Vagus Nerve Stimulation Therapy for Seizures

The protective role of vagus nerve stimulation in ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) encompasses the damage resulting from the restoration of blood supply following tissue ischemia. This phenomenon commonly occurs in clinical scenarios such as hemorrhagic shock, severe trauma, organ transplantation, and thrombolytic therapy. Despite its prevalence, existing treatments exhibit limited efficacy against IRI. Vagus nerve stimulation (VNS) is a widely utilized technique for modulating the autonomic nervous system. Numerous studies have demonstrated that VNS significantly reduces IRI in various organs, including the heart, brain, and liver. This article reviews the pathological processes during IRI and summarizes the role and possible mechanisms of VNS in IRI of different organs. Furthermore, this review addresses the current challenges of VNS clinical applications, providing a novel perspective on IRI treatment.

An optoelectronic implantable neurostimulation platform allowing full MRI safety and optical sensing and communication

A novel programmable implantable neurostimulation platform based on photonic power transfer has been developed for various clinical applications with the main focus of being safe to use with MRI scanners. The wires usually conveying electrical current from the neurostimulator to the electrodes are replaced by optical fibers. Photovoltaic cells at the tip of the fibers convert laser light to biphasic electrical impulses together with feedback signals with 54% efficiency. Furthermore, a biocompatible, implantable and ultra-flexible optical lead was developed including custom optical fibers. The neurostimulator platform incorporates advanced signal processing and optical physiological sensing capabilities thanks to a hermetically sealed transparent nonmetallic casing. Skin transparency also allowed the development of a high-speed optical transcutaneous communication channel. This implantable neurostimulation platform was first adapted to a vagus nerve stimulator for the treatment of epilepsy. This neurostimulator has been designed to fulfill the requirements of a class III long-term implantable medical device. It has been proven compliant with standard ISO/TS10974 for 1.5 T and 3 T MRI scanners. The device poses no related threat and patients can safely undergo MRI without specific or additional precautions. Especially, the RF induced heating near the implant remains below 2 °C whatever the MRI settings used. The main features of this unique advanced neurostimulator and its architecture are presented. Its functional performance is evaluated, and results are described with a focus on optoelectronics aspects and MRI safety.

Single-interface bioelectronic medicines - concept, clinical applications and preclinical data

Presently, large groups of patients with various diseases are either intolerant, or irresponsive to drug therapies and also intractable by surgery. For several diseases, one option which is available for such patients is the implantable neurostimulation therapy. However, lacking closed-loop control and selective stimulation capabilities, the present neurostimulation therapies are not optimal and are therefore used as only "third" therapeutic options when a disease cannot be treated by drugs or surgery. Addressing those limitations, a next generation class of closed-loop controlled and selective neurostimulators generically named bioelectronic medicines seems within reach. A sub-class of such devices is meant to monitor and treat impaired functions by intercepting, analyzing and modulating neural signals involved in the regulation of such functions using just one neural interface for those purposes. The primary objective of this review is to provide a first broad perspective on this type of single-interface devices for bioelectronic therapies. For this purpose, the concept, clinical applications and preclinical studies for further developments with such devices are here analyzed in a narrative manner.

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.

Vagus nerve stimulation: a pre-hospital case report

Introduction:

Vagus nerve stimulation (VNS) is an adjunct therapy to anti-epileptics in patients where combination drug therapy alone has failed. The VNS device resembles an implantable defibrillator, and can be found underneath the clavicle on either side of the chest. By using a strong ring magnet, the device can be manipulated to seize function or operate on higher intensities, depending on how it is applied. The use of vagal stimulation is increasingly common and VNS is being explored for a range of other medical complaints.

Case:

This case study discusses the encounter between a paramedic and a woman presenting with a choking sensation, isolated uvular deviation and stable cardiorespiratory functions. Following a short period of observation without adverse events, she was discharged on scene and advised to see her specialist epilepsy nurse.

Conclusion:

Side effects of VNS increase with intensity of stimulation and can manifest throughout any branch of the vagus nerve. Its therapeutic mechanism of action is yet to be fully understood. The symptoms of over-stimulation are often frightening but benign, and although life-threatening events are rare, they require rapid recognition and immediate intervention.

