24 months duration.

INTERVENTIONS

Direct end-to-trunk masseteric to facial nerve anastomosis.

OUTCOME MEASURES

Outcome measures included time to first movement, development of synkinesis, and an objective assessment of the resting tone and dynamic movement that was achieved.

RESULTS

Patient age at the time of transfer ranged from 6 to 61. Follow-up ranged from 12 to 24 months. No patients had any perioperative complications. No patient experienced significant mass movement or synkinetic facial movement with chewing. No patient had worsened chewing or swallowing. Patients have not yet recovered significant resting tone. All patients achieved smile activity when biting down with a median (interquartile range) oral commissure excursion of 7.57 mm (5.19-9.94 mm), starting 3 to 5 months after transfer.

CONCLUSIONS

End-to-trunk masseteric to facial nerve transfer is a safe and effective procedure. Patients had rapid reinnervation with good excursion and achieved a natural appearing smile. The rehabilitated smile appears better than that achieved with hypoglossal-facial nerve transfer. The procedure can be performed coincident with cross-facial nerve grafting, and in some cases may produce dynamic facial movement that obviates the need for free muscle transfer.

A supportive donor nerve for long-term facial paralysis: Anatomical analysis of the posterior auricular nerve and micro-anatomical comparison with zygomatic nerve

BACKGROUND

The posterior auricular nerve (PAN) is an inspiring candidate for the additional axonal source in long-term facial paralysis to improve the functional results of the cross-facial nerve (FN) graft technique. However, no studies have analyzed the PAN's axonal load and its microscopic anatomy to assess its utilization in facial reanimation. The present study aims to examine the anatomical and microscopic features of the PAN to analyze its feasibility as a donor nerve.

METHODS

The bilateral facial side of 14 fresh frozen adult human cadavers was examined for the study. The PAN's anatomical course was recorded, and nerve specimens from the PAN and zygomatic nerve (ZN) were obtained to compare their microscopic anatomy and axon counts using a light microscope and transmission electron microscope.

RESULTS

The PAN's average branching distance and its course length were 5.8 ± 2.69 mm and 59.2 ± 5.85, respectively. The mean number of myelinated axons was 600.28 ± 69.97 in the PAN and 728.85 ± 166.31 in the ZN. This difference between the two nerves was statistically significant (p = 0.002). However, considering the gender variable, the mean axon counts of PAN and ZN were statistically similar for face sides and their average. Furthermore, the ultrastructural anatomy of both nerves was similar in electron microscopic evaluation.

CONCLUSIONS

The present study confirms that the PAN is a proper candidate to be a supportive donor nerve due to its isolated site, consistent anatomical course, convenient ultrastructural anatomy as well as axonal load.

Masseteric nerve transference with sling tendon for symmetry in the restoration of facial paralysis: An effective combination of dynamic and static correction

Masseteric nerve transposition has shown to be an effective technique for the treatment of facial paralysis. Due to its low morbidity at the donor site, its consistent anatomy, and one-stage operation, it constitutes a reliable option for both complete and incomplete facial paralysis. Masseteric nerve transference has proven to achieve good commissural excursion and dynamic symmetry. However, some patients with heavy faces and complete facial paralysis recover incompletely after surgery characterized by an asymmetrical smile with asymmetry at rest, affecting the cosmetic appearance. For these patients, we propose a novel combination of masseteric nerve transposition for the dynamic rehabilitation of the smile with a tendon sling suspension to create symmetry at rest. A detailed description of the surgical technique is given and results after using it with eight patients show good functional and aesthetic satisfaction. A combination of both dynamic and static techniques for complete facial paralysis rehabilitation may provide adequate symmetry with the contralateral healthy side both at rest and when smiling.

The Masseteric-Facial Anastomosis With Intratemporal Translocation of the Facial Nerve: Step-by-Step Technique and Results

BACKGROUND

In the absence of a viable proximal nerve stump, damaged after surgical procedures around the skull base, numerous techniques for facial reanimation have been developed over time, aiming to restore baseline symmetry and active mimicry.

OBJECTIVE

To report experience using the masseteric nerve as a direct transfer to the facial nerve rerouted after intratemporal translocation. This paper illustrates the main steps of the technique and the quality of results.

METHODS

Eleven patients were treated with a masseteric direct transfer to the facial nerve. Its extratemporal rerouting toward the zygoma allowed tension-free coaptation between donor and recipient nerves.

