Facial nerve sacrifice in lateral approaches to the skull base: Simultaneous reconstruction by graft interposition.

PURPOSE: To evaluate the outcome of facial nerve (FN) cable graft interposition in lateral skull base surgery. MATERIALS AND METHODS: A group of 16 patients who underwent FN graft interposition procedure was retrospectively considered. Postoperative FN function was evaluated using the House-Brackmann (HB) grading system, the Sunnybrook Facial Grading System (SFGS), the Facial Disability Index (FDI) and the Oral Functioning Scale (OFS) questionnaires. RESULTS: 56.2% of patients had a good postoperative FN outcome (HB grade II-III). Postoperative electromyography (EMG) showed re-innervation potentials in 60% of patients; median age of these patients was significantly lower compared to who did not manifest re-innervation (p = 0.039). CONCLUSION: FN primary reconstruction remains the advisable rehabilitative option when the nerve is interrupted during lateral skull base surgeries, allowing to satisfactory postoperative results in more than half of patients. EMG confirmed the restoring of nerve conduction and it was more frequent in younger patients. The SFGS, the FDI and the OFS are important tools especially in the setting of a rehabilitation program.

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.

Anatomical Feasibility Study of the Digastric Branch of the Facial Nerve: A Potential Donor for Facial Nerve Reanimation.

PURPOSE: The digastric branch is the second branch of the facial nerve after emerging from the stylomastoid foramen. To the best of our knowledge, few detailed anatomic studies of the digastric branch have been performed. Moreover, the use of the digastric branch for facial nerve reanimation has not been explored. MATERIALS AND METHODS: Nine sides of 5 fresh frozen cadavers were dissected for anatomic observation of the digastric branch and exploration of the feasibility of the digastric branch as a donor for facial nerve reanimation. The facial nerve trunk (FNT) and digastric branch were readily found by dissection using the tragal cartilage and tragal pointer as landmarks. The length and diameter of the digastric branch were measured, and the digastric branch was repositioned anterior to the FNT and the 2 major extracranial divisions of the FNT. RESULTS: On all sides, the digastric branch existed as a single branch and innervated only the posterior belly of the digastric muscle. The available length of the digastric branch was 13.28 ± 2.47 mm (range, 8.87 to 16.38 mm), and the mean diameter was 0.98 ± 0.31 mm (range, 0.64 to 1.64 mm). The digastric branch reached the FNT and its 2 major divisions without tension. CONCLUSIONS: The results of the present study have clarified the anatomic findings of the digastric branch in detail and the feasibility of using the digastric branch as a potential donor for facial nerve reanimation. The surgeon might consider the use of the digastric branch as a feasible donor for facial nerve reanimation based on the findings from our cadaveric study.

The Feasibility of Using the Posterior Auricular Branch of the Facial Nerve as a Donor for Facial Nerve Reanimation Procedures: A Cadaveric Study.

PURPOSE: Facial nerve paralysis can result in critical complications, including those to the visual, respiratory, and digestive systems. The facial nerve has been reanimated using various nerves, but the posterior auricular nerve (PAN) branching off the facial nerve has not been explored for this purpose. MATERIALS AND METHODS: Ten sides from 6 fresh-frozen adult cadavers were used for dissection of the PAN to explore its potential as a donor for facial nerve reanimation. The facial nerve trunk (FNT) and PAN were consistently and readily identified by deep dissection using the tragal cartilage and tragal pointer as landmarks. The PAN was transected at the point of insertion of its innervated muscles. Its length and diameter were measured, and it was transposed anteriorly to the FNT and its 2 major extracranial divisions. RESULTS: The PAN was observed on all sides. Its available length was 27.11 ± 5.02 mm and its mean diameter was 0.85 ± 0.20 mm. In all specimens, the PAN readily reached the FNT and its 2 major divisions without tension. CONCLUSION: No previous study has explored the use of the PAN as a donor for facial nerve reanimation. Based on the present cadaveric study, surgeons might consider it for this purpose.

Endoscopic Transcanal Approach to Geniculate Ganglion Hemangioma and Simultaneous Facial Nerve Reinnervation: A Case Report.

