Development and characterization of a chronic implant mouse model for vagus nerve stimulation

Vagus nerve stimulation (VNS) suppresses inflammation and autoimmune diseases in preclinical and clinical studies. The underlying molecular, neurological, and anatomical mechanisms have been well characterized using acute electrophysiological stimulation of the vagus. However, there are several unanswered mechanistic questions about the effects of chronic VNS, which require solving numerous technical challenges for a long-term interface with the vagus in mice. Here, we describe a scalable model for long-term VNS in mice developed and validated in four research laboratories. We observed significant heart rate responses for at least 4 weeks in 60-90% of animals. Device implantation did not impair vagus-mediated reflexes. VNS using this implant significantly suppressed TNF levels in endotoxemia. Histological examination of implanted nerves revealed fibrotic encapsulation without axonal pathology. This model may be useful to study the physiology of the vagus and provides a tool to systematically investigate long-term VNS as therapy for chronic diseases modeled in mice.

Early Implantation as a Main Predictor of Response to Vagus Nerve Stimulation in Childhood-Onset Refractory Epilepsy

OBJECTIVE

We describe a multicenter experience with vagus nerve stimulator implantation in pediatric patients with drug-resistant epilepsy. Our goal was to assess vagus nerve stimulation efficacy and identify potential predictors of favorable outcome.

METHODS

This is a retrospective study. Inclusion criteria: ≤18 years at time of vagus nerve stimulator implantation, at least 1 year of follow-up. All patients were previously found to be unsuitable for an excisional procedure. Favorable clinical outcome and effective vagus nerve stimulation therapy were defined as seizure reduction >50%. Outcome data were reviewed at 1, 2, 3, and 5 years after vagus nerve stimulator implantation. Fisher exact test and multiple logistic regression analysis were employed.

RESULTS

Eighty-nine patients met inclusion criteria. Responder rate (seizure frequency reduction >50%) at 1-year follow-up was 25.8% (4.5% seizure-free). At last follow-up, 31.5% had a favorable outcome and 5.2% were seizure free. The only factor significantly predicting favorable outcome was time to vagus nerve stimulator implantation, with the best outcome achieved when vagus nerve stimulator implantation was performed within 3 years of seizure onset. Implantation between 3 and 5 years after epilepsy onset correlated with better long-term seizure freedom (13.3% at T5). Overall, 65.2% of patients evidenced improved quality of life at last follow-up. However, 12.4% had adverse events, but most were mild and disappeared after 3-4 months.

CONCLUSIONS

Early vagus nerve stimulator implantation within 5 years of seizure onset was the only predictor of favorable clinical outcome in pediatric patients. Improved quality of life and a low incidence of significant adverse events were observed.

Therapeutic Potential of Vagus Nerve Stimulation for Inflammatory Bowel Diseases

The vagus nerve is a mixed nerve, comprising 80% afferent fibers and 20% efferent fibers. It allows a bidirectional communication between the central nervous system and the digestive tract. It has a dual anti-inflammatory properties via activation of the hypothalamic pituitary adrenal axis, by its afferents, but also through a vago-vagal inflammatory reflex involving an afferent (vagal) and an efferent (vagal) arm, called the cholinergic anti-inflammatory pathway. Indeed, the release of acetylcholine at the end of its efferent fibers is able to inhibit the release of tumor necrosis factor (TNF) alpha by macrophages via an interneuron of the enteric nervous system synapsing between the efferent vagal endings and the macrophages and releasing acetylcholine. The vagus nerve also synapses with the splenic sympathetic nerve to inhibit the release of TNF-alpha by splenic macrophages. It can also activate the spinal sympathetic system after central integration of its afferents. This anti-TNF-alpha effect of the vagus nerve can be used in the treatment of chronic inflammatory bowel diseases, represented by Crohn’s disease and ulcerative colitis where this cytokine plays a key role. Bioelectronic medicine, via vagus nerve stimulation, may have an interest in this non-drug therapeutic approach as an alternative to conventional anti-TNF-alpha drugs, which are not devoid of side effects feared by patients.

The cholinergic anti-inflammatory pathway in chronic kidney disease-review and vagus nerve stimulation clinical pilot study

Inflammation and autonomic dysfunction are common findings in chronic and end-stage kidney disease and contribute to a markedly increased risk of mortality in this patient population. The cholinergic anti-inflammatory pathway (CAP) is a vagal neuro-immune circuit that upholds the homoeostatic balance of inflammatory activity in response to cell injury and pathogens. CAP models have been examined in preclinical studies to investigate its significance in a range of clinical inflammatory conditions and diseases. More recently, cervical vagus nerve stimulation (VNS) implants have been shown to be of potential benefit for patients with chronic autoimmune diseases such as rheumatoid arthritis and inflammatory bowel disease. We have previously shown that dialysis patients have a functional CAP ex vivo. Here we review the field and the potential role of the CAP in acute kidney injury and chronic kidney disease (CKD) as well as in hypertension. We also present a VNS pilot study in haemodialysis patients. Controlling inflammation by neuroimmune modulation may lead to new therapeutic modalities for improved treatment, outcome, prognosis and quality of life for patients with CKD.

