Masseteric Nerve Research Articles

Dual innervation of free gracilis muscle for facial reanimation: What we know so far

BackgroundIn the last decade, some institutions have begun combining the CFNG and masseteric nerve to provide dual innervation to the gracilis muscle for dynamic facial reanimation in facial paralysis patients. We reviewed the various ways that these two nerves have been coapted to provide dual innervation, and summarized the functional outcome for these methods. MethodsA search of the Ovid EMBASE, MEDLINE, Cochrane, and Scopus databases was performed from 1946 to May 2019 for dual innervation of gracilis muscle using CFNG plus masseteric nerve for facial reanimation. ResultsA total of 184 articles were identified in the initial search, of which seven met our inclusion criteria. Three additional abstracts with 43 patients were identified but the level of details was not sufficient to include the results in the analysis. A total of 57 patients were reviewed (mean age of 42.1 years (6–79 years)). The majority of dual innervation procedures were performed using the ipsilateral masseteric nerve sutured end-to-end to the obturator nerve, and an additional CFNG connected end-to-side to the obturator nerve. In the 26 patients with Terzis scores available, there were no differences between masseteric nerve coapted end-to-end and CFNG as end-to-side to the obturator, or the reverse coaptation. All but two patients achieved function of the gracilis activated by the masseteric nerve within 2–5 months. ConclusionsThis review shows that dual innervation of the gracilis is safe; and in some cases, does appear to provide early onset gracilis activation as well as an eventual spontaneous smile.

Ascending projection of jaw-closing muscle-proprioception to the intralaminar thalamic nuclei in rats

An invasive intralaminar thalamic stimulation and a non-invasive application of oral splint are both effective in treating tic symptoms of patients with Tourette syndrome (TS). Therefore, these two treatments may exert some influence on the same brain region in TS patients. We thus hypothesized that the proprioceptive input arising from the muscle spindles of jaw-closing muscles (JCMSs), known to be increased by the application of oral splint, is transmitted to the intralaminar thalamic nuclei. To test this issue, we morphologically and electrophysiologically examined the thalamic projections of proprioceptive input from the JCMSs to the intralaminar thalamic nuclei of rats. We first injected an anterograde tracer, biotinylated dextranamine, into the electrophysiologically identified supratrigeminal nucleus, which is known to receive proprioceptive inputs from the JCMSs via the trigeminal mesencephalic neurons. A moderate number of biotinylated dextranamine-labeled axon terminals were bilaterally distributed in the oval paracentral nucleus (OPC) of the intralaminar thalamic nuclei. We also detected electrophysiological responses to the electrical stimulation of bilateral masseter nerves and to sustained jaw-opening in the OPC. After injection of retrograde tracer (cholera toxin B subunit or Fluorogold) into the OPC, neuronal cell bodies were retrogradely labeled in the rostrodorsal portion of the bilateral supratrigeminal nucleus. Here, we show that proprioceptive inputs from the JCMSs are conveyed to the OPC in the intralaminar nuclei via the supratrigeminal nucleus. This study can help to understand previously unrecognized pathways of proprioception ascending inputs from the brainstem to the thalamus, which may contribute to treatments of TS patients.

