Automated Segmentation of the Brainstem,Cranial Nerves and Vessels for Trigeminal Neuralgia and Hemifacial Spasm

Accurate localization of cranial nerves and responsible blood vessels is important for diagnosing trigeminal neuralgia(TN)and hemifacial spasm(HFS).Manual delineation of the nerves and vessels on medical images is time-consuming and labor-intensive.Due to the development of convolutional neural networks(CNNs),the performance of medical image segmentation has been improved.In this work,we investigate the plans for automated segmentation of cranial nerves and responsible vessels for TN and HFS,which has not been comprehensively studied before.Different inputs are given to the CNN to find the best training configuration of segmenting trigeminal nerves,facial nerves,responsible vessels and brainstem,including the image modality and the number of segmentation targets.According to multiple experiments with seven training plans,we suggest training with the combination of three-dimensional fast imaging employing steady-state acquisition(3D-FIESTA)and three-dimensional time-of-flight magnetic resonance angiography(3DTOF-MRA),and separate segmentation of cranial nerves and vessels.

Different sensitivities to rocuronium of the neuromuscular junctions innervated by normal/damaged facial nerves and somatic nerve in rats： the role of the presynaptic acetylcholine quantal release

Background Muscles present different responses to muscle relaxants, a mechanism of importance in surgeries requiring facial nerve evoked electromyography under general anaesthesia. The non-depolarizing muscle relaxants have multiple reaction formats in the neuromuscular junction, in which pre-synaptic quantal release of acetylcholine was one of the important mechanisms. This study was to compare the pre-synaptic quantal release of acetylcholine from the neuromuscular junctions innervated by normal/damaged facial nerves and somatic nerve under the effect of rocuronium in rats in vitro. Methods Acute right-sided facial nerve injury was induced by nerve crush axotomies. Both sided facial nerve connected orbicularis oris strips and tibial nerve connected gastrocnemius strips were isolated to measure endplate potentials （EPP） and miniature endplate potentials （MEPP） using an intracellular microelectrode gauge under different rocuronium concentrations. Then, the pre-synaptic quantal releases of acetylcholine were calculated by the ratios of the EPPs and the MEPPs, and compared among the damaged or normal facial nerve innervated orbicularis oris and tibial nerve innervated gastrocnemius. Results The EPP/MEPP ratios of the three neuromuscular junctions decreased in a dose dependent manner with the increase of the rocuronium concentration. With the concentrations of rocuronium being 5 pg/ml, 7.5 IJg/ml and 10 pg/ml, the decrease of the EPP/MEPP ratio in the damaged facial nerve group was greater than that in the normal facial nerve group. The decrease in the somatic nerve group was the biggest, with significant differences. Conclusions Rocuronium presented different levels of inhibition on the pre-synaptic quantal release of acetylcholine in the three groups of neuromuscular junctions. The levels of the inhibition showed the following sequence： somatic nerve 〉 damaged facial nerve 〉 normal facial nerve. The difference may be one of the reasons causing the different sensitivities to rocuronium among the muscles innervated by the normal/injured facial nerves and the somatic nerve. The results may provide some information for the proper usage of muscle relaxants in surgeries requiring electromyographic monitoring for the pre-surgically impaired facial nerves.

Development and Validation of a Deep Learning Predictive Model Combining Clinical and Radiomic Features for Short-Term Postoperative Facial Nerve Function in Acoustic Neuroma Patients

