Vagal nerve stimulation in epileptic encephalopathies

Predictive factors for successful vagus nerve stimulation in patients with refractory epilepsy: real-life insights from a multicenter study

Introduction

Vagus nerve stimulation (VNS) therapy is an established treatment for patients with drug-resistant epilepsy that reduces seizure frequency by at least 50% in approximately half of patients; however, the characteristics of the patients with the best response have not yet been identified. Thus, it is important to identify the profile of patients who would have the best response to guide early indications and better patient selection.

Methods

This retrospective study evaluated vagus nerve stimulation (VNS) as an adjuvant therapy for patients with drug-resistant epilepsy from six epilepsy centers in Brazil. Data from 192 patients aged 2-66 years were analyzed, and all patients received at least 6 months of therapy to be included.

Results

Included patients were aged 2-66 years (25.6 ± 14.3), 105 (54.7%) males and 87 (45.8%) females. Median follow-up interval was 5 years (range, 2005-2018). Overall, the response rate (≥50% seizure reduction) after VNS implantation was 65.6% (126/192 patients). Most patients had 50-90% seizure reduction (60.9%) and nine patients became seizure-free. There were no serious complications associated with VNS implantation. The rate of a ≥ 50% seizure reduction response was significantly higher in patients with no history of neurosurgery. The presence of focal without generalized seizures and focal discharges on interictal EEG was associated with better response. Overall, etiological predictors of a better VNS response profile were tumors while a worse response to VNS was related to the presence of vascular malformations and Lennox-Gastaut Syndrome.

Discussion

We observed an association between a better response to VNS therapy no history of neurosurgery, focal interictal epileptiform activity, and focal seizure pattern. Additionally, it is important to highlight that age was not a determinant factor of the response, as children and adults had similar response rates. Thus, VNS therapy should be considered in both adults and children with DRE.

Callosotomy vs Vagus Nerve Stimulation in the Treatment of Lennox-Gastaut Syndrome: A Systematic Review With Meta-Analysis

BACKGROUND

Lennox-Gastaut syndrome (LGS) is a severe drug-resistant epileptic syndrome. Palliative treatments such as corpus callosotomy (CC) and vagus nerve stimulation (VNS) have emerged as treatments to reduce the number of seizures in patients. The aim of this study is to compare the effectiveness of CC and VNS in patients with LGS studied in the last 30 years.

MATERIALS AND METHODS

We conducted a systematic review with meta-analysis and collected papers from PubMed (MEDLINE), Ovidsp, Web of Science, and Cochrane Library data bases. The articles analyzed were published between January 1990 and December 2020. Keywords were chosen based on internal and external validation in the PubMed data base (the analysis is available in the Supplementary Data Supplementary Appendix). Prospective or retrospective case reports (n ≥ 2), case series, cohort studies, or case-control studies involving patients with LGS were included in the analysis. We selected studies that had no age or sex restriction and that provided data on seizures before and after treatments. Studies not written in English, published without peer review, or not indexed in the data bases were excluded. Other exclusion criteria were the absence of seizure data and the impossibility of extracting this information from the studies. To analyze the results, we used the random-effects model based on the assessment of heterogeneity (I² statistics) in two scenarios. In scenario 1, we assessed the incidence of patients with a seizure reduction ≥ 50%; in scenario 2, we assessed the incidence of patients with a seizure reduction > 0%.

RESULTS

Of the 7418 articles found using the keywords, 32 were considered eligible. Of these, 18 articles were on VNS (175 patients) and 14 on CC (107 patients). For scenario 1 (seizure reduction ≥ 50%), CC had an incidence of 65% (95% CI, 37%-94%), with an I² value of 82.7%; VNS had an incidence of 34% (95% CI, 11%-57%), with an I² value of 80.7%. For scenario 2 (seizure reduction > 0%), CC had an incidence of 80% (95% CI, 58%-100%), with an I² value of 84.7%; VNS had an incidence of 64% (95% CI, 38%-89%), with an I² value of 90.8%. There was an overlap of confidence intervals, with no statistical difference between the treatments in both scenarios.

DISCUSSION

Our analysis of LGS showed that the CC and VNS treatments are significantly beneficial to reducing seizures, without superiority between them.

A Comprehensive Review of Vagus Nerve Stimulation for Depression

OBJECTIVES

Vagus nerve stimulation (VNS) is reemerging as an exciting form of brain stimulation, due in part to the development of its noninvasive counterpart transcutaneous auricular VNS. As the field grows, it is important to understand where VNS emerged from, including its history and the studies that were conducted over the past four decades. Here, we offer a comprehensive review of the history of VNS in the treatment of major depression.

MATERIALS AND METHODS

Using PubMed, we reviewed the history of VNS and aggregated the literature into a narrative review of four key VNS epochs: 1) early invention and development of VNS, 2) path to Food and Drug Administration (FDA) approval for depression, 3) refinement of VNS treatment parameters, and 4) neuroimaging of VNS.

RESULTS

VNS was described in the literature in the early 1900s; however, gained traction in the 1980s as Zabara and colleagues developed an implantable neurocybernetic prosthesis to treat epilepsy. As epilepsy trials proceed in the 1990s, promising mood effects emerged and were studied, ultimately leading to the approval of VNS for depression in 2005. Since then, there have been advances in understanding the mechanism of action. Imaging techniques like functional magnetic resonance imaging and positron emission tomography further aid in understanding direct brain effects of VNS.

CONCLUSIONS

The mood effects of VNS were discovered from clinical trials investigating the use of VNS for reducing seizures in epileptic patients. Since then, VNS has gone on to be FDA approved for depression. The field of VNS is growing, and as noninvasive VNS quickly advances, it is important to consider a historical perspective to develop future brain stimulation therapies.

The role of vagus nerve stimulation in genetic etiologies of drug-resistant epilepsy: a meta-analysis

OBJECTIVE

Drug-resistant epilepsy (DRE) affects many children. Vagus nerve stimulation (VNS) may improve seizure control; however, its role in children with genetic etiologies of epilepsy is not well described. The authors systematically reviewed the literature to examine the effectiveness of VNS in this cohort.

METHODS

In January 2021, the authors performed a systematic review of the PubMed/MEDLINE, SCOPUS/Embase, Cochrane, and Web of Science databases to investigate the impact of VNS on seizure outcomes in children with genetic etiologies of epilepsy. Primary outcomes included seizure freedom rate, ≥ 90% seizure reduction rate, and ≥ 50% seizure reduction rate. Secondary outcomes were seizure severity and quality of life (QOL), including cognitive, functional, and behavioral outcomes. A random-effects meta-analysis was performed.