Ten-year outcome of vagus nerve stimulation-implanted patients with treatment-resistant depression: two Italian cases

Over the last 15 years, vagus nerve stimulation (VNS) has been used as an augmentative therapeutic intervention in patients with treatment-resistant depression (TRD), whether with a lifetime diagnosis of major depressive disorder or bipolar disorder. From being a potentially effective treatment in the acute phase of TRD, recently published treatment guidelines seemed to converge on the indication that VNS's greatest benefit may be seen mostly beyond the short term. However, with the exception of a recent multicenter American report, very few studies have assessed the long-term efficacy of VNS in TRD patients. Herein, we present the cases of two Italian patients with TRD, with 10-year VNS follow-up evaluation. Both patients were found to benefit from augmentative VNS, and the latency of their stimulation response, tolerability, associated pharmacological treatment, number and duration of recurrences, and overall level of functioning are described and discussed. Further reports with larger samples are needed to support the long-term efficacy and tolerability of VNS in TRD patients, particularly beyond 5 years of follow-up.

Brain stimulation treatments in bipolar disorder: A review of the current literature

OBJECTIVES

Brain stimulation techniques are non-pharmacologic strategies which offer additional therapeutic options for treatment-resistant depression (TRD). The purpose of this paper is to review the current literature regarding the use of brain stimulation in resistant bipolar disorder (BD), with particular reference to hypomanic/manic symptoms.

METHODS

Keywords pertaining to the brain simulation techniques used in the treatment of depression (either unipolar or bipolar) along with their role in regard to hypomanic/manic symptoms were used to conduct an electronic search of the literature. Pertinent findings were identified by the authors and reviewed.

RESULTS

Brain stimulation techniques represent a valid therapeutic option in TRD. They have been extensively studied in unipolar depression and, to a minor extent, in the depressive phase of BD, showing encouraging but often limited results. With exception of electroconvulsive therapy, the efficacy of brain stimulation in the treatment of manic symptoms of bipolar patients is still uncertain and needs to be fully evaluated.

CONCLUSIONS

Brain stimulation in BD is derived from its use in unipolar depression. However, there are many important differences between these two disorders and more studies with a systematic approach need to be conducted on larger samples of bipolar patients with treatment-resistant characteristics.

Effect of Cardiac-Cycle-Synchronized Selective Vagal Stimulation on Heart Rate and Blood Pressure in Rats

INTRODUCTION

Activation of the baroreflex system through the selective vagal nerve stimulation (sVNS) may become a treatment option for therapy-resistant hypertension, which is a frequently observed problem in the antihypertensive therapy. In previous studies, we used continuous sVNS to lower blood pressure (BP) without major side effects in a rat model. As continuous stimulation is energy consuming and sVNS could be implemented in an antihypertensive stimulator, it was the aim of this study to investigate the efficacy of pulsatile, cardiac-cycle-synchronized sVNS (cssVNS) on the reduction of BP.

METHODS

A multichannel cuff electrode was wrapped around the left vagal nerve in six male Wistar rats under Isoflurane anesthesia. BP was recorded in the left carotid artery. An electrocardiogram (ECG) was obtained via subcutaneous needle electrodes. The aortic depressor nerve fibers in the vagal nerve bundle were selectively stimulated with 18 parameter settings within a window of 15-30 ms after the R-peak in the ECG. The stimulation paradigm included every heartbeat, every second heart beat, and every third heart beat. BP and heart rate were initially recorded over 10 min.

RESULTS

Using cssVNS, BP could be significantly reduced over 30 min and maintained at this level. While the highest BP reduction was seen during cssVNS at every heartbeat with minimal bradycardia, less-yet significant-BP reduction was seen during cssVNS at every second or third heartbeat without causing detectable bradycardia.

CONCLUSION

cssVNS can chronically reduce BP in rats avoiding measurable bradycardic side effects. This energy-efficient technique might allow the implementation of sVNS using an implantable device to permanently lower BP in patients.

FUNDING

The study was funded by Bundesministerium fur Bildung und Forschung/German Federal Ministry of Education and Research among the call "Individualisierte Medizintechnik" under the grant number FKZ 13GW0120B.

Haemodynamic Responses to Selective Vagal Nerve Stimulation under Enalapril Medication in Rats

