Electroacupuncture Promotes Functional Recovery after Facial Nerve Injury in Rats by Regulating Autophagy via GDNF and PI3K/mTOR Signaling Pathway.

OBJECTIVE: To explore the mechanism of electroacupuncture (EA) in promoting recovery of the facial function with the involvement of autophagy, glial cell line-derived neurotrophic factor (GDNF), and phosphatidylinositol-3-kinase (PI3K)/mammalian target of rapamycin (mTOR) signaling pathway. METHODS: Seventy-two male Sprague-Dawley rats were randomly allocated into the control, sham-operated, facial nerve injury (FNI), EA, EA+3-methyladenine (3-MA), and EA+GDNF antagonist groups using a random number table, with 12 rats in each group. An FNI rat model was established with facial nerve crushing method. EA intervention was conducted at Dicang (ST 4), Jiache (ST 6), Yifeng (SJ 17), and Hegu (LI 4) acupoints for 2 weeks. The Simone's 10-Point Scale was utilized to monitor the recovery of facial function. The histopathological evaluation of facial nerves was performed using hematoxylin-eosin (HE) staining. The levels of Beclin-1, light chain 3 (LC3), and P62 were detected by immunohistochemistry (IHC), immunofluorescence, and reverse transcription-polymerase chain reaction, respectively. Additionally, IHC was also used to detect the levels of GDNF, Rai, PI3K, and mTOR. RESULTS: The facial functional scores were significantly increased in the EA group than the FNI group (P<0.05 or P<0.01). HE staining showed nerve axons and myelin sheaths, which were destroyed immediately after the injury, were recovered with EA treatment. The expressions of Beclin-1 and LC3 were significantly elevated and the expression of P62 was markedly reduced in FNI rats (P<0.01); however, EA treatment reversed these abnormal changes (P<0.01). Meanwhile, EA stimulation significantly increased the levels of GDNF, Rai, PI3K, and mTOR (P<0.01). After exogenous administration with autophagy inhibitor 3-MA or GDNF antagonist, the repair effect of EA on facial function was attenuated (P<0.05 or P<0.01). CONCLUSIONS: EA could promote the recovery of facial function and repair the facial nerve damages in a rat model of FNI. EA may exert this neuroreparative effect through mediating the release of GDNF, activating the PI3K/mTOR signaling pathway, and further regulating the autophagy of facial nerves.

[Professor LI De-hua's experience in treating facial nerve injury after total parotidectomy with blade needle based on jingjin theory].

The paper summarizes the academic thought and clinical experience of professor LI De-hua in treatment of facial nerve injury after total parotidectomy with blade needle based on jingjin (muscle region of meridian, sinew/fascia) theory. This disease is located at muscle regions of hand-/foot-three yang meridians; and the sinew/fascia adhesion is its basic pathogenesis, manifested by "transversely-distributed collaterals" and "knotted tendons". In treatment, the knotted tendons are taken as the points. Using the relaxation technique of blade needle, the lesions of sinews/fascia are dissected and removed to release the stimulation or compression to the nerves and vessels so that the normal function of sinews/fascia can be restored.

Comparison of the effects of methylprednisolone, hyperbaric oxygen and hesperidin + diosmin on the facial nerve injury: an experimental animal model.

BACKGROUND: Necessity of new and alternative treatments in traumatic facial nerve injury. AIMS/OBJECTIVE: In this experimental study, we aimed to evaluate the histopathologic and functional effects of methylprednisolone, hyperbaric oxygen and hesperidin + diosmin treatments on traumatic facial nerve regeneration in rats. METHODS: After facial nerve injury, five groups were formed with eight rats in each group: Group 1 (negative control), 2 (operation), 3 (corticosteroid), 4 (hyperbaric oxygen), 5 (hesperidin + diosmin). Blink reflex of rats evaluated a day after the operation and at the first, second and third weeks. Facial nerve samples from sacrificed animals were examined under a light microscope. RESULTS: According to our results, in group 4; axonal degeneration and vascular congestion were significantly lower than group 2 and 3, and myelin sheath thickness was significantly higher than group 3. In group 5; axonal degeneration was significantly lower than group 2 and vascular congestion was significantly lower than group 2 and 3. In terms of functional recovery; there was no statistically significant difference between the groups. CONCLUSIONS AND SIGNIFICANCE: It has been shown that both hyperbaric oxygen and hesperidin + diosmin treatments have positive effects on facial nerve regeneration. Both treatments may be good alternatives for ameliorating traumatic nerve injury, but these treatment modalities need to be further explored.

