Anti-inflammatory effects of vagus nerve stimulation in pediatric patients with epilepsy

Introduction

The neural control of the immune system by the nervous system is critical to maintaining immune homeostasis, whose disruption may be an underlying cause of several diseases, including cancer, multiple sclerosis, rheumatoid arthritis, and Alzheimer's disease.

Methods

Here we studied the role of vagus nerve stimulation (VNS) on gene expression in peripheral blood mononuclear cells (PBMCs). Vagus nerve stimulation is widely used as an alternative treatment for drug-resistant epilepsy. Thus, we studied the impact that VNS treatment has on PBMCs isolated from a cohort of existing patients with medically refractory epilepsy. A comparison of genome-wide changes in gene expression was made between the epilepsy patients treated and non-treated with vagus nerve stimulation.

Results

The analysis showed downregulation of genes related to stress, inflammatory response, and immunity, suggesting an anti-inflammatory effect of VNS in epilepsy patients. VNS also resulted in the downregulation of the insulin catabolic process, which may reduce circulating blood glucose.

Discussion

These results provide a potential molecular explanation for the beneficial role of the ketogenic diet, which also controls blood glucose, in treating refractory epilepsy. The findings indicate that direct VNS might be a useful therapeutic alternative to treat chronic inflammatory conditions.

Impact of Vagus Nerve Stimulation for the Treatment of Drug-Resistant Epilepsy on Patterns of Use and Cost of Health Care Services and Pharmacotherapy: Comparisons of the 24-Month Periods Before and After Implantation

PURPOSE

This study examines the impact of vagus nerve stimulation (VNS) as treatment for drug-resistant epilepsy (DRE) on the use and cost of health care services and pharmacotherapy.

METHODS

Using a large US health care claims database, we identified all patients with DRE who underwent VNS between January 1, 2012 and December 31, 2019. VNS implantation date was designated as the index date, and patients had to be continuously enrolled for the 24-month period before this date (preindex period). Outcomes included all-cause and epilepsy-related hospitalization, emergency department (ED) visits, and health care costs; health care claims resulting in an epilepsy diagnosis and all claims for antiseizure medications were deemed epilepsy related. Preindex data, except care related to preoperative medical clearance for VNS, were used to estimate multivariate regression models predicting outcomes during the 24-month postindex period (follow-up period). Predicted outcomes during follow-up were then compared with observed values. As a sensitivity analysis, we also replicated all analyses among subgroups defined by comorbid depression.

FINDINGS

A total of 659 patients underwent VNS for DRE and met the selection criteria. For the composite outcome of all-cause hospitalizations and ED visits, observed values were 42% lower than expected during the 24-month follow-up period; for the composite outcome of epilepsy-related hospitalizations and ED visits, observed values were 49% lower (P < 0.001 for both). Observed mean total all-cause costs, inclusive of costs of the procedure, were not significantly different than expected costs by month 19 of follow-up; mean total epilepsy-related costs were comparable by month 18. Findings were similar in subgroups with and without depression, although nominally greater differences (observed - expected) were seen in those with comorbid depression.

IMPLICATIONS

Our findings suggest that VNS is associated with decreased risk of hospitalization or ED visits (all cause and epilepsy related) during the 2-year period subsequent to implantation and may become cost-neutral within 2 years of implantation (vs continued medical management of DRE without VNS). Although expected outcomes were estimated based on the 24-month period before implantation, the degree to which they approximated what would have happened in the absence of VNS is unknowable. Further research is needed to better understand the extend and duration of the impact of VNS on seizure frequency and severity and health-related quality of life, including its performance among those with and without comorbid depression.

Brain stimulation treatment for bipolar disorder

AIMS

Bipolar disorders are clinically complex, chronic and recurrent disorders. Few treatment options are effective across hypomanic, manic, depressive and mixed states and as continuation or maintenance treatment after initial symptom remission. The aim of this review was to provide an up-to-date overview of research on the efficacy, tolerability and cognitive effects of electroconvulsive therapy (ECT), transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), magnetic seizure therapy (MST), deep brain stimulation (DBS) and vagus nerve stimulation (VNS).

METHODS

References included in this review were identified through multiple searches of the Embase, PubMed/MEDLINE and APA PsycINFO electronic databases for articles published from inception until February 2022. Published reviews, meta-analyses, randomised controlled trials and recent studies were prioritised to provide a comprehensive and up-to-date overview of research on brain stimulation in patients with bipolar disorders.

RESULTS

The evidence base for brain stimulation as an add-on or alternative to pharmacological and psychological treatments in patients with bipolar disorders is limited but rapidly expanding. Brain stimulation treatments represent an opportunity to treat all bipolar disorder states, including cognitive dysfunction during euthymic periods.

CONCLUSION

Whilst findings to date have been encouraging, larger randomised controlled trials with long-term follow-up are needed to clarify important questions regarding treatment efficacy and tolerability, the frequency of treatment-emergent affective switches and effects on cognitive function.