Targeting the Autonomic Nervous System for Risk Stratification, Outcome Prediction and Neuromodulation in Ischemic Stroke

Ischemic stroke is a worldwide major cause of mortality and disability and has high costs in terms of health-related quality of life and expectancy as well as of social healthcare resources. In recent years, starting from the bidirectional relationship between autonomic nervous system (ANS) dysfunction and acute ischemic stroke (AIS), researchers have identified prognostic factors for risk stratification, prognosis of mid-term outcomes and response to recanalization therapy. In particular, the evaluation of the ANS function through the analysis of heart rate variability (HRV) appears to be a promising non-invasive and reliable tool for the management of patients with AIS. Furthermore, preclinical molecular studies on the pathophysiological mechanisms underlying the onset and progression of stroke damage have shown an extensive overlap with the activity of the vagus nerve. Evidence from the application of vagus nerve stimulation (VNS) on animal models of AIS and on patients with chronic ischemic stroke has highlighted the surprising therapeutic possibilities of neuromodulation. Preclinical molecular studies highlighted that the neuroprotective action of VNS results from anti-inflammatory, antioxidant and antiapoptotic mechanisms mediated by α7 nicotinic acetylcholine receptor. Given the proven safety of non-invasive VNS in the subacute phase, the ease of its use and its possible beneficial effect in hemorrhagic stroke as well, human studies with transcutaneous VNS should be less challenging than protocols that involve invasive VNS and could be the proof of concept that neuromodulation represents the very first therapeutic approach in the ultra-early management of stroke.

The role of surgery in the management of Lennox-Gastaut syndrome: A systematic review and meta-analysis of the clinical evidence

Lennox-Gastaut syndrome (LGS) is a severe form of childhood onset epilepsy in which patients require multiple medications and may be candidates for palliative surgical intervention. In this meta-analysis, we sought to evaluate the impact of palliative vagus nerve stimulation (VNS), corpus callosotomy (CC), and resective surgery (RS) by analyzing their impact on seizure control, antiepileptic drug (AED) usage, quality of life (QOL), behavior, cognition, prognostic factors, and complications. A systematic search of PubMed MEDLINE, Scopus, and Cochrane Database of Systematic Reviews was performed to find articles that met the following criteria: (1) prospective/retrospective study with original data, (2) at least one LGS surgery patient aged less than 18 years, and (3) information on seizure frequency reduction (measured as percentage, Engel class, or qualitative comment). Seizures were analyzed quantitatively in a meta-analysis of proportions and a random-effects model, whereas other outcomes were analyzed qualitatively. Forty studies with 892 LGS patients met the selection criteria, with 19 reporting on CC, 17 on VNS, four on RS, two on RS + CC, one on CC + VNS, and one on deep brain stimulation. CC seizure reduction rate was 74.1% (95% confidence interval [CI] = 64.5%-83.7%), and VNS was 54.6% (95% CI = 42.9%-66.3%), which was significantly different (p < .001). RS seizure reduction was 88.9% (95% CI = 66.1%-99.7%). Many VNS patients reported alertness improvements, and most had no major complications. VNS was most effective for atonic/tonic seizures; higher stimulation settings correlated with better outcomes. CC patients reported moderate cognitive and QOL improvements; disconnection syndrome, transient weakness, and respiratory complications were noted. Greater callosotomy extent correlated with better outcomes. AED usage most often did not change after surgery. RS showed considerable QOL improvements for patients with localized seizure foci. In the reported literature, CC appeared to be more effective than VNS for seizure reduction. VNS may provide a similar or higher level of QOL improvement with lower aggregate risk of complications. Patient selection, anatomy, and seizure type will inform decision-making.

Activation of the Cholinergic Anti-Inflammatory Pathway as a Novel Therapeutic Strategy for COVID-19

The outbreak of coronavirus disease 2019 (COVID-19) underlined the urgent need for alleviating cytokine storm. We propose here that activating the cholinergic anti-inflammatory pathway (CAP) is a potential therapeutic strategy. However, there is currently no approved drugs targeting the regulatory pathway. It is evident that nicotine, anisodamine and some herb medicine, activate the CAP and exert anti-inflammation action in vitro and in vivo. As the vagus nerve affects both inflammation and specific immune response, we propose that vagus nerve stimulation by invasive or non-invasive devices and acupuncture at ST36, PC6, or GV20, are also feasible approaches to activate the CAP and control COVID-19. It is worth to investigate the efficacy and safety of the strategy in patients with COVID-19.