The effect of charge-balanced transcutaneous electrical nerve stimulation on rodent facial nerve regeneration.

This study aimed to investigate the effect of charge-balanced transcutaneous electrical nerve stimulation (cb-TENS) in accelerating recovery of the facial function and nerve regeneration after facial nerve (FN) section in a rat model. The main trunk of the left FN was divided and immediately sutured just distal to the stylomastoid foramen in 66 Sprague-Dawley rats. The control group had no electrical stimulus. The other two groups received cb-TENS at 20 Hz (20 Hz group) or 40 Hz (40 Hz group). Cb-TENS was administered daily for seven days and then twice a week for three weeks thereafter. To assess the recovery of facial function, whisker movement was monitored for four weeks. Histopathological evaluation of nerve regeneration was performed using transmission electron microscopy (TEM) and confocal microscopy with immunofluorescence (IF) staining. In addition, the levels of various molecular biological markers that affect nerve regeneration were analyzed. Whisker movement in the cb-TENS groups showed faster and better recovery than the control group. The 40 Hz group showed significantly better movement at the first week after injury (p < 0.0125). In histopathological analyses using TEM, nerve axons and Schwann cells, which were destroyed immediately after the injury, recovered in all groups over time. However, the regeneration of the myelin sheath was remarkably rapid and thicker in the 20 Hz and 40 Hz groups than in the control group. Image analysis using IF staining showed that the expression levels of S100B and NF200 increased over time in all groups. Specifically, the expression of NF200 in the 20 Hz and 40 Hz groups increased markedly compared to the control group. The real-time polymerase chain reaction was performed on ten representative neurotrophic factors, and the levels of IL-1ß and IL-6 were significantly higher in the 20 and 40 Hz groups than in the control group (p < 0.015). Cb-TENS facilitated and accelerated FN recovery in the rat model, as it significantly reduced the recovery time for the whisker movement. The histopathological study and analysis of neurotrophic factors supported the role of cb-TENS in the enhanced regeneration of the FN.

Selective Facial Muscle Activation with Acute and Chronic Multichannel Cuff Electrode Implantation in a Feline Model.

OBJECTIVES: Facial paralysis is a debilitating condition with substantial functional and psychological consequences. This feline-model study evaluates whether facial muscles can be selectively activated in acute and chronic implantation of 16-channel multichannel cuff electrodes (MCE). METHODS: Two cats underwent acute terminal MCE implantation experiments, 2 underwent chronic MCE implantation in uninjured facial nerves (FN) and tested for 6 months, and 2 underwent chronic MCE implantation experiments after FN transection injury and tested for 3 months. The MCE were wrapped around the main trunk of the skeletonized FN, and data collection consisted of EMG thresholds, amplitudes, and selectivity of muscle activation. RESULTS: In acute experimentation, activation of specific channels (ie, channels 1-3 and 6-8) resulted in selective activation of orbicularis oculi, whereas activation of other channels (ie, channels 4, 5, or 8) led to selective activation of levator auris longus with higher EMG amplitudes. MCE implantation yielded stable and selective facial muscle activation EMG thresholds and amplitudes up to a 5-month period. Modest selective muscle activation was furthermore obtained after a complete transection-reapproximating nerve injury after a 3-month recovery period and implantation reoperation. Chronic implantation of MCE did not lead to fibrosis on histology. Field steering was achieved to activate distinct facial muscles by sending simultaneous subthreshold currents to multiple channels, thus theoretically protecting against nerve damage from chronic electrical stimulation. CONCLUSION: Our proof-of-concept results show the ability of an MCE, supplemented with field steering, to provide a degree of selective facial muscle stimulation in a feline model, even following nerve regeneration after FN injury. LEVEL OF EVIDENCE: N/A.

Photobiomodulation at a wavelength of 633 nm leads to faster functional recovery than 804 nm after facial nerve injury.

