Vagus nerve stimulation in cerebral stroke:biological mechanisms,therapeutic modalities,clinical applications,and future directions

Stroke is a major disorder of the central nervous system that poses a serious threat to human life and quality of life.Many stro ke victims are left with long-term neurological dysfunction,which adversely affects the well-being of the individual and the broader socioeconomic impact.Currently,poststroke brain dysfunction is a major and difficult area of treatment.Vagus nerve stimulation is a Food and Drug Administration-approved exploratory treatment option for autis m,refractory depression,epilepsy,and Alzheimer’s disease.It is expected to be a novel therapeutic technique for the treatment of stroke owing to its association with multiple mechanisms such as alte ring neurotransmitters and the plasticity of central neuro ns.In animal models of acute ischemic stroke,vagus nerve stimulation has been shown to reduce infarct size,reduce post-stroke neurological damage,and improve learning and memory capacity in rats with stroke by reducing the inflammatory response,regulating bloodbrain barrier permeability,and promoting angiogenesis and neurogenesis.At present,vagus nerve stimulation includes both invasive and non-invasive vagus nerve stimulation.Clinical studies have found that invasive vagus nerve stimulation combined with rehabilitation therapy is effective in im proving upper limb motor and cognitive abilities in stroke patients.Further clinical studies have shown that non-invasive vagus nerve stimulation,including ear/ce rvical vagus nerve stimulation,can stimulate vagal projections to the central nervous system similarly to invasive vagus nerve stimulation and can have the same effect.In this paper,we first describe the multiple effects of vagus nerve stimulation in stroke,and then discuss in depth its neuroprotective mechanisms in ischemic stroke.We go on to outline the res ults of the current major clinical applications of invasive and non-invasive vagus nerve stimulation.Finally,we provide a more comprehensive evaluation of the advantages and disadvantages of different types of vagus nerve stimulation in the treatment of cerebral ischemia and provide an outlook on the developmental trends.We believe that vagus nerve stimulation,as an effective treatment for stroke,will be widely used in clinical practice to promote the recovery of stroke patients and reduce the incidence of disability.

Vagus nerve stimulation is a potential treatment for ischemic stroke

Microglia are the brain’s primary innate immune cells,and they are activated and affect pro-inflammatory phenotype or regulatory phenotype after ischemic stroke.Vagus nerve stimulation was shown to activate microglial phenotypic changes and exhibit neuroprotective effects in ischemia/reperfusion injury.In this study,we established rat models of ischemic stroke by occlusion of the middle cerebral artery and performed vagus nerve stimulation 30 minutes after modeling.We found that vagus nerve stimulation caused a shift from a pro-inflammatory phenotype to a regulatory phenotype in microglia in the ischemic penumbra.Vagus nerve stimulation decreased the levels of pro-inflammatory phenotype markers inducible nitric oxide synthase and tumor necrosis factorαand increased the expression of regulatory phenotype markers arginase 1 and transforming growth factorβthrough activatingα7 nicotinic acetylcholine receptor expression.Additionally,α7 nicotinic acetylcholine receptor blockade reduced the inhibition of Toll-like receptor 4/nuclear factor kappa-B pathwayassociated proteins,including Toll-like receptor 4,myeloid differentiation factor 88,I kappa B alpha,and phosphorylated-I kappa B alpha,and also weakened the neuroprotective effects of vagus nerve stimulation in ischemic stroke.Vagus nerve stimulation inhibited Toll-like receptor 4/nuclear factor kappa-B expression through activatingα7 nicotinic acetylcholine receptor and regulated microglial polarization after ischemic stroke,thereby playing a role in the treatment of ischemic stroke.Findings from this study confirm the mechanism underlying vagus nerve stimulation against ischemic stroke.