Objective This study aims to construct and validate a predictable deep learning model associated with clinical data and multi-sequence magnetic resonance imaging(MRI)for short-term postoperative facial nerve function in patients with acoustic neuroma.Methods A total of 110 patients with acoustic neuroma who underwent surgery through the retrosigmoid sinus approach were included.Clinical data and raw features from four MRI sequences(T1-weighted,T2-weighted,T1-weighted contrast enhancement,and T2-weighted-Flair images)were analyzed.Spearman correlation analysis along with least absolute shrinkage and selection operator regression were used to screen combined clinical and radiomic features.Nomogram,machine learning,and convolutional neural network(CNN)models were constructed to predict the prognosis of facial nerve function on the seventh day after surgery.Receiver operating characteristic(ROC)curve and decision curve analysis(DCA)were used to evaluate model performance.A total of 1050 radiomic parameters were extracted,from which 13 radiomic and 3 clinical features were selected.Results The CNN model performed best among all prediction models in the test set with an area under the curve(AUC)of 0.89(95%CI,0.84–0.91).Conclusion CNN modeling that combines clinical and multi-sequence MRI radiomic features provides excellent performance for predicting short-term facial nerve function after surgery in patients with acoustic neuroma.As such,CNN modeling may serve as a potential decision-making tool for neurosurgery.

The Anti-Inflammatory Effects of NaCl with KCl as a Potent Graphene Exfoliator in a Patient with Guillaine-Barré Syndrome and Facial Nerve Palsy

Guillain-Barré syndrome is a rare but fatal autoimmune disease of unknown origin. Infectious disease is the most common etiology of Guillain-Barré syndrome. We had a 75-year-old female patient with Guillain-Barré syndrome and a 90-year-old male patient with facial nerve palsy admitted to our hospital. Both patients experienced recovery from early Guillain-Barré syndrome and peripheral facial nerve palsy after receiving intravenous infusion of NaCl with KCl solution and taking vitamin C.

Autogenous inside-out versus standard vein and skeletal muscle-combined grafting for facial nerve repair

BACKGROUND： In the repair of nerve defects, collapse of the venous wall, as a result of vein grafting alone, could impede nerve regeneration. Therefore, vein lumens filled with muscle and nerve segments have been used to bridge nerve defects. OBJECTIVE： To compare the effects of autogenous, inside-out, vein-skeletal, muscle-combined grafting versus standard, vein-skeletal, muscle-combined grafting for the repair of facial nerve defects. DESIGN, TIME AND SETTING： A randomized, controlled, neuroanatomical, animal study was performed at the Animal Experimental Center and Laboratories of the Capital Medical University Xuanwu Hospital and the Peking Union Medical College Hospital from September 2007 to October 2008.MATERIALS： A total of 10 healthy, male, New Zealand rabbits, aged 6 months, were randomly assigned to inside-out, vein-skeletal, muscle-combined grafting and standard, vein-skeletal, muscle-combined grafting groups, with 5 rabbits in each group. METHODS： A 20-mm gap in the buccal branch of the right facial nerve was made in each animal, which was respectively repaired with inside-out, vein-skeletal, muscle-combined grafts or standard vein-skeletal muscle-combined grafts.MAIN OUTCOME MEASURES： At 6 months after implantation, evoked maximal compound muscle action potentials were recorded on bilateral facial nerves using electromyogram. Myelinated nerve fibers of the regenerating nerves were quantified using myelin sheath osmic acid staining. RESULTS： There was no significant difference between the groups in terms of ratios of bilateral amplitude and latency of compound muscle action potential （P 〉 0.05）. Moreover, morphology of regenerating nerves and quantity of myelinated nerve fibers were similar between the groups （P 〉 0.05）. CONCLUTION： Compared with standard vein grafting, the inside-out vein grafting did not significantly improve nerve regeneration. Therefore, it is not necessary to utilize inside-out vein grafting for the repair of nerve defects, in particular with the combined use of autogenous vein and skeletal muscle grafts.