Sudarshan Kriya Yoga: A Breath of Hope during COVID-19 Pandemic

Important counter measures to combat an infectious disease pandemic include vaccination, antiviral therapy, and immunomodulation therapy. Vaccinations are disease specific and moreover strain specific, so the protection provided is also specific and limited. Antiviral therapies are costly and require bulk production of drugs, hence globally there is an increased interest toward low-risk, cost-effective complementary alternative therapies, such as Yoga and Ayurveda to tackle the infectious pandemic, coronavirus disease 2019 (COVID-19). There is clinical evidence available on the potential complementary role of yogic practices in the management of noncommunicable and communicable diseases. Various online databases were searched for articles published between 2000 and 2020. Databases explored were Medline, EMBASE, Indian Citation Index, PsycINFO, Index Medicus for South-East Asia Region, and Google Scholar. All search results were screened, and articles related to keywords such as COVID-19, yoga therapy, and Sudarshan Kriya Yoga (SKY) were selected for data extraction. Quality of the studies included was evaluated on the basis of the construct validity, content validity, relevance, bias, credibility relating to information, and data sources. SKY is a unique yogic practice that includes specific sequential breathing techniques. It balances the autonomic nervous system and thus can alleviate anxiety, routine stress, depression, stress-related medical disorders, and posttraumatic stress. It potentiates natural host immune defenses that are essential to tackle a plethora of microbial infections. This narrative review article provides an overview of potential therapeutic benefits that SKY can offer to the population at large during this COVID-19 pandemic.

Transcutaneous Vagal Nerve Stimulation in Treatment-Resistant Depression: A Feasibility Study

BACKGROUND

Major depression (MD) contributes significantly to the global burden of disease with up to one-third of patients being treatment resistant. Therefore, the development of new treatment options for treatment-resistant depression (TRD) is needed. Vagus nerve stimulation (VNS) has shown mood improvements in patients with TRD. However, due to high costs related to the implantation and the invasive nature of VNS, an application with transcutaneous VNS (t-VNS) has been developed stimulating a vagal nerve branch in the earlobe (Arnold's nerve). A few studies with t-VNS in MD has shown a possible antidepressant effect, but feasibility is poorly described and patients with TRD have not been investigated.

OBJECTIVES

As the full antidepressant effect of t-VNS takes months we wanted to assess feasibility and side effects of daily treatments.

MATERIALS AND METHODS

Single-arm feasibility trial assessing compliance, usability, side effects, cognitive speed, and depression in a four-week period with a recommended t-VNS stimulation duration of four hours per day in patients with TRD. The primary outcome was compliance with 80% of the recommended daily treatment time.

RESULTS

Compliance threshold was reached for 80.0% of the 20 included participants. Usability was acceptable. Side effects were few, mild or moderate, mostly as local effects at the contact point in the ear. The device was difficult to use for some participants. A statistically significant reduction in depression severity and an increase in cognitive speed were seen with unchanged suicidal ideation and sleep.

CONCLUSIONS

We would recommend larger long-term randomized studies of t-VNS to access any antidepressant effect in TRD. The design of the device might be improved for higher usability.

Effects of acute transcutaneous vagus nerve stimulation on emotion recognition in adolescent depression

BACKGROUND

Transcutaneous vagus nerve stimulation (tVNS) is a promising therapeutic option for major depressive disorder (MDD) in adults. Alternative third-line treatments for MDD in adolescents are scarce. Here we aimed to assess the effects of acute tVNS on emotion recognition in adolescents with MDD.

METHODS

Adolescents (14-17 years) with MDD (n = 33) and non-depressed controls (n = 30) received tVNS or sham-stimulation in a cross-sectional, case-control, within-subject cross-randomized controlled trial, while performing different tasks assessing emotion recognition. Correct responses, response times, and errors of omission and commission on three different computerized emotion recognition tasks were assessed as main outcomes. Simultaneous recordings of electrocardiography and electro dermal activity, as well as sampling of saliva for the determination of α-amylase, were used to quantify the effects on autonomic nervous system function.

RESULTS

tVNS had no effect on the recognition of gradually or static expressed emotions but altered response inhibition on the emotional Go/NoGo-task. Specifically, tVNS increased the likelihood of omitting a response toward sad target-stimuli in adolescents with MDD, while decreasing errors (independent of the target emotion) in controls. Effects of acute tVNS on autonomic nervous system function were found in non-depressed controls only.

CONCLUSIONS

Acute tVNS alters the recognition of briefly presented facial expressions of negative valence in adolescents with MDD while generally increasing emotion recognition in controls. tVNS seems to specifically alter early visual processing of stimuli of negative emotional valence in MDD. These findings suggest a potential therapeutic benefit of tVNS in adolescent MDD that requires further evaluation within clinical trials.