Clinical Benefit of Vagus Nerve Stimulation for Epilepsy: Assessment of Randomized Controlled Trials and Prospective Non-Randomized Studies

We examined the efficacy of vagal nerve stimulation (VNS) for patients suffering from medically intractable epilepsy. Four randomized controlled trials (RCTs - 3 adult RCTs and 1 pediatric RCT) were identified in our comprehensive literature search. Across the 4 studies, high frequency VNS stimulation (frequency >20 Hz) consistently achieved a greater seizure frequency reduction (23.4-33.1%) relative to low frequency VNS stimulation (1 Hz, .6-15.2%). We identified 2 RCTs examining whether the parameters of stimulation influenced seizure control. These studies reported that VNS achieved seizure control comparable to those reported by the first 4 RCTs (22-43% seizure frequency reduction), irrespective of the parameters utilized for VNS stimulation. In terms of VNS associated morbidity, these morbidities were consistently higher in adults who underwent high frequency VNS stimulation (eg dysphonia 37-66%, dyspnea 6-25.3%). However, no such differences were observed in the pediatric population. Moreover, <2% of patients withdrew from the RCTs/prospective studies due to intolerable symptoms. To provide an assessment of how the risks and benefits of VNS impact the patient experience, 1 study assessed the well-being of enrolled patients (as a secondary end point) and found VNS was associated with an overall improvement in well-being. Consistent with this observation, we identified a prospective, non-randomized study that demonstrated improved quality of life for epilepsy patients managed with VNS and best medical practice relative to best medical practice alone. In aggregate, these RCT studies support the efficacy and benefit of VNS as a neuro-modulatory platform in the management of a subset of medically refractory epilepsy patients.

Vagus nerve stimulation for pharmacoresistant epilepsy secondary to encephalomalacia: A single-center retrospective study

Objective

Vagus nerve stimulation (VNS) is an adjunctive treatment for pharmacoresistant epilepsy. Encephalomalacia is one of the most common MRI findings in the preoperative evaluation of patients with pharmacoresistant epilepsy. This is the first study that aimed to determine the effectiveness of VNS for pharmacoresistant epilepsy secondary to encephalomalacia and evaluate the potential predictors of VNS effectiveness.

Methods

We retrospectively analyzed the seizure outcomes of VNS with at least 1 year of follow-up in all patients with pharmacoresistant epilepsy secondary to encephalomalacia. Based on the effectiveness of VNS (≥50% or <50% reduction in seizure frequency), patients were divided into two subgroups: responders and non-responders. Preoperative data were analyzed to screen for potential predictors of VNS effectiveness.

Results

A total of 93 patients with epilepsy secondary to encephalomalacia who underwent VNS therapy were recruited. Responders were found in 64.5% of patients, and 16.1% of patients achieved seizure freedom at the last follow-up. In addition, the responder rate increased over time, with 36.6, 50.5, 64.5, and 65.4% at the 3-, 6-, 12-, and 24-month follow-ups, respectively. After multivariate analysis, seizure onset in adults (>18 years old) (OR: 0.236, 95%CI: 0.059-0.949) was found to be a positive predictor, and the bilateral interictal epileptic discharges (IEDs) (OR: 3.397, 95%CI: 1.148-10.054) and the bilateral encephalomalacia on MRI (OR: 3.193, 95%CI: 1.217-8.381) were found to be negative predictors of VNS effectiveness.

Conclusion

The results demonstrated the effectiveness and safety of VNS therapy in patients with pharmacoresistant epilepsy secondary to encephalomalacia. Patients with seizure onset in adults (>18 years old), unilateral IEDs, or unilateral encephalomalacia on MRI were found to have better seizure outcomes after VNS therapy.

Cerebral cortex and hippocampus neural interaction during vagus nerve stimulation under in vivo large-scale imaging

Objective

The purpose of this study was to study mechanisms of VNS modulation from a single neuron perspective utilizing a practical observation platform with single neuron resolution and widefield, real-time imaging coupled with an animal model simultaneously exposing the cerebral cortex and the hippocampus.

Methods

We utilized the observation platform characterized of widefield of view, real-time imaging, and high spatiotemporal resolution to obtain the neuronal activities in the cerebral cortex and the hippocampus during VNS in awake states and under anesthesia.

Results

Some neurons in the hippocampus were tightly related to VNS modulation, and varied types of neurons showed distinct responses to VNS modulation.

Conclusion

We utilized such an observation platform coupled with a novel animal model to obtain more information on neuron activities in the cerebral cortex and the hippocampus, providing an effective method to further study the mechanisms of therapeutic effects modulated by VNS.

Brain functional connectivity and network characteristics changes after vagus nerve stimulation in patients with refractory epilepsy

Objective

This study aims to investigate the impact of vagus nerve stimulation (VNS) on the connectivity and small-world metrics of brain functional networks during seizure periods.

Methods

Ten refractory epilepsy patients underwent video encephalographic monitoring before and after VNS treatment. The 2-min electroencephalogram segment containing the ictal was selected for each participant, resulting in a total of 20 min of seizure data. The weighted phase lag index (wPLI) and small-world metrics were calculated for the whole frequency band and different frequency bands (delta, theta, alpha, beta, and gamma). Finally, the relevant metrics were statistically analyzed, and the false discovery rate was used to correct for differences after multiple comparisons.