RESULTS

The authors identified 125 articles, of which 47 with 216 nonduplicate patients were analyzed. Common diagnoses were Dravet syndrome (DS) (92/216 patients [42.6%]) and tuberous sclerosis complex (TSC) (63/216 [29.2%]). Seizure freedom was not reported in any patient with DS; the pooled proportion (95% CI) of patients with ≥ 50% seizure reduction was 41% (21%-58%). Secondary cognitive outcomes of VNS were variable in DS patients, but these patients demonstrated benefits in seizure duration and status epilepticus. In TSC patients, the pooled (95% CI) seizure freedom rate was 40% (12%-71%), ≥ 90% seizure reduction rate was 31% (8%-56%), and ≥ 50% reduction rate was 68% (48%-91%). Regarding the secondary outcomes of VNS in TSC patients, several studies reported decreased seizure severity and improved QOL outcomes. There was limited evidence regarding the use of VNS to treat patients with other genetic etiologies of epilepsy, such as mitochondrial disease, Rett syndrome, Doose syndrome, Landau-Kleffner syndrome, Aicardi syndrome, Angelman syndrome, ring chromosome 20 syndrome, and lissencephaly; variable responses were reported in a limited number of cases.

CONCLUSIONS

The authors conducted a systematic review of VNS outcomes in children with genetic etiologies of DRE. Among the most studied conditions, patients with TSC had substantial seizure reduction and improvements in QOL, whereas those with DS had less robust seizure reduction. Increased testing, diagnosis, and long-term follow-up studies are necessary to better characterize VNS response in these children.

The Future Is Noninvasive: A Brief Review of the Evolution and Clinical Utility of Vagus Nerve Stimulation

Vagus nerve stimulation (VNS) is a form of neuromodulation that stimulates the vagus nerve. VNS had been suggested as an intervention in the late 1800s and was rediscovered in the late 1980s as a promising treatment for refractory epilepsy. Since then, VNS has been approved by the U.S. Food and Drug Administration (FDA) for treatment of epilepsy, morbid obesity, and treatment-resistant depression. Unfortunately, VNS is underutilized, as it is costly to implant and often only suggested when all other treatment options have been exhausted. Discovery of a noninvasive method of VNS known as transcutaneous auricular VNS (taVNS), which activates the vagus through stimulation of the auricular branch of the vagus nerve, has reignited excitement around VNS. taVNS has immense potential as a safe, at-home, wearable treatment for various neuropsychiatric disorders. Major strides are being made in both invasive and noninvasive VNS that aim to make this technology more accessible to patients who would find benefit, including the ongoing RECOVER trial, a randomized controlled trial in up to 1,000 individuals to further evaluate the efficacy of VNS for treatment-resistant depression. In this brief review, we first discuss the early history of VNS; then its clinical utility in FDA-approved indications; and, finally, noninvasive VNS.

Short- and Long-Term Response of Vagus Nerve Stimulation Therapy in Drug-Resistant Epilepsy: A Systematic Review and Meta-Analysis

OBJECTIVES

To compare the short- and long-term efficacies as well as tolerability of vagus nerve stimulation (VNS) for the patients with drug-resistant epilepsy (DRE) in comparison with status at baseline.

MATERIALS AND METHODS

We conducted a specific and systematic search in online data bases for relevant literature published prior to December 2020. The literature retrieved, including randomized clinical trials (RCTs) and observational studies, were then reviewed, and analyzed. A fixed-effect model was used to evaluate the pooled odds ratio (OR) of responder rates and complications associated with RCTs. A random-effect model was used to generate overall responder rates and overall incidences of complication.

RESULTS

A total of 61 studies, featuring 5223 patients, were included in our study. The pooled ORs of responder rates, hoarseness/voice change, throat pain, coughing, dyspnea, paresthesia, muscle pain, and headache during the short-term phase were 2.195 (p = 0.001), 5.527 (p = 0.0001), 0.935 (p = 0.883), 1.119 (p = 0.655), 2.901 (p = 0.005), 1.775 (p = 0.061), 3.606 (p = 0.123), and 0.928 (p = 0.806), respectively. The overall responder rates in 3, 6, 12, 24, 36, 48, and 60 months postoperatively were 0.421, 0.455, 0.401, 0.451, 0.482, 0.502, and 0.508, respectively. The overall incidences of complication were 0.274 for hoarseness/voice change, 0.099 for throat pain, 0.133 for coughing, 0.099 for dyspnea, 0.102 for paresthesia, 0.062 for muscle pain, 0.101 for headache, 0.015 for dysphagia, 0.013 for neck pain, 0.040 for infection, 0.030 for lead fracture, 0.019 for vocal cord palsy, and 0.020 for device malfunction, respectively.

CONCLUSIONS

The estimating of efficacy and tolerability, using data from the existing literature, indicated VNS therapy is a safe and effective treatment option for patients with DRE.

The efficacy and tolerability of auto-stimulation-VNS in children with Lennox-Gastaut syndrome

OBJECTIVE

Lennox-Gastaut syndrome (LGS) is a severe drug-resistant epilepsy (DRE) of childhood. The Vagus Nerve Stimulator (VNS) is established as a safe and effective treatment for DRE. This study assesses efficacy and tolerability of the auto-stimulation VNS models in pediatric patients with LGS.

METHODS

This is a retrospective chart review of a cohort of pediatric patients (Age 1-18 years old) with LGS implanted with an auto-stimulation VNS model at a single level four pediatric epilepsy center. Patient responder's rate was measured as seizure reduction over baseline and improvements in five quality-of-life measures as reported by the patients and families. Efficacy and tolerability were assessed at 1, 3, 6, 12, 18 and 24 months compared to baseline.

RESULTS

This cohort includes 71 consecutive children with Lennox-Gastaut syndrome who underwent implantation with one of two models of the auto-stimulation VNS. The average age of the children at implantation was 20.82 months. Of those patients, 55 % of patients achieved greater than 50 % seizure reduction at six months, 67.7 % at 12 months, and 65 % at 24 months. At 12 months 11 % of the patients were completely seizure free and at 24 months 17 % were seizure free. By 24 months post implantation most of the patient families reported at least a 50 % improvement rate in one or more of the quality-of-life measures. The most commonly reported adverse events were dysphonia, paresthesia, and shortness of breath, all of which were tolerated and subsided by 24 months.

SIGNIFICANCE

This study provides evidence that VNS models with the auto-stimulation paradigm based on detection of tachycardia are well tolerated and effective in a pediatric population with LGS. Furthermore, this study shows that for this population, the auto-stimulation models of the VNS may provide additional benefits over the earlier VNS versions.

Vagus Nerve Stimulation for the Treatment of Epilepsy

Vagus nerve stimulation (VNS) was the first neuromodulation device approved for treatment of epilepsy. In more than 20 years of study, VNS has consistently demonstrated efficacy in treating epilepsy. After 2 years, approximately 50% of patients experience at least 50% reduced seizure frequency. Adverse events with VNS treatment are rare and include surgical adverse events (including infection, vocal cord paresis, and so forth) and stimulation side effects (hoarseness, voice change, and cough). Future developments in VNS, including closed-loop and noninvasive stimulation, may reduce side effects or increase efficacy of VNS.