Vagus nerve stimulation protects against cerebral injury after cardiopulmonary resuscitation by inhibiting inflammation through the TLR4/NF-κB and α7nAChR/JAK2 signaling pathways

BACKGROUND: Our previous research proved that vagus nerve stimulation(VNS) improved the neurological outcome after cardiopulmonary resuscitation(CPR) by activating α7 nicotinic acetylcholine receptor(α7nAChR) in a rat model, but the underlying mechanism of VNS in neuroprotection after CPR remains unclear.METHODS: In vivo, we established a mouse model of cardiac arrest(CA)/CPR to observe the survival rate, and the changes in inflammatory factors and brain tissue after VNS treatment. In vitro, we examined the effects of α7nAChR agonist on ischemia/reperfusion(I/R)-induced inflammation in BV2 cells under oxygen-glucose deprivation/reoxygenation(OGD/R) conditions. We observed the changes in cell survival rate, the levels of inflammatory factors, and the expressions of α7nAChR/Janus kinase 2(JAK2) and toll-like receptor 4(TLR4)/nuclear factor-κB(NF-κB).RESULTS: In vivo, VNS preconditioning enhanced functional recovery, improved the survival rate, and reduced hippocampal CA1 cell damage, and the levels of inflammatory mediators after CA/CPR. The application of α7nAChR agonists provided similar effects against cerebral injury after the return of spontaneous circulation(ROSC), while α7nAChR antagonists reversed these neuroprotective impacts. The in vitro results mostly matched the findings in vivo. OGD/R increased the expression of tumor necrosis factor-alpha(TNF-α), TLR4 and NF-κB p65. When nicotine was added to the OGD/R model, the expression of TLR4, NF-κB p65, and TNF-α decreased, while the phosphorylation of JAK2 increased, which was prevented by preconditioning with α7nAChR or JAK2 antagonists.CONCLUSION: The neuroprotective effect of VNS correlated with the activation of α7nAChR. VNS may alleviate cerebral IR injury by inhibiting TLR4/NF-κB and activating the α7nAChR/JAK2 signaling pathway.

Advances of Research on Auricular Vagus Nerve Stimulation for Treatment of Nervous System Diseases

As a new type of nerve regulation technology, Vagus Nerve Stimulation is currently used in the treatment of nervous system diseases. Auricular Vagus Nerve Stimulation has become one of the research hotspots in this field, because there is no implantation risk. However, there is no unified standard for the treatment parameters of aVNS for nervous system diseases. In this paper, the research progress of the anatomical structure and parameters of the vagus nerve and its role in nervous system diseases are reviewed to provide basis for further research.

Wake-promoting effects of vagus nerve stimulation after traumatic brain injury: upregulation of orexin-A and orexin receptor type 1 expression in the prefrontal cortex

Orexins, produced in the lateral hypothalamus, are important neuropeptides that participate in the sleep/wake cycle, and their expres- sion coincides with the projection area of the vagus nerve in the brain. Vagus nerve stimulation has been shown to decrease the amounts of daytime sleep and rapid eye movement in epilepsy patients with traumatic brain injury. In the present study, we investigated whether vagus nerve stimulation promotes wakefulness and affects orexin expression. A rat model of traumatic brain injury was established using the free fall drop method. In the stimulated group, rats with traumatic brain injury received vagus nerve stimulation （frequency, 30 Hz, current, 1.0 mA; pulse width, 0.5 ms; total stimulation time, 15 minutes）. In the antagonist group, rats with traumatic brain injury were intracerebroventricularly injected with the orexin receptor type 1 （OXIR） antagonist SB334867 and received vagus nerve stimulation. Changes in consciousness were observed after stimulation in each group. Enzyme-linked immunosorbent assay, western blot assay and immunohistochemistry were used to assess the levels of orexin-A and OX1R expression in the prefrontal cortex. In the stimulated group, consciousness was substantially improved, orexin-A protein expression gradually increased within 24 hours after injury and OX1R expres- sion reached a peak at 12 hours, compared with rats subjected to traumatic brain injury only. In the antagonist group, the wake-promoting effect of vagus nerve stimulation was diminished, and orexin-A and OX1R expression were decreased, compared with that of the stim- ulated group. Taken together, our findings suggest that vagus nerve stimulation promotes the recovery of consciousness in comatose rats after traumatic brain injury. The upregulation of orexin-A and OXIR expression in the prefrontal cortex might be involved in the wake-promoting effects of vagus nerve stimulation.