Results

In the whole band, the wPLI was notably enhanced, and the network metrics, including degree (D), clustering coefficient (CC), and global efficiency (GE), increased, while characteristic path length (CPL) decreased (P < 0.01). In different frequency bands, the wPLI between the parieto-occipital and frontal regions was significantly strengthened in the delta and beta bands, while the wPLI within the frontal region and between the frontal and parieto-occipital regions were significantly reduced in the beta and gamma bands (P < 0.01). In the low-frequency band (<13 Hz), the small-world metrics demonstrated significantly increased CC, D, and GE, with a significantly decreased CPL, indicating a more efficient network organization. In contrast, in the gamma band, the GE decreased, and the CPL increased, suggesting a shift toward less efficient network organization.

Conclusion

VNS treatment can significantly change the wPLI and small-world metrics. These findings contribute to a deeper understanding of the impact of VNS therapy on brain networks and provide objective indicators for evaluating the efficacy of VNS.

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

INTRODUCTION

People with recurrent epileptic seizures are typically treated with anti-seizure medications (ASMs). Around a third of epilepsy patients fail to achieve an adequate response to ASMs and may be eligible to receive vagus nerve stimulation (VNS) therapy for their drug-resistant epilepsy (DRE) if they are unsuited to surgery. VNS received approval from the United States (US) Food and Drug Administration agency. However, there has to date been no comprehensive cost effectiveness evaluation of VNS within the US setting. This study was designed, using a US Medicare perspective, to estimate costs and quality-adjusted life years (QALYs) associated with VNS as an adjunct to ongoing ASM therapy, compared to ASMs alone.

METHODS

We developed a cohort state transition model in Microsoft Excel, with four health states defined by different percentage reductions in seizure frequency, with a 3-month cycle and transition probabilities derived from published clinical trials and registry data. Sensitivity analyses were conducted to understand the impact of parameter uncertainty. Costs included the VNS device, placement, programming, battery changes, and removal; ASM therapy; adverse events associated with VNS (dyspnea, hoarseness, and cough); and costs associated with seizure burden (i.e. hospitalizations, emergency department visits, neurologist visits).

RESULTS

Under base case assumptions, treatment with VNS was associated with a 0.385 QALY gain and a $109,678 saving per patient, when compared with ASM therapy alone. The incremental net monetary benefit (iNMB) was $128,903 at a threshold of $50,000 per QALY, with the positive iNMB indicating that VNS is a highly cost effective treatment. This result is explained by the modeled reduction in relative seizure frequency and associated reduction in healthcare resource use that the VNS group experienced. Sensitivity analyses supported this conclusion.

CONCLUSIONS

VNS was evaluated as a cost effective addition to the current standard of care in the treatment of DRE in the US Medicare context.

Electroconvulsive therapy use for refractory status epilepticus in an implantable vagus nerve stimulation patient: A case report

INTRODUCTION

Status epilepticus (SE) has a mortality rate of 20 to 50%, with acute symptomatic SE having a higher risk compared to chronic SE. Electroconvulsive therapy (ECT) has been utilized for the treatment of refractory SE with a success rate estimate of 57.9%. There are no known reported cases of concomitant use of vagus nerve stimulation (VNS) and ECT for the treatment of super refractory SE (SRSE) available in the literature.

CASE DESCRIPTION

We present a 44-year-old female with a history of developmental delay, epilepsy, an implantable VNS for 6 years, and traumatic brain injury with subsequent hygroma who presented with progressive aphasia, declining mental status, and daily generalized seizures lasting up to 20 min. Seizures had increased from her baseline of one seizure per day controlled with topiramate 200 mg three times daily and lamotrigine 400 mg twice daily. She was diagnosed with SRSE after being intubated and placed on eight anti-epileptic drugs (AEDs) that failed to abort SE. ECT was attempted to terminate SE. Due to a prior right craniotomy with subsequent right hygroma, eight treatments of ECT were performed over three sessions using a right anterior, left temporal (RALT) and subsequently a bitemporal electrode placement. The VNS remained active throughout treatment. Various ECT dosing parameters were attempted, varying pulse width and frequency. Although ECT induced mild transient encephalographic (EEG) changes following ECT stimulations, it was unable to terminate SE.

DISCUSSION

This case describes various treatment strategies, constraints, and device limitations when using ECT for the treatment of SE. With wide variability in efficacy rates of ECT in the treatment of SE in the literature, successful and unsuccessful cases offer information on optimizing ECT total charge dose and parameters that yielded success. This case demonstrates an instance of ECT inefficacy in the treatment of SRSE. Here, we discuss the rationale behind the various ECT settings that were selected, and constraints arising from the antiepileptic burden, VNS, and intrinsic limitations of the ECT device itself.

