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

Efficacy and Safety of Vagus Nerve Stimulation in Lennox-Gastaut Syndrome: A Scoping Review

Lennox-Gastaut syndrome (LGS) is a severe developmental and epileptic encephalopathy characterized by drug-resistant seizures, cognitive impairments, and abnormal electroencephalographic patterns. Vagus nerve stimulation (VNS) is a widely used neuromodulation therapy for LGS, but its effects on seizure outcomes, different seizure types, non-seizure outcomes, and adverse events in this population have not been comprehensively reviewed. To conduct a scoping review on the use of VNS in LGS, a literature search was performed in PubMed, OVID, Web of Science, and Embase from inception to 9 June 2024, using relevant keywords and without restrictions on study design. The search yielded forty eligible studies (twenty-four retrospective cohorts, fourteen prospective cohorts, and two registry analyses) comprising 1400 LGS patients treated with VNS. No randomized controlled trials were identified. Across studies, the median seizure reduction ranged from 20.6% to 65%, with 0% to 100% of patients achieving a ≥50% seizure reduction. No consistent preoperative biomarker of VNS responsiveness was identified in LGS. Although inconsistent among different studies, tonic, atonic, and tonic-clonic seizures responded best, while focal seizures responded worst. Improvements in seizure severity, alertness, and quality of life were reported in some studies, but cognitive and adaptive functioning generally remained unchanged. Adverse events were mostly mild and transient, including hoarseness, cough, and paresthesia. Device-related complications and infections were uncommon. In conclusion, further research is needed to better understand VNS's position in the evolving LGS treatment landscape and its cost effectiveness.

Degraded inferior colliculus responses to complex sounds in prenatally exposed VPA rats

BACKGROUND

Individuals with autism spectrum disorders (ASD) often exhibit altered sensory processing and deficits in language development. Prenatal exposure to valproic acid (VPA) increases the risk for ASD and impairs both receptive and expressive language. Like individuals with ASD, rodents prenatally exposed to VPA exhibit degraded auditory cortical processing and abnormal neural activity to sounds. Disrupted neuronal morphology has been documented in earlier processing areas of the auditory pathway in VPA-exposed rodents, but there are no studies documenting early auditory pathway physiology. Therefore, the objective of this study is to characterize inferior colliculus (IC) responses to different sounds in rats prenatally exposed to VPA compared to saline-exposed rats.

METHODS

In vivo extracellular multiunit recordings from the inferior colliculus were collected in response to tones, speech sounds, and noise burst trains.

RESULTS

Our results indicate that the overall response to speech sounds was degraded in VPA-exposed rats compared to saline-exposed controls, but responses to tones and noise burst trains were unaltered.

CONCLUSIONS

These results are consistent with observations in individuals with autism that neural responses to complex sounds, like speech, are often altered, and lays the foundation for future studies of potential therapeutics to improve auditory processing in the VPA rat model of ASD.

Epilepsy Surgery for Cognitive Improvement in Epileptic Encephalopathy

Epileptic encephalopathies are defined by the presence of frequent epileptiform activity that causes neurodevelopmental slowing or regression. Here, we review evidence that epilepsy surgery improves neurodevelopment in children with epileptic encephalopathies. We describe an example patient with epileptic encephalopathy without drug refractory seizures, who underwent successful diagnostic and therapeutic surgeries. In patients with epileptic encephalopathy, cognitive improvement alone is a sufficient indication to recommend surgical intervention in experienced centers.

Perianaesthetic management on a child with Lennox-Gastaut Syndrome for vagus nerve stimulation (VNS) placement

Vagus nerve stimulation (VNS) is a neurostimulatory modality in treating patients with medically resistant epilepsy (MRE). It was introduced in 1997 and has been proven to reduce patients' dependency on antiepileptic drugs and seizure frequency. However, the usage of VNS in children with MRE has been limited, especially those with Lennox Gastaut Syndrome (LGS). Our teenage boy with this syndrome developed MRE and successfully underwent VNS placement. We discuss the perianaesthetic challenges, a brief description of VNS and the reported successes in patients with LGS.

Significant vomiting and weight loss in a pediatric epilepsy patient secondary to vagus nerve stimulation: A case report and review of the literature

Vagus nerve stimulation is a neuromodulatory treatment option for individuals with drug resistant epilepsy who are not resective surgical candidates. As the vagus nerve has widespread neural connections, stimulation can lead to an array of adverse effects. While vomiting and weight loss are known side effects of vagus nerve stimulation, these are typically transient, mild, and do not limit the ability to continue treatment. We describe a 17-year-old female with drug resistant focal epilepsy secondary to tuberous sclerosis complex, who began to experience daily emesis and significant weight loss approximately 2.5 years after VNS device insertion. Her body mass index progressively fell from between the 75th-85th percentiles to less than the first percentile. She underwent extensive workup by neurology, gastroenterology, and adolescent medicine services with no obvious cause identified. Prior to the insertion of an enteral tube for feeding support and urgent weight restoration, her vagus nerve stimulator was switched off, resulting in immediate cessation of her vomiting and a dramatically rapid recovery of weight over the ensuing few months. This case emphasizes the need to consider adverse effects of vagus nerve stimulation in the differential diagnosis of patients with otherwise unexplained new medical sequelae, and provides evidence potentially linking vagal stimulation to significant malnutrition-related complications. Outside of GI-related effects, few studies have shown late-onset adverse effects from VNS, including laryngeal and facial pain as well as bradyarrhythmia. Further research is needed to elucidate the exact mechanisms of vagus nerve stimulation to better anticipate and mitigate adverse effects, and to understand the pathophysiology of late-onset adverse effects in previously tolerant VNS patients.