We analyzed the effects of photobiomodulation (PBM) of various wavelengths on regeneration of the facial nerve using in vitro and in vivo experimental models. We assessed the antioxidative effect of PBM in geniculate ganglion neurons irradiated with a diode laser at 633 nm, 780 nm and 804 nm. Wavelengths of 633 and 780 nm but not 804 nm inhibited cell death by oxidative stress. We assessed the effects of PBM on functional and morphologic recovery in rats divided into control, facial nerve damage (FND) and FND irradiated with a 633 nm or 804 nm lasers. Injured rats treated with 633-nm light had better facial palsy scores, larger axon diameter and higher expression of Schwann cells compared with the FND group. No positive results were observed in rats irradiated at 804-nm light. These findings indicate that 633-nm PBM promotes accelerated nerve regeneration and improved functional recovery in an injured facial nerve.

Optimizing Location of Subdermal Recording Electrodes for Intraoperative Facial Nerve Monitoring.

OBJECTIVE: The purpose of this study is to determine if different facial muscle groups demonstrate different responses to facial nerve stimulation, the results of which could potentially improve intraoperative facial nerve monitoring (IOFNM). METHODS: IOFNM data were prospectively collected from patients undergoing cochlear implantation. At different stages of nerve exposure, three sites were stimulated using a monopolar pulse. Peak electromyography (EMG) amplitude (µV) in four muscle groups innervated by four different branches of the facial nerve (frontalis-temporal, inferior orbicularis oculi-zygomatic, superior oribularis oris-buccal, and mentalis-marginal mandibular) were recorded. RESULTS: A total of 279 peak EMG amplitudes were recorded in 93 patients. At all three stimulating sites, the zygomatic branch mean peak EMG amplitudes were statistically greater than those of the temporal, buccal, and marginal mandibular branches (P < .05). At stimulating Site C, the marginal mandibular branch mean peak EMG was stronger than the temporal or buccal branches (P < .05). Of the 279 stimulations, the zygomatic branch demonstrated the highest amplitude in 128 (45.9%) trials, followed by the marginal mandibular branch (22.2%). CONCLUSIONS: When utilized, IOFNM should be performed with at least two electrodes, one of which is placed in the orbicularis oculi muscles and the other in the mentalis muscle. However, there is wide variability between patients. As such, in cases of suspected variant nerve anatomy or increased risk of injury (intradural procedures), surgeons should consider using more than two recording electrodes, with at least one in the orbicularis oculi muscle. LEVEL OF EVIDENCE: 3 Laryngoscope, 131:E2329-E2334, 2021.

Advances in facial nerve management in the head and neck cancer patient.

PURPOSE OF REVIEW: The purpose of this review is to summarize best practices in facial nerve management for patients with head and neck cancer. In addition, we provide a review of recent literature on novel innovations and techniques in facial reanimation surgery. RECENT FINDINGS: Although recommended when tumor ablation surgery requires facial nerve sacrifice, facial reanimation procedures are not always performed. Concurrent dynamic facial reanimation with masseteric nerve transfers and cable graft repair can preserve native facial muscle function. Static suspension can provide facial support and immediate resting symmetry for patients. Eyelid weight and eye care should not be delayed, particularly in patients with trigeminal sensory deficits. Choice of neural source to innervate a gracilis-free muscle transfer for smile reanimation remains controversial; however, new techniques, such as dual innervation and multivector muscle transfer, may improve aesthetic and functional outcomes. SUMMARY: Management of the facial nerve in the setting of head and neck cancer presents unique challenges. When possible, simultaneous oncologic resection and facial reanimation is ideal given the open surgical field, newly dissected and electrically stimulatable facial nerve branches, as well as minimizing postoperative healing time to prevent postsurgical treatment delays. A coordinated approach to facial nerve management with a multidisciplinary surgical team may help provide optimal, comprehensive care.

Acupuncture as Part of Iatrogenic Facial Nerve Palsy Rehabilitation-First Report.

BACKGROUND: Facial paresis is one of the complications after treatment for vestibular schwannoma (VS). Acupuncture has been used for Bell palsy but not in iatrogenic facial paresis. The objective of this study is to measure the efficacy of using acupuncture for iatrogenic facial nerve palsy and patients' satisfaction. METHODS: This is a single-center retrospective study with patients from 2007-2019 received treatment for newly diagnosed or recurrent VS. Some patients who suffered facial paresis after surgery had self-initiated acupuncture. All patients who had facial paresis were included. Their facial nerve status before and immediately after surgery, postoperative 6 months and 12 months, were recorded. Those who received acupuncture also answered 6- and 12-month patient satisfaction surveys over the phone. Adverse effects were also assessed. RESULTS: There were 123 patients in this period. Of these, 29 patients had iatrogenic facial paresis and 23 of them received acupuncture. There was significant improvement of facial paresis for the acupuncture group compared with the nonacupuncture group at 6 and 12 months. More than 80% of patients who received acupuncture were satisfied. They had motor improvement and experienced less pain and tightness. No adverse effects were reported. CONCLUSIONS: Acupuncture for postresection VS facial paresis seemed to speed up its recovery. Both patients' recovery and satisfaction were good after acupuncture, and it seemed to be a safe procedure in trained hands.