Powering the Gracilis for Facial Reanimation

Free gracilis transfer for dynamic reanimation in chronic facial paralysis is the gold standard, but there remains a need to better understand outcomes with respect to the donor nerve. To characterize outcomes in adults undergoing primary gracilis transfer for facial paralysis stratified by donor nerve used for neurotization. Search strategies were used in Ovid MEDLINE (1946-2019), Embase (1947-2019), Scopus (1823-2019), Cochrane Central Register of Controlled Trials (CENTRAL), and ClinicalTrials.gov (1997-2019). Inclusion and exclusion criteria were designed to capture studies in adults with unilateral chronic facial paralysis undergoing single-paddle free gracilis transfer. All study types were included except case reports. Abstracts and full texts were reviewed in duplicate. Of 130 unique citations, 10 studies including 295 patients were included after applying inclusion and exclusion criteria. Data were analyzed between November 2018 and December 2019. PRISMA guidelines were followed. The Newcastle-Ottawa scale was used to assess study quality, and the Cochrane Risk of Bias tool was used to assess risk of bias. Independent extraction by 2 authors (P.M.V. and J.J.C.) was performed. Data were pooled using a random-effects model. Owing to heterogeneity in reporting of facial reanimation outcomes, we first performed a systematic review, and then compiled available outcomes for meta-analysis. Outcomes studied for meta-analysis were oral commissure excursion and facial symmetry. Meta-analysis of masseteric nerve (MN) (n = 56) vs cross-facial nerve graft (CFNG) (n = 52) in 3 retrospective studies showed no statistical heterogeneity between these studies (I2 = 0%), and the standardized mean difference (SMD) was greater for MN (0.55; 95% CI, 0.17 to 0.94). Meta-analysis of angles of symmetry in 2 retrospective studies comparing MN (n = 51) to CFNG (n = 47) both at rest (-0.22; 95% CI, -0.63 to 0.18) and with smiling (-0.14; 95% CI, -0.73 to 0.46) were better with MN, though the difference was not statistically significant. Owing to heterogeneity in reported outcomes from facial reanimation, we were unable to make definitive conclusions regarding the optimal donor nerve. Establishing a reporting standard at peer-reviewed journals to improve results reporting is one method to allow for improved collaboration in the future. Standardizing follow-up times, assessing spontaneity in an objective and reproducible fashion, and use of consistent outcome measures would allow for future meta-analyses and better understanding of options for facial reanimation.

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.

Orbicularis Oculi Muscle Reinnervation Confers Corneal Protective Advantages over Static Interventions Alone in the Subacute Facial Palsy Patient.

Corneal protection is a priority in flaccid facial palsy patients. Denervation of the orbicularis oculi muscle results in weak palpebral closure and predisposes patients to severe corneal sequelae. While periorbital static procedures enhance corneal coverage in repose, voluntary closure is only regained through dynamic reinnervation of the muscle. This study aims to elucidate the added effect of dynamic reinnervation of the orbicularis oculi muscle on long-term corneal integrity as well as on dynamic closure of the palpebral aperture. Retrospective review was performed on two groups of complete palsy patients: those who received solely periorbital static procedures and those who underwent concomitant orbicularis oculi muscle reinnervation and static lid procedures. Only patients with complete ophthalmic examinations were included. Corneal punctate epithelial erosions in addition to static and dynamic palpebral measurements were serially assessed preoperatively and postoperatively. Of 272 facial palsy patients, 26 fit the inclusion criteria. Eleven patients underwent combined muscle reinnervation involving facial-to-masseteric nerve coaptation in addition to static eye procedures, and 15 patients underwent solely static interventions. Analysis revealed a 65.3 percent lower mean punctate epithelial erosion score in reinnervation patients as compared with static patients when evaluated at more than 9 months postoperatively (p < 0.01). Reinnervation patients were also found to have 25.3 percent greater palpebral aperture closure (p < 0.05) and 32.8 percent higher closure velocity (p < 0.01) compared with static patients. In patients with subacute facial palsy, dynamic reanimation of the orbicularis oculi muscle with concomitant static interventions provides lasting corneal protection not seen in patients who receive solely static interventions. Therapeutic, III.

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.

Is there a primitive reflex residue underlying Marcus Gunn Syndrome? Rat electrophysiology.

To make an electrophysiological demonstration of a possible jaw muscle afferents-oculomotor neural pathway that was proposed by our previous works on rats, which substantiates an early "release hypothesis" on pathogenesis of human Marcus Gunn Syndrome (MGS). Extracellular unit discharge recording was applied and both orthodromic and spontaneous unitary firing were recorded in the oculomotor nucleus (III), and the complex of pre-oculomotor interstitial nucleus of Cajal and Darkschewitsch nucleus (INC/DN), following electric stimulation of the ipsilateral masseter nerve (MN) in rats. Extracellular orthodromic unit discharges, with latencies of 3.7±1.3 and 4.7±2.9ms, were recorded unilaterally in the III, and the INC/DN neurons, respectively. Spontaneous unit discharges were also recorded mostly in the INC/DN and less frequently in the III. Train stimulation could prompt either facilitation or inhibition on those spontaneous unit discharges. The inhibition pattern of train stimulation on the spontaneous discharging was rather different in the III and INC/DN. A slow inhibitory pattern in which spontaneous firing rate decreased further and further following repeated train stimulation was observed in the III. While, some high spontaneous firing rate units, responding promptly to the train stimuli with a short-term inhibition and recovered quickly when stimuli are off, were recorded in the INC/DN. However, orthodromic unit discharge was not recorded in the III and INC/DN in a considerable number of experiment animals. A residual neuronal circuit might exist in mammals for the primitive jaw-eyelid reflex observed in amphibians, which might not be well-developed in all experimental mammals in current study. Nonetheless, this pathway can be still considered as a neuroanatomic substrate for development of MGS in some cases among all MGS with different kind of etiology.