Aesthetic transaxillary subpectoral placement of vagus nerve stimulator in children and young adults: A technical note

INTRODUCTION

Vagus nerve stimulation (VNS) is a neuromodulation therapy for drug-resistant epilepsy (DRE), refractory status epilepticus, and treatment-resistant depression. The lead is tunneled into the subcutaneous space and connected to the generator, which is usually implanted in a subcutaneous pocket below the clavicle. Surgical complications in the chest region include skin breakdown or infection. An alternative approach is to perform a subclavear subpectoral implantation. In our surgical series, we report a new aesthetic implantation method for VNS generators in children and young patients: the transaxillary subpectoral placement.

MATERIALS AND METHODS

From May 2021 to May 2023, 10 vagus nerve stimulation generators were placed subpectorally with a transaxillary approach by the authors. We considered operative time, surgical complications such as blood loss, infections, device migration, pain, and adverse events at follow-up.

RESULTS

In this surgical series, we reviewed all cases of subpectoral implantation of VNS generators in children and young adults at our institution in the last 2 years. All patients were treated with subpectoral Sentiva 1000 (Livanova PLC) insertion with axillary access by a neurosurgeon and a pediatric surgeon. The operative time was slightly longer compared to the traditional subcutaneous implant. All generators reported impedances within the optimal range. Blood loss was not significant and no other perioperative complications were reported. Patients and families were highly satisfied with the outcomes in terms of comfort and aesthetic results after surgery and at the last follow-up. No cases of infection occurred, and no malfunctions or displacements of the generator were registered at clinical follow-up.

CONCLUSION

The transaxillary subpectoral placement of theVNS generator is an aesthetic and anatomic approach, which provides several benefits to children and young adults.

Efficacy and Tolerability of Ultra Rapid Duty Cycling Vagus Nerve Stimulation for Medically Refractory Absence Seizures

BACKGROUND

Significant knowledge gap exists on vagus nerve stimulation (VNS) efficacy and tolerability in medically refractory absence seizures (MRAS). This retrospective review of patients with MRAS aims to narrow this knowledge gap by comparing ultra rapid duty cycling ([URDC] ON time seven seconds, OFF time 0.2 minutes) with less frequent stimulations of rapid duty cycling (RDC, OFF time <1.1 minutes) and normal duty cycling (NDC, OFF time ≥1.1 minutes).

METHODS

Patients with MRAS aged less than 21 years who underwent VNS implantation were identified. Patient demographics, antiepileptic medications, seizure types, frequency, VNS parameters, outcomes of seizure reduction rate (SRR), and seizure freedom were extracted and compared among NDC, RDC, and URDC patient cohorts.

RESULTS

Thirty-six patients with MRAS were identified. After a mean follow-up of 32.6 months, responder rate ([RR], SRR ≥50%) for URDC was 80% for absence seizures and 80% for all seizure types versus 66.67% and 66.77% for NDC and 78.57% and 57.14% for RDC, respectively. Six of 10 patients (60%) on URDC achieved complete seizure freedom. A higher rate of subjective improvement in academic performance, attention, and developmental gain was noted in the URDC group. Patients on URDC tolerated higher output current (mean 3.025 mA) with minimal side effects but required a battery change sooner.

CONCLUSIONS

VNS is a safe and effective nonpharmacologic management choice in patients with MRAS. The data presented demonstrate that the combination of URDC and high output current provides better RR and seizure freedom. Apart from a reduced battery life, this parameter modality seems to be well-tolerated.

Degraded inferior colliculus responses to complex sounds in prenatally exposed VPA rats

Background

Individuals with autism spectrum disorders (ASD) often exhibit altered sensory processing and deficits in language development. Prenatal exposure to valproic acid (VPA) increases the risk for ASD and impairs both receptive and expressive language. Like individuals with ASD, rodents prenatally exposed to VPA exhibit degraded auditory cortical processing and abnormal neural activity to sounds. Disrupted neuronal morphology has been documented in earlier processing areas of the auditory pathway in VPA-exposed rodents, but there are no studies documenting early auditory pathway physiology. Therefore, the objective of this study is to characterize inferior colliculus (IC) responses to different sounds in rats prenatally exposed to VPA compared to saline-exposed rats.

Methods

Neural recordings from the inferior colliculus were collected in response to tones, speech sounds, and noise burst trains.

Results

Our results indicate that the overall response to speech sounds was degraded in VPA-exposed rats compared saline-exposed controls, but responses to tones and noise burst trains were unaltered.

Conclusions

These results are consistent with observations in individuals with autism that neural responses to complex sounds, like speech, are often altered, and lays the foundation for future studies of potential therapeutics to improve auditory processing in the VPA rat model of ASD.