RESULTS

Of the 11 patients, 8 had a good to excellent recovery, showing different patterns of time and scores, according to age, surgical timing, and masseteric nerve function quality. The return of activity in the frontalis muscle, never obtained after reinnervation via the hypoglossal nerve, is of particular interest. The quality of the smile can be improved with re-education and practice but remains under volitional control. A true emotional response is still lacking.

CONCLUSION

The masseteric nerve is an excellent alternative to the hypoglossal nerve and can reinnervate the whole territory of the facial nerve rerouted after intratemporal translocation. The overall results are remarkable, but the low quality of the trigeminal nerve, eventually affected by the first surgery, may be an important limitation. Even if the patients appear more at ease in re-education than with other techniques, a fully natural facial expression remains impossible to obtain.

Facial reanimation with interposition nerve graft or masseter nerve transfer: a comparative retrospective study

Both interposition nerve grafts and masseter nerve transfers have been successfully used for facial reanimation after irreversible injuries to the cranial portion of the facial nerve. However, no comparative study of these two procedures has yet been reported. In this two-site, two-arm, retrospective case review study, 32 patients were included. Of these, 17 patients (eight men and nine women, mean age 42.1 years) underwent interposition nerve graft after tumor extirpation or trauma between 2003 and 2006 in the Ear Institute, School of Medicine, Shanghai Jiao Tong University, China, and 15 patients (six men and nine women, mean age 40.6 years) underwent masseter-to-facial nerve transfer after tumor extirpation or trauma between November 2010 and February 2016 in Shanghai Ninth People's Hospital, China. More patients achieved House-Brackmann III recovery after masseter nerve repair than interposition nerve graft repair (15/15 vs. 12/17). The mean oral commissure excursion ratio was also higher in patients who underwent masseter nerve transfer than in patients subjected to an interposition nerve graft. These findings suggest that masseter nerve transfer results in strong oral commissure excursion, avoiding obvious synkinesis, while an interposition nerve graft provides better resting symmetry. This study was approved by the Institutional Ethics Committee, Shanghai Ninth People's Hospital, China (approval No. SH9H-2019-T332-1) on December 12, 2019.

Facial Reanimation and Reconstruction of the Radical Parotidectomy

Radical parotidectomy may result from treating advanced parotid malignancies invading the facial nerve. Survival is often enhanced with multimodality treatment protocols, including postoperative radiation therapy. In addition to the reconstructive challenge of restoring facial nerve function, patients may be left with a significant cervicofacial concavity and inadequate skin coverage. This should be addressed with stable vascularized tissue that is resistant to radiation-induced atrophy. This article describes a comprehensive strategy, includes the use of the anterolateral thigh free flap, the temporalis regional muscle transfer, motor nerve to vastus lateralis grafts, nerve to masseter transfer, and fascia lata grafts for static suspension.

Reinnervation with Selective Nerve Grafting from Multiple Donor Nerves

Nerve substitution is an important tool in facial reanimation. The goal is to reinnervate the distal facial nerve and musculature using an alternative cranial nerve in order to achieve facial movement, symmetry, and tone. Multiple donor nerves have been used for nerve transfer procedures, the most common being hypoglossal, masseteric, and cross-facial nerve graft. Each donor nerve has its advantages and disadvantages. Multiinnervation uses the use of multiple donor nerves in order to leverage the benefits while balancing the pitfalls of each nerve. The nerve transfer depends on the type of nerve injury, time since injury, and patient factors.

Maximizing the Smile Symmetry in Facial Paralysis Reconstruction: An Algorithm Based on Twenty Years' Experience