Investigating the Effect of Short Term Responsive VNS Therapy on Sleep Quality Using Automatic Sleep Staging

OBJECTIVE

The goal of this work is to objectively evaluate the effectiveness of responsive (or closed-loop) Vagus nerve stimulation (VNS) therapy in sleep quality in patients with medically refractory epilepsy.

METHODS

Using quantitative features obtained from electroencephalography, we first developed a new automatic sleep-staging framework that consists of a multi-class support vector machine (SVM) classification, based on a decision tree approach. To train and evaluate the performance of the framework, we used polysomnographic data of 23 healthy subjects from the PhysioBank database where the sleep stages have been visually annotated. We then used the trained classifier to label the sleep stages using data from 22 patients with epilepsy, treated with short term responsive VNS therapy during an epilepsy-monitoring unit visit, one month after VNS implantation, and ten VNS-naïve patients with epilepsy.

RESULTS

Application of multi-class SVM classifier to classify the three sleep stages of awake, light sleep + rapid eye movement, and deep sleep achieved a classification accuracy of 90%. Results of the application of this methodology to VNS-treated and VNS-naïve patients revealed that the patients treated with short term responsive VNS therapy showed significant increase in sleep efficiency, and significant decrease in seizures plus interictal epileptiform discharges and awakenings.

CONCLUSION

These results indicate that VNS treatment can reduce the epileptiform activities and thus help in achieving better sleep quality for patients with epilepsy.

SIGNIFICANCE

The proposed approach can be used to investigate the effect of long-term VNS therapy on sleep quality.

Vagus nerve stimulation (VNS) therapy update

Epilepsy affects millions of people worldwide. Approximately one-third have pharmacoresistant epilepsy, and of these, the majority are not candidates for epilepsy surgery. Vagus nerve stimulation (VNS) therapy has been an option to treat pharmacoresistant seizures for 30 years. In this update, we will review the clinical data that support the device's efficacy in children, adolescents, and adults. We will also review its side-effect profile, quality of life and cost benefits, and the impact the device has on sudden unexpected death in epilepsy (SUDEP). We will then discuss candidate selection and provide guidance on dosing and future models. Vagus nerve stimulation therapy is an effective treatment for many seizure types and epilepsy syndromes with a predictable and benign side-effect profile that supports its role as the most commonly prescribed device to treat pharmacoresistant epilepsy. "This article is part of the Supplement issue Neurostimulation for Epilepsy."

Health Care Utilization Following Vagus Nerve Stimulation Therapy in Pediatric Epilepsy Patients From a Pediatric Accountable Care Organization

BACKGROUND

Vagus nerve stimulation has been a therapy for epilepsy approved by the US Food and Drug Administration (FDA) for patients 4 and older and shown efficacy and safety in younger pediatric patients.

METHODS

The authors performed a retrospective analysis utilizing Medicaid claims from an accountable care organization to measure the intervention of vagus nerve stimulation therapy in regard to unplanned health care utilization. Thirteen unique patients were included who had vagus nerve stimulation therapy who had at least 6 months of continuous enrollment in a managed Medicaid health plan. Comparison with 12 months of data before and after vagus nerve stimulation implantation was performed.

RESULTS

Patients had statistically significant fewer unplanned inpatient visits per patient per enrollment month after vagus nerve stimulation implantation.

CONCLUSION

Utilizing claims data, vagus nerve stimulation implantation demonstrates a reduction in unplanned hospitalizations.

Rates and Predictors of Seizure Freedom With Vagus Nerve Stimulation for Intractable Epilepsy

Supplemental Digital Content is Available in the Text.

BACKGROUND:

Neuromodulation-based treatments have become increasingly important in epilepsy treatment. Most patients with epilepsy treated with neuromodulation do not achieve complete seizure freedom, and, therefore, previous studies of vagus nerve stimulation (VNS) therapy have focused instead on reduction of seizure frequency as a measure of treatment response.

OBJECTIVE:

To elucidate rates and predictors of seizure freedom with VNS.

METHODS:

We examined 5554 patients from the VNS therapy Patient Outcome Registry, and also performed a systematic review of the literature including 2869 patients across 78 studies.

RESULTS:

Registry data revealed a progressive increase over time in seizure freedom after VNS therapy. Overall, 49% of patients responded to VNS therapy 0 to 4 months after implantation (≥50% reduction seizure frequency), with 5.1% of patients becoming seizure-free, while 63% of patients were responders at 24 to 48 months, with 8.2% achieving seizure freedom. On multivariate analysis, seizure freedom was predicted by age of epilepsy onset >12 years (odds ratio [OR], 1.89; 95% confidence interval [CI], 1.38-2.58), and predominantly generalized seizure type (OR, 1.36; 95% CI, 1.01-1.82), while overall response to VNS was predicted by nonlesional epilepsy (OR, 1.38; 95% CI, 1.06-1.81). Systematic literature review results were consistent with the registry analysis: At 0 to 4 months, 40.0% of patients had responded to VNS, with 2.6% becoming seizure-free, while at last follow-up, 60.1% of individuals were responders, with 8.0% achieving seizure freedom.

CONCLUSION:

Response and seizure freedom rates increase over time with VNS therapy, although complete seizure freedom is achieved in a small percentage of patients.

ABBREVIATIONS:

AED, antiepileptic drug

VNS, vagus nerve stimulation

The role of vagus nerve stimulation in refractory epilepsy

ABSTRACT Vagus nerve stimulation is an adjunctive therapy used to treat patients with refractory epilepsy who are not candidates for resective surgery or had poor results after surgical procedures. Its mechanism of action is not yet fully comprehended but it possibly involves modulation of the locus coeruleus, thalamus and limbic circuit through noradrenergic and serotonergic projections. There is sufficient evidence to support its use in patients with focal epilepsy and other seizure types. However, it should be recognized that improvement is not immediate and increases over time. The majority of adverse events is stimulation-related, temporary and decreases after adjustment of settings. Future perspectives to improve efficacy and reduce side effects, such as different approaches to increase battery life, transcutaneous stimulation and identification of prognostic factors, should be further investigated.

Vagus nerve stimulation as a potential adjuvant to behavioral therapy for autism and other neurodevelopmental disorders

Background

Many children with autism and other neurodevelopmental disorders undergo expensive, time-consuming behavioral interventions that often yield only modest improvements. The development of adjunctive interventions that can increase the benefit of rehabilitation therapies is essential in order to improve the lives of individuals with neurodevelopmental disorders.