A novel ex-vivo isolated rabbit heart preparation to explore the cardiac effects of cervical and cardiac vagus nerve stimulation

The cardiac responses to vagus nerve stimulation (VNS) are still not fully understood, partly due to uncontrollable confounders in the in-vivo experimental condition. Therefore, an ex-vivo Langendorff-perfused rabbit heart with intact vagal innervation is proposed to study VNS in absence of cofounding anesthetic or autonomic influences. The feasibility to evoke chronotropic responses through electrical stimulation ex-vivo was studied in innervated isolated rabbit hearts (n = 6). The general nerve excitability was assessed through the ability to evoke a heart rate (HR) reduction of at least 5 bpm (physiological threshold). The excitability was quantified as the charge needed for a 10-bpm HR reduction. The results were compared to a series of in-vivo experiments rabbits (n = 5). In the ex-vivo isolated heart, the baseline HR was about 20 bpm lower than in-vivo (158 ± 11 bpm vs 181 ± 19 bpm). Overall, the nerve remained excitable for about 5 h ex-vivo. The charges required to reduce HR by 5 bpm were 9 ± 6 µC and 549 ± 370 µC, ex-vivo and in-vivo, respectively. The charges needed for a 10-bpm HR reduction, normalized to the physiological threshold were 1.78 ± 0.8 and 1.22 ± 0.1, in-vivo and ex-vivo, respectively. Overall, the viability of this ex-vivo model to study the acute cardiac effects of VNS was demonstrated.

Vagus nerve stimulator revision in pediatric epilepsy patients: a technical note and case series

INTRODUCTION

Vagus nerve stimulation (VNS) is an adjunctive treatment in children with intractable epilepsy. When lead replacement becomes necessary, the old leads are often truncated and retained and new leads are implanted at a newly exposed segment of the nerve. Direct lead removal and replacement are infrequently described, with outcomes poorly characterized. We aimed to describe our experience with feasibility of VNS lead removal and replacement in pediatric patients.

METHODS

Retrospective review examined 14 patients, at a single, tertiary-care, children's hospital, who underwent surgery to replace VNS leads, with complete removal of the existing lead from the vagus nerve and placement of a new lead on the same segment of the vagus nerve, via blunt and sharp dissection without use of electrocautery. Preoperative characteristics, stimulation parameters, and outcomes were collected.

RESULTS

Mean age at initial VNS placement was 7.6 years (SD 3.5, range 4.5-13.4). Most common etiologies of epilepsy were genetic (5, 36%) and cryptogenic (4, 29%). Lead replacement was performed at a mean of 6.0 years (SD 3.8, range 2.1-11.7) following initial VNS placement. Reasons for revision included VNS lead breakage or malfunction. There were no perioperative complications, including surgical site infection, voice changes, dysphagia, or new deficits postoperatively. Stimulation parameters after replacement surgery at last follow-up were similar compared to preoperatively, with final stimulation parameters ranging from 0.25 mA higher to 1.5 mA lower to maintain baseline seizure control. The mean length of follow-up was 7.9 years (SD 3.5, range 3.1-13.7).

CONCLUSION

Removal and replacement of VNS leads are feasible and can be safely performed in children. Further characterization of surgical technique, associated risk, impact on stimulation parameters, and long-term outcomes are needed to inform best practices in VNS revision.

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.

Development of localized interictal epileptiform discharges following vagus nerve stimulation for lennox-gastaut syndrome: a case report

Background

Lennox-gastaut syndrome (LGS) is an epileptic encephalopathy often associated with behavioral and psychiatric disorders. Vagus nerve stimulation (VNS) has been approved effective for LGS treatment. Surgical resection is also an option for LGS patients with focal pathology, offering a high probability of seizure control. However, it is challenging to accurately localize the seizure focus.

Case presentation

The case presented here is a 19-year-old male with a 16-year history of epilepsy with comorbid severe cognitive and psychiatric disorders. He was diagnosed with LGS due to generalized slow spike-wave discharges and multiple seizure types. He was treated with VNS in 2017 at the age of 15. After that, the frequency of the short tonic seizures decreased from 4–5 times per day to 2–5 times per year, and the generalized tonic–clonic seizure pattern did not recur, which had a frequency of 2–4 times per month before the surgery. In 2019, the generalized abnormal interictal epileptiform discharges changed to be localized in the right frontal–temporal lobe at the age of 17 years (2019).

Conclusions

This case report suggested that the generalized epileptiform discharges evolve into localized discharges after VNS treatment, which may help reveal the primary seizure focus for resection surgery in patients with LGS.

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.

Up to What Extent Does Dravet Syndrome Benefit From Neurostimulation Techniques?

Background

Dravet syndrome (DS) is a refractory developmental and epileptic encephalopathy (EE) with a variety of comorbidities, including cognitive impairment, autism-like behavior, speech dysfunction, and ataxia, which can seriously affect the quality of life of patients and impose a great burden on society and their families. Currently, the pharmacological therapy is patient dependent and may work or not. Neuromodulation techniques, including vagus nerve stimulation (VNS), deep brain stimulation (DBS), transcranial magnetic stimulation (TMS), responsive neurostimulation (RNS), and chronic subthreshold cortical stimulation (CSCS), have become common adjuvant therapies for neurological diseases, but their efficacy in the treatment of DS is unknown.