Twin Block in Myogenous Orofacial Pain: Applied Anatomy, Technique Update, and Safety.

The twin block, introduced in 2014, has proven to be more advantageous for the management of myogenous orofacial pain than the masseteric nerve block, which was introduced in 2009. The twin block is an extraoral nerve block injection which passes through the temporal fossa to anesthetize both the masseteric and the deep temporal nerves as they exit the infratemporal fossa at the infratemporal crest. Similar to the masseteric nerve block, the twin block has demonstrated efficacy with expeditious and sustained relief of myogenous face pain originating from the masseter muscle. Furthermore, in a 6-month prospective treatment study, that has been accepted for publication, the twin block has been demonstrated as comparable to trigger point injections in the management of chronic myofascial pain of masseteric origin. The twin block's ability to mitigate myogenous pain from both the masseter and temporalis muscles and its ease of administration are the key advantages over the masseteric nerve block. Since its inception, we have refined the technique for administering the twin block and our clinical experience corroborates its safety and efficacy. This review describes the refined technique and its safety in the context of the region's applied anatomy.

Dual Coaptation of Facial Nerve Using Masseteric Branch of Trigeminal Nerve for Iatrogenic Facial Palsy: Preliminary Reports.

Immediate facial nerve substitution or graft technique has been used for the repair of facial nerve defects occurring as a result of tumour dissection. However, some patients report unsatisfactory outcomes, such as difficulty in maintaining resting or smiling symmetry, due to persistent flaccid facial palsy. Here we evaluated the functional outcomes of transferring the masseteric branch of the trigeminal nerve to the facial nerve adjunct to facial nerve graft. We reviewed the medical records of seven patients who underwent facial reanimation surgery between 2014 and 2016. The patients were divided into two groups according to the type of facial reanimation surgery: group A, masseteric nerve innervation with interposition graft; group B, interposition graft only. The postoperative resting symmetry and dynamic movement were compared. Facial contraction was first observed in group A at 4 months and in group B at 7.3 months. Most of the patients achieved reliable resting symmetry; however, one patient in group B exhibited unsatisfactory facial weakness on the affected side. Group A patients showed better dynamic movement than group B patients. Eye closure, oral excursion and oral continence were better in group A than in group B patients. Smile symmetry in both groups was similar due to hyperkinetic movement in group A patients and flaccidity in group B patients. Dual innervation of the masseteric branch of the trigeminal nerve improves the dynamic movement of paralysed facial muscles and shortens the recovery period in patients with iatrogenic facial palsy.

Masseteric-Facial Nerve Anastomosis: Surgical Techniques and Outcomes-A Pilot Indian study.

Masseteric-facial anastomosis has gained popularity in recent days compared to the facial-hypoglossal anastomosis. Masseteric nerve has numerous advantages like its proximity to the facial nerve, stronger motor impulse, its reliability, low morbidity in harvesting and sacrificing the nerve and faster re-innervation that is achievable in most patients. The present case series demonstrate the surgical technique and the effectiveness of the masseteric nerve as donor for early facial reanimation. Between January 2017 and February 2019, 6 patients (2 male, 4 female) with iatrogenic unilateral complete facial paralysis (grade VI, House Brackmann scale) who underwent masseteric-facial nerve anastomosis were included in the study. The time interval between the onset of paralysis and surgery ranged from 4 to 18months (mean 8.5months). In all patients pre-operative electromyography had facial mimetic muscle fibrillation potentials. All patients underwent end to end anastomosis except for one patient where greater auricular interposition graft was used. In all cases, the facial muscles showed earliest sign of recovery at 2-5months. These movements were first noticed on the cheek musculature when the patients activated their masseter muscle. Eye movements started appearing at 6-9months (in 3 cases) and forehead movements at 18months (in 1 case). According to the modified House-Brackmann grading scale, one patient had Grade I function, two patients had Grade II function, and three had Grade V function. There was no morbidity except one patient who underwent interposition graft had numbness in the ear lobule. None of the patients could feel the loss of masseteric nerve function. Masseteric facial nerve anastomosis is a versatile, powerful early facial dynamic reanimation tool with almost negligible morbidity compared to other neurotization procedures for patients with complete facial nerve paralysis.