Main text

Vagus nerve stimulation (VNS) is an FDA approved therapy that is safe and effective in reducing seizure frequency and duration in individuals with epilepsy. Individuals with neurodevelopmental disorders often exhibit decreased vagal tone, and studies indicate that VNS can be used to overcome an insufficient vagal response. Multiple studies have also documented significant improvements in quality of life after VNS therapy in individuals with neurodevelopmental disorders. Moreover, recent findings indicate that VNS significantly enhances the benefits of rehabilitative training in animal models and patients, leading to greater recovery in a variety of neurological diseases. Here, we review these findings and provide a discussion of how VNS paired with rehabilitation may yield benefits in the context of neurodevelopmental disorders.

Conclusions

VNS paired with behavioral therapy may represent a potential new approach to enhance rehabilitation that could significantly improve the outcomes of individuals with neurodevelopmental disorders.

Transcutaneous Vagus Nerve Stimulation: A Promising Method for Treatment of Autism Spectrum Disorders

Transcutaneous Vagus Nerve Stimulation (tVNS) on the auricular branch of the vagus nerve has been receiving attention due to its therapeutic potential for neuropsychiatric disorders. Although the mechanism of tVNS is not yet completely understood, studies have demonstrated the potential role of vagal afferent nerve stimulation in the regulation of mood and visceral state associated with social communication. In addition, a growing body of evidence shows that tVNS can activate the brain regions associated with Autism Spectrum Disorder (ASD), trigger neuroimmune modulation and produce treatment effects for comorbid disorders of ASD such as epilepsy and depression. We thus hypothesize that tVNS may be a promising treatment for ASD, not only for comorbid epilepsy and depression, but also for the core symptoms of ASD. The goal of this manuscript is to summarize the findings and rationales for applying tVNS to treat ASD and propose potential parameters for tVNS treatment of ASD.

Meta-analysis of vagus nerve stimulation treatment for epilepsy: correlation between device setting parameters and acute response

BACKGROUND

Vagus nerve stimulation (VNS) is an adjunctive neurophysiological treatment for those patients who have pharmacoresistant or surgically resistant partial onset epilepsy.

OBJECTIVE

The aim of this study is to determine the effects of high and low stimulation paradigms on a responder rate of ≥50 and ≥75% reduction in seizure frequency and associated adverse effects in adults and children.

METHOD

A literature search was performed using Medline, PubMed, EMBASE, and Cochrane library for studies using vagus nerve stimulation published from January 1980 until July 2014 for medically or surgically resistant partial onset seizures, in children and adults. No restrictions on languages were imposed.

DATA COLLECTION AND ANALYSIS

Four authors reviewed and selected studies for inclusion and exclusion. The search identified five randomized control trials that fit with our inclusion criteria. The following outcomes were evaluated: 50% or greater reduction in total seizure frequency, 75% or greater reduction in total seizure frequency, and adverse effects.

RESULTS

Four randomized controlled trials were analyzed in this meta-analysis. Results indicate high stimulation is more effective in adult patients who experienced ≥50 and ≥75% reduction in seizure frequency with a significant difference within both high and low stimulation groups. In children, there was no significant difference between the two groups and patients with ≥50 % reduction in seizures. Adverse effects such as hoarseness and dyspnea were more common in the high stimulation group where the remaining side effects were not statistically different among both groups.

CONCLUSION

High stimulation is more effective than low stimulation in producing a greater reduction in seizure frequency in patients with medically and surgically resistant epilepsy.

Autistic spectrum disorder, epilepsy, and vagus nerve stimulation

PURPOSE

In individuals with a comorbid autistic spectrum disorder and medically refractory epilepsy, vagus nerve stimulation may offer the potential of seizure control and a positive behavioral side effect profile. We aimed to examine the behavioral side effect profile using longitudinal and quantitative data and review the potential mechanisms behind behavioral changes.

METHODS

We present a case report of a 10-year-old boy with autistic spectrum disorder and epilepsy, who underwent vagus nerve stimulation subsequent to unsuccessful treatment with antiepileptic medication.

RESULTS

Following vagus nerve stimulation implantation, initial, if temporary, improvement was observed in seizure control. Modest improvements were also observed in behavior and development, improvements which were observed independent of seizure control.

CONCLUSIONS

Vagus nerve stimulation in autistic spectrum disorder is associated with modest behavioral improvement, with unidentified etiology, although several candidates for this improvement are evident.

The Epileptic Encephalopathies of Infancy and Childhood

The epileptic encephalopathies comprise a group of devastating seizure syndromes which begin in infancy and early childhood and usually result in intractable epilepsy. While some syndromes are relatively easily diagnosed early in their course, others take time to evolve, hampering an early, confident diagnosis. Epileptic encephalopathies are associated with slowing of cognitive function and evolution of severe behavioral disorders, which are often more distressing to families than the epilepsy. While an underlying etiology may explain some of this co-morbidity, many children have no identifiable etiology found for their seizures. In these “idiopathic” cases, recurrent subtle seizures, frequent epileptiform discharge and non-convulsive status epilepticus probably all play a role in deterioration of cognitive function and evolution of behavior disorders. This paper will review the most common epileptic encephalopathy syndromes, discuss the cognitive and behavioral co-morbidities and review current therapeutic options.

Can we predict the response in the treatment of epilepsy with vagus nerve stimulation?

Despite the introduction of new antiepileptic drugs and advances in the surgical treatment of epilepsy, an important group of patients still remains uncontrolled by any of these methods. The relatively recent introduction of vagus nerve stimulation is yet another possible treatment for refractory epilepsy. This safe, simple, and adjustable technique reduces the number of seizures and multiple publications support its increasing efficacy and effectiveness, with few adverse effects. The goal of our study is to determine the efficacy of this procedure and the factors predicting a response, particularly in the presence of a temporal lobe discharge on the video electroencephalogram (video-EEG) and magnetic resonance imaging (MRI) lesions. We undertook a retrospective study of all the patients with refractory epilepsy who underwent implantation of a vagus nerve stimulator between 2003 and 2009, and with a minimum follow-up of 6 months. The statistical analysis was done with SPSS for Windows. The stimulator was implanted in 40 patients, of whom 38 had a minimum follow-up of 6 months. In one patient, the device had to be removed due to infection, so the series comprised 37 patients. These were divided into different groups, according to the epidemiologic, clinical, radiologic, and electroencephalographic data. In addition, an analysis of the response was performed. The efficacy of the procedure was established according to the reduction in the mean seizure frequency. The baseline value of these seizures was 80.97 ± 143.59, falling to 37 ± 82.51 at the last revision. The response rate (reduction in seizures ≥ 50 %) at 6 months was 51.4 %, with 62.2 % of the patients showing this reduction at the last evaluation. Significant differences in the response were seen for the variables: baseline frequency of seizures, temporal lobe discharge on VideoEEG and MRI lesions. The mean time to response was 10 months in patients with lower rate of seizures versus 25 months of those with the higher rate (p = 0.024), and the response at 6 months was higher (p = 0.05). Patients with temporal lobe discharge alone or in combination with discharges over other regions had a mean time to response of 11 months versus 26 months in those without temporal discharge (p = 0.037). In the analysis of the MRI, we had seen that at the last revision, 82.4 % of the patients with lesion had achieved response versus 45 % without lesion (p = 0.02). Vagus nerve stimulation reduces the frequency of seizures. A temporal lobe discharge on the video-EEG is an indicator of an early response and the presence of an MRI lesion indicates a late response. Patients with fewer rates of seizures have a better prognosis.