Neuroprotective effects of vagus nerve stimulation on traumatic brain injury

Previous studies have shown that vagus nerve stimulation can improve the prognosis of trau- matic brain injury. The aim of this study was to elucidate the mechanism of the neuroprotective effects of vagus nerve stimulation in rabbits with brain explosive injury. Rabbits with brain ex- plosive injury received continuous stimulation （10 V, 5 Hz, 5 ms, 20 minutes） of the right cervical vagus nerve. Tumor necrosis factor-a, interleukin-l~ and interleukin-10 concentrations were detected in serum and brain tissues, and water content in brain tissues was measured. Results showed that vagus nerve stimulation could reduce the degree of brain edema, decrease tumor necrosis factor-a and interleukin-1β concentrations, and increase interleukin-10 concentration after brain explosive injury in rabbits. These data suggest that vagus nerve stimulation may exert neuroprotective effects against explosive injury via regulating the expression of tumor necrosis factor-a, interleukin-1 β and interleukin-10 in the serum and brain tissue.

The mechanisms through which auricular vagus nerve stimulation protects against cerebral ischemia/reperfusion injury

Previous studies have shown that vagus nerve stimulation can improve patients' locomotor function.The stimulation of the auricular vagus nerve,which is the only superficial branch of the vagus nerve,may have similar effects to vagus nerve stimulation.However,the precise mechanisms remain poorly understood.In this study,rat models of cerebral ischemia/reperfusion injury were established by modified Longa ligation.Twenty-four hours later,7-day auricular vagus nerve stimulation was performed.The results showed that auricular vagus nerve stimulation promoted the secretion of acetylcholine,inhibited the secretion of interleukin-1β,interleukin-6,and tumor necrosis factor-α,and reduced connexin 43 phosphorylation in the ischemic penumbra and motor cortex,promoting locomotor function recovery in rats with cerebral ischemia/reperfusion injury.These findings suggested that auricular vagus nerve stimulation promotes the recovery of locomotor function in rats with cerebral ischemia/reperfusion injury by altering the secretion of acetylcholine and inflammatory factors and the phosphorylation of connexin 43.This study was approved by the Animal Use and Management Committee of Shanghai University of Traditional Chinese Medicine on November 8,2019(approval No.PZSHUTCM191108014).

Left-sided vagus nerve stimulation improves cardiopulmonary resuscitation outcomes in rats as effectively as right-sided vagus nerve stimulation

BACKGROUND: Our group previously reported that right-sided vagus nerve stimulation(RVNS) significantly improved outcomes after cardiopulmonary resuscitation(CPR) in a rat model of cardiac arrest(CA). However, whether left-sided vagus nerve stimulation(LVNS) could achieve the same effect as RVNS in CPR outcomes remains unknown.METHODS: A rat model of CA was established using modified percutaneous epicardial electrical stimulation to induce ventricular fibrillation(VF). Rats were treated with LVNS or RVNS for 30 minutes before the induction of VF. All animals were observed closely within 72 hours after return of spontaneous circulation(ROSC), and their health and behavior were evaluated every 24 hours.RESULTS: Compared with those in the RVNS group, the hemodynamic measurements in the LVNS group decreased more notably. Vagus nerve stimulation(VNS) decreased the serum levels of tumor necrosis factor-alpha(TNF-α) and the arrhythmia score, and attenuated inflammatory infiltration in myocardial tissue after ROSC, regardless of the side of stimulation, compared with findings in the CPR group. Both LVNS and RVNS ameliorated myocardial function and increased the expression of α-7 nicotinic acetylcholine receptor in the myocardium after ROSC. Moreover, a clear improvement in 72-hour survival was shown with VNS pre-treatment, with no significant difference in efficacy when comparing the laterality of stimulation. CONCLUSIONS: LVNS may have similar effects as RVNS on improving outcomes after CPR.