Methods

We searched Web of Science, PubMed, and SpringerLink for all published cases related to the neuromodulation techniques of DS until January 15, 2022. The systematic review was supplemented with relevant articles from the references. The results reported by each study were summarized narratively.

Results

The Web of science, PubMed and SpringerLink search yielded 258 items. A total of 16 studies published between 2016 and 2021 met the final inclusion criteria. Overall, 16 articles (109 cases) were included in this study, among which fifteen (107 patients) were involved VNS, and one (2 patients) was involved DBS. After VNS implantation, seizures were reduced to ≥50% in 60 cases (56%), seizure free were found in 8 cases (7.5%). Only two DS patients received DBS treatment, and the initial outcomes of DBS implantation were unsatisfactory. The seizures significantly improved over time for both DBS patients after the addition of antiepileptic drugs.

Conclusion

More than half of the DS patients benefited from VNS, and VNS may be effective in the treatment of DS. However, it is important to note that VNS does not guarantee improvement of seizures, and there is a risk of infection and subsequent device failure. Although DBS is a safe and effective strategy for the treatment of refractory epilepsy, the role of DBS in DS needs further study, as the sample size was small. Thus far, there is no strong evidence for the role of DBS in DS.

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 effect of transcutaneous auricular vagus nerve stimulation on HRV in healthy young people

Transcutaneous auricular vagus nerve stimulation (taVNS) has shown positive effects on a variety of diseases. Considering that decreased heart rate variability (HRV) is closely associated with morbidity and mortality for a variety of diseases, it is important to investigate the effect of taVNS on HRV. In Study 1, we conducted a two-stage cross-over trial to compare the effects of taVNS and sham taVNS (staVNS) on HRV. In Study 2, we systematically tested the effects of different taVNS parameters on high frequency (HF) component of HRV. The results showed that taVNS significantly increased measurements of root mean square of the difference between successive RR intervals (RMSSD), percentage of number of pairs of adjacent RR intervals differing greater than 50ms (pRR50), standard deviation of all RR intervals (SDRR), HF. Significantly, enhancement of HF and pRR50 persisted into recovery period. In addition, higher baseline LF/HF ratio was associated with greater LF/HF ratio decrease. Findings also showed that there was no significant difference in measurements of HF between different taVNS parameters. These studies suggest that taVNS could increase HRV, it may help taVNS in the treatment of low HRV related diseases. However, taVNS may not have parameter-specific effects on HRV.

Hospital costs associated with vagus nerve stimulation and medical treatment in pediatric patients with refractory epilepsy

Objectives

Refractory epilepsy is a diagnosis of recurrent seizures that requires multiple resources for optimal chronic management. The disease negatively impacts the lives of affected patients and families and poses an economic burden to the health care system. This study compares hospital costs between pediatric patients treated with antiseizure medications (ASMs) only and ASMs plus vagus nerve stimulation (VNS).

Methods

Patients 0–17 years of age who were diagnosed with refractory epilepsy between January 1, 2011 and December 31, 2016, were identified from the Children's Hospital Association's Pediatric Health Information System (PHIS) database. Patients treated with ASMs only or ASMs plus VNS were included in the study and were followed 1 year prior and 2 years after meeting pre‐determined criteria for refractory epilepsy. The difference‐in‐difference (DID) approach along with the two‐part model was used to compare the changes in mean hospital costs captured in the PHIS database over time between the two cohorts.

Results

One thousand one hundred thirteen patients treated with ASMs plus VNS and 3471 patients treated with ASMs only were included. At a follow‐up time of 2 years, for the ASMs‐only cohort, the adjusted all‐cause and epilepsy‐related mean annual total costs increased by $14 715 (95% confidence interval [CI]: $12 375–$17 055) and $18 437 (95% CI: $15 978–$20 896), respectively. By comparison, the adjusted all‐cause and epilepsy‐related mean annual total costs of the ASMs plus VNS cohort increased by $12 838 (95% CI: $8171–$17 505) and $15 183 (95% CI: $10 253–$20 113), respectively. Compared to ASMs only, ASMs plus VNS generated a cost savings of $3254 for epilepsy‐related annual costs per year after the index date.

Significance

Compared to ASMs alone, ASMs plus VNS is a treatment modality associated with lower annual hospital costs over time. Our study shows that VNS is a cost‐beneficial treatment for a national cohort of pediatric patients with refractory epilepsy.