Neuroactive peptides as putative mediators of antiepileptic ketogenic diets

Various ketogenic diet (KD) therapies, including classic KD, medium chain triglyceride administration, low glycemic index treatment, and a modified Atkins diet, have been suggested as useful in patients affected by pharmacoresistant epilepsy. A common goal of these approaches is to achieve an adequate decrease in the plasma glucose level combined with ketogenesis, in order to mimic the metabolic state of fasting. Although several metabolic hypotheses have been advanced to explain the anticonvulsant effect of KDs, including changes in the plasma levels of ketone bodies, polyunsaturated fatty acids, and brain pH, direct modulation of neurotransmitter release, especially purinergic (i.e., adenosine) and γ-aminobutyric acidergic neurotransmission, was also postulated. Neuropeptides and peptide hormones are potent modulators of synaptic activity, and their levels are regulated by metabolic states. This is the case for neuroactive peptides such as neuropeptide Y, galanin, cholecystokinin, and peptide hormones such as leptin, adiponectin, and growth hormone-releasing peptides (GHRPs). In particular, the GHRP ghrelin and its related peptide des-acyl ghrelin are well-known controllers of energy homeostasis, food intake, and lipid metabolism. Notably, ghrelin has also been shown to regulate the neuronal excitability and epileptic activation of neuronal networks. Several lines of evidence suggest that GHRPs are upregulated in response to starvation and, particularly, in patients affected by anorexia and cachexia, all conditions in which also ketone bodies are upregulated. Moreover, starvation and anorexia nervosa are accompanied by changes in other peptide hormones such as adiponectin, which has received less attention. Adipocytokines such as adiponectin have also been involved in modulating epileptic activity. Thus, neuroactive peptides whose plasma levels and activity change in the presence of ketogenesis might be potential candidates for elucidating the neurohormonal mechanisms involved in the beneficial effects of KDs. In this review, we summarize the current evidence for altered regulation of the synthesis of neuropeptides and peripheral hormones in response to KDs, and we try to define a possible role for specific neuroactive peptides in mediating the antiepileptic properties of diet-induced ketogenesis.

Surgical treatment of pediatric epileptic encephalopathies

Pediatric epileptiform encephalopathies are a group of neurologically devastating disorders related to uncontrolled ictal and interictal epileptic activity, with a poor prognosis. Despite the number of pharmacological options for treatment of epilepsy, many of these patients are drug resistant. For these patients with uncontrolled epilepsy, motor and/or neuropsychological deterioration is common. To prevent these secondary consequences, surgery is often considered as either a curative or a palliative option. Magnetic resonance imaging to look for epileptic lesions that may be surgically treated is an essential part of the workup for these patients. Many surgical procedures for the treatment of epileptiform encephalopathies have been reported in the literature. In this paper the evidence for these procedures for the treatment of pediatric epileptiform encephalopathies is reviewed.

Behavioural and cognitive effects during vagus nerve stimulation in children with intractable epilepsy - a randomized controlled trial

BACKGROUND/AIMS

In addition to effects on seizure frequency in intractable epilepsy, multiple studies report benefits of vagus nerve stimulation (VNS) on behavioural outcomes and quality of life. The present study aims to investigate the effects of VNS on cognition, mood in general, depression, epilepsy-related restrictions and psychosocial adjustment in children with intractable epilepsy, as well as the relation between these effects and seizure reduction.

METHODS

We conducted a randomized, active-controlled, double-blinded, add-on study in 41 children (age 4-18) with medically refractory epilepsy. We performed cognitive and behavioural testing at baseline (12 weeks), at the end of the blinded phase (20 weeks) in children receiving either high-output or low-output (active control) stimulation, and at the end of the open label phase (19 weeks) with all children receiving high-output stimulation. Seizure frequency was recorded using seizure diaries.

RESULTS

VNS did not have a negative effect on cognition nor on psychosocial adjustment. At the end of the follow-up phase we noted an improvement of mood in general and the depression subscale for the entire group, unrelated to a reduction of seizure frequency. At the end of the blinded phase a ≥50% reduction of seizure frequency occurred in 16% of the high-stimulation group and 21% of the low-stimulation group. At the end of the open-label follow-up phase, 26% of the children experienced a seizure frequency reduction of 50% or more (responders).

CONCLUSIONS

VNS has additional beneficial effects in children with intractable epilepsy. As opposed to anti-epileptic drugs, there are no negative effects on cognition. Moreover, we observed an improvement of mood in general and depressed feelings in particular, irrespective of a reduction in seizure frequency. These beneficial effects should be taken into account when deciding whether to initiate or continue VNS treatment in these children.

Vagus nerve stimulation in drug-resistant epilepsies. Analysis of potential prognostic factors in a cohort of patients with long-term follow-up

BACKGROUND

The results of vagus nerve stimulation (VNS) for the treatment of drug-resistant epilepsies are highly variable due to the lack of defined patient's selection criteria and a follow-up of published studies being generally too short. Here we report the outcome of VNS in a series with long-term follow-up and try to identify subgroups of patients who could be better candidates for this procedure.

METHOD

We studied 53 patients (33 male, 20 female) with a prospectively recorded follow-up (mean, 55.96 ± 43.53 months). The monthly average seizure frequency for each patient at baseline, 3, 6, 12 months, and each year until the latest follow-up after implant was measured and the percentage of "responders" and response time (RT) were calculated. We investigated the following potential prognostic role of these factors: age of onset of epilepsy, pre-implant epilepsy duration, etiology, and age at implant.

RESULTS

Globally, 40 % of patients responded to VNS (mean RT, 14.85 ± 16.85 months). Lesional etiology (p = 0.0179, logrank test), particularly ischemia (p = 0.011, Fisher exact test) and tuberous sclerosis (p = 0.0229, Fisher exact test), and age at implant <18 years (p = 0.0242, logrank test) were associated to better response to VNS. In the lesional subgroup the best results were observed in patients with a pre-implant epilepsy duration <15 years (p = 0.0204, logrank test) and an age at implant <18 years (p = 0.0187 logrank test).

CONCLUSIONS

The best candidate to VNS seems to be a patient with lesional etiology epilepsy (particularly post-ischemic and tuberous sclerosis) and a short duration of epilepsy who undergo VNS younger than 18 years.