End-to-end and end-to-side neurorrhaphy between thick donor nerves and thin recipient nerves:an axon regeneration study in a rat model

During nerve reconstruction,nerves of different thicknesses are often sutured together using end-to-side neurorrhaphy and end-to-end neurorrhaphy techniques.In this study,the effect of the type of neurorrhaphy on the number and diameter of regenerated axon fibers was studied in a rat facial nerve repair model.An inflow-type end-to-side and end-to-end neurorrhaphy model with nerve stumps of different thicknesses（2：1 diameter ratio） was created in the facial nerve of 14 adult male Sprague-Dawley rats.After 6 and 12 weeks,nerve regeneration was evaluated in the rats using the following outcomes：total number of myelinated axons,average minor axis diameter of the myelinated axons in the central and peripheral sections,and axon regeneration rate.End-to-end neurorrhaphy resulted in a significantly greater number of regenerated myelinated axons and rate of regeneration after 6 weeks than end-to-side neurorrhaphy;however,no such differences were observed at 12 weeks.While the regenerated axons were thicker at 12 weeks than at 6 weeks,no significant differences in axon fiber thickness were detected between end-to-end and end-toside neurorrhaphy.Thus,end-to-end neurorrhaphy resulted in greater numbers of regenerated axons and increased axon regeneration rate during the early postoperative period.As rapid reinnervation is one of the most important factors influencing the restoration of target muscle function,we conclude that end-to-end neurorrhaphy is desirable when suturing thick nerves to thin nerves.

Olfactory ensheathing cells promote nerve regeneration and functional recovery after facial nerve defects

Olfactory ensheathing cells from the olfactory bulb and olfactory mucosa have been tbund to increase axonal sprouting and pathfinding and promote the recovery of vibrissae motor performance in facial nerve transection injured rats. However, it is not yet clear whether olfactory ensheathing cells promote the reparation of facial nerve defects in rats. In this study, a collagen sponge and silicone tube neural conduit was implanted into the 6-mm defect of the buccal branch of the facial nerve in adult rats. Olfactory ensheathing cells isolated from the olfactory bulb of newborn Sprague-Dawley rats were injected into the neural conduits connecting the ends of tile broken nerves, the morphology and function of the regenerated nerves were compared between the rats implanted with olfactory ensheathing cells with the rats injected with saline. Facial paralysis was assessed. Nerve electrography was used to measure facial nerve-induced action potentials. Visual inspection, anatomical microscopy and hematoxylin-eosin staining were used to assess the histomorphology around the trans planted neural conduit and the morphology of the regenerated nerve. Using fluorogold retrograde tracing, toluidine blue staining and lead uranyl acetate staining, we also measured the number of neurons in the anterior exterior lateral f：acial nerve motor nucleus, the number of myelinated nerve fibers, and nerve fiber diameter and myelin sheath thickness, respectively. After surgery, olfactory ensheathing cells de- creased facial paralysis and the latency of the facial nerve-induced action potentials. There were no differences in the general morphology of the regenerating nerves between the rats implanted with olfactory ensheathing cells and the rats injected with saline. Between-group results showed that olfactory ensheathing cell treatment increased the number of regenerated neurons, improved nerve fiber morphology, and increased the number of myelinated nerve fibers, nerve fiber diameter, and myelin sheath thickness. In conclusion, implantation of olfactory ensheathing cells can promote regeneration and functional recovery after facial nerve damage in rats.

Transcriptome analysis of molecular mechanisms underlying facial nerve injury repair in rats

Although the transcriptional alterations inside the facial nucleus after facial nerve injury have been well studied,the gene expression changes in the facial nerve trunk after injury are still unknown.In this study,we established an adult rat model of facial nerve crush injury by compressing the right lateral extracranial nerve trunk.Transcriptome sequencing,differential gene expression analysis,and cluster analysis of the injured facial nerve trunk were performed,and 39 intersecting genes with significant variance in expression were identified.Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway analyses of the 39 intersecting genes revealed that these genes are mostly involved in leukocyte cell-cell adhesion and phagocytosis and have essential roles in regulating nerve repair.Quantitative real-time polymerase chain reaction assays were used to validate the expression of pivotal genes.Finally,nine pivotal genes that contribute to facial nerve recovery were identified,including Arhgap30,Akr1b8,C5ar1,Csf2ra,Dock2,Hcls1,Inpp5d,Sla,and Spi1.Primary Schwann cells were isolated from the sciatic nerve of neonatal rats.After knocking down Akr1b8 in Schwann cells with an Akr1b8-specific small interfering RNA plasmid,expression levels of monocyte chemoattractant protein-1 and interleukin-6 were decreased,while cell proliferation and migration were not obviously altered.These findings suggest that Akr1b8 likely regulates the interaction between Schwann cells and macrophages through regulation of cytokine expression to promote facial nerve regeneration.This study is the first to reveal a transcriptome change in the facial nerve trunk after facial nerve injury,thereby revealing the potential mechanism underlying repair of facial nerve injury.This study was approved by the Animal Ethics Committee of Nantong University,China in 2018(approval No.S20180923-007).