A review of studies on the therapeutic effect of vagus nerve stimulation

BACKGROUND： Vagus nerve widely innervates in the human body, and it has diverse physiological functions. Many new physiological functions are gradually found. Studies on its action mechanism have been gradually deepened. Vagus nerve stimulation （VNS） has been used for treatment of epilepsy and depression in clinic. OBJECTIVE： To retrospectively investigate the therapeutic effects and mechanism of VNS. RETRIEVE STRATEGY： A computer-based online research in Pubmed with the key words of ＂vagus nerve stimulation＂ published between February 1990 and October 2006 in English were systemically reviewed. Totally 583 articles were collected and primarily selected. Inclusive criteria： the mechanism of therapeutic effects of VNS-related literatures. Exclusive criteria： repetitive study. LITERATURE EVALUATION： According to inclusive criteria, of the 57 articles, which met the inclusive criteria, 42 were associated with the therapeutic function of VNS, and 15 with the mechanism of these related functions. DATA SYNTHESIS： Vagus nerve has special nerve innervation and wide projection with extensive physiological effects. Till now, VNS has been used in the therapy of epilepsy and depression, and exact clinical effects have been obtained. Further studies have discovered other functions of VNS, such as the effect on the memory power, cognition, and perception to pain. Thus, the studies about VNS become diverse. Just because of the special physiological functions of vagus nerve, VNS can bring some adverse reactions such as foreign body sensation, hoarseness, trigeminal neuralgia, etc. The mechanism of therapeutic function of VNS is still under exploration. CONCLUSION： As a mature surgical technique, VNS has been widely used in the therapy of epilepsy, depression, inflammation, analgesia, relieving itching, etc. Although the mechanism is still unclear, it brings obvious clinical effects.

Effects of vagus nerve stimulation on parafascicular nucleus neuronal activities in rats

BACKGROUND： Vagal nerve fibers have many projections to the central nervous system. The anti-epileptic effects of vagus nerve stimulation （VNS） are associated with the thalamus, insular cortex, and other brain regions. OBJECTIVE： To validate the inhibitory effects of vagus nerve stimulation on firing activities of parafascicular nucleus （Pf） neurons in rats. DESIGN, TIME, AND SETTING： The experiment was performed in the Electrophysiological Laboratory of Department of Neurobiology, Liaoning Medical University between September 2006 and September 2007 with multiple-factor self-controlled design. MATERIALS： Twenty-two healthy adult male Sprague Dawley rats were obtained for this experiment. Main instruments： A320R constant electrical stimulation was made by United States World Precision Instruments, Spike2 Biological Signal Processing Systems was provided by British CED Company. METHODS： Under general anesthesia, the left cervical vagus nerve of rats was separated by approximately 1.0 cm. A stimulation electrode was deployed on the vagus nerve, with various settings for VNS parameters. MAIN OUTCOME MEASURES： ① Firing rates of Pf before and after various VNS parameters were measured according to effect （R） ≥ 20%： excited effect, R ≤ -20%： inhibited effect, -20% 〈 R 〈 20%： no effect. ② Firing rates of excited Pf neurons after various VNS parameters were measured. RESULTS： ① One rat died prior to recording, another was recorded in the wrong brain location, but the remaining 20 rats were included in the final analysis. ② A total of 221 Pf neurons in healthy rats were recorded. The spontaneous firing rats were （6.70 ± 0.56） Hz and varied between 0.34-52.5 Hz. The spontaneous firing rates were significantly increased in 146 neurons （66.1%）, increasing from （5.36 ± 0.59） Hz to （8.22 ± 0.81） Hz （P 〈 0.01）. A total of 40 （18.1%） neurons did not respond, and 35 （15.8%） neurons were inhibited. ③ The excitation rates of Pf neurons did not increase with increasing current intensity from 3.0 mA to 5.0 mA. ④ When the current intensity was set to 3.0-4.0 mA, excitation rates of Pf neurons decreased with increasing stimulation frequency of 30 -50 Hz. The excitation ratios were not reduced by an intensity of 5.0 mA. CONCLUSION： VNS may result in excited Pf neurons that may inhibit cerebral cortical activities.

Young children with multidrug-resistant epilepsy and vagus nerve stimulation responding to perampanel: A case report

BACKGROUND Perampanel(PER),a third-generation antiepileptic drug,is a selective and noncompetitiveα-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist,and has been approved for the treatment of adults and adolescents with focal epilepsy.However,there are only a few studies about the efficacy and tolerability of PER in young children with multidrug-resistant epilepsy.In this case,we aimed to share our clinical experience in this group.CASE SUMMARY A 4-year-old boy without perinatal asphyxia and familial history of epilepsy began to have ictal seizures from age 14 mo,with jerky movement of four limbs and head nodding.Abnormal multifocal discharge and background activity were recorded through electroencephalography,and no pathogenic mutation was found in the whole exome sequencing for the patient and his parents.He had received valproate,levetiracetam,topiramate,oxcarbazepine,clonazepam and lacosamide sequentially at different times,but he still had frequent seizures even after vagus nerve stimulation(VNS)implantation.He was diagnosed with idiopathic multidrug-resistant epilepsy.However,his seizure frequency was significantly reduced after PER administration in a dose-dependent manner,and better cognitive behavior was observed.In addition,the adverse reactions of anger and aggression also appeared.CONCLUSION PER is effective as add-on therapy for young children with multidrug-resistant epilepsy who have previously undergone VNS implantation.