Vagal nerve stimulation for pharmacoresistant epilepsy in children

Vagus nerve stimulation (VNS) is an adjunctive treatment for adult patients with pharmacoresistant epilepsy. Little is known about VNS therapy for children with epilepsy. This article will: (1) Review the contemporary medical literature related to VNS therapy in children with epilepsy, (2) describe the experience of VNS treatment in 153 children less than 18 years of age, in the University of California, Los Angeles (UCLA) Pediatric Epilepsy Surgery Program, from 1998 to 2012, and (3) describe the surgical technique used for VNS implantation at UCLA. Review of the literature finds that despite different etiologies and epilepsy syndromes in children, VNS appears to show a similar profile of efficacy for seizure control compared to adults, and low morbidity and mortality. The UCLA experience is similar to that reported in the literature for children. VNS constitutes about 21% of our pediatric epilepsy surgery volume. We have implanted VNS in infants as young as six months of age and the most common etiology is the Lennox-Gastaut Syndrome. About 5% of the patients are seizure-free with VNS therapy and there is a low rate of surgically related complications. The UCLA surgical approach emphasizes minimal direct manipulation of the vagus nerve and adequate wire loops, to prevent a lead fracture. In summary, VNS is a viable palliative treatment for medically refractory epilepsy in children, with outcomes and complications equal to adult patients. Being a small child is not a contraindication for VNS therapy, if needed for refractory epilepsy.

Vagus nerve stimulation vs. corpus callosotomy in the treatment of Lennox-Gastaut syndrome: a meta-analysis

PURPOSE

Lennox-Gastaut syndrome (LGS) is an epileptogenic disorder that arises in childhood and is typically characterized by multiple seizure types, slow spike-and-wave complexes on EEG and cognitive impairment. If medical treatment fails, patients can proceed to one of two palliative surgeries, vagus nerve stimulation (VNS) or corpus callosotomy (CC). Their relative seizure control rates in LGS have not been well studied. The purpose of this paper is to compare seizure reduction rates between VNS and CC in LGS using meta-analyses of published data.

METHODS

A systematic search of Pubmed, Ovidsp, and Cochrane was performed to find articles that met the following criteria: (1) prospective or retrospective study, (2) at least one patient diagnosed with Lennox-Gastaut syndrome, and (3) well-defined measure of seizure frequency reduction. Seizure reduction rates were divided into seizure subtypes, as well as total seizures, and categorized as 100%, >75%, and >50%. Patient groups were compared using chi-square tests for categorical variables and t-test for continuous measures. Pooled proportions with 95% confidence interval (95% CI) of seizure outcomes were estimated for total seizures and seizure subtypes using random effects methods.

RESULTS

17 VNS and 9 CC studies met the criteria for inclusion. CC had a significantly better outcome than VNS for >50% atonic seizure reduction (80.0% [67.0-90.0%] vs. 54.1% [32.1-75.4%], p<0.05) and for >75% atonic seizure reduction (70.0% [48.05-87.0%] vs. 26.3% [5.8-54.7%], p<0.05). All other seizure types, as well as total number of seizures, showed no statistically significant difference between VNS and CC.

CONCLUSIONS

CC may be more beneficial for LGS patients whose predominant disabling seizure type is atonic. For all other seizure types, VNS offers comparable rates to CC.

Vagus nerve stimulation in children with intractable epilepsy: a randomized controlled trial

AIM

The aim of this study was to evaluate the effects of vagus nerve stimulation (VNS) in children with intractable epilepsy on seizure frequency and severity and in terms of tolerability and safety.

METHOD

In this study, the first randomized active controlled trial of its kind in children, 41 children (23 males; 18 females; mean age at implantation 11y 2mo, SD 4y 2mo, range 3y 10mo-17y 8mo) were included. Thirty-five participants had localization-related epilepsy (25 symptomatic; 10 cryptogenic), while six participants had generalized epilepsy (four symptomatic; two idiopathic). During a baseline period of 12 weeks, seizure frequency and severity were recorded using seizure diaries and the adapted Chalfont Seizure Severity Scale (NHS3), after which the participants entered a blinded active controlled phase of 20 weeks. During this phase, half of the participants received high-output VNS (maximally 1.75mA) and the other half received low-output stimulation (0.25mA). Finally, all participants received high-output stimulation for 19 weeks. For both phases, seizure frequency and severity were assessed as during the baseline period. Overall satisfaction and adverse events were assessed by semi-structured interviews.

RESULTS

At the end of the randomized controlled blinded phase, seizure frequency reduction of 50% or more occurred in 16% of the high-output stimulation group and in 21% of the low-output stimulation group (p=1.00). There was no significant difference in the decrease in seizure severity between participants in the stimulation groups. Overall, VNS reduced seizure frequency by 50% or more in 26% of participants at the end of the add-on phase The overall seizure severity also improved (p<0.001).

INTERPRETATION

VNS is a safe and well-tolerated adjunctive treatment of epilepsy in children. Our results suggest that the effect of VNS on seizure frequency in children is limited. However, the possible reduction in seizure severity and improvement in well-being makes this treatment worth considering in individual children with intractable epilepsy.

Short-term results of vagus nerve stimulation in pediatric patients with refractory epilepsy

BACKGROUND

Vagus nerve stimulation (VNS), an alternative method to manage patients with medically intractable epilepsy, has shown favorable results in reducing seizure relapse and improvements in quality of life. In 1997, the U.S. Food and Drug Administration approved the use of this device as an adjunctive therapy for intractable seizure in adults and adolescents older than 12 years of age.

METHODS

We present a preliminary study of pediatric patients, who suffered from medically intractable seizure and underwent VNS implantation after observation of the baseline seizure frequency. Classification of epileptic syndrome, seizure patterns, age of onset, seizure frequency reduction and adverse effects were recorded.

RESULTS

Patients who underwent VNS implantation included four adolescents and four children. The follow-up duration ranged from 9-33 months. All the patients were responders after the beginning of the stimulation. Five of the eight patients responded to VNS with a seizure frequency reduction rate > 50%, and four of the eight patients experienced a ≥ 90% seizure reduction. No significant adverse effects were noted in all patients during the observation period.

CONCLUSION

The effective management of medically intractable seizure remains challenging to most clinical physicians. In addition to ketogenic diet and epilepsy surgery, VNS provides an alternative way to manage this issue. Our results suggest that VNS is well tolerated in pediatric patients, and is a favorable and safe method of treating intractable seizure in common clinical practice.

Neurostimulation: vagus nerve stimulation and beyond

Patients with medically intractable epilepsy who are not candidates for epilepsy surgery could benefit from neurostimulation. At this time, vagus nerve stimulation (VNS) therapy is the only Food and Drug Administation-approved neurostimulation modality; it has been shown to be efficacious and just as well tolerated in children and adolescents as in adults. Notwithstanding the initial cost of the device and implantation, VNS therapy has been shown to be a cost-effective treatment, reducing direct medical costs and improving health-related quality of life measures. Deep brain stimulation of various brain regions, especially the anterior nucleus of the thalamus and responsive neurostimulation, also appear effective but are not yet approved for clinical use. Repetitive transcranial magnetic stimulation, which is also in early clinical development, is promising and could become available in the not too distant future.