Artificial facial nerve reflex restores eyelid closure following orbicularis oculi muscle denervation

To date, treatment of peripheral facial paralysis has focused on preservation of facial nerve integrity. However, with seriously damaged facial nerve cases, it is difficult to recover anatomical and functional integrity using present therapies. Therefore, the present study utilized artificial facial nerve reflex to obtain orbicularis oculi muscle （OOM） electromyography signals on the uninjured side through the use of implanted recording electrodes. The implanted electrical chips analyzed facial muscle motion on the uninjured side and triggered an electrical stimulator to emit current pulses, which resulted in stimulation of injured OOM contraction and maintained bilateral symmetry and consistency. Following signal recognition, extraction, and computer analysis, electromyography signals in the uninjured OOM resulted in complete eyelid closure, which was consistent with the voltage threshold for eye closure. These findings suggested that artificial facial nerve reflex through the use of implanted microelectronics in unilateral peripheral facial paralysis could restore eyelid closure following orbicularis oculi muscle denervation.

Scala tympani drill-out technique for oval window atresia with malformed facial nerve: A report of three cases

Objective: To report a scala tympani drill-out technique for managing malformed facial nerve covering the entire oval window(OW).Methods: Data from three cases with OW atresia, malformed stapes and abnormal facial nerve courses were reported, in which a scala tympani drill-out technique was employed with a TORP between the tympanic membrane and scala tympani fenestration for hearing reconstruction.Results: Air conduction hearing improved in two of the three cases following surgery. In the third case, there was no improvement in air conduction hearing following a canal wall up mastoidectomy and tympanoplasty. There were no vertigo, tinnitus or sensorineural hearing loss in the three cases.Conclusion: The scala tympani drill-out technique, which is basically fenestration at the initial part of the basal turn, provides a choice in hearing reconstruction when the OW is completely covered by abarrently coursed facial nerve.

Structural remodeling in related brain regions in patients with facial synkinesis

Facial synkinesis is a troublesome sequelae of facial nerve malfunction.It is difficult to recover from synkinesis,despite improved surgical techniques for isolating the peripheral facial nerve branches.Furthermore,it remains unclear whether long-term dysfunction of motor control can lead to irreversible plasticity-induced structural brain changes.This case-control study thus investigated the structural brain alterations associated with facial synkinesis.The study was conducted at Shanghai Ninth People’s Hospital,Shanghai Jiao Tong University School of Medicine,China.Twenty patients with facial synkinesis(2 male and 18 female,aged 33.35±6.97 years)and 19 healthy volunteers(2 male and 17 female,aged 33.21±6.75 years)underwent magnetic resonance imaging,and voxel-based and surface-based morphometry techniques were used to analyze data.There was no significant difference in brain volume between patients with facial synkinesis and healthy volunteers.Patients with facial synkinesis exhibited a significantly reduced cortical thickness in the contralateral superior and inferior temporal gyri and a reduced sulcal depth of the ipsilateral precuneus compared with healthy volunteers.In addition,sulcal depth of the ipsilateral precuneus was negatively correlated with the severity of depression.These findings suggest that there is a structural remodeling of gray matter in patients with facial synkinesis after facial nerve malfunction.This study was approved by the Ethics Review Committee of the Ninth People’s Hospital,Shanghai Jiao Tong University School of Medicine,China(approval No.2017-365-T267)on September 13,2017,and was registered with the Chinese Clinical Trial Registry(registration number:ChiCTR1800014630)on January 25,2018.