Research progress on the electrophysiological indicators to predict the efficacy of vagus nerve stimulation for drug-refractory epilepsy

Vagus nerve stimulation(VNS)is an important treatment option for drug-refractory epilepsy(DRE),with well-established efficacy and safety in clinical practice for more than 20 years.However,it is very difficult to find the optimal electrophysiological indicators for the effectiveness of VNS on DRE because the mechanism of action is unknown.In this review,we provide an update of the potential applications of VNS outcomes in patients with drug-resistant epilepsy.Electroencephalographic(EEG)activity,event-related potentials,EEG synchronization levels,magnetoencephalographic,laryngeal muscle evoked potentials,and heart rate variability are potential biomarkers for VNS outcomes in people with DRE.

Transcutaneous auricular vagus nerve stimulation would be an alternative to implantable cervical vagus nerve stimulation in some situation

Implantable cervical vagus nerve stimulation(i VNS) is a representative and promising neuromodulation.However,the invasive nature restricts its application.Traditional auricular acupuncture treatment has a long history.The auricular branch of the vagus nerve(ABVN) is a branch on the surface of the ear.Some studies demonstrates that transcutaneous auricular vagus nerve stimulation(ta VNS) would achieve similar effects as i VNS.Ta VNS and i VNS share a common anatomical basis and acting mechanism.In this article,we made a comparison between i VNS and ta VNS in indications and efficacy.The recent studies have revealed similar clinical efficacy of ta VNS,ta VNS would expand the indication of i VNS.Highquality clinical evidences are needed before ta VNS become be an alternative of i VNS.

Electrical stimulation of the vagus nerve protects against cerebral ischemic injury through an anti-inflammatory mechanism

Vagus nerve stimulation exerts protective effects against ischemic brain injury; however, the underlying mechanisms remain unclear. In this study, a rat model of focal cerebral ischemia was established using the occlusion method, and the right vagus nerve was given electrical stimula-tion （constant current of 0.5 mA; pulse width, 0.5 ms; frequency, 20 Hz; duration, 30 seconds; every 5 minutes for a total of 60 minutes） 30 minutes, 12 hours, and 1, 2, 3, 7 and 14 days after surgery. Electrical stimulation of the vagus nerve substantially reduced infarct volume, improved neurological function, and decreased the expression levels of tumor necrosis factor-α and in-terleukin-6 in rats with focal cerebral ischemia. The experimental findings indicate that the neuroprotective effect of vagus nerve stimulation following cerebral ischemia may be associated with the inhibition of tumor necrosis factor-α and interleukin-6 expression.

Transcutaneous Auricular Vagus Nerve Stimulation: From Concept to Application

Whether in the West or the East,the connection between the ear and the rest of the body has been explored for a long time.Especially in the past century or more,the relevant theoretical and applied research on the ear has greatly promoted the development of ear therapy,and finally the concept of transcutaneous auricular vagus nerve stimulation(taVNS)has been proposed.The purpose of taVNS is to treat a disease non-invasively by applying electrical current to the cutaneous receptive field formed by the auricular branch of the vagus nerve in the outer ear.In the past two decades,taVNS has been a topic of basic,clinical,and transformation research.It has been applied as an alternative to drug treatment for a variety of diseases.Based on the rapid understanding of the application of taVNS to human health and disease,some limitations in the development of this field have also been gradually exposed.Here,we comprehensively review the origin and research status of the field.