Selective vagal nerve stimulation (sVNS) has been demonstrated to lower blood pressure (BP) in rats without causing major side effects. This method might be adapted for the treatment of therapy-resistant hypertension in patients. Converting enzyme inhibitors (CEIs) are among the first drugs that are administered for arterial hypertension and prominently reduce BP primarily by interacting with the renin-angiotensin system of the kidneys. Beyond the reduction of BP, CEI have a positive effect on the survival rate after myocardial infarction; they reduce the rates of stroke and improve the neurohormonal status in heart-failure patients. If sVNS might be introduced as a therapy against resistant hypertension, patients will at least partially stay on their CEI medication. It is therefore the aim of this study to investigate the influence of the CEI enalapril on the haemodynamic and respiratory effects of sVNS. In 10 male Wistar rats, a polyimide-based multichannel-cuff-electrode was placed around the vagal nerve bundle to selectively stimulate the aortic depressor nerve fibres. Stimulation parameters were adapted to the thresholds of the individual animals and included repetition frequencies between 30 and 50 Hz, amplitudes of 0.5 to 1.5 mA and pulse widths between 0.4 ms and 1.0 ms. BP responses were detected with a microtip transducer in the left carotid artery, and electrocardiography was recorded with subcutaneous electrodes. After intravenous administration of enalapril (2 mg/kg bodyweight), the animals’ mean arterial blood pressures (MAPs) decreased significantly, while the heart rates (HRs) were not significantly influenced. The effects of sVNS on BP and HR were attenuated by enalapril but were still present. We conclude that sVNS can lower the MAP during enalapril treatment without relevant side effects.

An electrical cause of stridor: pediatric vagal nerve stimulators

Vagal nerve stimulators (VNS) are surgically implantable medical devices which are approved by the food and drug administration (FDA) for treatment of medically refractory epilepsy in children. Two children with seizures disorders presented to the pediatric otolaryngology clinic with complaints of stridor and sleep apnea following implantation of VNS devices. Both children were evaluated with flexible laryngoscopy, direct laryngoscopy and bronchoscopy. The children were noted to have contraction of their vocal folds and supraglottis and the settings of their VNS were adjusted until no further contractions were noted. Each child had resolution of their symptoms following adjustment.

A controlled trial of transcutaneous vagus nerve stimulation for the treatment of pharmacoresistant epilepsy

This study explored the efficacy and safety of transcutaneous vagus nerve stimulation (t-VNS) in patients with pharmacoresistant epilepsy. A total of 60 patients were randomly divided into two groups based on the stimulation zone: the Ramsay-Hunt zone (treatment group) and the earlobe (control group). Before and after the 12-month treatment period, all patients completed the Self-Rating Anxiety Scale (SAS), the Self-Rating Depression Scale (SDS), the Liverpool Seizure Severity Scale (LSSS), and the Quality of Life in Epilepsy Inventory (QOLIE-31). Seizure frequency was determined according to the patient's seizure diary. During our study, the antiepileptic drugs were maintained at a constant level in all subjects. After 12 months, the monthly seizure frequency was lower in the treatment group than in the control group (8.0 to 4.0; P=0.003). This reduction in seizure frequency was correlated with seizure frequency at baseline and duration of epilepsy (both P>0.05). Additionally, all patients showed improved SAS, SDS, LSSS, and QOLIE-31 scores that were not correlated with a reduction in seizure frequency. The side effects in the treatment group were dizziness (1 case) and daytime drowsiness (3 cases), which could be relieved by reducing the stimulation intensity. In the control group, compared with baseline, there were no significant changes in seizure frequency (P=0.397), SAS, SDS, LESS, or QOLIE-31. There were also no complications in this group.

Clinical outcomes, quality of life, and costs associated with implantation of vagus nerve stimulation therapy in pediatric patients with drug-resistant epilepsy

BACKGROUND

VNS (Vagus Nerve Stimulation Therapy) is approved in the USA to treat refractory epilepsy as adjunctive to antiepileptic drugs (AEDs) in patients ≥12 years with complex partial seizures.

AIMS

To evaluate clinical outcomes, quality-adjusted life years (QALY), and costs associated with VNS in pediatric patients with drug-resistant epilepsy in a real-world setting.

METHODS

A retrospective analysis was conducted using Medicaid data (USA). Patients had ≥1 neurologist visits with epilepsy diagnosis (ICD-9 345.xx, 780.3x), ≥1 procedure claims for VNS implantation, ≥1 AEDs, ≥6-months of Pre- and Post-VNS continuous enrollment. Pre-VNS period was 6-months and Post-VNS period extended from implantation until device removal, death, Medicaid disenrollment, or study end (up to 3 years). Incidence rate ratios (IRR) and costs ($2010) were estimated. QALYs were estimated using number of seizure-related events.

RESULTS

For patients 1-11 years old (N = 238), hospitalizations and emergency room visits were reduced Post-VNS vs. Pre-VNS (adjusted IRR = 0.73 [95% CI: 0.61-0.88] and 0.74 [95% CI: 0.65-0.83], respectively). Average total healthcare costs were lower Post-VNS vs. Pre-VNS ($18,437 vs. $18,839 quarterly [adjusted p = 0.052]). For patients 12-17 years old (N = 207), hospitalizations and status epilepticus events were reduced Post-VNS vs. Pre-VNS (adjusted IRR = 0.43 [95% CI: 0.34-0.54] and 0.25 [95% CI: 0.16-0.39], respectively). Average total healthcare costs were lower Post-VNS vs. Pre-VNS period ($14,546 vs. $19,695 quarterly [adjusted p = 0.002]). Lifetime QALY gain after VNS was 5.96 (patients 1-11 years) and 4.82 years (patients 12-17 years).