USP10 is a potential mediator for vagus nerve stimulation to alleviate neuroinflammation in ischaemic stroke by inhibiting NF-κB signalling pathway

Background

Vagus nerve stimulation (VNS) has a protective effect on neurological recovery in ischaemic stroke. However, its underlying mechanism remains to be clarified. Ubiquitin-specific protease 10 (USP10), a member of the ubiquitin-specific protease family, has been shown to inhibit the activation of the NF-κB signalling pathway. Therefore, this study investigated whether USP10 plays a key role in the protective effect of VNS against ischemic stroke and explore its mechanism.

Methods

Ischaemic stroke model was constructed by transient middle cerebral artery occlusion (tMCAO) in mice. VNS was performed at 30 min, 24hr, and 48hr after the establishment of tMCAO model. USP10 expression induced by VNS after tMCAO was measured. LV-shUSP10 was used to establish the model with low expression of USP10 by stereotaxic injection technique. The effects of VNS with or without USP10 silencing on neurological deficits, cerebral infarct volume, NF-κB pathway activation, glial cell activation, and release of pro-inflammation cytokines were assessed.

Results

VNS enhanced the expression of USP10 following tMCAO. VNS ameliorated neurological deficits and reduced cerebral infarct volume, but this effect was inhibited by silencing of USP10. Activation of the NF-κB pathway and the expression of inflammatory cytokines induced by tMCAO were suppressed by VNS. Moreover, VNS promoted the pro-to-anti-inflammatory response of microglia and inhibited activation of astrocytes, while silencing of USP10 prevented the neuroprotective and anti-neuroinflammatory effects of VNS.

Conclusion

USP10 is a potential mediator for VNS to alleviate neurological deficits, neuroinflammation, and glial cell activation in ischaemic stroke by inhibiting NF-κB signalling pathway.

Bibliometric analysis of publication trends and research hotspots in vagus nerve stimulation: A 20-year panorama

Background

As a promising neuromodulation technique, vagus nerve stimulation (VNS) has been utilized to treat diverse diseases and the number of VNS studies has grown prosperously. Nonetheless, publication trends and research hotspots in this field remain unknown. This study aimed to perform a bibliometric analysis to systematically identify publication trends and research hotspots in VNS research within a 20-year panorama.

Methods

The Web of Science Core Collection (WoSCC) database was retrieved to screen eligible VNS-related publications from 2002 to 2021. The online analytic tool of the WoSCC database was used to analyze various bibliometric parameters, such as the number of annual publications, the output of countries/regions, journals, total citations, citations per publication, and the Hirsch index. Bibliometrics (http://bibliometric.com/) and CiteSpace (version 5.6.R3) were used to identify research trends and hotspots.

Results

A total of 7,283 publications were included for analysis. The annual number of publications increased stably but it increased significantly in recent years. The top five prolific countries were the United States, China, Germany, England, and France. The top five productive institutions were the University of California (Los Angeles), Harvard Medical School, Harvard University, University College London, and the University of Texas at Dallas. Notably, there was a geographical imbalance in countries and institutions. In addition, Epilepsy & Behavior, Epilepsia, and Plos One were the top three journals with the largest number of VNS publications. Michael P Kilgard was the most prolific author. Moreover, evolving research hotspots mainly included the effectiveness and mechanism of VNS on epilepsy, the role of VNS as an anti-inflammatory regulator, the application of VNS for psychiatric disorders, and the neuromodulation effect of VNS in headache management.

Conclusion

This study has revealed the overall publication trends and evolving research trends at a global level over a 20-year panorama. The potential collaborators, institutions, hotspots, and future research trends are also identified in this field, which will help guide new research directions of VNS.

Effectiveness of vagus nerve stimulation therapy in refractory hypoxic-ischemic encephalopathy-induced epilepsy

Background

Epilepsy is one of the important long-term sequelae of neonatal hypoxic-ischemic encephalopathy (HIE) and is typically characterized by drug resistance and poor surgical outcomes. Vagus nerve stimulation (VNS) is a promising neuromodulation therapy for refractory epilepsy.

Objectives

The present study aimed to first evaluate the effectiveness of VNS in patients with refractory HIE-induced epilepsy and scrutinize potential clinical predictors.

Methods

We retrospectively collected the outcomes of VNS in all patients with refractory HIE-induced epilepsy and at least 2 years of follow-up. Subgroups were classified as responders and nonresponders according to the effectiveness of VNS (⩾50% or <50% reduction in seizure frequency). Preoperative data were analyzed to screen for potential predictors of VNS effectiveness.

Results

A total of 55 patients with refractory HIE-induced epilepsy who underwent VNS therapy were enrolled. Responders represented 56.4% of patients, and 12.7% of patients achieved seizure freedom at the last follow-up. In addition, the responder rate increased over time with rates of 23.6%, 38.2%, 50.9%, and 56.4% at the 3-, 6-, 12- and 24-month follow-ups, respectively. After multivariate analysis, neonatal seizure was identified as a negative predictor (OR: 4.640, 95% CI: 1.129-19.066), and a predominant seizure type of generalized onset was identified as a positive predictor (OR: 0.261, 95% CI: 0.078-0.873) of VNS effectiveness.