Treatment of drug-resistant epilepsy with vagus nerve stimulation m review of 45 cases

Background Vagus nerve stimulation （VNS） is an alternative treatment for drug-resistant epilepsy （DRE）. The study aimed to explore the potential factors of prognosis, safety and effect of VNS treatment in patients with DRE. Methods We retrospectively examined 45 cases of DRE that received VNS treatment in our center from June 2004 to June 2010 and analyzed the parameters （age of patient receiving VNS, seizure frequency before and after VNS as well as treatment duration） by Student＇s t test, Fisher＇s exact and Mann-Whitney U tests, and multivariate Logistic regression. Results The overall response rate was 64% （29/45）, 67% （6/9） for adults and 64% （23/36） for children, with no significant difference （P=0.28）. Twenty-two cases had been in VNS therapy for over 1 year with a treatment efficacy of 73% （16/22）, whereas 23 cases had been in VNS therapy no more than 1 year with a treatment effecacy of 57% （13/23）, and has statistically significant difference （P=0.03）. The main side effect included hoarseness of voice and cough. One patient＇s device was removed due to infection. One patient＇s VNS was half-way terminated due to seizure aggravation. One patient died due to status epilepticus. Conclusions VNS is a safe and effective treatment for DRE. Duration of VNS therapy may be a crucial factor on prognosis.

Vagus Nerve Stimulation for Pediatric and Adult Patients with Pharmaco-resistant Epilepsy

Background：Over past two decades,vagus nerve stimulation （VNS） has been widely used and reported to alleviate seizure frequency worldwide,however,so far,only hundreds of patients with pharmaco-resistant epilepsy （PRE） have been treated with VNS in China's Mainland.The study aimed to evaluate the effectiveness of VNS for Chinese patients with PRE and compare its relationship with age cohort and gender.Methods：We retrospectively assessed the clinical outcome of 94 patients with PRE,who were treated with VNS at Beijing Fengtai Hospital and Beij ing Tiantan Hospital between November 2008 and April 2014 from our database of 106 consecutive patients.The clinical data analysis was retrospectively examined.Results：Seizure frequency significantly decreased with VNS therapy after intermittent stimulation of the vagus nerve.At last follow-up,we found McHugh classifications of Class Ⅰ in 33 patients （35.1％）,Class Ⅱ in 27 patients （28.7％）,Class Ⅲ in 20 patients （21.3％）,Class Ⅳ in 3 patients （3.2％）,and Class Ⅴ in 11 patients （l 1.7％）.Notably,8 （8.5％） patients were seizure-free while ≥50％ seizure frequency reduction occurred in as many as 60 patients （63.8％）.Furthermore,with regard to the modified Engel classification,12 patients （12.8％） were classified as Class Ⅰ,l l patients （11.7％） were classified as Class Ⅱ,37 patients （39.4％） were classified as Class Ⅲ,34 patients （36.2％） were classified as Class Ⅳ.We also found that the factors of gender or age are not associated with clinical outcome.Conclusions：This comparative study confirmed that VNS is a safe,well-tolerated,and effective treatment for Chinese PRE patients.VNS reduced the seizure frequency regardless of age or gender of studied patients.

Efficacy and brain mechanism of transcutaneous auricular vagus nerve stimulation for adolescents with mild to moderate depression:Study protocol for a randomized controlled trial

Background Depression is a common mental illness in childhood and adolescence,with an incidence of 4%–5%;it can lead to impairments in learning and social functioning.Transcutaneous auricular vagus nerve stimulation(taVNS)is a commonly used method of auricular acupuncture point stimulation,which is regarded as an effective treatment for adults with depression.The aim of this study was to investigate the efficacy and mechanism of taVNS for adolescents with mild to moderate depression.Methods This randomized controlled clinical trial will include 120 patients aged 12–16 years,all of whom are diagnosed with mild to moderate depression.Patients will be randomly assigned to a taVNS group and a drug control group(sertraline hydrochloride)at a ratio of 1:1.Patients will be evaluated using the 17‐item Hamilton Depression Scale,Hamilton Anxiety Rating Scale,Self‐Rating Depression Scale,Self‐Rating Anxiety Scale,and Pittsburgh Sleep Quality Index scores at baseline,as well as at the 2nd,4th,6th,8th,and 12th weeks.To investigate the underlying neural mechanisms of taVNS treatment from the perspective of the default mode network,multimodal magnetic resonance imaging(MRI;i.e.,structural MRI[sMRI],resting state MRI[rsMRI],and pseudocontinuous arterial spin‐labeled[pcASL]MRI)will be used to compare cerebral images among groups.MRI data will also be collected from 40 healthy volunteers to assess whether the participants exhibit normal development of structural and functional components.Discussion Depression is the most common mental disorder in adolescence.Drug treatment can improve depression symptoms;however,the side effects of drug treatments are often severe.This study proposes a simple physiotherapy that aims to treat adolescents with mild to moderate depression.The mechanism of taVNS in the treatment of depression will also be investigated.The results of this study will provide evidence to guide the application of taVNS in adolescents with depression.