CONCLUSIONS

VNS in pediatric patients is associated with decreased resource use and epilepsy-related events, cost savings, and QALY gain.

Systematic review and meta-analysis of vagus nerve stimulation in the treatment of depression: variable results based on study designs

PURPOSE

To determine the efficacy of vagus nerve stimulation (VNS) for treatment of depression.

METHODS

We conducted a systematic review and meta-analysis of analytical studies. Efficacy was evaluated according to severity of illness and percentage of responders.

RESULTS

We identified 687 references. Of these, 14 met the selection criteria and were included in the review. The meta-analysis of efficacy for uncontrolled studies showed a significant reduction in scores at the Hamilton Depression Rating Scale endpoint, and the percentage of responders was 31.8% ([23.2% to 41.8%], P<0.001). However, the randomised control trial which covered a sample of 235 patients with depression, reported no statistically significant differences between the active intervention and placebo groups (OR=1.61 [95%CI 0.72 to 3.62]; P=0.25). To study the cause of this heterogeneity, a meta-regression was performed. The adjusted coefficient of determination (R2(Adj)) was 0.84, which implies that an 84% variation in effect size across the studies was explained by baseline severity of depression (P<0.0001).

CONCLUSION

Currently, insufficient data are available to describe VNS as effective in the treatment of depression. In addition, it cannot be ruled out that the positive results observed in the uncontrolled studies might have been mainly due to a placebo effect.

Epilepsy and anesthesia

BACKGROUND AND OBJECTIVES

Epilepsy is one of the most frequent chronic neurological diseases. Although anesthesia for epilepsy patients is more common in neurosurgery, this group of patients needs, just as the general population, anesthesia for different diagnostic and therapeutic procedures. This article aims to address the issues of greatest interest to the anesthesiologist in the perioperative management of epileptic patients undergoing anesthesia for non-neurosurgical procedures.

CONTENT

We discuss relevant aspects of pathophysiology, classification and diagnosis of epilepsy; anticonvulsant therapy and interactions with anesthetic drugs; surgery and the ketogenic diet; pro-and anticonvulsant effects of drugs used in anesthesia; preoperative evaluation, intra- and postoperative conduct in epileptic patients, as well as the diagnosis and treatment of perioperative seizures.

CONCLUSIONS

In the perioperative management of epileptic patients is important for anesthesiologists to identify the type of epilepsy, the frequency, severity and the factors triggering the epileptogenic crises; the use of anticonvulsant drugs and possible interactions with drugs used in anesthesia; the presence of ketogenic diet and stimulatory of the vagus nerve, and its implications in anesthetic techniques. It is essential the understanding of pro- and anticonvulsant properties of drugs used in anesthesia, minimizing the risk of seizure activity in the intra- and postoperative. Finally, it is important to outline the diagnosis and initiate treatment of seizures, perioperative, which offers lower both morbidity and mortality.

The effect of right vagus nerve stimulation on focal cerebral ischemia: an experimental study in the rat

BACKGROUND

The aim of this study was to determine the effect of vagus nerve stimulation (VNS) on infarct size after transient and after permanent focal cerebral ischemia in rats and to test the hypothesis that VNS-induced neuroprotection is due to changes in cerebral blood flow.

METHODS

Ischemia was produced by either temporary proximal middle cerebral artery occlusion (TMCAO) or permanent distal middle cerebral artery occlusion (PMCAO). Stimulating electrodes were implanted on the cervical part of the right vagus nerve, and electrical stimulation was initiated 30 minutes after the induction of ischemia and delivered for 30 seconds every 5 minutes for 1 hour. All the procedures were duplicated but no stimulus was delivered in control groups. Cerebral blood flow in the MCA territory was continuously monitored with laser speckle contrast imaging. A neurologic evaluation was undertaken after 24 hours of ischemia, and animals were euthanized and neuronal damage evaluated.

RESULTS

Ischemic lesion volume was smaller in VNS-treated animals in both the temporary and permanent ischemic groups (P<.01). VNS-treated animals in TMCAO had better functional scores at 24 hours as compared with control animals (P<.01), but there were no statistically significant differences in the neurobehavioral scores in PMCAO (P=.089). Cerebral blood flow changes in the MCA territory during ischemia did not differ between the VNS-treated animals and control animals in either group.