Novel Method of Double Innervated Free Gracilis Muscle Functional Transfer for Facial Reanimation

PURPOSE: Dynamic facial reanimation is the gold standard treatment for a paralyzed face. The use of cross-face nerve graft (CFNG) in combination with the masseteric nerve to innervate free gracilis muscle has been reported in various configurations, with the goal of providing both spontaneity from the CFNG and strong innervation from the masseteric nerve. We report a novel modification to the existing nerve configuration, with presentation of outcomes of our case series. METHODS: A total of 8 patients received free gracilis muscle transfer using the new double innervation method between September 2014 and December 2017. The CFNG, which was performed 9 months prior, was sutured in an end-to-end fashion to the obturator nerve. The ipsilateral masseter nerve was coapted to a nerve graft obtained from extra length of obturator nerve obtained during the harvest of the gracilis muscle. This nerve graft was then sutured in an end-to-side fashion to the sural nerve graft proximal to the end-to-end obturator coaptation (Figure will be provided during presentation). Video analysis was performed on preoperative and all postoperative follow-up. Two independent experienced raters performed Terzis 5 stages classification on the videos. Time to smile with biting down and time to natural smile were also assessed. RESULT: All patients recover smile function with teeth clenching (average, 7.5 months; range, 3–12). Two patients did not recover smile function at 4 and 8 months follow-up, but achieved smile at their 10 and 12 months follow-up. Seven of 8 patients recover spontaneous smile by average of 8.4 months (range, 7–12), with 1 patient having no function after 12 months of follow-up. Average follow-up time was 22 months. Based on the Terzis reanimation grading, 4 patients achieved moderate result, 2 achieved good result, and 2 achieved excellent result. CONCLUSION: Our new novel method of dual gracilis innervation represents a viable technique that does not risk denervation of the gracilis muscle, and provide good spontaneous emotional smile and esthetic symmetry. We hypothesize that placing the masseter nerve at a disadvantage by using the extra nerve graft which requires the signal to go through 3 anastomosis, the CFNG has more time to provide a stronger signal without being taken over by the masseter.

Facial reanimation: an update on nerve transfers in facial paralysis.

The aim of this article is to review the recent literature on nerve transfers in facial paralysis. The discussion focuses on direct nerve repair and three types of nerve transfers, cross facial nerve graft, hypoglossal, and masseter nerve transfers. Masseteric nerve transfers have a high probability of creating significant movement, although tone is poor. The hypoglossal to facial nerve transfer is reliable in affording facial tone and has been updated to involve a transposition technique that offers good results with minimal morbidity. Combination nerve transfer techniques using multiple cranial nerves or cross-face nerves are increasingly described. Reinnervation of the facial nerve and neural regeneration in general are areas of intense research and novel surgical approaches continue to be explored. Although direct nerve repair is the most ideal, other nerve transfers can be performed with good results. More specifically, the masseteric nerve transfer can provide excellent movement and the hypoglossal transfer good tone. Combination transfers may afford the benefits of multiple nerves.

Evaluation of Masseteric Nerve-Based Selective Neurotization for Multivectorial Augmentation of the Weak Smile.

This cohort study of 11 patients evaluates the use of masseteric nerve–based selective neurotization for the multivectorial augmentation of the weak smile.

Obturator Nerve Split for Gracilis Free-flap Double Reinnervation in Facial Paralysis.