Vagus Nerve Stimulation Decreases Pancreatitis Severity in Mice

Background

Vagus nerve stimulation (VNS) is effective in reducing inflammation in various diseases, such as rheumatoid arthritis, colitis and acute kidney injury. The anti-inflammatory effect of vagus nerve in these diseases necessitates the interactions of neural activation and α7 nicotinic acetylcholine receptors (α7nAChRs) on splenic macrophages. In this study, we aimed to investigate the effect of VNS on severity in experimental acute pancreatitis (AP).

Methods

Two independent AP models were used, which induced in ICR mice with caerulein or pancreatic duct ligation (PDL). Thirty minutes after modeling, the left cervical carotid sheath containing the vagus nerve was electrically stimulated for 2 min. Plasma lipase and amylase activities, TNF-α levels and pancreas histologic damage were evaluated. In caerulein mice, the percentages of α7nAChR⁺ macrophage in pancreas and spleen were assessed by flow cytometry. Furthermore, splenectomy and adoptive transfer of VNS-conditioned α7nAChR splenocytes were performed in caerulein mice to evaluate the role of spleen in the protective effect of VNS.

Results

VNS reduced plasma lipase and amylase activities, blunted the concentrations of TNF-α and protected against pancreas histologic damage in two AP models. Survival rates were improved in the PDL model after VNS. In caerulein AP mice, VNS increased the percentages of α7nAChR⁺ macrophages in pancreas and spleen. Adoptive transfer of VNS-treated α7nAChR splenocytes provided protection against pancreatitis in recipient mice. However, splenectomy did not abolish the protective effect of VNS.

Conclusions

VNS reduces disease severity and attenuates inflammation in AP mice. This effect is independent of spleen and is probably related to α7nAChR on macrophage.

Effect of Long-Term Treatment with Vagus Nerve Stimulation on Mood and Quality of Life in Korean Patients with Drug-Resistant Epilepsy

BACKGROUND AND PURPOSE

This study aimed to determine the long-term effects of vagus nerve stimulation (VNS) treatment on suicidality, mood-related symptoms, and quality of life (QOL) in patients with drug-resistant epilepsy (DRE). We also investigated the relationships among these main effects, clinical characteristics, and VNS parameters.

METHODS

Among 35 epilepsy patients who underwent VNS implantation consecutively in our epilepsy center, 25 patients were recruited to this study for assessing the effects of VNS on suicidality, mood-related symptoms, and QOL. The differences in these variables between before and after VNS treatment were analyzed statistically using paired t-tests. Multiple linear regression analyses were also performed to determine how the patients' demographic and clinical characteristics influenced the variables that showed statistically significant changes after long-term VNS treatment.

RESULTS

After VNS, our patients showed significant improvements not only in the mean seizure frequency but also in suicidality, depression, and QOL. The reduction in depression was associated with the improvement in QOL and more-severe depression at baseline. The reduction in suicidality was associated with higher suicidality at baseline, smaller changes in depression, and less-severe depression at baseline. Improved QOL was associated with lower suicidality at baseline.

CONCLUSIONS

This study found that VNS decreased the mean seizure frequency in patients with DRE, and also improved their depression, suicidality, and QOL. These results provide further evidence for therapeutic effect of VNS on psychological comorbidities of patients with DRE.

An economic evaluation of vagus nerve stimulation as an adjunctive treatment to anti-seizure medications for the treatment of drug-resistant epilepsy in England

INTRODUCTION

Anti-seizure medications (ASMs) are commonly used to prevent recurring epileptic seizures, but around a third of people with epilepsy fail to achieve an adequate response. Vagus nerve stimulation (VNS) is clinically recommended for people with drug-resistant epilepsy (DRE) who are not suitable for surgery, but the cost-effectiveness of the intervention has not recently been evaluated. The study objective is to estimate costs and quality-adjusted life-years (QALYs) associated with using VNS as an adjunct to ongoing ASM therapy, compared to the strategy of using only ASMs in the treatment of people with DRE, from an English National Health Service perspective.

METHODS

A cohort state transition model was developed in Microsoft Excel to simulate costs and QALYs of the VNS + ASM and ASM only strategies. Patients could transition between five health states, using a 3-month cycle length. Health states were defined by an expected percentage reduction in seizure frequency, derived from randomized control trial data. Costs included the VNS device as well as its installation, setup, and removal; ASM therapy; adverse events associated with VNS (dyspnea, hoarseness, and cough); and health-state costs associated with epilepsy including hospitalizations, emergency department visits, neurologist visits, and primary care visits. A range of sensitivity analyses, including probabilistic sensitivity analysis, were run to assess the impact of parameter and structural uncertainty.