Conclusion

VNS therapy was effective in patients with refractory HIE-induced epilepsy and was well tolerated over a 2-year follow-up period. VNS therapy demonstrated better effectiveness in patients without neonatal seizures or with a predominant seizure type of generalized onset.

Vagus Nerve Stimulation for Drug Resistant Epilepsy: Clinical Outcome, Adverse Events, and Potential Prognostic Factors in a Single Center Experience

OBJECTIVE

Vagus nerve stimulation (VNS) has been used for adjunctive treatment in drug resistant epilepsy (DRE) for decades. Nevertheless, information is lacking on possible potential prognostic factors. Our study presents the efficacy and safety of VNS with a focus on prognostic factors in 45 patients with DRE.

METHODS

We retrospectively evaluated the clinical outcome of 45 consecutive patients with DRE undergoing VNS implantation in The First Affiliated Hospital of Anhui Medical University between November 2016 and August 2021. Medical records were aggregated across all patient visits. Cox proportional hazards regression was used to estimate the prognostic factors.

RESULTS

Significant decrease in seizure frequency was observed after intermittent stimulation of the vagus nerve. According to the modified McHugh classification, 11 patients (24.4%) were Class I, 11 patients (24.4%) were Class II, four patients (8.9%) were Class III, 10 patients (22.2%) were Class IV, and nine patients (20.0%) were Class V. Notably, 22 patients (48.9%) were responders and four patients (8.9%) were seizure-free at the final follow-up. No significant prognostic factors were found in this cohort. Furthermore, 37 patients reported improved quality of life. Of the patients, 22 (48.9%) experienced adverse events after surgery; hoarseness, discomfort at the surgical site, and coughing were the most common.

CONCLUSION

The results confirmed the efficacy and safety of VNS. No prognostic factors were identified.

Vagus Nerve Stimulation: A Personalized Therapeutic Approach for Crohn's and Other Inflammatory Bowel Diseases

Inflammatory bowel diseases, including Crohn's disease and ulcerative colitis, are incurable autoimmune diseases characterized by chronic inflammation of the gastrointestinal tract. There is increasing evidence that inappropriate interaction between the enteric nervous system and central nervous system and/or low activity of the vagus nerve, which connects the enteric and central nervous systems, could play a crucial role in their pathogenesis. Therefore, it has been suggested that appropriate neuroprosthetic stimulation of the vagus nerve could lead to the modulation of the inflammation of the gastrointestinal tract and consequent long-term control of these autoimmune diseases. In the present paper, we provide a comprehensive overview of (1) the cellular and molecular bases of the immune system, (2) the way central and enteric nervous systems interact and contribute to the immune responses, (3) the pathogenesis of the inflammatory bowel disease, and (4) the therapeutic use of vagus nerve stimulation, and in particular, the transcutaneous stimulation of the auricular branch of the vagus nerve. Then, we expose the working hypotheses for the modulation of the molecular processes that are responsible for intestinal inflammation in autoimmune diseases and the way we could develop personalized neuroprosthetic therapeutic devices and procedures in favor of the patients.

Cervical vagal nerve schwannoma induced arrhythmia: a rare case report and literature review

Background

Schwannomas are benign tumors deriving from the sheath of cranial and peripheral nerves. The vagus nerve is comprised of a complex neuro-endocrine-immune network that maintains homeostasis, most tracts of it play a role in parasympathetic activity. We present an example of a rare cervical vagal schwannoma case accompanied by arrhythmia.

Case presentation

A 35-year-old female patient with a left cervical vagus schwannoma and ventricular arrhythmia underwent schwannoma resection in the operating room. The patient’s suppressed heart rate increased after tumor removal, and the cardiac rhythm returned to normal postoperatively. Pathological examination demonstrated the diagnosis of schwannoma.

Conclusions

This case explains the link between the vagus nerve and the cardiovascular system, proving that a damaged cervical vagus nerve can inhibit the heart rate and lead to arrhythmias, and eventually requiring surgical intervention.

Wireless optoelectronic devices for vagus nerve stimulation in mice

Objective.Vagus nerve stimulation (VNS) is a promising approach for the treatment of a wide variety of debilitating conditions, including autoimmune diseases and intractable epilepsy. Much remains to be learned about the molecular mechanisms involved in vagus nerve regulation of organ function. Despite an abundance of well-characterized rodent models of common chronic diseases, currently available technologies are rarely suitable for the required long-term experiments in freely moving animals, particularly experimental mice. Due to challenging anatomical limitations, many relevant experiments require miniaturized, less invasive, and wireless devices for precise stimulation of the vagus nerve and other peripheral nerves of interest. Our objective is to outline possible solutions to this problem by using nongenetic light-based stimulation.Approach.We describe how to design and benchmark new microstimulation devices that are based on transcutaneous photovoltaic stimulation. The approach is to use wired multielectrode cuffs to test different stimulation patterns, and then build photovoltaic stimulators to generate the most optimal patterns. We validate stimulation through heart rate analysis.Main results.A range of different stimulation geometries are explored with large differences in performance. Two types of photovoltaic devices are fabricated to deliver stimulation: photocapacitors and photovoltaic flags. The former is simple and more compact, but has limited efficiency. The photovoltaic flag approach is more elaborate, but highly efficient. Both can be used for wireless actuation of the vagus nerve using light impulses.Significance.These approaches can enable studies in small animals that were previously challenging, such as long-termin vivostudies for mapping functional vagus nerve innervation. This new knowledge may have potential to support clinical translation of VNS for treatment of select inflammatory and neurologic diseases.