Effects of Stable Vagus Nerve Stimulation Efficacy on Autistic Behaviors in Ten Pediatric Patients With Drug Resistant Epilepsy: An Observational Study

Vagus nerve stimulation (VNS) is a safe and effective therapy for pediatric patients with drug-resistant epilepsy (DRE). However, in children with DRE, the effects of VNS on autistic behaviors remain controversial. We retrospectively collected data from 10 children with DRE who underwent VNS implantation and regular parameter regulation in three pediatric epilepsy centers, and completed the behavioral assessments, including the autistic behavior checklist and the child behavior checklist, at follow-ups 1 (mean 2.16 years) and 2 (mean 2.98 years). The 10 children maintained stable seizure control between the two follow-ups. Their autistic behaviors, especially in language, social and self-help, were reduced at follow-up 2 compared to follow-up 1 (p = 0.01, p = 0.01, respectively). Moreover, these improvements were not associated with their seizure control, whether it was positive or negative. These results suggested that the VNS had a positive effect on autistic behaviors, which provided a preliminary clinical basis that VNS may benefit to younger children with DRE comorbidity autism spectrum disorder (ASD).

Comparison of healthcare resource utilization in pediatric patients with refractory epilepsy: Vagus nerve stimulation and medical treatment cohorts

OBJECTIVES

Refractory epilepsy imposes a substantial burden on affected patients, families, and healthcare system. In terms of treating seizures in children, vagus nerve stimulation (VNS) has been proved to be comparable to that of antiepileptic drugs (AEDs). This study compared healthcare resource utilization between pediatric patients treated with AEDs only and AEDs plus VNS.

METHODS

Pediatric patients diagnosed with refractory epilepsy between the 1st of January 2011 and the 31st of December 2016 were identified from the Pediatric Health Information System Database. Patients treated with AEDs only or AEDs plus VNS were included in the study and were followed up from one year before to two years after the date when defined criteria for refractory epilepsy were met. The difference-in-difference approach along with the hurdle model was used to compare the changes in healthcare resource utilization over time between patients treated with AEDs only and AEDs plus VNS.

RESULTS

The study included 1502 patients treated with AEDs plus VNS and 4541 patients treated with AEDs only. There was a difference in post-index all-cause and epilepsy-related inpatient visits compared to the pre-index period: inpatient hospitalizations were decreased in the AEDs plus VNS cohort, and increased in the AEDs only cohort. There was no significant difference in the pre-index to post-index change for all-cause and epilepsy-related emergency department visits between the two treatment cohorts. For outpatient encounters in the initial post-index period, patients treated with AEDs plus VNS had significantly higher increase in all-cause and epilepsy-related outpatient visits compared to the AEDs only cohort.

CONCLUSIONS

Compared to those treated with AEDs only, pediatric patients with refractory epilepsy treated with AEDs plus VNS have fewer inpatient visits and more outpatient visits within a 2-year follow-up. Given the lower acuity of care in outpatient versus inpatient settings, this study can inform treatment choices for children with refractory epilepsy.

Advances in Epilepsy Surgery

BACKGROUND

A large number of patients have epilepsy that is intractable and adversely affects a child's lifelong experience with addition societal burden that is disabling and expensive. The last two decades have seen a major explosion of new antiseizure medication options. Despite these advances, children with epilepsy continue to have intractable seizures. An option that has been long available but little used is epilepsy surgery to control intractable epilepsy.

METHODS

This article is a review of the literature as well as published opinions.

RESULTS

Epilepsy surgery in pediatrics is an underused modality to effectively treat children with epilepsy. Adverse effects of medication should be weighed against risks of surgery as well as risks of nonefficacy.

CONCLUSIONS

We discuss an approach to selecting the appropriate pediatric patient for consideration, a detailed evaluation including necessary evaluation, and the creation of an algorithm to approach patients with both generalized and focal epilepsy. We then discuss surgical options available including outcome data. New modalities are also addressed including high-frequency ultrasound and co-registration techniques including magnetic resonance imaging-guided laser therapy.

Monitoring the frequency and duration of epileptic seizures: "A journey through time"

Seizure monitoring plays an undeniably important role in diagnosing and managing epileptic seizures. Establishing the frequency and duration of seizures is crucial for assessing the burden of this chronic neurological disease, selecting treatment methods, determining how frequently these methods are applied, and informing short and long-term therapeutic decisions. Over the years, seizure monitoring tools and methods have evolved and become increasingly sophisticated; from home seizure diaries to EEG monitoring to cutting-edge responsive neurostimulation systems. In this article, the various methods of seizure monitoring are reviewed.

Epilepsy Surgery is a Viable Treatment for Lennox Gastaut Syndrome

Lennox Gastaut Syndrome (LGS) is a severe developmental epileptic encephalopathy with onset in childhood characterized by multiple seizure types and characteristic electroencephalogram findings. The majority of patients develop drug resistant epilepsy, defined as failure of 2 appropriate anti-seizure medications used at adequate doses. Epilepsy surgery can reduce seizure burden, in some cases leading to seizure freedom, and improve neuro-developmental outcomes and quality of life. Epilepsy surgery should be considered for all patients with drug resistant LGS. Herein, we review current surgical treatment options for patients with LGS, both definitive and palliative, including: focal cortical resection, vagus nerve stimulation and corpus callosotomy. Newer neuromodulation techniques will be explored, as well as the concept of LGS as a secondary network disorder.