RESULTS

In the base case, VNS + ASM had an estimated incremental cost-effectiveness ratio (ICER) of £17,771 per QALY gained compared to ASMs alone. The cost-effective ICER was driven by relative reductions in expected seizure frequency and the differences in health care resource use associated therewith. Sensitivity analyses found that the amount of resource use per epilepsy-related health state was a key driver of the cost component.

CONCLUSIONS

VNS is expected to be a cost-effective intervention in the treatment of DRE in the English National Health Service.

The Vagal Autonomic Pathway of COVID-19 at the Crossroad of Alzheimer's Disease and Aging: A Review of Knowledge

Coronavirus Disease 2019 (COVID-19) pandemic-triggered mortality is significantly higher in older than in younger populations worldwide. Alzheimer's disease (AD) is related to aging and was recently reported to be among the major risk factors for COVID-19 mortality in older people. The symptomatology of COVID-19 indicates that lethal outcomes of infection rely on neurogenic mechanisms. The present review compiles the available knowledge pointing to the convergence of COVID-19 complications with the mechanisms of autonomic dysfunctions in AD and aging. The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is prone to neuroinvasion from the lung along the vagus nerve up to the brainstem autonomic nervous centers involved in the coupling of cardiovascular and respiratory rhythms. The brainstem autonomic network allows SARS-CoV-2 to trigger a neurogenic switch to hypertension and hypoventilation, which may act in synergy with aging- and AD-induced dysautonomias, along with an inflammatory "storm". The lethal outcomes of COVID-19, like in AD and unhealthy aging, likely rely on a critical hypoactivity of the efferent vagus nerve cholinergic pathway, which is involved in lowering cardiovascular pressure and systemic inflammation tone. We further discuss the emerging evidence supporting the use of 1) the non-invasive stimulation of vagus nerve as an additional therapeutic approach for severe COVID-19, and 2) the demonstrated vagal tone index, i.e., heart rate variability, via smartphone-based applications as a non-serological low-cost diagnostic of COVID-19. These two well-known medical approaches are already available and now deserve large-scale testing on human cohorts in the context of both AD and COVID-19.

Saudi Arabian Consensus Statement on Vagus Nerve Stimulation for Refractory Epilepsy

Vagus nerve stimulation (VNS) is an approved adjunctive therapy for refractory epilepsy and used in patients who are not candidates for resective epilepsy surgery. In Saudi Arabia, VNS device implantation is being performed since 2008 by several comprehensive epilepsy programs, but with variable protocols. Therefore, to standardize the use of VNS, a task force was established to create a national consensus. This group consisted of epileptologists, epilepsy surgeons and a VNS nurse coordinator working in comprehensive epilepsy centers and dealing with refractory epilepsy cases. The group intensively reviewed the literature using Medline, EMBASE, Web of Science and Cochrane Library, in addition to physician's manual. Evidence is reported as three stages: preimplantation and patient selection, a perioperative phase involving all stakeholders and post-operative care with specific programming pathways.

Vagus Nerve Stimulation Transiently Mitigates Chemotherapy-Induced Peripheral Neuropathy in Rats

Background

Chemotherapy-induced peripheral neuropathy is a severe side effect of chemotherapeutic agents. Vagus nerve stimulation attenuates neuroinflammation by activating the cholinergic anti-inflammatory pathway and thus may attenuate CIPN.

Methods

Adult male Sprague-Dawley rats received intraperitoneal paclitaxel injection (2 mg/kg) every other day for a total of 4 injections. Three weeks later, the left cervical vagus nerve was exposed under general anesthesia, and the rats randomly received 20-min stimulation (1 V, 2 ms, 5 Hz, 30 s ON/5 min OFF) or sham stimulation. Heat and mechanical pain sensitivity was evaluated using Hargreaves and von Frey tests before and after treatment (n=12 per group per time point). Additionally, rats receiving paclitaxel or saline but no surgery were included. Expression of representative pro- and anti-inflammatory cytokines in dorsal root ganglia was assessed by Western blotting assays and immunohistochemistry.

Results

Paclitaxel significantly reduced the sensitivity for heat (withdrawal latency: paclitaxel 6.16 ± 0.54 s vs saline 9.93 ± 0.78 s, p<0.001) and mechanical pain (withdrawal frequency: paclitaxel 32.22 ± 15.51% vs saline 3.33 ± 4.92%, p<0.001). Compared with sham-stimulated rats, rats receiving vagus nerve stimulation had significantly higher sensitivity for heat (withdrawal latency: VNS 10.28 ± 1.15 s vs sham 6.27 ± 0.56 s, p<0.001) and mechanical pain (withdrawal frequency: VNS 10.00 ± 9.54% vs Sham 31.67 ± 18.99%, p=0.003) on +1 day, but not 7 days later (withdrawal latency: VNS 6.97 ± 1.13 s vs Sham 6.23 ± 0.79 s, p=0.080; withdrawal frequency: VNS 21.67 ± 11.93% vs Sham 23.33 ± 7.79%, p=0.689). Western blotting assays and immunohistochemistry revealed that interleukin-10 level was elevated in the dorsal root ganglia of rats receiving vagus nerve stimulation while no apparent changes in NF-κB or TNF-α levels were observed.

