Cross-facial nerve transplants: why are spontaneous smiles not restored?

Cross-Facial Nerve Grafting Used Independently in Facial Reanimation: A Narrative Review

Importance: Cross-Facial Nerve Grafting (CFNG) for facial palsy offers potential to restore spontaneous facial expression, but specific indications and associated outcomes are limited. Updates to this technique have aided in its successful employment in select cases. This review aims to explore the context in which CFNG has been successfully utilized as a primary modality. Observations: Literature review was performed auditing all studies investigating CFNG as a primary modality, which reported outcomes. A total of 326 cases reporting outcomes for primary CFNG were included. Eye closure outcomes were 83.3% successful at ages 0-18, 77.3% successful at ages 19-40, and 57.1% successful at ages 41+. Smile outcomes were 73.7% successful at ages 0-18, 81.5% successful at ages 19-40, and 52.8% successful at ages 41+. For synkinesis, 89% of cases were considered successful; 100% successful at ages 0-18, and 78.4% successful in adults. Conclusions and Relevance: CFNG may offer return of spontaneous facial function in select cases. Higher percentages of successful outcomes are observed in younger patients, when performed in two stages, and when performed earlier from the onset of FP in cases of eye closure restoration. In the modern era, CFNG has been more commonly employed as an adjunctive procedure to other reanimation techniques.

A Novel Approach to Facial Reanimation and Restoration Following Radical Parotidectomies

Background: Parotidectomies are indicated for a variety of reasons. Regardless of the indication for surgery, facial reanimation may be required because of facial nerve sacrifice or iatrogenic damage. In these cases, facial restoration performed concurrently with ablative surgery is considered the gold standard, and delayed reanimation is usually not attempted. Methods: A retrospective review of all patients who underwent parotidectomies from 2009 to 2022 in a single institution was performed. Indications, surgical techniques, and outcomes of an algorithmic template were applied to these cases using the Sunnybrook, Terzis scores, and Smile Index. A comparison was made between immediate vs. late repairs. Results: Of a total of 90 patients who underwent parotidectomy, 17 (15.3%) had a radical parotidectomy, and 73 (84.7%) had a total or superficial parotidectomy. Among those who underwent complete removal of the gland and nerve sacrifice, eight patients (47.1%) had facial restoration. There were four patients each in the immediate (n = 4) and late repair (n = 4) groups. Surgical techniques ranged from cable grafts to vascularized cross facial nerve grafts (sural communicating nerve flap as per the Koshima procedure) and vascularized nerve flaps (chimeric vastus lateralis and anterolateral thigh flaps, and superficial circumflex perforator flap with lateral femoral cutaneous nerve). Conclusions: The algorithm between one technique and another should take into consideration age, comorbidities, soft tissue defects, presence of facial nerve branches for reinnervation, and donor site morbidity. While immediate facial nerve repair is ideal, there is still benefit in performing a delayed repair in this algorithm.

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.

Powering the Gracilis for Facial Reanimation: A Systematic Review and Meta-analysis of Outcomes Based on Donor Nerve

Importance

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.

Objective

To characterize outcomes in adults undergoing primary gracilis transfer for facial paralysis stratified by donor nerve used for neurotization.

Data Sources

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).

Study Selection

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.

Data Extraction and Synthesis

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.

Main Outcomes and Measures

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.

Results

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.

Conclusions and Relevance

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.

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.

The Deep Temporal Nerve Transfer: An Anatomical Feasibility Study and Implications for Upper Facial Reanimation

BACKGROUND

Facial paralysis has a profound impact on the brow, and currently static procedures are the mainstay of treatment. The deep temporal branches of the trigeminal nerve, given their proximity to the brow, may serve as possible donor nerves for both potential innervation of a free muscle transfer in patients with prolonged facial palsy or nerve transfers in acute or subacute palsy. As such, the authors present the detailed surgical anatomy of the deep temporal nerve, assessing feasibility for both functional muscle and nerve transfers, including a proposed surgical technique.

METHODS

Thirty cadaver hemifaces were dissected to establish deep temporal nerve anatomy and perform axonal analysis.

RESULTS

Two (53 percent) or three (47 percent) divisions of the deep temporal nerve were noted, with the most consistent division being the middle division (30 of 30 specimens). This division was consistently found approximately 4.1 cm (range, 3.7 to 4.5 cm) anterior to the tragus at the level of the zygomatic arch. For each 1 cm cranial to the arch, the nerve courses approximately 1 mm posteriorly. The number of axons in the proposed temporal branch is 1469 as it emerges from behind the zygomatic arch, 889 at 1 cm, 682 at 2 cm, 534 at 3 cm, 355 at 4 cm, 377 at 5 cm, and 256 at 6 cm.