Immunobiology of Facial Nerve Repair and Regeneration

Immunobiological study is a key to revealing the important basis of facial nerve repair and regeneration for both research and development of clinic treatments. The microenvironmental changes around an injuried facial motoneuron, i.e., the aggregation and expression of various types of immune cells and molecules in a dynamic equilibrium, impenetrate from the start to the end of the repair of an injured facial nerve. The concept of 'immune microenvironment for facial nerve repair and regeneration', mainly concerns with the dynamic exchange between expression and regulation networks and a variaty of immune cells and immune molecules in the process of facial nerve repair and regeneration for the maintenance of a immune microenvironment favorable for nerve repair. Investigation on microglial activation and recruitment, T cell behavior, cytokine networks, and immunological cellular and molecular signaling pathways in facial nerve repair and regeneration are the current hot spots in the research on immunobiology of facial nerve injury. The current paper provides a comprehensive review of the above mentioned issues. Research of these issues will eventually make immunological interventions practicable treatments for facial nerve injury in the clinic.

Classification of facial nerve aberration in congenital malformation of middle ear:Implications for surgery of hearing restoration

Objectives: Facial nerve aberration is the most troublesome situation in congenital malformations of middle ear.The aim of our study is to investigate its imaging and clinical features as well as relevant choice of surgical techniques for hearing improvement.Methods: A retrospective study involving review of clinical data of 227 patients(256 ears) with congenital middle ear anomaly was undertaken, including preoperative computed tomography(CT) data, surgical records and videos.Results: Aberration involving intratemporal facial nerve was found in 82/256 ears(32.03%) with congenital middle ear anomaly. The most common forms of aberration included overhanging over the oval window(50/82 ears, 60.98%), bifurcation(3/82 ears, 3.66%) and transverse over the promontory(3/82 ears, 3.66%), counting for 68.29%(56/82) of the cases with facial nerve aberration. Concomitant stapes malformation was found in 76/82 ears(92.68%) and atresia or stenosis of the oval window in 27/82 ears(32.93%). In 9/82 ears(10.98%) both stapes and oval window was absent. Elective surgeries for the purpose of hearing improvement included stapodotomy + piston implantation, labyrinthotomy, labyrinthotomy + total ossicular replacement prosthesis(TORP) implantation and Vibrant Soundbridge(VSB) implantation.Conclusion: The majority of facial nerve aberration in congenital malformation of middle ear involves displacement of facial nerve, in addition to concomitant malformations of the stapes and/or oval window, which may influence the choice of surgery for hearing improvement. VSB implantation may be considered as a useful option.

Muscarinic receptor-mediated calcium changes in a rat model of facial nerve nucleus injury

The muscarinic receptor modulates intracellular free calcium ion levels in the facial nerve nucleus via different channels. In the present study, muscarinic receptor-mediated free calcium ions levels were detected by confocal laser microscopy in the facial nerve nucleus following facial nerve injury in rats. There was no significant difference in muscarinic receptor expression at the affected facial nerve nucleus compared with expression prior to injury, but muscarinic receptor-mediated free calcium ion levels increased in the affected side following facial nerve injury （P 〈 0.01）. At day 30 after facial nerve injury, 50 pmol/L muscarinic-mediated free calcium ion levels were significantly inhibited at the affected facial nerve nucleus in calcium-free artificial cerebrospinal fluid, and the change range was 82% of artificial cerebrospinal fluid （P 〈 0.05）. These results suggest that increased free calcium ion concentrations are achieved by intracellular calcium ion release, and that the transmembrane flow of calcium ions is also involved in this process.