Optimization of respiratory-gated auricular vagus afferent nerve stimulation for the modulation of blood pressure in hypertension

Background

The objective of this pilot study was to identify frequency-dependent effects of respiratory-gated auricular vagus afferent nerve stimulation (RAVANS) on the regulation of blood pressure and heart rate variability in hypertensive subjects and examine potential differential effects by sex/gender or race.

Methods

Twenty hypertensive subjects (54.55 ± 6.23 years of age; 12 females and 8 males) were included in a within-person experimental design and underwent five stimulation sessions where they received RAVANS at different frequencies (i.e., 2 Hz, 10 Hz, 25 Hz, 100 Hz, or sham stimulation) in a randomized order. EKG and continuous blood pressure signals were collected during a 10-min baseline, 30-min stimulation, and 10-min post-stimulation periods. Generalized estimating equations (GEE) adjusted for baseline measures were used to evaluate frequency-dependent effects of RAVANS on heart rate, high frequency power, and blood pressure measures, including analyses stratified by sex and race.

Results

Administration of RAVANS at 100 Hz had significant overall effects on the reduction of heart rate (β = -2.03, p = 0.002). It was also associated with a significant reduction of diastolic (β = -1.90, p = 0.01) and mean arterial blood pressure (β = -2.23, p = 0.002) in Black hypertensive participants and heart rate in female subjects (β = -2.83, p = 0.01) during the post-stimulation period when compared to sham.

Conclusion

Respiratory-gated auricular vagus afferent nerve stimulation exhibits frequency-dependent rapid effects on the modulation of heart rate and blood pressure in hypertensive patients that may further differ by race and sex. Our findings highlight the need for the development of optimized stimulation protocols that achieve the greatest effects on the modulation of physiological and clinical outcomes in this population.

Narrative Review of Noninvasive Brain Stimulation in Stroke Rehabilitation

Stroke is a disease with a high incidence and disability rate, resulting in changes in neural network and corticoid-subcortical excitability and various functional disabilities. The aim of the present study was to discuss the current status of research and limitations and potential direction in the application of noninvasive brain stimulation (NIBS) on post-stroke patients. This literature review focused on clinical studies and reviews. Literature retrieval was conducted in PubMed, Cochrane, Scopus, and CNKI, using the following keywords: Repeated transcranial magnetic stimulation, Transcranial direct current stimulation, Transcranial alternating current stimulation, Transcranial alternating current stimulation, Transcranial focused ultrasound, Noninvasive vagus nerve stimulation, Stroke, and Rehabilitation. We selected 200 relevant publications from 1985 to 2022. An overview of recent research on the use of NIBS on post-stroke patients, including its mechanism, therapeutic parameters, effects, and safety, is presented. It was found that NIBS has positive therapeutic effects on dysfunctions of motor, sensory, cognitive, speech, swallowing, and depression after stroke, but standardized stimulus programs are still lacking. The literature suggests that rTMS and tDCS are more beneficial to post-stroke patients, while tFUS and tVNS are currently less studied for post-stroke rehabilitation, but are also potential interventions.

Totally Organic Hydrogel-Based Self-Closing Cuff Electrode for Vagus Nerve Stimulation

An intrinsically soft organic electrode consisting of poly(3,4-ethylenedioxythiophene)-modified polyurethane (PEDOT-PU) is embedded into a bilayer film of polyvinyl alcohol (PVA) hydrogels for developing a self-closing cuff electrode for neuromodulation. The curled form of the PVA hydrogel is prepared by releasing internal stress in the bilayer structure. The inner diameter of the cuff electrode is set to less than 2 mm for immobilization to the vagus nerve (VN) of humans and pigs. The stability of the immobilization is examined, while the pressure applied to a nerve bundle is at a harmless level (≈200 Pa). Since the electrode is totally organic, MRI measurements can be conducted without image artifacts. The large electric capacitance of the PEDOT-PU (≈27 mF cm^-2 ) ensures a safe stimulation of living tissues without Faradaic reactions. The practical performance of the cuff electrode for VN stimulation is demonstrated by observation of bradycardia induction in a pig.