CONCLUSION

Given its anatomical consistency, and expendability, the middle division of the deep temporal nerve is a viable donor nerve for dynamic upper facial reanimation with either nerve transfer or functional muscle transfer, depending on the length of facial palsy.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

Nerve sources for facial reanimation with muscle transplant in patients with unilateral facial palsy: clinical analysis of 3 techniques

Ninety-one patients with long-standing unilateral facial palsy and submitted to reanimation of the face with muscle transplant were divided into 3 nonrandomized groups: group I: 2-stage facial reanimation, cross face followed by gracilis muscle transplant, 58 patients; group II: 1-stage reanimation with latissimus dorsi muscle transplant, 11 patients (a branch of the facial nerve on the nonparalyzed side of the face was used as the nerve source for reanimation in groups I and II); group III: 1-stage reanimation with gracilis muscle transplant and neural coaptation of the respective nerve and the ipsilateral masseteric branch of the trigeminal nerve, 22 patients. No microvascular complications were observed. The average interval between surgery and initial muscle contractions was 11.1 months, 7.2 months, and 3.7 months in group I, group II, and group III, respectively. The quality (intensity and shape) of the smile, voluntary or involuntary, obtained on the reanimated side in relation to the unaffected side was considered good or excellent in 53.4%, 54.5%, and 86.3% of the patients in groups I, II, and III, respectively. In group I, the average age of the patients with excellent or good results (19.8 + 10.5 years) was significantly lower than that of the patients with fair or poor results or absence of movement (36.5 + 13.3 years). The smile was considered emotional or involuntary in 34% of the patients in group I and 45% in group II. Most of the patients in each group were only able to produce "voluntary smiles". Crossed synkinesis with lip puckering was observed in 48% of the patients in group I and 90% in group II. The results obtained with 1-stage facial reanimation with masseteric nerve were more uniform and predictable than those obtained with the other techniques evaluated in this study.

Location of the extracranial extent of leprous facial nerve pathology may allow leprous facial palsy to be reanimated by free muscle transfer

Leprosy is a mycobacterial nerve and skin infection, which can be eradicated by antibiotics. Some patients affected by leprosy, once cured, have residual nerve impairment with paralysis and sensory neuropathy. A series of patients with facial nerve paralysis, investigated using clinical, histological and electrophysiological techniques, demonstrated that the nerve pathology was distal to the section of main trunk prior to its bifurcation. Facial reanimation was achieved with a free gracilis-muscle transfer, coapting its motor nerve to the ipsilateral facial nerve trunk proximal to the site of the leprosy pathology, with a moderate clinical result.

Multi-channel orbicularis oculi stimulation to restore eye-blink function in facial paralysis

Facial paralysis due to facial nerve injury results in the loss of function of the muscles of the hemiface. The most serious complication in extreme cases is the loss of vision. In this study, we compared the effectiveness of single- and multiple-channel electrical stimulation to restore a complete and cosmetically acceptable eye blink. We established bilateral orbicularis oculi muscle (OOM) paralysis in eight dogs; the OOM of one side was directly stimulated using single-channel electrical stimulation and the opposite side was stimulated using multi-channel electrical stimulation. The changes in the palpebral fissure and complete palpebral closure were measured. The difference in current intensities between the multi-channel and single-channel simulation groups was significant, while only multi-channel stimulation produced complete eyelid closure. The latest electronic stimulation circuitry with high-quality implantable electrodes will make it possible to regulate precisely OOM contractions and thus generate complete and cosmetically acceptable eye-blink motion in patients with facial paralysis.

Human facial muscles: dimensions, motor endplate distribution, and presence of muscle fibers with multiple motor endplates

BACKGROUND

Extrafusal muscle fibers of human striated skeletal muscles are known to have a uniform innervation pattern. Motor endplates (MEP) of the "en plaque" type are located near the center of muscle fibers and distributed within the muscles in a narrow band. The aim of this study was to evaluate the innervation pattern of human facial muscles and compare it with that of skeletal muscles.

METHODS

Ten facial muscles from 11 human cadavers were dissected, the nerve entrance points located, and the dimensions measured. All muscles were stained in toto for MEPs using Acetylcholinesterase (AChE) and examined under the microscope to determine their location. Single muscle fibers were teased to evaluate the stained MEPs.

RESULTS

The length of the different facial muscles varied from 29 to 65 mm, which correlated to the length of the corresponding muscle fibers. MEP zones were found on the muscles in the immediate vicinity of the nerves' entrance points and located eccentrically. Numbers and locations varied from muscle to muscle. Three MEP zone distribution patterns were differentiated: numerous small MEP zones were evenly spread over the muscle, a predominant MEP zone and two to three small zones were spread at random, and two to four MEP zones of equal size were randomly scattered. One MEP of the "en plaque" type was found in 73.8% of the muscle fibers and two to five MEPs were found in 26.2%. The distances between the multiple MEPs on one muscle fiber varied from 10 to 500 microm.

CONCLUSIONS

This study suggests that facial muscles differ from skeletal muscles regarding distribution and number of MEPs. The eccentric location of MEP zones and multiple MEPs suggests there is an independent mechanism of neural regulation in the facial muscle system.

Reanimation for facial palsy using gracilis muscle grafts

Twelve patients have been reviewed at least 2 years after gracilis muscle transfer, preceded by crossface nerve grafting, for complete unilateral facial palsy. Levels of satisfaction among the patients were good. Examination showed all had voluntary movement of the graft which could produce reasonable mouth symmetry in most patients. However, the involuntary spontaneity and expressive movements were not so satisfactory, though still worthwhile. The technique and some lessons learned from this experience are discussed. It appears from electromyographic studies that continuing innervation and activity can occur in these grafts for many years postoperatively.