Repairing whole facial nerve defects with xenogeneic acellular nerve grafts in rhesus monkeys

Acellular nerve allografts conducted via chemical extraction have achieved satisfactory results in bridging whole facial nerve defects clinically,both in terms of branching a single trunk and in connecting multiple branches of an extratemporal segment.However,in the clinical treatment of facial nerve defects,allogeneic donors are limited.In this experiment,we exposed the left trunk and multiple branches of the extratemporal segment in six rhesus monkeys and dissected a gap of 25 mm to construct a monkey model of a whole left nerve defect.Six monkeys were randomly assigned to an autograft group or a xenogeneic acellular nerve graft group.In the autograft group,the 25-mm whole facial nerve defect was immediately bridged using an autogenous ipsilateral great auricular nerve,and in the xenogeneic acellular nerve graft group,this was done using a xenogeneic acellular nerve graft with trunk-branches.Examinations of facial symmetry,nerve-muscle electrophysiology,retrograde transport of labeled neuronal tracers,and morphology of the regenerated nerve and target muscle at 8 months postoperatively showed that the faces of the monkey appeared to be symmetrical in the static state and slightly asymmetrical during facial movement,and that they could actively close their eyelids completely.The degree of recovery from facial paralysis reached House-Brackmann grade II in both groups.Compound muscle action potentials were recorded and orbicularis oris muscles responded to electro-stimuli on the surgical side in each monkey.Fluoro Gold-labeled neurons could be detected in the facial nuclei on the injured side.Immunohistochemical staining showed abundant neurofilament-200-positive axons and soluble protein-100-positive Schwann cells in the regenerated nerves.A large number of mid-graft myelinated axons were observed via methylene blue staining and a transmission electron microscope.Taken together,our data indicate that xenogeneic acellular nerve grafts from minipigs are safe and effective for repairing whole facial nerve defects in rhesus monkeys,with an effect similar to that of autologous nerve transplantation.Thus,a xenogeneic acellular nerve graft may be a suitable choice for bridging a whole facial nerve defect if no other method is available.The study was approved by the Laboratory Animal Management Committee and the Ethics Review Committee of the Affiliated Wuxi No.2 People's Hospital of Nanjing Medical University,China(approval No.2018-D-1)on March 15,2018.

Negative regulation of gamma-aminobutyric acid type A receptor on free calcium ion levels following facial nerve injury

Previous studies have demonstrated that muscarinic, and nicotinic receptors increase free Ca2＋ levels in the facial nerve nucleus via various channels following facial nerve injury. However, intracellular Ca2＋ overload can trigger either necrotic or apoptotic cell death. Gamma-aminobutyric acid （GABA）, an important inhibitory neurotransmitter in the central nervous system, exists in the facial nerve nucleus. It is assumed that GABA negatively regulates free Ca2＋ levels in the facial nerve nucleus. The present study investigated GABA type A （GABAA） receptor expression in the facial nerve nucleus in a rat model of facial nerve injury using immunohistochemistry and laser confocal microscopy, as well as the regulatory effects of GABAA receptor on nicotinic receptor response following facial nerve injury. Subunits α1, α3, α5, β1, β2, δ, and γ3 of GABAA receptors were expressed in the facial nerve nucleus following facial nerve injury. In addition, GABAA receptor expression significantly inhibited the increase in nicotinic receptor-mediated free Ca2＋ levels in the facial nerve nucleus following facial nerve injury in a concentration-dependent fashion. These results suggest that GABAA receptors exhibit negative effects on nicotinic receptor responses following facial nerve injury.

Nicotine alpha 4 beta 2 receptor-mediated free calcium in an animal model of facial nucleus injury

Previous studies have demonstrated that the cholinergic system, via nicotinic receptors, regulates intracellular free calcium levels in the facial nucleus under normal physiological conditions. However, the regulation of nicotinic receptors on free calcium levels following facial nerve injury remains unclear. In the present study, an animal model of facial nerve injury was established, and changes in nicotinic receptor expression following facial nerve injury in rats were detected using reverse transcription polymerase chain reaction. Nicotinic receptor-mediated changes of free calcium levels following facial nucleus injury were determined by laser confocal microscopy. Results showed no significant difference in nicotinic receptor expression between the normal group and the affected facial nerve nucleus. The nicotinic receptor a4132 subtype increased free calcium levels following facial nerve injury by promoting calcium transmembrane influx, and L-type voltage-gated calcium channel-mediated influx of calcium ions played an important role in promoting calcium transmembrane influx. The nicotinic receptor-mediated increase of free calcium levels following facial nerve injury provides an important mechanism for the repair of facial nerve injury.