Drug-resistant epilepsy and mortality-Why and when do neuromodulation and epilepsy surgery reduce overall mortality

Patients with drug-resistant epilepsy have an increased mortality rate, with the majority of deaths being epilepsy related and 40% due to sudden unexpected death in epilepsy (SUDEP). The impact of epilepsy surgery on mortality has been investigated since the 1970s, with increased interest in this field during the past 15 years. We systematically reviewed studies investigating mortality rate in patients undergoing epilepsy surgery or neuromodulation therapies. The quality of available evidence proved heterogenous and often limited by significant methodological issues. Perioperative mortality following epilepsy surgery was found to be <1%. Meta-analysis of studies that directly compared patients who underwent surgery to those not operated following presurgical evaluation showed that the former have a two-fold lower risk of death and a three-fold lower risk of SUDEP compared to the latter (odds ratio [OR] 0.40, 95% confidence interval [CI]: 0.29-0.56; p < .0001 for overall mortality and OR 0.32, 95% CI: 0.18-0.57; p < .001 for SUDEP). Limited data are available regarding the risk of death and SUDEP in patients undergoing neuromodulation therapies, although some evidence indicates that vagus nerve stimulation might be associated with a lower risk of SUDEP. Several key questions remain to be addressed in future studies, considering the need to better inform patients about the long-term benefit-risk ratio of epilepsy surgery. Dedicated long-term prospective studies will thus be required to provide more personalized information on the impact of surgery and/or neuromodulation on the risk of death and SUDEP.

Right vagus nerve stimulation improves motor behavior by exerting neuroprotective effects in Parkinson's disease rats

Background

Parkinson's disease (PD) is a common movement disorder disease. Left vagus nerve stimulation (LVNS) is a potential treatment option for PD. Compared with the left vagus nerve, the right vagus nerve is more closely connected with the midbrain dopaminergic neurons, which are the lesion locations of PD. However, whether right vagus nerve stimulation (RVNS) has a therapeutic effect on PD has not yet been studied. Therefore, in this study, we studied the therapeutic effect and underlying mechanism of RVNS using a PD rat model.

Methods

To establish the PD rat model, 8-week-old male Sprague-Dawley rats were intraperitoneally injected with rotenone for 21 days. The cuff electrodes were implanted into the right cervical vagal carotid sheaths of the rats. The right vagus nerve was continuously stimulated for 14 days using a radio stimulation system. Behavioral tests were performed before and after stimulation. Finally, tyrosine hydroxylase (TH), vesicular monoamine transporter 2 (VMAT2), and α-synuclein in the midbrain, including the substantia nigra (SN) and ventral tegmental area (VTA), were detected by immunofluorescence.

Results

A markedly lower distance traveled and rearing number was observed in the rotenone, rotenone + sham, and rotenone + RVNS groups compared to the vehicle group. After the stimulation days, the distance traveled and rearing number were both higher in the rotenone + RVNS group compared to the rotenone and rotenone + sham groups (P<0.01, P<0.0001). A remarkable increase in distance traveled and rearing number was observed in the rotenone + RVNS group after stimulation. TH expression in the vehicle group was significantly up-regulated than the other groups. RVNS markedly up-regulated TH expression level. A significantly higher expression of α-synuclein was observed in the rotenone, rotenone + sham, and rotenone + RVNS groups compared to the vehicle group. The expression of α-synuclein was lower in the rotenone + RVNS group compared to the rotenone and rotenone + sham groups. A markedly higher VMAT2 expression was observed in the vehicle group compared to other groups. RVNS significantly up-regulated VMAT2 expression.

Conclusions

The improved motor behavior and neuroprotective effects on the midbrain dopaminergic neurons in the PD rat model suggest that RVNS could be used as a potential treatment for PD.

Brain-clinical signatures for vagus nerve stimulation response

AIM

Vagus nerve stimulation (VNS) is a valuable treatment for drug-resistant epilepsy (DRE) without the indication of surgical resection. The clinical heterogeneity of DRE has limited the optimal indication of choice and diagnosis prediction. The study aimed to explore the correlations of brain-clinical signatures with the clinical phenotype and VNS responsiveness.

METHODS

A total of 89 DRE patients, including VNS- (n = 44) and drug-treated (n = 45) patients, were retrospectively recruited. The brain-clinical signature consisted of demographic information and brain structural deformations, which were measured using deformation-based morphometry and presented as Jacobian determinant maps. The efficacy and presurgical differences between these two cohorts were compared. Then, the potential of predicting VNS response using brain-clinical signature was investigated according to the different prognosis evaluation approaches.

RESULTS

The seizure reduction was higher in the VNS-treated group (42.50%) as compared to the drug-treated group (12.09%) (p = 0.11). Abnormal imaging representation, showing encephalomalacia (p_corrected  = 0.03), was commonly observed in the VNS-treated group (p = 0.04). In the patients treated with VNS, the mild/subtle brain abnormalities indicated higher seizure frequency (p = 0.03) and worse VNS response (p = 0.04). The partial least square regression analysis showed a moderate prediction potential of brain-clinical signature for VNS response (p < 0.01). The increase in the pre-VNS seizure frequency and structural etiology could indicate a worse prognosis (higher McHugh classification).

CONCLUSION

The brain-clinical signature illustrated its clinical potential in predicting the VNS response, which might allow clinicians to personalize treatment decisions for DRE patients.