Vagus nerve stimulation for epilepsy: a meta-analysis of efficacy and predictors of response

Vagus nerve stimulation (VNS) was approved by the US FDA in 1997 as an adjunctive treatment for medically refractory epilepsy. It is considered for use in patients who are poor candidates for resection or those in whom resection has failed. However, disagreement regarding the utility of VNS in epilepsy continues because of the variability in benefit reported across clinical studies. Moreover, although VNS was approved only for adults and adolescents with partial epilepsy, its efficacy in children and in patients with generalized epilepsy remains unclear. The authors performed the first meta-analysis of VNS efficacy in epilepsy, identifying 74 clinical studies with 3321 patients suffering from intractable epilepsy. These studies included 3 blinded, randomized controlled trials (Class I evidence); 2 nonblinded, randomized controlled trials (Class II evidence); 10 prospective studies (Class III evidence); and numerous retrospective studies. After VNS, seizure frequency was reduced by an average of 45%, with a 36% reduction in seizures at 3-12 months after surgery and a 51% reduction after > 1 year of therapy. At the last follow-up, seizures were reduced by 50% or more in approximately 50% of the patients, and VNS predicted a ≥ 50% reduction in seizures with a main effects OR of 1.83 (95% CI 1.80-1.86). Patients with generalized epilepsy and children benefited significantly from VNS despite their exclusion from initial approval of the device. Furthermore, posttraumatic epilepsy and tuberous sclerosis were positive predictors of a favorable outcome. In conclusion, VNS is an effective and relatively safe adjunctive therapy in patients with medically refractory epilepsy not amenable to resection. However, it is important to recognize that complete seizure freedom is rarely achieved using VNS and that a quarter of patients do not receive any benefit from therapy.

Vagal nerve stimulation for drug-resistant epilepsies in different age, aetiology and duration

PURPOSE

The aim of the study was to compare the outcome with respect to age of implant, aetiology and duration of epilepsy.

METHODS

One hundred thirty-five drug-resistant epileptic patients, excluded from ablative surgery, were submitted to vagal nerve stimulation (1995-2007). Aetiology was cryptogenic in 57 and symptomatic in 78 patients. Ages of implant were 0.5-6 years (18 patients), 7-12 years (32 patients), 13-18 years (31 patients) and more than 18 years (54 patients). Epilepsy types were Lennox-Gastaut (18 patients), severe multifocal epilepsy (33 patients) and partial (84 patients). Duration of epilepsy is 3 months to 57 years. Clinical outcome was determined by comparing the seizure frequency after stimulation at 3-6-12-18-24-36 months with the previous 3 months. 'Responders' were the patients experiencing a seizure frequency reduction of 50% or more during follow-up. In statistical analysis, Wilcoxon and McNemar tests, general linear model for repeated measures, logistic regression and survival analysis were used.

RESULTS

The seizure frequency reduction was significant in the group as a whole between baseline and the first follow-up (Wilcoxon test). The percentage of responder increases with time (McNemar test p = 0.04). Univariate analysis showed a significant effect of the age of implant on seizure frequency reduction: Adult patient had worst clinical outcome than children (p < 0.001) and adolescents (p = 0.08). Patients with severe multifocal epilepsy had better percentage seizure reduction compared with Lennox-Gastaut and partial (p = 0.03). Lesser duration of epilepsy had positive influence on outcome. Multivariate analysis confirmed age of implant to be the strongest factor influencing prognosis. Furthermore, positive is the association between lesional aetiology and young age.

CONCLUSIONS

The best responder could be a young lesional epileptic patient; after 3 years of follow-up, the percentage of responders is still in progress.

Dramatic first words spoken in 2 children after vagus nerve stimulation

Vagus nerve stimulation has become an accepted adjunctive treatment for refractory epilepsy with more recent FDA approval in the treatment of depression. Many "positive" effects have been noted in patients with epilepsy namely increased alertness, improved cognition, behavior and mood. These changes appear to be independent of seizure reduction and antiepileptic drug decrease. We present two children (aged 8 and 9 years) who were non-verbal and spoke their first words shortly after vagus nerve stimulators were implanted. The mechanism is unclear although vagus nerve stimulation has been clearly shown to induce neuronal, chemical and perfusion changes in both subcortical and cortical regions of the brain. There is likely a combined effect on primary speech areas as well subcortical and mamillothalamic tracts, and possibly even stimulation and changes at the local vocal cord level contributing to this phenomenon. Our observation has important implications in encephalopathic patients both with and without epilepsy.

Vagus nerve stimulation for refractory epilepsy in children: More to VNS than seizure frequency reduction

PURPOSE

Vagus nerve stimulation (VNS) is used increasingly as adjunctive therapy for refractory epilepsy. Studies of VNS in children report mainly seizure frequency reduction as a measure of efficacy and clinical details are often scanty. We report our experience with VNS in children with refractory epilepsy and emphasize the positive effects of VNS in terms of seizure severity.

METHODS

We reviewed 26 consecutive children who had VNS with a minimum follow-up period of 18 months. We examined their clinical characteristics, seizure types, seizure frequency, epilepsy syndrome diagnosis, and response to VNS in terms of seizure frequency and seizure severity.

RESULTS

Fifty-four percent of patients responded to VNS with >or=50% seizure frequency reduction. Patients with Lennox-Gastaut syndrome (LGS) and tonic seizures had a higher responder rate; 78% (seven of nine patients) (p < 0.01). Status epilepticus (SE) episodes were reduced or ceased in the four patients with recurrent SE. Seizure severity, duration, and recovery time decreased in all responders. Increased alertness was reported in all responders and three nonresponders.

CONCLUSION

Decreased seizure severity, recovery time, abolition of daytime drop attacks, and reduced hospitalization due to SE improved patients' lives over and above the benefit from seizure frequency reduction.

Vagus nerve stimulation in children with intractable epilepsy: indications, complications and outcome

PURPOSE

To analyze the indication, complications and outcome of vagus nerve stimulation in intractable childhood epilepsy.

MATERIALS AND METHODS

We retrospectively reviewed the data of 69 children who had insertion of vagal nerve stimulator (VNS) between June 1995 and August 2006 for medically intractable epilepsy. Outcome was based on the Engel's classification. Statistical analysis of the data was also done to see if any of the parameters significantly influenced the outcome.

RESULT

Thirty-eight patients (55.08 %) had a satisfactory outcome (Engel class I, II or III), and in 31 patients (44.92 %), there was no worthwhile improvement of seizures (Engel class IV). There was no statistical significance between the type of seizure and outcome (Fisher's exact test, p = 0.351). Statistical analysis also showed that the following parameters did not significantly influence the outcome (p > 0.05): age at insertion of VNS, age of first fit, duration between first fit and insertion of VNS and the length of follow-up. Complications included infection, lead fracture, fluid collection around the stimulator, neck pain and difficulty swallowing.