Hemangioma of the facial nerve (FN) is a very rare benign tumor whose origin is the vascular plexi that surround the nerve. The transpetrous, retrosigmoid, and middle cranial fossa (MCF) routes are the traditional and most widely used approaches to reach these lateral skull base neoformations. However, this very complex region can be reached through an exclusive transcanal endoscopic procedure in selected cases. One of these was a 42-year-old patient who had been presenting a worsening left FN paralysis (grade VI according to the House-Brackmann scale at the time of visit) for 22 months without a history of trauma or infection. Radiological studies showed a lesion in the region of the geniculate ganglion. A suprageniculate endoscopic approach was performed to remove the lesion, with the sacrifice of the FN and a simultaneous hypoglossal-facial anastomosis. The aim of this minimally invasive surgery is the complete excision of the disease, maintaining the hearing function intact and restoration of facial function, whenever possible, avoiding more invasive approaches.

Facial Nerve Trauma: Clinical Evaluation and Management Strategies.

The field of facial paralysis requires the reconstructive surgeon to apply a wide spectrum of reconstructive and aesthetic principles, using a comprehensive array of surgical tools, including microsurgery, peripheral nerve surgery, and aesthetic facial surgery on the road to optimize patient outcomes. The distinct deficits created by different anatomical levels of facial nerve injury require a fundamental understanding of facial nerve anatomy. Palsy duration, followed by location and mechanism, will determine mimetic muscle salvageability, by means of either direct repair, grafting, or nerve transfers, whereas longer palsy durations will necessitate introducing a new neuromuscular unit, whether by muscle transfer or free functional muscle transplant. A thorough history, physical examination, and basic understanding of ancillary studies, emphasizing palsy duration, location, and mechanism of injury, are critical in evaluation, prognostication, and treatment strategies in traumatic facial palsy patients. The importance of ancillary and aesthetic procedures cannot be overstated. Although these do not provide motion, they constitute essential tools in the treatment of facial paralysis, providing both protective and improved aesthetic outcomes, yielding the highest impact in final surgeon and patient satisfaction, bringing our patients to smile not only on the outside, but also on the inside.

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.

Fascicular turnover flap in the reconstruction of facial nerve defects: an experimental study in rats.

The purpose of this study was to assess the utility of a fascicular turnover flap for facial nerve repair and to investigate its possible application in the field of facial nerve repair using a rat model of facial paralysis. Twenty-four Wistar rats were used in this study. A left vibrissal muscle palsy model was established via excision of the buccal and marginal branches through a periauricular incision. In Group 1, the nerve gap was not reconstructed. In Group 2, the nerve gap of the marginal mandibular branch was reconstructed using an autograft, and in Group 3, the gap was reconstructed using a fascicular turnover flap. At 12 weeks after the operation, the nerve regeneration was assessed based on clinical, histopathological and electrophysiological evaluations. The functional recovery of the vibrissal muscle was observed with a fascicular turnover flap. The functional recovery of whisker movement was almost same between Groups 2 and 3 (p = .57). The histopathological examinations almost same result between Groups 2 and 3 (p = .17). The compound muscle action potential after reconstruction was also almost same between Groups 2 and 3 (p = .99). We found that the fascicular turnover flap could be applied to facial nerve gap reconstruction. However, further evaluations will be necessary to clarify its indication and mechanism in human.

Effects of Melatonin and Dexamethasone on Facial Nerve Neurorrhaphy.