Over the last two decades, the senior author (B.H.) has had an extensive experience with facial paralysis reconstruction. During this period, the techniques have evolved substantially based on the experience and after observing and analyzing the surgical outcomes. The purpose of this article is to relay the lessons learned from the 20 years' experience and suggest an algorithm. In this retrospective study, we have included 343 cases of facial paralysis cases. Complete facial paralysis cases were 285 and 58 were incomplete facial paralyses, both requiring surgical procedures. Complete facial paralyses were divided in to short term (n = 83) and long term (n = 202). In total, 58% of the patients were women and 42% were men. The age range was 6 to 82 years. The techniques employed were direct suture, nerve grafts, cross-facial nerve grafts (CFNGs), masseteric-to-facial nerve transference, hypoglossal-to-facial nerve transference, free muscle transplants, and lengthening temporal myoplasty to achieve the best symmetry after reanimation of unilateral, bilateral, complete, and incomplete facial paralysis. The type of paralysis, objective measurements, the personal patient's smile, and the gender are key concepts to be considered before scheduling a dynamic facial paralysis reconstruction. For unilateral facial paralysis, the time of onset, the type of paralysis, the patient's comorbidities, and the healthy side status are some of the determining factors when selecting the correct technique. The preferred techniques for unilateral facial paralysis are direct repair, CFNG, masseteric-to-facial transposition, and free gracilis transfer. For incomplete facial paralysis, the masseteric-to-facial nerve transference is preferred. In bilateral facial paralysis, bilateral free gracilis transfer is performed in two stages using the nerve of the masseter muscle as the source of innervation. The authors provide an algorithm which simplifies facial paralysis reconstruction to achieve the greatest facial symmetry while thinking about the potential comorbidities and developing spontaneity smile according to the gender of the patient.

Hypoglossal and Masseteric Nerve Transfer for Facial Reanimation: A Systematic Review and Meta-Analysis

Background: Hypoglossal and masseteric nerve transfer are currently the most popular cranial nerve transfer techniques for patients with facial paralysis. The authors performed a systematic review and meta-analysis to compare functional outcomes and adverse effects of these procedures. Methods: A review of online databases was performed to include studies with four or more patients undergoing hypoglossal or masseter nerve transfer without muscle transfer or other cranial nerve transposition. Facial nerve outcomes, time to reinnervation, and adverse events were pooled and studied. Results: A total of 71 studies were included: 15 studies included 220 masseteric-facial transfers, and 60 studies included 1312 hypoglossal-facial transfers. Oral commissure symmetry at rest was better for hypoglossal transfer (2.22 ± 1.6 mm vs. 3.62 ± 2.7 mm, p = 0.047). The composite Sunnybrook Facial Nerve Grading Scale was better for masseteric transfer (47.7 ± 7.4 vs. 33.0 ± 6.4, p < 0.001). Time to first movement (in months) was significantly faster in masseteric transfer (4.6 ± 2.6 vs. 6.3 ± 1.3, p < 0.001). Adverse effects were rare (<5%) for both procedures. Conclusions: Both nerve transfer techniques are effective for facial reanimation, and the surgeon should consider the nuanced differences in selecting the correct procedure for each patient.

Progress in facial reinnervation

Facial nerve injury often results in facial paralysis, which seriously affects the patients both aesthetically and functionally. Facial nerve reinnervation methods, including direct anastomosis, nerve graft, nerve transposition, cross-facial nerve graft, and combined surgeries, have recently become a hot topic with many new procedures being explored. This study summarizes the relevant literatures and discusses the scope of application, advantages, and disadvantages of the different methods. The treatment options or combined surgeries for facial nerve reinnervation should be individualized for specific patients to achieve the best reanimation outcome with good static symmetry, facial tone, and spontaneous, natural, symmetrical, and strong facial movements.

Masseter nerve-based facial palsy reconstruction

Facial paralysis is a devastating disease, the treatment of which is challenging. The use of the masseteric nerve in facial reanimation has become increasingly popular and has been applied to an expanded range of clinical scenarios. However, appropriate selection of the motor nerve and reanimation method is vital for successful facial reanimation. In this literature review on facial reanimation and the masseter nerve, we summarize and compare various reanimation methods using the masseter nerve. The masseter nerve can be used for direct coaptation with the paralyzed facial nerve for temporary motor input during cross-facial nerve graft regeneration and for double innervation with the contralateral facial nerve. The masseter nerve is favorable because of its proximity to the facial nerve, limited donor site morbidity, and rapid functional recovery. Masseter nerve transfer usually leads to improved symmetry and oral commissure excursion due to robust motor input. However, the lack of a spontaneous, effortless smile is a significant concern with the use of the masseter nerve. A thorough understanding of the advantages and disadvantages of the use of the masseter nerve, along with careful patient selection, can expand its use in clinical scenarios and improve the outcomes of facial reanimation surgery.