Implant- and anesthesia-related factors affecting cardiopulmonary threshold intensities for vagus nerve stimulation

Objective.Vagus nerve stimulation (VNS) is typically delivered at increasing stimulus intensity until a neurological or physiological response is observed ('threshold') for dose calibration, preclinically and therapeutically. Factors affecting VNS thresholds have not been studied systematically. In a rodent model of VNS we measured neural and physiological responses to increasing VNS intensity, determined neurological and physiological thresholds and examined the effect of implant- and anesthesia-related factors on thresholds.Approach.In acute and chronic vagus implants (45 and 20 rats, respectively) VNS was delivered under isoflurane, ketamine-xylazine, or awake conditions. Evoked compound action potentials (CAPs) were recorded and activation of different fiber types was extracted. Elicited physiological responses were registered, including changes in heart rate (HR), breathing rate (BR), and blood pressure (BP). CAP and physiological thresholds were determined.Main results. The threshold for evoking discernable CAPs (>10µV) (CAP threshold) is significantly lower than what elicits 5%-10% drop in heart rate (heart rate threshold, HRT) (25µA ± 1.8 vs. 80µA ± 5.1, respectively; mean ± SEM). Changes in BP and small changes in BR (bradypnea) occur at lowest intensities (70µA ± 8.3), followed by HR changes (80µA ± 5.1) and finally significant changes in BR (apnea) (310μA ± 32.5). HRT and electrode impedance are correlated in chronic (Pearson correlationr= 0.47;p< 0.001) but not in acute implants (r= -0.34;pNS); HRT and impedance both increase with implant age (r= 0.44;p< 0.001 andr= 0.64;p< 0.001, respectively). HRT is lowest when animals are awake (200µA ± 35.5), followed by ketamine-xylazine (640µA ± 151.5), and isoflurane (1000µA ± 139.5). The sequence of physiological responses with increasing VNS intensity is the same in anesthetized and awake animals. Pulsing frequency affects physiological responses but not CAPs.Significance. Implant age, electrode impedance, and type of anesthesia affect VNS thresholds and should be accounted for when calibrating stimulation dose.

Vagus nerve stimulation in patients with Lennox-Gastaut syndrome: A meta-analysis

Objectives

Lennox‐Gastaut syndrome (LGS) is among the most severe epileptic and developmental encephalopathies. A meta‐analysis was performed to evaluate the effectiveness of adjunctive vagus nerve stimulation (VNS Therapy) in patients with LGS.

Materials & Methods

PubMed database was queried (January 1997 to September 2018) to identify publications reporting on the efficacy of VNS Therapy in patients with LGS, with or without safety findings. Primary endpoint of the meta‐analysis was the proportion of responders (≥50% reduction in seizure frequency). Random‐effects analysis was used to calculate weighted mean estimates and confidence intervals. Heterogeneity was evaluated by statistical tests including I².

Results

Of 2752 citations reviewed, 17 articles (480 patients) were eligible including 10 retrospective studies and seven prospective studies. A random‐effects model produced a pooled proportion of 54% (95% confidence intervals [CI]: 45%, 64%) of patients with LGS who responded to adjunctive VNS Therapy (p for heterogeneity <0.001, I²=72.9%). Per an exploratory analysis, the calculated incidence of serious adverse events associated with VNS Therapy was 9% (95% CI: 5%, 14%); the rate was higher than in long‐term efficacy studies of heterogeneous cohorts with drug‐resistant epilepsy and likely attributed to variable definitions of serious adverse events across studies.

Conclusions

The meta‐analysis of 480 patients with LGS suggests that 54% of patients responded to adjunctive VNS Therapy and that the treatment option was safe and well‐tolerated. The response in patients with LGS was comparable to heterogeneous drug‐resistant epilepsy populations. A clinical and surgical overview has been included to facilitate the use of VNS in LGS.

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

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

Atonic seizures in children: a meta-analysis comparing corpus callosotomy to vagus nerve stimulation

PURPOSE

Atonic seizures are associated with a particularly poor response to medical treatment. We performed a systematic review and meta-analysis to compare the efficacy of corpus callosotomy (CC) and vagus nerve stimulation (VNS) in the management of atonic seizures in the pediatric population.

METHODS

A literature search was performed in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and recommendations, focusing on atonic seizures, CC, and VNS in pediatric populations. Pertinent clinical data were extracted and analyzed. Pooled effects between groups were calculated as standardized error (SE) with 95% confidence intervals (CIs). To assess for statistical significance, the Z-test was performed, using the pooled effect size (ES) and 95% CI for each intervention.

RESULTS

A total of 31 studies met the inclusion criteria, with 24 studies encompassing 425 children treated with CC and 7 studies encompassing 108 children treated with VNS. Twenty-four studies were included in a meta-analysis. There was a statistically significant difference in the primary outcome of atonic seizure control in favor of CC (overall effect size (ES) 0.73, 95% CI 0.69-0.77 for CC, ES 0.4, 95% CI 0.28-0.51 for VNS, p = 0.003). There was a higher rate of complications requiring reoperation in the CC cohort (6.6% vs. 3.8%) and a 14% rate of symptomatic disconnection syndrome.

CONCLUSIONS

While both techniques are safe, CC provides a much higher chance of effectively managing this morbid seizure type albeit with a higher risk of re-operation and disconnection syndrome.