Transcutaneous Auricular Vagus Nerve Stimulation Improves Inflammation but Does Not Interfere with Cardiac Modulation and Clinical Symptoms of Individuals with COVID-19: A Randomized Clinical Trial

Transcranial auricular vagus nerve stimulation (taVNS) has shown effectiveness in reducing inflammation and depression. Thus, this study evaluated its effect on inflammation, cardiac autonomic modulation, and clinical symptoms in individuals affected by COVID-19. Methods: There were 52 randomized participants hospitalized with COVID-19 diagnosis who were to receive active (a-taVNS) or sham taVNS (s-taVNS) for 90 min twice a day for seven consecutive days. Interleukin 6 (IL-6), 10 (IL-10), cortisol, C-reactive protein (CRP), heart rate variability (HRV), and clinical symptoms were assessed before and after seven days of treatment. There were also seven- and fourteen-day follow-ups for clinical symptoms, including anxiety and depression levels, as well as a six-month follow-up for memory and attention levels. Results: There was significant reduction in CRP −23.9%, (95% CI −46.3 to −1.4) and IL-6 −37.7%, (95% CI −57.6 to −17.7) for the a-taVNS group. There were no changes in IL-10, cortisol levels, or in HRV results (p > 0.05) in both groups. There were no changes regarding clinical symptoms, except for a significant decrease in depression level (−2.85, 95% CI −5.44 to −0.27) in the a-taVNS group. Conclusion: taVNS showed effects on CRP, IL-6, and depression levels; however, it did not affect other clinical symptoms.

Modulating Heart Rate Variability through Deep Breathing Exercises and Transcutaneous Auricular Vagus Nerve Stimulation: A Study in Healthy Participants and in Patients with Rheumatoid Arthritis or Systemic Lupus Erythematosus

Rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) are associated with an impaired autonomic nervous system and vagus nerve function. Electrical or physiological (deep breathing-DB) vagus nerve stimulation (VNS) could be a potential treatment approach, but no direct comparison has been made. In this study, the effect of transcutaneous auricular VNS (taVNS) and DB on vagal tone was compared in healthy participants and RA or SLE patients. The vagal tone was estimated using time-domain heart-rate variability (HRV) parameters. Forty-two healthy participants and 52 patients performed 30 min of DB and 30 min of taVNS on separate days. HRV was recorded before and immediately after each intervention. For the healthy participants, all HRV parameters increased after DB (SDNN + RMSSD: 21-46%), while one HRV parameter increased after taVNS (SDNN: 16%). For the patients, all HRV parameters increased after both DB (17-31%) and taVNS (18-25%), with no differences between the two types of VNS. DB was associated with the largest elevation of the HRV parameters in healthy participants, while both types of VNS led to elevated HRV parameters in the patients. The findings support a potential use of VNS as a new treatment approach, but the clinical effects need to be investigated in future studies.

In vivo peripheral nerve activation using sinusoidal low-frequency alternating currents

BACKGROUND

The sinusoidal low-frequency alternating current (LFAC) waveform was explored recently as a novel means to evoke nerve conduction block. In the present work, we explored whether increasing the amplitude of the LFAC waveform results in nerve fiber activation in autonomic nerves. In-silico methods and preliminary work in somatic nerves indicated a potential frequency dependency on the threshold of activation. The Hering-Breuer (HB) reflex was used as a biomarker to detect cervical vagus nerve activation.

METHODS

Experiments were conducted in isoflurane-anesthetized swine (n = 5). Two stimulating bipolar cuff electrodes and a tripolar recording cuff electrode were implanted on the left vagus nerve. To ensure the electrical stimulation affects only the afferent pathways, the nerve was crushed caudal to the electrodes to eliminate cardiac effects. (1) Standard pulse stimulation (Vstim) using a monophasic train of pulses was applied through the caudal electrode to elicit HB reflex and to identify the activated nerve fiber type. (2) Continuous sinusoidal LFAC waveform with a frequency ranging from 5 through 20 Hz was applied to the rostral electrode without Vstim to explore the activation thresholds at each LFAC frequency. In both cases, the activation of nerve fibers was detected by a HB reflex-induced reduction in the breathing rate.

RESULTS

LFAC was found to be capable of eliciting an HB response. The LFAC activation thresholds were found to be frequency-dependent. The HB threshold was 1.02 ± 0.3 mA_p at 5 Hz, 0.66 ± 0.3 mA_p at 10 Hz, and 0.44 ± 0.2 mA_p at 20 Hz. In comparison, it was 0.7 ± 0.47 mA for a 100 μs pulse. The LFAC amplitude was within the linear limits of the electrode interface. Damage to the cuff electrodes or the nerve tissues was not observed. Analysis of Vstim-based compound nerve action potentials (CNAP) indicated that the decrease in breathing rate was found to be correlated with the activation of slower components of the CNAP suggesting that LFAC reached and elicited responses from these slower fibers associated with afferents projecting to the HB response.

CONCLUSIONS

These results suggest the feasibility of the LFAC waveform at 5, 10, and 20 Hz to activate autonomic nerve fibers and potentially provide a new modality to the neurorehabilitation field.