Summary:The use of a double-powered free muscle transfer for facial reanimation has been reported by several authors with different types of nerve coaptation. A new nerve coaptation strategy is presented herein. We performed a 1-stage double-powered free gracilis muscle flap transfer in a patient with long-standing facial paralysis by splitting the obturator nerve and anastomosing the 2 free ends to the contralateral facial nerve (through a sural graft) and to the masseteric nerve. Voluntary movement of the transferred muscle with teeth clenching was observed at 6 months after the operation and a symmetric smile with bilateral elevation of the mouth angle at 10 months. Our limited experience suggests that in case of a large cross-section of the obturator nerve, the latter can be split and sutured to the ipsilateral masseteric nerve and to the contralateral facial nerve with a sural graft by double end-to-end anastomosis.

Facial Nerve Translocation for Low Tension Neurorrhaphy to Masseteric Nerve.

The techniques of facial reanimation are continually evolving in search of the ideal method for rehabilitating the paralyzed face. In the past, alternative cranial nerve motor nuclei have been used to power facial musculature. The trigeminal nerve is gaining popularity as a promising nerve to drive facial motion, particularly in the lower face. This article describes a low-tension technique of using the transposed facial nerve to the trigeminal nerve (masseteric branch) for facial reanimation. Six patients over 2.5 years were treated with facial nerve translocation with division at the geniculate and direct neurorrhaphy to the motor branch of the masseter. Patients were evaluated by physical examination, measurement of oral commissure excursion using MEEI FACE-gram software, video assessment, Sunnybrook Facial Grading System, Facial Disability Index, and Facial Clinimetric Evaluation Scale (FaCE). Patients demonstrated early motion within 4 months postoperatively and were placed into facial physical therapy. All demonstrated improvements in oral competence, strong oral commissure excursion with good symmetry, speech improvements, and variable results in facial tone. Synkinesis to the smile antagonists in the lower face was noted and treated with chemodenervation in three of six. No upper division synkinesis was noted. The motor branch of the trigeminal nerve is an effective option for facial reanimation via facial nerve translocation and end-to-end neurorrhaphy. Variable results in facial tone were noted with excellent oral commissure excursion. This procedure is safe in the reoperated mastoid.

P83-F Reinnervation in masseteric nerve supercharge bypass in primary reconstruction of facial nerve

Background Facial paralysis is a severe disease. A wide variety of surgical procedures to facial nerve reconstruction are available. We demonstrate reinnervation after infratemporal end-to-end anastomosis following nerve rerouting and concomitant masseteric nerve transfer to the side of facial nerve trunk. Masseteric nerve transfer seems to have strong reinnervation potential. Material and methods Patient presented with complete unilateral facial nerve palsy on the left side with the absence of clinical movement and no signs of reinnervation on needle electromyography. The ipsilateral masseteric muscle nerve electromyography and function was without deterioration. After reconstruction, the patient was regularly clinically and electromyographically evaluated throughout a three-month postoperative period. Results The first control showed no electromyographic signs of reinnervation. Reinnervation in both upper and lower part of face after six months was observed with richer and more mature voluntary activity in orbicularis oris muscle. Synkinetic activity with biting was observed. Three months later, the patient achieved facial symmetry at rest and palpebral closing significantly improved with a residual 3 mm gap. Electrophysiological evaluation 12 months after surgery showed improved reinnervation of mimic muscles during biting and relaxation of chewing muscles at both donor nerve sites, as well as clinical recovery of the capacity to spontaneously blink, complete eyelid closure and initials signs of smile. Conclusions Double innervation of muscular transfer allows additional target muscle reinnervation, with simultaneous preservation of donor nerve function. Electromyography needle evaluation 12 months after surgery declares independent reinnervation through both donors.

Heteronymous H reflex in temporal muscle as sign of hyperexcitability in ALS patients

ObjectiveThe stimulation of the masseteric nerve elicits a homonymous and a heteronymous H reflex in the masseter muscle and in the temporalis one. The presence of the H reflex may be considered a sign of upper motor neuron (UMN) involvement in amyotrophic lateral sclerosis (ALS) patients. The aim of this study was to evaluate the presence of the heteronymous H reflex in patients with ALS and compare it with normal subjects. MethodsWe enrolled 36 ALS patients and 52 healthy subjects. We stimulated the masseteric nerve in the infratemporal fossa and recorded the muscle responses ipsilaterally to the stimulation. ResultsThe heteronymous temporalis H reflex was elicitable in 88.9% of ALS patients and in none of the controls. ConclusionThe heteronymous H reflex does not disappear when the stimulation intensity is increased. It can be used as sign of UMN involvement and may prove useful in patients with suspected MND/ALS with purely lower motor neurons (LMN) signs and no signs of UMN involvement. SignificanceThe heteronymous H reflex is present far more often in ALS patients than in healthy people. It is a simple test that may be used to detect UMN involvement in patients in whom the only evident signs are LMN impairment, improving diagnosis of ALS.