Conclusion

Vagus nerve stimulation could transiently attenuate paclitaxel-induced hyperalgesia in rats. Future studies are needed to investigate whether stimulation with different protocols could achieve durable effects.

Complex sleep-disordered breathing after vagus nerve stimulation: broadening the spectrum of adverse events of special interest

Two young males with refractory epilepsy of unknown aetiology were referred for vagus nerve stimulation (VNS). Sleep disturbances emerged following VNS parameter changes. In Patient 1, video-polysomnogram (PSG) disclosed snoring and catathrenia in non-REM sleep. Central apnoea also occurred, but more rarely. In Patient 2, video-PSG showed mixed apnoea with desaturation and episodes of stridor followed by a catathrenia-like sound. A drug-induced sleep endoscopy (DISE) revealed, during VNS OFF time, glossoptosis, "trap door" of the epiglottis, and paresis of the left side of the larynx and ipsilateral vocal cords. During ON time, there were periods of pharyngeal collapse, in which video-PSG revealed patterns suggestive of both obstructive and central sleep apnoea. All these sleep-related phenomena were coincident with VNS ON time. In the first patient, VNS parameter adjustment was sufficient to successfully reverse all the symptoms, whereas the other patient required concomitant treatment with continuous positive airway pressure. The data broaden our knowledge about sleep disorders related to VNS, in particular stridor and catathrenia. We suggest that central sleep apnoea may be associated with laryngeal occlusion. DISE may be considered in selected cases as a valuable clinical tool to evaluate, in a single session, the effectiveness of multiple VNS parameter changes on respiration and laryngeal side effects. [Published with video sequences].

Celiac Vagus Nerve Stimulation Recapitulates Angiotensin II-Induced Splenic Noradrenergic Activation, Driving Egress of CD8 Effector Cells

Angiotensin II (AngII) is a peptide hormone that affects the cardiovascular system, not only through typical effects on the vasculature, kidneys, and heart, but also through less understood roles mediated by the brain and the immune system. Here, we address the hard-wired neural connections within the autonomic nervous system that modulate splenic immunity. Chronic AngII infusion triggers burst firing of the vagus nerve celiac efferent, an effect correlated with noradrenergic activation in the spleen and T cell egress. Bioelectronic stimulation of the celiac vagus nerve, in the absence of other challenges and independently from afferent signals to the brain, evokes the noradrenergic splenic pathway to promote release of a growth factor mediating neuroimmune crosstalk, placental growth factor (PlGF), and egress of CD8 effector T cells. Our findings also indicate that the neuroimmune interface mediated by PlGF and necessary for transducing the neural signal into an effective immune response is dependent on α-adrenergic receptor signaling.

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Bioelectronic stimulation of celiac vagus nerve primes a splenic immune response

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Vagus nerve stimulation selectively drives the egress of CD8+ effector T cells

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Placental growth factor (PlGF) is a key mediator of the splenic neuroimmune coupling

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Vagus nerve stimulation induces splenic PlGF through α-adrenergic receptors signaling

Therapeutic effects of children with refractory epilepsy after vagus nerve stimulation in Taiwan

BACKGROUND

Vagus nerve stimulation (VNS) is used as an add-on treatment for epilepsy. This study aimed to use Taiwanese nationwide registry data to analyze the therapeutic effects of VNS in children with refractory epilepsy (RE) and try to explore predictive factors of VNS treatment effectiveness.

METHODS

This retrospective study collected data from December 2007 to December 2014. Patient variables included gender, age, VNS implantation date, epilepsy duration, seizure frequency, seizure type, etiology, and antiepileptic drug (AED) history. We divided patients into three groups: Group I as seizure frequency >80 times per month, Group II as seizure frequency 24-80 times per month, and Group III as seizure frequency <24 times per month. Multivariate regression analysis was performed to determine predictors of seizure frequency reduction after VNS treatment.

RESULTS

A total of 80 patients were included in this study. Three or more AED types were prescribed for 61 (77.1%) patients. Seizure frequency decreased significantly at 12 and 24 months after VNS treatment. The mean seizure reduction rates were 44.6% and 50.1% at 12 and 24 months after VNS treatment, with the difference between them reaching statistical significance (p = 0.001). In multivariate linear regression, high seizure frequency (Group I) was a positive predictor of seizure frequency reduction (p < 0.001). The most common complication was coughing (eight patients, 10%) and no patient had early withdrawal or premature termination of VNS use due to complications.