Long-term outcomes and prognosis factors of vagus nerve stimulation in patients with refractory epilepsy

Background:Vagus nerve stimulation(VNS)is an effective treatment for patients with refractory epilepsy,yet with varied predictive factors and heterogeneous long-term outcomes.Adjustment of VNS parameters is critical for obtaining favorable efficacy.In this study,we aimed to investigate the long-term outcomes and the possible predictive factors of VNS in patients with refractory epilepsy.Methods:Eighty-six patients(59 males and 27 females)who underwent VNS implantation for treatment of refractory epilepsy between May 2016 and May 2017 at five Epilepsy Centers were enrolled.The clinical data,including sex,age at epilepsy onset,VNS implantation,epilepsy duration,seizure type,MRI findings,history of neurosurgical operations,and responder rate(responders were those with≥50%seizure reduction),were analyzed.Results:Four-year follow-up data were available for 76 patients(53 males and 23 females).The mean current intensity at the last follow-up was 1.8±0.3 mA(range:0.75–2.5 mA).The mean seizure reduction was 36.2%at 6 months,38.5%at 1 year,69.4%at 3 years,and 56.7%at 4 years.A favorable outcome of≥50%reduction in seizure frequency occurred in 40.0%of the patients at 6 months,55.9%at 1 year with 4 patients being seizure-free,63.2%at 3 years with 5 patients being seizure-free,and 68.4%at 4 years with 5 patients being seizure-free.Earlier onset age(P<0.001)and shorter duration(P=0.042)were associated with favorable prognosis.Compared with generalized tonicclonic seizures,tonic seizures had a favorable outcome(P=0.026).Twenty-three patients underwent neurosurgical operations before VNS implantation,and the responder rate was 60.9%at the last follow-up.Conclusions:VNS is an adjunctive and effective treatment for patients with refractory epilepsy who are not good candidates for surgical resection or have failed to respond to surgical treatment.The stimulation efficacy increases over time after implantation,and earlier exposure to VNS improves the prognosis.

The Anticonvulsant Effect of Transcutaneous Auricular Vagus Nerve Stimulation is Associated with Balancing the Autonomic Dysfunction in Rats

Objective:The present study aims to investigate whether the anticonvulsant effect of transcutaneous auricular vagus nerve stimulation is associated with balancing the autonomic dysfunction in rats.Methods:Healthy adult male Sprague-Dawley rats were anesthetized with an intraperitoneal injection of 10% urethane.Seizures were evoked by intraperitoneal injection of pentylenetetrazol(PTZ,60 mg/kg).Femoral vein catheterization was performed for injection of sympathetic agonist and antagonists.Bipolar globe silver electrodes were utilized for epidural EEG recording.Three needles were inserted separately in subcutaneous muscles of left anterior limb,right anterior limb,and left hind limb to record ECG signals.ta-VNS was performed at auricular concha.Results:In comparison with preictal state,the mean heart rate(HR) increased slightly during epileptic seizures(P<0.05).In comparison with ictal state,the mean HR decreased a little at postictal state(P<0.05).When continuous epileptic seizures in EEG traces occurred(in ictal state),vein injection of propranolol hydrochloride(sympathetic antagonist) suppressed the epileptic seizures.When epileptic seizures occurred rarely(in postictal state),vein injection of adrenaline hydrochloride(sympathetic agonist) exacerbated the epileptic seizures.In comparison with prestimulation,the integral of EEG traces after ta-VNS decreased(P<0.05),the mean HR decreased(P<0.05),and the high power(HF) of HRV increased(P<0.05) after ta-VNS.Conclusion:The results showed that autonomic dysfunction occurred in epileptic rats characterized by enhanced sympathetic nerve activity.Epileptic seizures in EEG traces decreased,HR decreased and HF increased after ta-VNS,which indicated that ta-VNS may suppress epileptic seizures via balancing the autonomic dysfunction.