OBJECTIVES: To investigate the effects of topical and systemic administrations of melatonin and dexamethasone on facial nerve regeneration. MATERIALS AND METHODS: In total, 50 male albino Wistar rats underwent facial nerve axotomy and neurorrhaphy. The animals were divided into 5 groups: control, topical melatonin, systemic melatonin, topical dexamethasone, and systemic dexamethasone. Nerve conduction studies were performed preoperatively and at 3, 6, 9, and 12 weeks after drug administrations. Amplitude and latency of the compound muscle action potentials were recorded. Coapted facial nerves were investigated under light and electron microscopy. Nerve diameter, axon diameter, and myelin thickness were recorded quantitatively. RESULTS: Amplitudes decreased and latencies increased in both the melatonin and dexamethasone groups. At the final examination, the electrophysiological evidence of facial nerve degeneration was not significantly different between the groups. Histopathological examinations revealed the largest nerve diameter in the melatonin groups, followed by the dexamethasone and control groups (p<0.05). Axon diameter of the control group was smaller than those of the melatonin (topical and systemic) and topical dexamethasone groups (p<0.05). The melatonin groups had almost normal myelin ultrastructure. CONCLUSION: Electrophysiological evaluation did not reveal any potential benefit of dexamethasone and melatonin in contrast to histopathological examination, which revealed beneficial effects of melatonin in particular. These agents may increase the regeneration of facial nerves, but electrophysiological evidence of regeneration may appear later.

Use of the masseteric nerve to treat segmental midface paresis.

Segmental midface paresis with or without synkinesis reflects incomplete recovery from Bell's palsy, operations on the cranial base or parotid, or trauma, in 25%-30% of cases. To correct the deficit, the masseteric nerve was used to deliver a powerful stimulus to the zygomatic muscle complex, with the addition of a cross-face sural nerve graft to ensure more spontaneous smiling. By doing this, the orbicularis oculi muscle continues to have an appropriate stimulus from the facial nerve, and the zygomatic muscle complex is separately innervated, which considerably reduces synkinesis between the two muscle compartments. For those patients with muscular contractures of the midface, the new healthy neural stimulus relaxes muscles at rest. From January 2011 to March 2017, 20 patients presented with segmental facial paresis of the midface and were operated on using this new technique. All patients were evaluated before and after operation using Clinician-Graded Electronic Facial Paralysis Assessment (eFACE), and they showed considerable postoperative improvements in static, dynamic, and synkinetic variables. Our proposed use of the masseteric nerve to treat segmental facial paresis produces favourable results, but our initial data require confirmation by further studies.

Comprehensive approach to reestablishing form and function after radical parotidectomy.

INTRODUCTION: The reconstructive goals following radical parotidectomy include restoration of symmetry, reanimation of the face, and reestablishment of oral competence. We present our experience utilizing the anterolateral thigh (ALT) free flap, orthodromic temporalis tendon transfer (OTTT), and facial nerve cable grafting to reestablish form and function. MATERIAL AND METHODS: From 2010 to 2016, 17 patients underwent radical parotidectomy followed by immediate reconstruction. An ALT was harvested to accommodate the volume and skin defect. Additional fascia lata and motor nerve to vastus lateralis (MNVL) were obtained. Anastomosis of the ALT to recipient vessels was performed, most commonly using the facial artery and internal jugular vein. OTTT was performed by securing the medial tendon of the temporalis to orbicularis oris through a nasolabial incision. Fascia lata was tunneled through the lower lip, then secured laterally to the temporalis tendon. The MNVL was cable grafted from either the proximal facial nerve or masseteric nerve to the distal facial nerve branches. ALT fascia was suspended to the superficial muscular aponeurotic system. RESULTS: Average follow up was 19 months. Only one patient failed to achieve symmetry attributed to dehiscence of OTTT. All patients achieved oral competence and dynamic smile with OTTT activation. Facial nerve recovery was seen in 8 patients. 5 reached a House Brackman Score of 3. Two donor site seromas and two wound infections occurred. CONCLUSION: Simultaneous ALT, OTTT, and facial nerve cable grafting provides early reestablishment of facial symmetry, facial reanimation, and oral competence with minimal morbidity.

Comparison of Functional Results After Cross-Face Nerve Graft-, Spinal Accessory Nerve-, and Masseter Nerve-Innervated Gracilis for Facial Paralysis Reconstruction: The Chang Gung Experience.