Five-Year Experience with Fifth-to-Seventh Nerve Transfer for Smile.

Masseteric- or deep temporal-to-facial nerve transfer (five-to-seven nerve transfer) is increasingly used in facial reanimation; however, the indications and clinical variables affecting outcomes for five-to-seven nerve transfer have not been defined. The authors describe their early experience with five-to-seven nerve transfer, reporting function and patient-reported outcomes, to identify potential parameters that are predictive of outcome. The authors conducted a retrospective chart review of all patients who underwent five-to-seven nerve transfer for smile reanimation from 2012 to 2017. Age, sex, cause of facial paralysis, onset and duration of paralysis, history of adjuvant chemotherapy and/or radiation therapy, donor nerve used, adjunctive procedures, and final excursion were recorded. Standard photographs and videos, and data regarding clinical facial nerve function and patient-reported quality of life, were obtained preoperatively and postoperatively. Sixty patients were identified. Forty-seven had flaccid facial paralysis and 13 had postparalysis facial palsy. Among flaccid facial paralysis patients, masseteric nerve transfer was successful in 30 patients (88 percent) and deep temporal nerve transfer was successful in three cases (60 percent). Among postparalysis facial palsy patients, five-to-seven nerve transfer was successful in two patients (20 percent). Average quality-of-life scores improved significantly from preoperatively (46) to postoperatively (59) among flaccid facial paralysis patients with successful five-to-seven nerve transfer. Five-to-seven nerve transfer is a viable option in facial reanimation. Shorter denervation times and preoperative flaccidity are favorable predictors of outcome. Five-to-seven nerve transfer as an adjunct to primary repair appears highly effective for enhancing smile function. Five-to-seven nerve transfer results are not reliable in patients with postparalysis facial palsy. Therapeutic, IV.

Morphological and neurochemical plasticity of rat mesencephalic trigeminal neurons

The mesencephalic trigeminal nucleus (Me5) is a unique structure in the central nervous system (CNS), made up of pseudounipolar sensory neurons. It is also a suitable paradigm for studying the plastic alterations in neurons. It is known that the Me5 neurons utilize various neurotransmitters under normal conditions, though little information is available about the morphological and chemical events taking place in the nucleus after injury. This review provides concise description of the structural adaptive changes in Me5 neurons following peripheral axotomy of the masseteric nerve. Furthermore, it validates NADPH-diaphorase activity in them, and using immunohistochemistry for glutamate (Glu), substance P (SP), calcitonin-gene related protein (CGRP), neuropeptide tyrosine (NPY) and galanin (GAL), it deals with the altered neurochemical phenotype of the injured neurons. Our results distinctly show that the Me5 neurons in the rat are extremely sensitive to peripheral injury and we demonstrate their distinct structural and neurochemical plasticity. The adaptive morphological alterations comprise of both qualitative and quantitative alterations in the axotomized Me5 population which are statistically significant when compared with the number and phenotype of the neurons on the contralateral intact side. Besides, the axotomy-induced alterations in the neurochemical character of Me5 are best signified by the down-regulation of the classical neurotransmitters under normal conditions, and the up-regulation of nitric oxide synthase and de novo synthesis of certain neuroactive substances such as NPY, SP, GAL and VIP. It can be inferred that the described phenomena only occur in the nucleus in cases of injury and changes in the environmental cues, and serve as adaptive mechanisms and powerful trophic factors for the neuronal survival in the Me5. There is, undoubtedly, still a long way to go in order to clarify the dynamic and plastic alterations occurring in the CNS in health and disease, and also explain their role in such important functions as pain, perception, learning, cognition and memory.

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.