Management of Lennox-Gastaut syndrome beyond childhood: A comprehensive review

Lennox-Gastaut syndrome (LGS) is a childhood-onset epileptic encephalopathy characterized by multiple types of medically intractable seizures, cognitive impairment, and generalized slow spike-wave discharges in electroencephalography (EEG). Although the onset of this epileptic syndrome occurs typically before eight years of age with a peak age between 3 and 5 years, lifelong persistence of the syndrome is usual. The evolution of clinical features, EEG findings, and paucity of knowledge about LGS among adult health care providers can make LGS significantly underdiagnosed in the adult population. Management of LGS remains problematic beyond childhood due to intractable seizures, the difficult transition from pediatric to adult neurologists, challenging behaviors, impaired cognition, poor quality of life, and disabled social life. In focusing on the management of LGS beyond childhood, this narrative review describes medical and surgical management of epilepsy, the transition from pediatric to adult care, and management of other common comorbidities associated with LGS. Several antiepileptic drugs (AEDs) such as lamotrigine, topiramate, felbamate, rufinamide, clobazam, and Epidiolex (pure pharmaceutical grade cannabidiol (CBD) oil) have been noted to be effective in well-designed, randomized controlled trials. Other non-pharmacological therapies, such as vagus nerve stimulation, ketogenic diet, and epilepsy surgery, have been frequently utilized in the management of intractable seizures associated with LGS. However, effective management of LGS requires a broader perspective to not only control seizures but improve the quality of life by addressing cognitive and behavioral problems, sleep disturbances, physical disability, social disability, and educational and employment challenges.

Salvage therapy for vagal nerve stimulator infection; Literature review and report of a delayed recurrence

BACKGROUND

Vagal Nerve Stimulation (VNS) is one of the most common neuro-modulation based approaches for the treatment of medically intractable epilepsy. Despite advances in technology and surgical techniques, hardware infection remains a recognized and feared complication in VNS placement. Management of such infections is scarce in the literature with the majority of data available in case reports. It ranges from immediate removal of the VNS device to conservative treatment with antibiotics in an attempt to salvage the device, particularly in patients who demonstrated significant improvement in seizure frequency and quality of life.

METHODS

We performed a review of the literature in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines to identify reported cases of salvaged VNS infection. A literature search for relevant English articles was conducted using Medline. References of relevant articles were also reviewed. Articles that comprised an attempt to salvage an infected VNS were included.

RESULTS

We obtained 12 articles describing an attempt to salvage an infected VNS. Out of a total of 62 reported VNS infections and 43 salvage attempts using a variety of antibiotic-based approaches, 17 cases were successfully salvaged and 26 cases failed the salvage attempt and had to be explanted eventually. Moreover, we report a case of an 18-year-old male with Lennox-Gastaut syndrome who presented21 days after VNS placement with a MRSA deep tissue infection. An attempt was made to treat the infection with long-term culture-based intravenous antibiotics, but it recurred three years later with neck wound dehiscence and positive wound culture for the same organism, and ex-plantation was thus performed.

CONCLUSION

The management of VNS infections remains a dilemma for neurosurgeons. Although the idea of salvaging an infected VNS seems appealing, hardware removal seems to be inevitable despite adequate antibiotic treatment.

Efficacy of vagus nerve stimulation for drug-resistant epilepsy in children age six and younger

OBJECTIVES

The objective of the study were to examine the safety and efficacy of vagus nerve stimulation (VNS) for reducing seizure frequency and antiepileptic drugs (AEDs) in children younger than six years and to examine long-term VNS efficacy for children who receive the device at ages 1-3 and at ages 4-6.

METHODS

We conducted a 10-year retrospective analysis of VNS implantations at UPMC Children's Hospital of Pittsburgh. Relevant data were collected within 12 months of VNS implantation and at six months, one, two, and four years after VNS implantation.

RESULTS

This analysis included 99 patients ages 0-3 (n = 40) and 4-6 (n = 59) at first VNS implantation. Eighty-six patients followed up for ≥4 years. There were no significant differences between age at VNS implant (0-3 vs. 4-6) and seizure etiology or most seizure semiologies. Patients took an average of 3.01 ± 1.29 AEDs prior to VNS and 3.84 ± 1.68 AEDs at their latest follow-up. The overall response to VNS therapy (≥50% seizure reduction) at one year, two years, and four years after VNS implantation was 55%, 60%, and 52%, respectively. At two years, 59% of 0- to 3-year-old patients responded to VNS and 52% of 4- to 6-year-old patients responded to VNS. The overall major complication rate was 5.6%, consistent with VNS use for older age groups.

SIGNIFICANCE

This study demonstrates the safety and efficacy of VNS for children with drug-resistant epilepsy (DRE) younger than six. One, two, and four years after VNS implantation, 55%, 60%, and 52% of these patients, respectively, achieved ≥50% reduction in seizure frequency. The safety of VNS is also comparable with older, better studied, age groups. Based on these data, VNS therapy should be considered for children younger than six.