Traumatic facial nerve paralysis dilemma. Decision making and the novel role of endoscope

Objective: The management of traumatic facial nerve paralysis(FNP) has remained a controversial issue with conflicting findings arguing between surgical decompression and conservative management.However, recent advances in endoscopic surgery may consolidate the management plan for this condition.Methods: This prospective clinical study included patients with posttraumatic FNP at a tertiary referral center. Patients were categorized in two main groups: surgical and conservative. Indications for surgery included patients with immediate and complete FNP, no improvement in facial function on medical treatment, with electroneurography showing >90% degeneration or electromyography showing fibrillation potential. Patients who did not satisfy this criterion received the conservative approach. The transcanal endoscopic approach(TEA) or endoscopic assisted transmastoid approach was performed for facial nerve decompression in the surgical group.Outcome: The main outcome was facial function improvement, assessed using the House Brackmann grading scale(HBGS) 6 months after surgery, and hearing state assessed using the air bone gap(ABG).Results: The study included 38 patients, of whom 15 underwent had surgical decompression and 23underwent conservative therapy. A significant improvement in facial nerve function from a mean of4.66 ± 0.97 to 1.71 ± 0.69(P = 0.001) and ABG from a median of 30(10-40) to 20(10-25)(P = 0.002)was observed.Conclusion: Decision-making in cases of traumatic FNP is critical. The geniculate ganglion and tympanic segment were the most commonly affected areas in FNP cases. The TEA represents the most direct and least invasive approach for this area.

Agmatine promotes expression of brain-derived neurotrophic factor in brainstem facial nucleus in the rat facial nerve injury model

BACKGROUND： Studies have shown that agmatine can reduce inhibition of neuronal regeneration by increasing cyclic adenosine monophosphate and brain-derived neurotrophic factor （BDNF） in the hippocampus of morphine-dependent rats. The hypothesis that agmatine exerts similar effects on facial nerve injury deserves further analysis. OBJECTIVE： To study the effects of peritoneal agmatine injection on BDNF levels in the rat brainstem after facial nerve injury. DESIGN, TIME AND SETTING： A controlled animal experiment was performed at the Department of Otolaryngology-Head and Neck Surgery at the Second Affiliated Hospital, Chongqing University of Medical Sciences （Chongqing, China）, between October and December in 2007. MATERIALS： Twenty-four male Sprague-Dawley rats were randomly divided into a control, a lesion, and an agmatine treatment group, with eight rats in each group. Bilateral facial nerve anastomosis was induced in the lesion and agmatine treatment groups, while the control group remained untreated. A rat BDNF Enzyme-linked immunosorbent assay kit was used to measure BDNF levels in the brainstem facial nucleus. METHODS： Starting on the day of lesion, the agmatine group received a peritoneal injection of 100 mg/kg agmatine, once per day, for a week, whereas rats in the lesion group received saline injections. MAIN OUTCOME MEASURES： BDNF levels in the brainstem containing facial nucleus were measured by ELISA. RESULTS： Twenty-four rats were included in the final analysis without any loss. Two weeks after lesion, BDNF levels were significantly higher in the lesion group than in the control group （P 〈 0.01）. A significant increase was noted in the agmatine group compared to the lesion group （P 〈 0.01）. CONCLUSION： Agmatine can substantially increase BDNF levels in the rat brainstem after facial nerve injury.