Predicting Resting Oral Commissure Tone Outcomes Following Masseter Nerve Transfer in Facial Reanimation

Objective: To quantify the degree of oral commissure resting tone improvement in patients undergoing masseter to facial nerve transfer. Methods: A retrospective cohort study was completed in a tertiary academic medical practice. Consecutive cases of masseter nerve transfer patients within a patient database were evaluated from 6/2012 to 9/2017. Inclusion criteria were patients >18 years of age, with complete unilateral paralysis, receiving a masseter to facial nerve transfer, with at least 12 months of recovery, and possessing complete pre- and postoperative data. Patients were excluded if a simultaneous adjunctive procedure was performed so that tone could not be attributed to masseter transfer alone. The main outcome measure was the facial asymmetry index (FAI): the measured difference in distance between the medial canthus and oral commissure of the healthy and paralyzed sides. Results: Twenty-nine patients met inclusion and exclusion criteria and were further analyzed for this study. The oral commissure symmetry improved from 4.7 ± 2.8 mm preoperatively to 2.2 ± 2.3 mm postoperatively. In multivariate analysis, the preoperative FAI was the only significant predictive factor for improvement in commissure symmetry at rest (r = 0.589). This suggests that for each 1.0 mm of worse preoperatively oral commissure asymmetry, the improvement postoperatively was 0.6 mm. Age, gender, body mass index, side of paralysis, duration of paralysis, and recipient branch of facial nerve were not significant predictors in a multivariate analysis. Conclusion: Masseter to facial nerve transfer yields an estimated 60% correction in the oral commissure asymmetry. This estimation may be helpful in determining if adjunctive procedures should be utilized.

Amer's classification of territories of facial nerve injury in early cases and strategies for the management of different territories

Early cases of facial nerve injury are best treated by restoring the neural pathway to the same existing facial muscles. Knowledge of the exact territory of facial nerve injury is required to design a plane for the reconstruction of these injuries and to compare results. The current study aims to design a classification system for territories of facial nerve injury based on the location of nearest healthy fascicles to the site of injury both proximally and distally. Two hundred-one patients with early facial nerve injury were assessed for treatment. According to the results of the exploration, 13 territories of injury were identified. The management strategy was planned according to the territory of injury. The current classification system is a simple, easy and effective method for the classification of territories of facial nerve injury. The classification system accurately describes the nearest possible healthy proximal and distal fascicles and can be employed to easily report cases and implement a management plan. This classification scheme also allows us to more effectively compare results.

Changes in Electrical Activity of the Masseter Muscle and Masticatory Force after the Use of the Masseter Nerve as Donor in Facial Reanimation Surgery

Introduction  The masseter nerve has been used as a donor nerve for facial reanimation procedures due to the multiple advantages it offers; it has been generally considered that sacrifice of the masseter nerve does not alter the masticatory apparatus; however, there are no objective studies to support this claim. Objective  To evaluate the impact that the use of the masseter nerve in dynamic facial reconstruction has on the electrical activity of the masseter muscle and on bite force. Materials and Methods  An observational and prospective longitudinal study was performed measuring bite force and electrical activity of the masseter muscles before and 3 months after dynamic facial reconstructive surgery using the masseter nerve. An occlusal analyzer and surface electromyography were employed for measurements. Results  The study included 15 patients with unilateral facial paralysis, with a mean age of 24.06 ± 23.43. Seven patients were subjected to a masseter-buccal branch nerve transfer, whereas in eight patients, the masseter nerve was used as a donor nerve for gracilis free functional muscle transfer. Electrical activity of the masseter muscle was significantly reduced after surgery in both occlusal positions: from 140.86 ± 65.94 to 109.68 ± 68.04 ( p = 0.01) in maximum intercuspation and from 123.68 ± 75.64 to 82.64 ± 66.56 ( p = 0.01) in the rest position. However, bite force did not show any reduction, changing from 22.07 ± 15.66 to 15.56 ± 7.91 ( p = 0.1) after the procedure. Conclusion  Masseter nerve transfer causes a reduction in electromyographic signals of the masseter muscle; however, bite force is preserved and comparable to preoperative status.