Peripheral trigeminal branch stimulation for refractory facial pain: A single-center experience.

OBJECTIVE: Facial pain refractory to medical treatments may benefit from neurosurgical interventions. Only a few studies have reported on the efficacy of peripheral trigeminal stimulation and more specifically supraorbital nerve (SON) and infraorbital nerve (ION) stimulation for the treatment of facial pain. PATIENTS AND METHODS: In the present study, we identified all patients at our institution who underwent SON and/or ION stimulation for treatment of facial pain due to post-herpetic, traumatic or idiopathic etiology. Relevant pre and post-operative outcomes were analyzed. RESULTS: We identified 15 patients who underwent SON and/or ION stimulation. Among them, 12 (80 %) endorsed >50 % pain relief during the trial stimulation period. After a median follow-up of 5.8 months with permanent implantation, 1 patient (8.3 %) was diagnosed with lead erosion and IPG migration, two patients had lead infections (16.7 %) and one (8.3 %) had wound dehiscence. No lead migrations were identified during the long-term follow-up. The VAS score showed a statistically significant reduction from a median pre-operative score of 7 to a post-operative score of 1.8 (p = 0.011), which corresponded to a 74.3 % average pain reduction. CONCLUSION: SON and/or ION stimulation can be an effective treatment for intractable facial pain due to post-herpetic, traumatic or idiopathic etiology; however the complication rate is relatively high. Future prospective studies with longer follow-up periods are warranted.

Dopaminergic Modulation of Orofacial Mechanical Hypersensitivity Induced by Infraorbital Nerve Injury.

While the descending dopaminergic control system is not fully understood, it is reported that the hypothalamic A11 nucleus is its principle source. To better understand the impact of this system, particularly the A11 nucleus, on neuropathic pain, we created a chronic constriction injury model of the infraorbital nerve (ION-CCI) in rats. ION-CCI rats received intraperitoneal administrations of quinpirole (a dopamine D2 receptor agonist). ION-CCI rats received microinjections of quinpirole, muscimol [a gamma-aminobutyric acid type A (GABAA) receptor agonist], or neurotoxin 6-hydroxydopamine (6-OHDA) into the A11 nucleus. A von Frey filament was used as a mechanical stimulus on the maxillary whisker pad skin; behavioral and immunohistochemical responses to the stimulation were assessed. After intraperitoneal administration of quinpirole and microinjection of quinpirole or muscimol, ION-CCI rats showed an increase in head-withdrawal thresholds and a decrease in the number of phosphorylated extracellular signal-regulated kinase (pERK) immunoreactive (pERK-IR) cells in the superficial layers of the trigeminal spinal subnucleus caudalis (Vc). Following 6-OHDA microinjection, ION-CCI rats showed a decrease in head-withdrawal thresholds and an increase in the number of pERK-IR cells in the Vc. Our findings suggest the descending dopaminergic control system is involved in the modulation of trigeminal neuropathic pain.

The efficiency of ozone therapy and low-level laser therapy in rat facial nerve injury.