CONCLUSION

VNS is an effective palliative treatment for children with RE for different seizure types. Seizure reduction rate at 24 months after VNS was better than at 12 months after VNS. High seizure frequency can be regarded as a positive predictor for seizure frequency reduction in children with RE treated with VNS.

The Effectiveness of Vagus Nerve Stimulation in Drug-Resistant Epilepsy Correlates with Vagus Nerve Stimulation-Induced Electroencephalography Desynchronization

Introduction: VNS is an adjunctive neuromodulation therapy for patients with drug-refractory epilepsy. The antiseizure effect of VNS is thought to be related to a diffuse modulation of functional connectivity but remains to be confirmed.

Aim: To investigate electroencephalographic (EEG) metrics of functional connectivity in patients with drug-refractory epilepsy treated by vagus nerve stimulation (VNS), between VNS-stimulated “ON” and nonstimulated “OFF” periods and between responder (R) and nonresponder (NR) patients.

Methods: Scalp-EEG was performed for 35 patients treated by VNS, using 21 channels and 2 additional electrodes on the neck to detect the VNS stimulation. Patients were defined as VNS responders if a reduction of seizure frequency of ∼50% was documented. We analyzed the synchronization in EEG time series during “ON” and “OFF” periods of stimulation, using average phase lag index (PLI) in signal space and phase-locking value (PLV) between 10 sources. Based on graph theory, we computed brain network models and analyzed minimum spanning tree (MST) for responder and nonresponder patients.

Results: Among 35 patients treated by VNS for a median time of 7 years (range 4 months to 22 years), 20 were R and 15 were NR. For responder patients, PLI during ON periods was significantly lower than that during OFF periods in delta (p = 0.009), theta (p = 0.02), and beta (p = 0.04) frequency bands. For nonresponder patients, there were no significant differences between ON and OFF periods. Moreover, variations of seizure frequency with VNS correlated with the PLI OFF/ON ratio in delta (p = 0.02), theta (p = 0.04), and beta (p = 0.03) frequency bands. Our results were confirmed using PLV in theta band (p < 0.05). No significant differences in MST were observed between R and NR patients.

Conclusion: The correlation between VNS-induced interictal EEG time-series desynchronization and decrease in seizure frequency suggested that VNS therapeutic impact might be related to changes in interictal functional connectivity.

Sex Differences in Vagus Nerve Stimulation Effects on Rat Cardiovascular and Immune Systems

Background

Investigations into the benefits of vagus nerve stimulation (VNS) through pre-clinical and clinical research have led to promising findings for treating several disorders. Despite proven effectiveness of VNS on conditions such as epilepsy and depression, understanding of off-target effects and contributing factors such as sex differences can be beneficial to optimize therapy design.

New Methods

In this article, we assessed longitudinal effects of VNS on cardiovascular and immune systems, and studied potential sex differences using a rat model of long-term VNS. Rats were implanted with cuff electrodes around the left cervical vagus nerve for VNS, and wireless physiological monitoring devices for continuous monitoring of cardiovascular system using electrocardiogram (ECG) signals. ECG morphology and heart rate variability (HRV) features were extracted to assess cardiovascular changes resulting from VNS in short-term and long-term timescales. We also assessed VNS effects on expression of inflammatory cytokines in blood during the course of the experiment. Statistical analysis was performed to compare results between Treatment and Sham groups, and between male and female animals from Treatment and Sham groups.

Results

Considerable differences between male and female rats in cardiovascular effects of VNS were observed in multiple cardiovascular features. However, the effects seemed to be transient with approximately 1-h recovery after VNS. While short-term cardiovascular effects were mainly observed in male rats, females in general showed more significant long-term effects even after VNS stopped. We did not observe notable changes or sex differences in systemic cytokine levels resulting from VNS.

Comparison With Existing Methods

Compared to existing methods, our study design incorporated wireless physiological monitoring and systemic blood cytokine level analysis, along with long-term VNS experiments in unanesthetized rats to study sex differences.

Conclusion

The contribution of sex differences for long-term VNS off-target effects on cardiovascular and immune systems was assessed using awake behaving rats. Although VNS did not change the concentration of inflammatory biomarkers in systemic circulation for male and female rats, we observed significant differences in cardiovascular effects of VNS characterized using ECG morphology and HRV analyses.