Rapid and Precise Semi-Automatic Axon Quantification in Human Peripheral Nerves

We developed a time-efficient semi-automated axon quantification method using freeware in human cranial nerve sections stained with paraphenylenediamine (PPD). It was used to analyze a total of 1238 facial and masseteric nerve biopsies. The technique was validated by comparing manual and semi-automated quantification of 129 (10.4%) randomly selected biopsies. The software-based method demonstrated a sensitivity of 94% and a specificity of 87%. Semi-automatic axon counting was significantly faster (p < 0.001) than manual counting. It took 1 hour and 47 minutes for all 129 biopsies (averaging 50 sec per biopsy, 0.04 seconds per axon). The counting process is automatic and does not need to be supervised. Manual counting took 21 hours and 6 minutes in total (average 9 minutes and 49 seconds per biopsy, 0.52 seconds per axon). Our method showed a linear correlation to the manual counts (R = 0.944 Spearman rho). Attempts have been made by several research groups to automate axonal load quantification. These methods often require specific hard- and software and are therefore only accessible to a few specialized laboratories. Our semi-automated axon quantification is precise, reliable and time-sparing using publicly available software and should be useful for an effective axon quantification in various human peripheral nerves.

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.

Masseteric Nerve Transfer for Facial Nerve Paralysis: A Systematic Review and Meta-analysis

Importance

A review of the role of masseteric nerve transfer is needed to guide its use in facial reanimation.

Objective

To systematically review the available literature, and, when applicable, analyze the combined outcomes of masseteric nerve transfer to better define its role in reanimation and to guide further research.

Data Sources

Two independent researchers conducted the review using PubMed-NCBI and Scopus literature databases for studies on masseteric nerve transfer for facial nerve paralysis.

Study Selection

Studies that examined masseter nerve transfer with additional cranial nerve transposition/coaptation or muscle flap were excluded.

Data Extraction and Synthesis

Literature review and data extraction followed established PRISMA guidelines. Two researchers extracted data independently.

Main Outcomes and Measures

The main planned outcomes for the study were quantitative results of facial nerve movement after nerve transfer including oral commissure movement and time to nerve recovery.

Results

A total of 13 articles met inclusion criteria with a total of 183 patients undergoing masseteric nerve transfer. From those studies, there were a total of 183 patients who underwent masseteric nerve transfer. There were 85 men and 98 women with a mean (SD) age of 43 (12.2) years and mean (SD) follow up examination after surgery of 22 (7.6) months. Mean (SD) duration of nerve paralysis was 14 (6) months. Most common cause of paralysis was cerebellopontine angle tumors (81%). Six studies coapted the masseteric nerve to the main facial nerve trunk, whereas 7 used distal branches (buccal or zygomatic). Four studies used interposition nerve grafts with great auricular nerve. Two measures, improvement in oral commissure excursion and length from reanimation to facial movement, were measured consistently across the studies. Pooled analysis showed time from surgery to first facial movement, described in 10 studies, to be 4.95 months (95% CI, 3.66 to 6.24). Distal branch coaptation improved time to recovery vs main branch coaptation, 3.76 vs 5.76 months (95% CI, -0.33 to 4.32), but mean difference was not significant. The use of interposition graft significantly delayed time of nerve recovery, 6.24 vs 4.06 months (95% CI, 0.20 to 4.16). When controlled for main trunk coaptation only, interposition nerve graft delayed recovery but difference was no longer statistically significant, 6.24 vs 4.75 months (95% CI, -0.94 to 3.92). Reported complications were minor and rare occurring in only 6.5% (12 of 183) of patients.

Conclusions and Relevance

The masseteric nerve was found to be a good option for nerve transfer in this patient population, and showed favorable results in both time to nerve recovery and improvement in oral commissure excursion.

Level of Evidence

NA.

Single-stage cross-facial nerve grafting has a result equivalent to that of two-stage cross-facial nerve grafting

BACKGROUNDS

Cross-face nerve grafting (CFNG) is an important treatment for patients with facial palsy. Currently, two-stage CFNG is frequently performed. CFNG is performed first, followed by coaptation when innervation reaches the grafted nerve ending. The present study compared single-stage CFNG with conventional two-stage CFNG.

METHODS

We retrospectively reviewed data of 17 patients who underwent CFNG with zygomatic and buccal branch with hypoglossal crossover. Patients with single-stage (group 1) and two-stage (group 2) CFNG were comparatively analyzed 2 years postoperatively. There were nine and eight patients in groups 1 and 2, respectively. The patient's perioperative status was measured with imaging and animation using the Yanagihara grade, altitude, and angle differences of the oral commissure and eye closure.