PURPOSE: Comparison of low-level laser therapy (LLLT) and ozone therapy (OT) methods for the treatment of facial nerve injury (FNI) in rats, evaluated by histomorphometric measurement analysis. MATERIALS AND METHODS: Thirty rats were randomly divided into control (C), LLLT, and OT groups. The left facial nerves (FNs) of all rats (n = 30) were used in this study. These were held in a surgical clamp for 30 s to create neuropathic damage. The non-injured right FNs of the rats in the control group formed the fourth, sham (S) group in this study (n = 10). Therefore the total number of evaluated samples was 40. The injured FNs of rats in the control group were left to heal spontaneously, whereas LLLT was applied for 21 consecutive days (output 100 mW/cm2 and wavelength 850 nm) and OT (2 ml; 80 µm/ml) once every 2 days for 21 days. RESULTS: After histomorphological evaluation, the OT group revealed statistically significant outcomes following FNI compared with the OT and control groups in terms of branching of nerve fibers (p = 0.003), nerve fiber diameters (p = 0.0398), nerve fiber areas (p = 0.042), and axon numbers (p = 0.0327). Although the LLLT group revealed a better healing process than the control group, the outcome was not statistically significant in terms of branching of nerve fibers (p = 0.6804), nerve fiber diameters (p = 0.7424), nerve fiber areas (p = 0.7048), and axon numbers (p = 0.7588). CONCLUSIONS: OT resulted in statistically significant differences in outcome when compared with the LLLT and control groups, and provided a safe and effective treatment for FNI in rats. OT could therefore be considered as an alternative treatment of FNI. Clinical studies should now be performed to establish whether comparable results can be achieved in humans.

Common Complications in Rhytidectomy.

Complications of rhytidectomy are well known, yet often preventable. A thorough preoperative history and physical along with realistic patient expectations provide the surgeon and patient with insight into potential complications and postoperative management. Understanding of surgical pitfalls and avoidance are crucial in beginning to manage facelift complications. Possible complications of facelift techniques should not discourage surgeons from pursuing a particular technique as the majority of complications are temporary. Though, a strong patient-physician relationship is critical when complications occur. Complications may be frustrating for both the patient and surgeon, yet are overwhelmingly temporary and manageable without surgical intervention.

Brief Electrical Stimulation Improves Functional Recovery After Femoral But Not After Facial Nerve Injury in Rats.

Brief low-frequency electrical stimulation (ES, 1 h, 20 Hz) of the proximal nerve stump has emerged as a potential adjunct treatment for nerve injury. Despite available experimental and clinical data, the potentials and limitations of the ES therapy still have to be defined using different animal models, types of nerves, and clinical settings. Here, we show that brief ES of the proximal stump of the transected rat femoral nerve causes, as estimated by motion analysis, enhanced functional recovery reaching preoperative levels within 5 months of injury, in contrast to the incomplete restoration in sham-stimulated (SS) animals. The functional advantage seen in ES rats was associated with higher numbers, as compared with SS, of correctly targeted quadriceps motoneurons. In contrast, ES prior to facial nerve suture did not lead to improvement of whisking compared with SS. Lack of functional effects of the treatment was correlated with lack of changes, as compared with SS, in the precision of muscle reinnervation and frequency of abnormally innervated muscle fibers. These results show that ES is an effective therapy in a spinal nerve injury model leading to complete restoration of function. Although this finding and the safety of the procedure are encouraging, the results for the facial nerve model suggest that brief ES may not be a universal treatment for nerve injuries. Anat Rec, 302:1304-1313, 2019. © 2019 Wiley Periodicals, Inc.

Topical insulin in neurotrophic keratopathy after resection of acoustic neuroma. / Insulina tópica en queratopatía neurotrófica tras resección de neurinoma del acústico.

CASE REPORT: A patient with a history of surgical resection of an acoustic neuroma presented with involvement of both the left facial nerve and the left trigeminal nerve. She initially consulted for exposure keratitis, but two weeks later presented with an infectious keratitis. After taking the corneal sample, she presented with persistent epithelial defect, which did not respond to medical management. Topical insulin was indicated, and a decrease in the area of the lesion was seen in the following 5 days. A therapeutic contact lens was also placed at that time and finally, two weeks after the initiation of insulin, the epithelial defect completely closed. DISCUSSION: This was a complex case due to the confluence of facial paralysis, neurotrophic keratitis, and infectious keratitis, which finally had a successful outcome. Topical insulin can be an effective adjuvant therapy in cases of neurotrophic ulcers that do not respond to standard therapy.

[Progress of the Mechanism of Acupuncture to Promote Repair of Facial Nerve Injury].

Facial nerve injury results in facial muscle movement disorders that interferes with patient's life. Acupuncture is an effective therapy for facial nerve injury, but its mechanism has not been clarified. The evidence supports that acupuncture can accelerate the repair of facial nerve injury by adjusting the electric wave of patient's facial muscle, improving facial blood circulation, and promoting the expression of cell and protein molecule.

The effects of lipoic acid and methylprednisolone on nerve healing in rats with facial paralysis.