Application of a venous conduit as a stent for repairing rabbit facial nerve injury

BACKGROUND： Recently, many investigators have tried to use natural biomaterials, such as, artery, vein, decalcified bone, etc., as conduits for nerve repair. However, immunological rejection of conduits made of natural biomaterials limits their application. Therefore, it is essential to identify more suitable types of biomaterials. OBJECTIVE： To observe the characteristics of a bioengineering processing method using venous conduit as a stent for repairing facial nerve injury. DESIGN： A controlled observational experiment. SETTING： Animal Laboratories of the Third Hospital Affiliated to Sun Yat-sen University and the 157 Hospital. MATERIALS： Thirty-three male New Zealand rabbits of pure breed, weighing 1.5 to 2.0 kg, were provided by Medical Experimental Animal Room of Sun Yat-sen University. The protocol was carried out in accordance with animal ethics guidelines for the use and care of animals. Venous conduits and autogenous nerves were transplanted into the left and right cheeks, respectively. Eleven animals were chosen for anatomical observations at 5, 10 and 15 weeks after surgery. METHODS： This experiment was carried out in the Animal Laboratories of the Third Hospital Affdiated to Sun Yat-sen University and the 157 Hospital between May and November 2006. After animals were anesthetized, 15 mm of retromandibular vein was harvested for preparing a venous conduit. Approximately 3 cm of low buccal branch of facial nerve was exposed. A segment of 1.2 cm nerve was resected from the middle, and a gap of 1.5 cm formed due to bilateral retraction. The prepared venous conduit of 1.5 cm was sutured to the outer membrane of the severed ends of the nerve. Muscle and skin were sutured layer by layer. Using the same above-mentioned method, the low buccal branch of right autogenous facial nerve was resected, and the left facial nerve segment from the same animal was transplanted using end-to-end neurorrhaphy for control. MAIN OUTCOME MEASURES： （1）Post-operatively, food intake, vibrissae activity and wound healing of each animal were observed daily. （2） Animals were anesthetized at 5, 10 and 15 weeks after operation for observing the structural change of the venous conduit, the appearance of regenerated nerve, and the relationship between conduit and peripheral muscle tissue. （3） The action potential and latency of bilateral nerves of animals were measured by electrophysiologic examination, and nerve conduction velocity was calculated. （4）Neural myelination and neurite growth were observed by histological staining using an optical microscope. RESULTS： Thirty-three New Zealand rabbits were involved in the final analysis. （1）Immediately following the operation, vibrissae activity and orbicularis otis muscle activity of the upper lip on venous conduit side were more prominent, and their amplitudes of movement were larger as compared with autogenous nerve side. （2） At postoperative 10 weeks, by visual inspection, we found that on the venous conduit side, the venous conduit exhibited membrane structure which encased regenerated nerve. Regenerated nerve adhered to the muscle edge of orbicularis oris muscle. Muscle and nerve could be separated with a forceps. The muscle of musculus orbicularis oris of rabbit was darker and thicker as compared with autogenous nerve side. After the venous conduit was longitudinally split, the regenerated nerve and nerves at two the severed ends were connected together. When compared with postoperative 5 weeks, the connected nerve was thickened, texture was tough and its middle part was thicker than its two ends. On the autogenous nerve side, the regenerated nerve stem was enwrapped by scar tissue. It was bulky and adhered to peripheral muscle. Its neural profile structure was unclear. The two stomas were obviously enlarged. （3）At postoperative 10 weeks and 15 weeks, nerve action potentials could be elicited from both the venous conduit and autologous nerve side. The mean nerve conduction velocity on the venous conduit side was greater than that of the autologous nerve side. （4）At postoperative 10 weeks, using histochemical staining, it was found that in the venous conduit, regenerated medullated nerve fibers were densely distributed, with well split facial nerve structure, while on the autologous nerve side, nerve fibers were sparsely scattered, with immature medullated nerve structure. CONCLUSION： Biological natural venous conduit processed by bioengineering technology overcomes the tissue inflammatory reactions and connective tissue reactions caused by natural biomaterials. It is more conducive to promote neural regeneration and functional recovery than autologous nerve transplantation.