CONCLUSIONS

VNS offers neuroprotection against stroke in both temporary and permanent ischemia. Although the precise mechanism of this effect remains to be determined, alterations in cerebral blood flow do not appear to play a role. VNS could readily be translated to clinical practice.

Failure of a vagus nerve stimulator following a nearby lightning strike

We recently reported our experience with implanted vagus nerve stimulators (VNS) in 62 children over a 7-year period. Here, we present a case of a VNS that successfully reduced the number and severity of seizures in a patient with an unusual seizure pattern, and failed to function shortly after a lightning storm. To our knowledge, the failure of VNS or any implantable electrical devices by lightning has not been reported in the literature. This mechanism of electrical interference, while unusual, may require more attention as these devices are expected to be used more frequently.

Vagus nerve stimulator treatment in adult-onset Rasmussen's encephalitis

We describe a patient with adult-onset Rasmussen's encephalitis (RE) responsive to vagus nerve stimulation. This previously healthy woman developed RE in the right hemisphere at the age of 27. Despite antiepileptic drug polytherapy, she continued to experience subcontinuous, simple-partial left-sided motor seizures and slowly progressive cognitive impairment. Resective surgery was not considered owing to the preservation of left motor skills. She was implanted with a vagus nerve stimulator at the age of 41; after 6 months she experienced a greater than 50% reduction in seizure frequency, which persisted over 2 years together with improvement of her neurological and cognitive status.

[Perioperative anaesthetic management of an epileptic patient treated with a vagus nerve stimulation]

The vagal nerve stimulation is approved for medically refractory epilepsy and major depression. We report the perioperative management of an epileptic patient with this indwelling device. This observation summarizes the physiologic implications and the specific anaesthetic considerations for procedures with this pre-existing device.

Vagus nerve stimulation regulates hemostasis in swine

The central nervous system regulates peripheral immune responses via the vagus nerve, the primary neural component of the cholinergic anti-inflammatory pathway. Electrical stimulation of the vagus nerve suppresses proinflammatory cytokine release in response to endotoxin, I/R injury, and hypovolemic shock and protects against lethal hypotension. To determine the effect of vagus nerve stimulation on coagulation pathways, anesthetized pigs were subjected to partial ear resection before and after electrical vagus nerve stimulation. We observed that electrical vagus nerve stimulation significantly decreased bleeding time (pre-electrical vagus nerve stimulation = 1033 +/- 210 s versus post-electrical vagus nerve stimulation = 585 +/- 111 s; P < 0.05) and total blood loss (pre-electrical vagus nerve stimulation = 48.4 +/- 6.8 mL versus post-electrical vagus nerve stimulation = 26.3 +/- 6.7 mL; P < 0.05). Reduced bleeding time after vagus nerve stimulation was independent of changes in heart rate or blood pressure and correlated with increased thrombin/antithrombin III complex generation in shed blood. These data indicate that electrical stimulation of the vagus nerve attenuates peripheral hemorrhage in a porcine model of soft tissue injury and that this protective effect is associated with increased coagulation factor activity.

Vagus nerve stimulation for the management of seizures in children: an 8-year experience

BACKGROUND

Medication-resistant seizure disorder is a challenging, debilitating, and expensive condition. Although multiple interventions are now available, none is universally effective. In 1997, vagus nerve stimulation (VNS) was approved for treatment of refractory seizures in patients older than 12 years. Vagus nerve stimulation has shown some benefit for these individuals, but less is known about its use in patients younger than 12 years. This review analyzes the safety and efficacy of VNS in young children.

METHODS

From March 2000 to February 2008, patients with medication-resistant seizures were implanted with a neurocybernetic prosthesis. Two weeks later, the device was activated. The children were followed for at least 3 months, and adjustments were made. Retrospective chart review was performed to collect data.

RESULTS

Of 28 patients, the mean age at implantation was 8 years and 5 months. Twenty-one (75%) children were younger than 12 years. There were no surgical complications. Two children were reimplanted for lead malfunction, and 4 generators were replaced. Two children had transitory adverse effects (hoarseness and stridor). Mean follow-up was 3 years and 5 months. At 1 year, 52% of children had greater than 50% reduction in seizures.

CONCLUSIONS

Although the effectiveness of VNS is variable and unpredictable, safety is high even in young children. Because of the potential benefit for these complex patients, the implantation of this nerve stimulation device should be included in the armamentarium of pediatric surgeons.