OBJECTIVE: To investigate the effects of lipoic acid and methylprednisolone on nerve healing in rats with traumatic facial paralysis. MATERIALS AND METHODS: The rats were randomly divided into four groups, with six rats in the control group and eight each in the remaining three groups. The buccal branch of the facial nerve in all groups except the control group was traumatized by a vascular clamp for 40 minutes. Group 1 was given lipoic acid (LA), Group 2 was given methylprednisolone (MP), and Group 3 was given lipoic acid and methylprednisolone (LA + MP) for one week. Nerve stimulus thresholds were measured before trauma, after trauma and at the end of the one week treatment period. RESULTS: When the groups were compared with each other, post-treatment threshold levels of LA + MP were significantly lower than LA. Although post-treatment threshold levels of LA and MP were still higher than the control group, there was no significant difference between LA + MP and control values (p > .05). CONCLUSION: Lipoic acid has a positive effect on nerve healing and can enhance the effect of methylprednisolone treatment. It is a good alternative in cases where methylprednisolone cannot be used.

[Comparative Observation on Electroacupuncture and Manual Acupuncture in Rabbits with Facial Nerve Injury by Electron Microscope].

OBJECTIVE: To observe the effect of manual acupuncture and electroacupuncture (EA) on ultrastructure of facial nerve Schwann cells, myelin sheath and mitochondria in facial nerve injury rabbits, so as to explore its mechanism underlying improving facial palsy. METHODS: A total of 50 New Zealand rabbits were randomly divided into normal, sham-operation, model, MA and EA groups (n=10 in each group). Facial nerve injury model was made by clamping the facial nerve for 5 min using a pair of forceps. Manual needle stimulation (mild reinforcing-reducing) or EA (continuous wave, 20 Hz) was applied to "Dicang" (ST 4), "Xiaguan" (ST 7), "Taiyang" (EX-HN 5) and "Yangbai" (GB 14) on the injured sides for 4 weeks, 30 min each day. The facial nerve motion score was performed every 7 days. The ultrastructure of facial nerve was observed by electron microscope after 28 days' treatment. RESULTS: There were no significant differences in behavioral score and ultrastructure in normal and sham-operation groups (P<0.05). Compared with the normal group, facial nerve motion scores, ultrastructural morphological changes and the number of axons per unit area, myelin sheath thickness and axon area were worse in the model group (P<0.05). After treatment, facial nerve motion scores, ultrastructural morphological changes and the number of axons per unit area, myelin sheath thickness and axon area in the two treatment groups were better than those in the model group (P<0.05), and EA worked better than MA (P<0.05). CONCLUSIONS: In the treatment of facial nerve injury, EA can promote axoplasmic mitochondrial proliferation, myelin sheath recovery and axonal regeneration more effectively than MA, which may be one of the mechanisms that EA therapy is superior to MA.

Selective Stimulation of Facial Muscles Following Chronic Intraneural Electrode Array Implantation and Facial Nerve Injury in the Feline Model.

BACKGROUND: Our group has previously shown that activation of specific facial nerve (FN) fiber populations and selective activation of facial musculature can be achieved through acute intraneural multichannel microelectrode array (MEA) implantation in the feline model. HYPOTHESIS: Selective stimulation of facial muscles will be maintained in the setting of 1) chronic and 2) acute MEA implantation after FN injury and subsequent recovery. METHODS: This study included seven cats. In three cats with normal facial function, 4-channel penetrating MEAs were implanted chronically in the FN and tested biweekly for 6 months. Electrical current pulses were delivered to each channel individually, and elicited electromyographic (EMG) voltage outputs were recorded for each of several facial muscles. For FN injury experiments, two cats received a standardized hemostat-crush injury, and two cats received a transection-reapproximation injury to the FN main trunk. These four underwent acute implantation of MEA and EMG recording in terminal experiments 4 months postinjury. RESULTS: Stimulation through individual channels selectively activated restricted nerve populations, resulting in activation of individual muscles in cats with chronic MEA implantation and after nerve injury. Increasing stimulation current levels resulted in increasing EMG voltage responses in all patients. Nerve histology showed only minor neural tissue reaction to the implant. CONCLUSION: We have established in the animal model the ability of a chronically implanted MEA to selectively stimulate restricted FN fiber populations and elicit activations in specific facial muscles. Likewise, after FN injury, selective stimulation of restricted FN fiber populations and subsequent activation of discrete facial muscles can be achieved after acute MEA implantation.