RESULTS

Patients in group 1 could recognize their first postoperative spontaneous movement earlier than those in group 2 (268.3 ± 25.1 days vs. 327.5 ± 51.3 days, respectively, p = 0.015). The Yanagihara grade significantly improved for patients in both groups postoperatively (group 1: 12.8 ± 5.5 to 25.3 ± 6.1, p < 0.01; group 2: 12.4 ± 5.6 to 24.3 ± 5.0, p = 0.012). Height and angle difference of the oral commissure showed a significant improvement during resting and smiling in both groups. Eye closure also showed significant improvement in both groups (group 1: 4.1 ± 0.6 to 2.6 ± 0.5, p < 0.01; group 2: 4.0 ± 0.5 to 2.8 ± 0.7, p < 0.01). There was no significant difference in the postoperative improvement rate between the groups.

CONCLUSIONS

Single-stage CFNG shows results equivalent to those of two-stage CFNG. Single-stage CFNG is associated with a shorter treatment period and fewer operations.

Facial reanimation with masseter nerve-innervated free gracilis muscle transfer in established facial palsy patients

Background

The masseter nerve is a useful donor nerve for reconstruction in patients with established facial palsy, with numerous advantages including low morbidity, a strong motor impulse, high reliability, and fast reinnervation. In this study, we assessed the results of masseter nerve–innervated free gracilis muscle transfer in established facial palsy patients.

Methods

Ten patients with facial palsy who received treatment from January 2015 to January 2017 were enrolled in this study. Three patients received masseter nerve–only free gracilis transfer, and seven received double-innervated free gracilis transfer (masseter nerve and a cross-face nerve graft). Patients were evaluated using the Facial Assessment by Computer Evaluation software (FACEgram) to quantify oral commissure excursion and symmetry at rest and when smiling after muscle transfer.

Results

The mean time between surgery and initial movement was roughly 167.7 days. A statistically significant increase in excursion at rest and when smiling was seen after muscle transfer. There was a significant increase in the distance of oral commissure excursion at rest and when smiling. A statistically significant increase was observed in symmetry when smiling. Terzis’ functional and aesthetic grading scores showed significant improvements postoperatively.

Conclusions

Masseter nerve innervation is a good option with many uses in in established facial palsy patients. For some conditions, it is the first-line treatment. Free gracilis muscle transfer using the masseter nerve has excellent results with good symmetry and an effective degree of recovery.

Neurorrhaphy for Facial Reanimation with Interpositional Graft: Outcome in 23 Patients and the Impact of Timing on the Outcome

OBJECTIVE

Neurorrhaphy with interpositional graft is a practical technique to achieve facial reanimation when the continuity of the facial nerve is interrupted and a large gap between the proximal and distal stump exists. The aim of this study was to report long-term outcomes of neurorrhaphy for facial reanimation with interpositional graft. The roles of some variable factors in the outcome of neurorrhaphy with interpositional graft were also evaluated and compared.

METHODS

A retrospective case series from a single tertiary referral center comprised 23 patients with facial nerve interruptions who underwent neurorrhaphy with interpositional graft using either end-to-end anastomosis or end-to-side hypoglossal-facial technique. Preoperative data (age, sex, primary lesion, interval from paralysis to surgery, facial nerve function), intraoperative data (surgical approach, graft and type of neurorrhaphy), and postoperative data (facial nerve function) were collected and analyzed.

RESULTS

Mean follow-up time was 26.6 ± 11.9 months. Patients who underwent neurorrhaphy for facial reanimation within 1 year after onset of facial paralysis were more likely to achieve House-Brackmann grade ≤3 compared with patients who underwent neurorrhaphy >1 year after onset of facial paralysis (odds ratio = 23.85, P = 0.04). No other factors were associated with improved outcomes.

CONCLUSIONS

Early neurorrhaphy with interpositional graft (≤1 year) for facial reanimation resulted in better final facial nerve function outcomes compared with a delayed procedure.

A Rapid Protocol for Intraoperative Assessment of Peripheral Nerve Myelinated Axon Count and Its Application to Cross-Facial Nerve Grafting

BACKGROUND

Donor nerve myelinated axon counts correlate with functional outcomes in reanimation procedures; however, there exists no reliable means for their intraoperative quantification. In this article, the authors report a novel protocol for rapid quantification of myelinated axons from frozen sections, and demonstrate its applicability to surgical practice.