BACKGROUND: Using functioning free muscle transplantation (FFMT) for facial paralysis and postparalysis facial synkinesis reconstruction is our preferred technique. Gracilis was the first choice of muscle. Three motor neurotizers: cross-face nerve graft (CFNG), spinal accessory nerve (XI) and masseter nerve (V3) have been used as neurotizers for different indications. METHODS: A total of 362 cases of facial reanimation with FFMT were performed between 1986 and 2015. Of these, 350 patients with 361 FFMT were enrolled: 272 (78%) patients were treated by CFNG-gracilis, 56 (15%) by XI-gracilis, and 22 (6%) by V3-gracilis. Smile excursion score, cortical adaptation stage with tickle test for spontaneous smile, facial synkinesis, satisfaction score by questionnaire, and functional facial grading were used for outcome assessment. RESULTS: The CFNG-gracilis in a 2-stage procedure achieved most natural and spontaneous smile when longer observation (≥2 years) was followed. The single-stage procedure using the XI-gracilis has proven a good alternative. V3-gracilis provided high smile excursion score in the shortest rehabilitation period, but never obtained spontaneous smile. CONCLUSIONS: The CFNG-gracilis remains our first choice for facial paralysis reconstruction which can achieve natural and spontaneous smile. XI- or V3-gracilis can be selected as a save procedure when CFNG-gracilis fails. The V3-gracilis is indicated in some specific conditions, such as bilateral Möbius syndrome, older patients (age, >70 years), or patients with malignant disease.

The split hypoglossal nerve versus the cross-face nerve graft to supply the free functional muscle transfer for facial reanimation: A comparative study.

Long-standing cases of facial paralysis are currently treated with free functional muscle transfer. Several nerves are mentioned in the literature to supply the free muscle transfer. The aim of this study is to compare the split hypoglossal nerve and the cross-face nerve graft to supply the free functional muscle transfer in facial reanimation. Of 94 patients with long-standing, unilateral facial palsy, 49 were treated using the latissimus dorsi muscle supplied by the split hypoglossal nerve, and 45 patients were treated using the latissmus dorsi muscle supplied by healthy contralateral buccal branch of the facial nerve. The excursion gained by the free muscle transfer supplied by the split hypoglossal nerve (mean 19.20 ± 6.321) was significantly higher (P value 0.001) than that obtained by the contralateral buccal branch of the facial nerve (mean 14.59 ± 6.245). The split hypoglossal nerve appears to be a good possible option to supply the free vascularised muscle transfer in facial reanimation. It yields a stronger excursion in less time than the contralateral cross-face nerve graft.

Symmetry Restoration at Rest after Masseter-to-Facial Nerve Transfer: Is It as Efficient as Smile Reanimation?

BACKGROUND: Masseter-to-facial nerve transfer is a highly efficient technique for reanimating paralyzed muscle and has been reported to restore facial symmetry at rest. However, no systematic studies have been performed, and the effects of preoperative droop of the oral commissure on postoperative symmetry at rest have rarely been reported. METHODS: The authors retrospectively analyzed 35 patients with masseteric-to-facial nerve anastomosis and assessed the quality and quantity of the dynamic recovery and the oral commissure symmetry at rest. The dynamic and static effects were then compared. RESULTS: All of the patients' Terzis scores were increased postoperatively, and over half of the patients presented restored symmetric smiles (Terzis scores of 4 or 5). The postoperative symmetry scale of the oral commissure at rest improved in 18 of 35 patients. Both the mean postoperative altitude difference of oral commissure excursion and the postoperative altitude difference of bilateral oral commissure position were decreased compared with preoperative values. The preoperative symmetry had a significant effect on the postoperative altitude difference of the bilateral oral commissure position. The effects of the dynamic and static symmetry improvements were transformed to a comparable factor α. The dynamic α was significantly greater than the static α. CONCLUSIONS: Masseter-to-facial nerve transfer is a reliable technique for smile reanimation. However, it has only a limited effect on the improvement of symmetry at rest. Assessing the preoperative symmetry of the oral commissure at rest can be used to predict postoperative outcomes, and patients with severe droop of the oral commissure (symmetry scale grade III or IV) should receive static suspension.

Facial Nerve Axonal Analysis and Anatomical Localization in Donor Nerve: Optimizing Axonal Load for Cross-Facial Nerve Grafting in Facial Reanimation.