Quantified Morphology of the Cervical and Subdiaphragmatic Vagus Nerves of Human, Pig, and Rat

It is necessary to understand the morphology of the vagus nerve (VN) to design and deliver effective and selective vagus nerve stimulation (VNS) because nerve morphology influences fiber responses to electrical stimulation. Specifically, nerve diameter (and thus, electrode-fiber distance), fascicle diameter, fascicular organization, and perineurium thickness all significantly affect the responses of nerve fibers to electrical signals delivered through a cuff electrode. We quantified the morphology of cervical and subdiaphragmatic VNs in humans, pigs, and rats: effective nerve diameter, number of fascicles, effective fascicle diameters, proportions of endoneurial, perineurial, and epineurial tissues, and perineurium thickness. The human and pig VNs were comparable sizes (∼2 mm cervically; ∼1.6 mm subdiaphragmatically), while the rat nerves were ten times smaller. The pig nerves had ten times more fascicles-and the fascicles were smaller-than in human nerves (47 vs. 7 fascicles cervically; 38 vs. 5 fascicles subdiaphragmatically). Comparing the cervical to the subdiaphragmatic VNs, the nerves and fascicles were larger at the cervical level for all species and there were more fascicles for pigs. Human morphology generally exhibited greater variability across samples than pigs and rats. A prior study of human somatic nerves indicated that the ratio of perineurium thickness to fascicle diameter was approximately constant across fascicle diameters. However, our data found thicker human and pig VN perineurium than those prior data: the VNs had thicker perineurium for larger fascicles and thicker perineurium normalized by fascicle diameter for smaller fascicles. Understanding these differences in VN morphology between preclinical models and the clinical target, as well as the variability across individuals of a species, is essential for designing suitable cuff electrodes and stimulation parameters and for informing translation of preclinical results to clinical application to advance the therapeutic efficacy of VNS.

Vagus nerve stimulation for treatment-resistant depression: is this therapy distinct from other antidepressant treatments?

BACKGROUND

The treatment-resistant depression (TRD) is a very disabling disease.

OBJECTIVE

The aim of this article is to provide an overview of the therapeutic activity of vagus nerve stimulation (VNS) therapy system in TRD. We summarised the progress made during the last decade in this area.

METHODS

We conducted a non-systematic review on the efficacy and safety of the VNS therapy for this disease. We analysed the results from acute and long-term studies that utilised this technique. Major electronic databases were searched.

RESULTS

The patients with TRD may show acute and long-term benefit when treated with this technique. There are promising results for VNS therapy for these patients. The level of evidence as an acute treatment option is only 3, but as chronic treatment is 2. This therapy should be offered as an added long-term treatment option for patients with chronic and recurrent difficult to treat depression.

CONCLUSIONS

The antidepressant effects of this procedure remain controversial. The clinical trials have produced mixed results, but VNS therapy for TRD has two distinct features that differentiate it from other antidepressant treatments: a sustained therapeutic response obtained in highly resistant depressive disorders, a favourable safety profile and guaranteed compliance.

Impact of Cardiac-Based Vagus Nerve Stimulation Closed-Loop Stimulation on the Seizure Outcome of Patients With Generalized Epilepsy: A Prospective, Individual-Control Study

OBJECTIVES

We designed a prospective, individual-controlled study to evaluate the effect of cardiac-based VNS (cbVNS) in a cohort of patients with generalized epilepsy (GE).

MATERIALS AND METHODS

Twenty patients were included. They were followed up for six months under regular VNS (rVNS) and subsequently for six months during cbVNS. Stimulation parameters were 500 μsec, 30 Hz, and up to 2.5 mA. Seizure frequency was documented after two, four, and six months during the rVNS and cbVNS phases. Patients with at least 50% seizure frequency reduction were considered responders. The total and relative amount of stimulation cycles generated by both rVNS and cbVNS activation were documented. Findings during rVNS were compared to baseline and cbVNS data were compared to those during rVNS.

RESULTS

There was a significant decrease in mean seizure frequency (61% [95% CI, 48-74]; p < 0.001) during the rVNS phase compared to baseline. There was no additional significant (16% [95% CI, 4-35]; p = 0.097) mean seizure frequency reduction during cbVNS compared to the rVNS phase. Fifteen patients (75%) were considered responders after rVNS. Four patients (20%) were considered responders after six months of cbVNS. During the cbVNS phase, the mean total number of cycles/day was 346, 354, and 333 for months two, four, and six, respectively; the cycles generated by rVNS were 142, 138, and 146 for months two, four, and six, respectively; and cycles generated by cbVNS were 204, 215, and 186 for months two, four, and six, respectively. There was no relationship between the mean total number of cycles (-6[95% CI, -85 to 72]; p = 0.431), the mean number of auto-stimulation cycles (27[95% CI,-112 to 166]; p = 0.139), the mean number of regular cycles (-33[95% CI,-123 to 57]; p = 0.122), or the mean percentage of auto-stimulation cycles (13[95% CI,19- 45]; p = 0.109) and outcome during the cbVNS phase. Eight patients showed some decrease in seizure frequency during cbVNS.

CONCLUSIONS

rVNS was effective in reducing seizure frequency in patients with generalized epilepsy, but activation of the cbVNS feature did not add significantly to rVNS efficacy. On the other hand, although not statistically significant, 40% of the patients showed some reduction in seizure frequency, which might prove useful at an individual level.