METHODS

The impact of various fixation and FluoroMyelin Red staining strategies on resolved myelin sheath morphology from cryosections of rat and rabbit femoral and sciatic nerves was assessed. A protocol comprising fresh cryosection and rapid staining was developed, and histomorphometric results were compared against conventional osmium-postfixed, resin-embedded, toluidine blue-stained sections of rat sciatic nerve. The rapid protocol was applied for intraoperative quantification of donor nerve myelinated axon count in a cross-facial nerve grafting procedure.

RESULTS

Resolution of myelinated axon morphology suitable for counting was realized within 10 minutes of tissue harvest. Although mean myelinated axon diameter appeared larger using the rapid fresh-frozen as compared to conventional nerve processing techniques (mean ± SD; rapid, 9.25 ± 0.62 μm; conventional, 6.05 ± 0.71 μm; p < 0.001), no difference in axon counts was observed on high-power fields (rapid, 429.42 ± 49.32; conventional, 460.32 ± 69.96; p = 0.277). Whole nerve myelinated axon counts using the rapid protocol herein (8435.12 ± 1329.72) were similar to prior reports using conventional osmium processing of rat sciatic nerve.

CONCLUSIONS

A rapid protocol for quantification of myelinated axon counts from peripheral nerves using widely available equipment and techniques has been described, rendering possible intraoperative assessment of donor nerve suitability for reanimation.

Anatomical study of the masseteric and obturator nerves: Application to face transplant and reanimation procedures

The masseteric nerve (MN) and the anterior branch of the obturator nerve (ON) that innervate the transferred gracilis muscle have proved highly efficient for reanimating paralyzed facial muscles when muscle transfer is required. Previous researchers have published the total axonal load for myelinated fibers in both nerves. However, the real motor axonal load has not been established. We performed the study on 20 MN and 13 ON. The segments of the MN and the ON were embedded in paraffin, sectioned at 10 μm, and stained following a standard immunohistochemical procedure using anti-choline acetyltransferase to visualize the motor fibers. The MN has a higher axonal load than the ON. There were statistically significant differences between the axonal load of the proximal segment of the MN and the ON. These findings confirm that end-to-end anastomoses between the MN and the ON should preferably use the proximal segment. However, MN neurotomy should ideally be performed between the proximal and distal segments, preserving innervation to the deep fascicles. Our results show that the MN is ideal as a donor motor nerve for reinnervating transplanted muscle for dynamic reanimation of the paralyzed face. The neurotomy should ideally be performed between the first and second collateral branches of the MN. Clin. Anat. 32:612-617, 2019. © 2019 Wiley Periodicals, Inc.

Early Masseter to Facial Nerve Transfer May Improve Smile Excursion in Facial Paralysis

Supplemental Digital Content is available in the text.

Background:

Masseter-to-facial nerve transfer has been shown to be an effective and safe treatment option in patients with acute and subacute facial palsy. The present article aims to characterize whether there is a benefit in early nerve transfers while minimizing other confounding variables; we present a study that consist of only patients with complete facial nerve paralysis resulting from intratemporal facial nerve resections.

Methods:

Between 2012 and 2016, 7 masseter-to-facial nerve transfers were performed for complete facial nerve palsy after intratemporal proximal nerve resections. Pre- and postoperative photographic and video evaluations were performed using both the Sunnybrook facial grading scale and the MEEI FACE-gram software for more objective metric measurements. Statistical analysis was performed to determine which patient and surgical variables had significant effects on outcome.

Results:

Mean 14-month follow-up revealed that patients who underwent nerve transfer prior to 6 months’ denervation achieved postoperative oral commissural excursion of 11.1 mm versus 6.5 mm in patients who underwent nerve transfer after 6 months (P = 0.003). Performing masseter-to-facial nerve transfer to the main facial nerve trunk resulted in a significantly higher improvement in the modiolus-philtral ratio (31.6% versus 6.1%) than selective transfer in patients (P = 0.01) at the latest follow-up.

Conclusions:

Early masseter-to-facial nerve transfers, before 6 months of palsy duration, can potentially improve smile excursion and symmetry of open mouth smile. Additionally, truncal coaptations may provide improved tone over coapting to selective facial nerve branches. These findings necessitate larger studies regarding the importance of denervation time with fifth-to-seventh nerve transfers.