CONCLUSION

Vagus nerve stimulation is a relatively safe and potentially effective treatment for children with medically intractable epilepsy.

Vagus nerve stimulation

Vagus nerve stimulation (VNS) is a key tool in the treatment of patients with medically refractory epilepsy. Although the mechanism of action of VNS remains poorly understood, this modality is now the most widely used nonpharmacological treatment for drug-resistant epilepsy. The goal of this work is to review the history of VNS and provide information on recent advances and applications of this technology.

Vagal nerve stimulation--a 15-year survey of an established treatment modality in epilepsy surgery

Neurostimulation is an emerging treatment for neurological diseases. Electrical stimulation of the tenth cranial nerve or vagus nerve stimulation (VNS) has become a valuable option in the therapeutic armamentarium for patients with refractory epilepsy. It is indicated in patients with refractory epilepsy who are unsuitable candidates for epilepsy surgery or who have had insufficient benefit from such a treatment. Vagus nerve stimulation reduces seizure frequency with > 50% in 1/3 of patients and has a mild side effects profile. Research to elucidate the mechanism of action of vagus nerve stimulation has shown that effective stimulation in humans is primarily mediated by afferent vagal A- and B-fibers. Crucial brainstem and intracranial structures include the locus coeruleus, the nucleus of the solitary tract, the thalamus and limbic structures. Neurotransmitters playing a role may involve the major inhibitory neurotransmitter GABA but also serotoninergic and adrenergic systems. This manuscript reviews the clinical studies investigating efficacy and side effects in patients and the experimental studies aiming to elucidate the mechanims of action.

Treatment of Lennox-Gastaut syndrome: overview and recent findings

Lennox-Gastaut syndrome (LGS) is a rare, age-related syndrome, characterized by multiple seizure types, a specific electro-encephalographic pattern, and mental regression. However, published data on the etiology, evolution, and therapeutic approach of LGS are contradictory, partly because the precise definition of LGS used in the literature varies. In the most recent classification, LGS belongs to the epileptic encephalopathies and is highly refractory to all antiepileptic drugs. Numerous treatments, medical and non-medical, have been proposed and results mostly from open studies or case series have been published. Sometimes, patients with LGS are included in a more global group of patients with refractory epilepsy. Only 6 randomized double-blind controlled trials of medical treatments, which included patients with LGS, have been published. Overall, treatment is rarely effective and the final prognosis remains poor in spite of new therapeutic strategies. Co-morbidities need specific treatment. This paper summarizes the definition, diagnosis and therapeutic approach to LGS, including not only recognized antiepileptic drugs, but also "off label" medications, immune therapy, diet, surgery and some perspectives for the future.

Vagal nerve stimulation: exploring its efficacy and success for an improved prognosis and quality of life in cerebral palsy patients

Cerebral palsy (CP) continues to pose a cause for major socioeconomic concern and medical challenge worldwide. It is associated with a multi-faceted symptomatology warranting a multi-dimensional management-approach. Recent recognition of neurocognitive impairment and its hopefully possible treatment has opened up a new dimension in its management to the neurologists. Vagal nerve stimulation (VNS) technique is presently emerging as an effective alternative anti-epileptic therapeutic measure in intractable epilepsy. VNS has recently been shown to possess a suppressive effect also on interictal epileptiform discharges (IEDs) that are now being widely accepted as established associates of neurocognitive impairment. In this paper, the author proposes VNS technique implantation in CP patients on account of its dual therapeutic effectiveness, i.e. anti-epileptic and IED-suppression. These two effects are likely to control seizures that are quite often drug-resistant and also improve neurocognition in CP patients, thus hoping for a better overall prognostic outcome and an improved quality of life of the CP patients by VNS.

Vagus nerve stimulation in pediatric epileptic syndromes

Vagal nerve stimulation (VNS) has shown promising results in various cohorts of non-surgical refractory epilepsy in adults and children. However studies report a significant delay between implantation and clinical response. We describe a cohort of 28 children and adolescents prospectively followed, classified by epileptic syndromes and treated with VNS using a 6-week rapid ramping protocol between January 2000 and March 2005. Our cohort showed favorable outcome within 6 months which was sustained at 24 months: 68% (19/28) showing >or=50% reduction in seizure frequency, including 14% (4/28) who became seizure-free. VNS was particularly efficacious in children with cryptogenic generalized and partial epilepsies. Although adverse events occurred in 68% (19/28) of patients, most were transient. In conclusion, rapid ramping is associated with an early and lasting response in most children but with a slightly higher side-effect rate.

Misidentification of vagus nerve stimulator for intravenous access and other major adverse events

The vagus nerve stimulator has become a standard modality for intractable pediatric epilepsy. We reviewed our experience with major adverse events, after accidental puncture of a stimulator wire by an emergency room physician seeking intravenous access to treat status epilepticus. The Children's National Medical Center database was reviewed for patients undergoing vagus nerve stimulator placement between January 1988 and June 2006. Patient characteristics, duration of therapy, and treatment-limiting adverse events were noted. Of 62 patients implanted over 8 years, 22 (35%) had adverse events which led to a change in therapy. Adverse events included prominent drooling, coughing, throat discomfort, dysphagia, wound infection, difficulty breathing, vomiting, vocal-cord weakness, lead failure, and iatrogenic (piercing of wire; surgical clipping of wire during revision). Eight patients required nonroutine surgical intervention (13%). There were two unusual case presentations. In a 13-year-old boy with status epilepticus at an outlying emergency department, the stimulator line was pierced in search of intravenous access. In a 25-year-old housepainter, neck paresthesias upon right lateral neck turning were attributed to insufficient strain relief. Treatment-limiting adverse events occurred in approximately one-third of patients. Unanticipated adverse events included misidentification of the wire for intravenous access, clipping of the wire during surgical dissection, and cervical dysesthesias associated with head-turning.

Lack of effects of vagus nerve stimulation on drug-resistant epilepsy in eight pediatric patients with autism spectrum disorders: a prospective 2-year follow-up study

Vagus nerve stimulation (VNS) therapy has been reported to reduce seizure frequency in some children with drug-resistant epilepsy who are not suitable candidates for epilepsy surgery. It has been suggested that there may be positive cognitive and/or behavioral effects independent of seizure control. We describe the effects of VNS with respect to seizure frequency, cognition, and autistic symptoms and behavior in eight children and adolescents with medically intractable epilepsy and autism. In comparison to baseline, seizure frequency had not decreased in anyone in our series at the 2-year follow-up. In three cases, minor improvements in general functioning were noted, but there were no positive cognitive effects. This open prospective pilot study highlights the need for more prospective studies to prevent false expectations of improvement in this severely disabled group.