BACKGROUND: Donor nerve axonal count over 900 in two-stage reconstructions using cross-facial nerve grafts is possibly associated with improved outcomes in facial reanimation. Facial nerve axonal analysis was performed to determine the ideal location for optimizing axonal load. Correlation of axonal number, branch diameter, and age was also assessed. METHODS: Twenty-eight fresh unpreserved cadaveric hemifaces were dissected exposing the extracranial facial nerve branches. Axonal counts at 2-cm intervals from the pes anserinus along branches inserting into the zygomaticus major muscle were taken, noting position relative to the zygomatic arch, posterior ramus border, lateral border of the zygomaticus muscle, and anterior parotid gland border. Nerves were fixed, sectioned, and stained with SMI-31 antineurofilament stain for digital axonal analysis. RESULTS: All specimens had one or more intraparotid zygomatic branches with over 900 axons, and 96 percent had an extraparotid branch with over 900 axons. The likelihood that a zygomatic branch would have over 900 axons at its last intraparotid point (mean, 6 mm posterior to the parotid border) was 92 percent (range, 67 to 100 percent) in contrast to 61 percent (range, 25 to 100 percent) when sampled at the first extraparotid point (mean, 14 mm anterior to the parotid border). Nerve cross-sectional area was positively correlated to its axonal count (R° = 78 percent; p < 0.0001), with nerve diameter over 0.6 mm predicting over 900 axons. Age did not correlate with axonal counts. CONCLUSIONS: Branches with adequate axonal load were found in all specimens. The likelihood of adequate branch selection improved from 61 percent to 92 percent with short retrograde intraparotid dissection. Nerve diameter correlated with axonal load.

A comparative study of acellular nerve xenografts and allografts in repairing rat facial nerve defects.

Acellular nerves are composed of a basal lamina tube, which retains sufficient bioactivity to promote axon regeneration, thereby repairing peripheral nerve gaps. However, the clinical application of acellular allografts has been restricted due to its limited availability. To investigate whether xenografts, a substitute to allograft acellular nerves in abundant supply, could efficiently promote nerve regeneration, rabbit and rat acellular nerve grafts were used to reconstruct 1 cm defects in Wistar rat facial nerves. Autologous peroneal nerve grafts served as a positive control group. A total of 12 weeks following the surgical procedure, the axon number, myelinated axon number, myelin sheath thickness, and nerve conduction velocity of the rabbit and rat­derived acellular nerve grafts were similar, whereas the fiber diameter of the rabbit­derived acellular xenografts decreased, as compared with those of rat­derived acellular allografts. Autografts exerted superior effects on nerve regeneration; however, no significant difference was observed between the axon number in the autograft group, as compared with the two acellular groups. These results suggested that autografts perform better than acellular nerve grafts, and chemically extracted acellular allografts and xenografts have similar effects on the regeneration of short facial nerve defects.

Collagen scaffolds combined with collagen-binding ciliary neurotrophic factor facilitate facial nerve repair in mini-pigs.

The preclinical studies using animal models play a very important role in the evaluation of facial nerve regeneration. Good models need to recapitulate the distance and time for axons to regenerate in humans. Compared with the most used rodent animals, the structure of facial nerve in mini-pigs shares more similarities with humans in microanatomy. To evaluate the feasibility of repairing facial nerve defects by collagen scaffolds combined with ciliary neurotrophic factor (CNTF), 10-mm-long gaps were made in the buccal branch of mini-pigs' facial nerve. Three months after surgery, electrophysiological assessment and histological examination were performed to evaluate facial nerve regeneration. Immunohistochemistry and transmission electron microscope observation showed that collagen scaffolds with collagen binding (CBD)-CNTF could promote better axon regeneration, Schwann cell migration, and remyelination at the site of implant device than using scaffolds alone. Electrophysiological assessment also showed higher recovery rate in the CNTF group. In summary, combination of collagen scaffolds and CBD-CNTF showed promising effects on facial nerve regeneration in mini-pig models.