Efficacy of VNS for Drug-Resistant Epilepsy in Structural Brain Lesions

Background:

Vagus nerve stimulation (VNS) has been used for the treatment of drug-resistant epilepsy, especially in patients who are not candidates for surgical intervention. In fact, it was approved by the US FDA in 1997 as an adjunctive treatment for medically intractable epilepsy.

Objective:

In this study, we investigated the efficacy of VNS in drug-resistant epilepsy associated with structural brain lesions (SBLs).

Methods:

We retrospectively analyzed the effect of VNS on 25 patients diagnosed with intractable epilepsy-associated SBL, and compared the results to 19 patients with intractable epilepsy and normal neuroimaging. All patients underwent VNS insertion at the National Neurosciences Institute, King Fahad Medical City (Riyadh, Saudi Arabia) between 2008 and 2018.

Results:

The response rate (RR) for patients with drug-resistant epilepsy-associated SBL was 24% after 3 months, 36% after 6 months, and 48% after 1 year, reaching 76% over time. The mean follow-up period was 63.3 months. For non-SBL patients, the RR was 10.5% after 3 months, 36.8% after 6 months, and 47.4% after 1 year, reaching 73.7% over time. The mean follow-up period was 59.2 months. There was no statistically significant difference between the two groups regarding RR, VNS settings, and other parameters, including anti-epileptic drug use and demographics data.

Conclusion:

VNS is strongly considered for intractable epilepsy in SBL patients, especially if they are not candidates for surgical intervention. Over time, those patients will receive increased benefits from VNS therapy.

Learnings from 30 years of reported efficacy and safety of vagus nerve stimulation (VNS) for epilepsy treatment: A critical review

Three decades after its introduction as an adjuvant therapeutic option in the management of selective drug-resistant epilepsy cases (DRE), vagus nerve stimulation (VNS) retains growing interest. An implantable device was first approved for epilepsy in Europe in 1994 and in the United States (US) in 1997. Subsequent modifications improved the safety and the efficacy of the system. The most recent application of vagal neurostimulation is represented by transcutaneous devices that are claimed to have strong therapeutic potential. In this review, we sought to analyze the most meaningful available data describing the indications, safety and efficacy of the different approaches of VNS in clinical practice. Therefore, we identified studies reporting VNS efficacy and/or safety in epilepsy and its comorbidities from January 1990 to February 2020 from various databases including PubMed, Scopus, Cochrane, US government databases and VNS manufacturer published resources. In general, VNS efficacy becomes optimal around the sixth month of treatment and a 50-100 % seizure frequency reduction is achieved in approximately 45-65 % of the patients. However, some clinically relevant differences have been reported with specific factors such as epilepsy etiology or type, patient age as well as the delay of VNS therapy onset. VNS efficacy on seizure frequency has been demonstrated in both children and adults, in lesional and non-lesional cases, in focal and generalized epilepsies, on both seizures and epilepsy comorbidities. Regarding the latter, VNS can lead to an improvement of about 25-35 % in depression scores, 35 % in anxiety scores and 25 % in mood assessment scores. If non-invasive devices are undeniably safer, their efficacy is limited due to the scarcity of large cohort studies and the disparity of methodological approaches (study design and stimulation parameters). Overall, we believe that there is a progress margin for improving the safety of implantable devices and, above all, the effectiveness of the various VNS approaches.

Vagus nerve stimulation in patients with therapy-resistant generalized epilepsy

BACKGROUND

For patients with generalized epilepsy who do not respond to antiseizure medications, the therapeutic options are limited. Vagus nerve stimulation (VNS) is a treatment mainly approved for therapy-resistant focal epilepsy. There is limited information on the use of VNS on generalized epilepsies, including Lennox-Gastaut Syndrome (LGS) and genetic generalized epilepsy (GGE).

METHODS

We identified patients with a diagnosis of generalized epilepsy (including LGS and GGE), who underwent VNS implantation at the London Health Sciences Centre and Western University, London, Ontario, since this treatment became available in Canada in 1997 until July 2018. We assessed response to the treatment, including admissions to hospital and complications.

RESULTS

A total of 46 patients were included in this study with a history of therapy-resistant generalized epilepsy. The mean age at implantation was 24 years (interquartile range [IQR] = 17.8-31 years), significantly younger in the LGS group (p = 0.02) and 50% (n = 23) were female. The most common etiologies were GGE in 37% (n = 17) and LGS in 63% (n = 29). Median follow-up since VNS implantation was 63 months (IQR: 31-112.8 months). Of the LGS group 41.7% (n = 12) of patients had an overall seizure reduction of 50% or more, and 64.7% (n = 11) in the GGE group without statistical significance between the groups. The best response in seizure reduction was seen in generalized tonic-clonic seizures, with a significant reduction in the GGE group (p = 0.043). There was a reduction of seizure-related hospital admissions from 91.3% (N = 42) preimplantation, to 43.5% (N = 20) postimplantation (p < 0.05). The frequency of side effects due to the stimulation was almost equal in both groups (62.1% in LGS and 64.7% in GGE).

CONCLUSIONS

Vagus nerve stimulation should be considered as a treatment in patients with therapy-resistant generalized epilepsy, especially in cases with GGE.

Health Technology Assessment Report on Vagus Nerve Stimulation in Drug-Resistant Epilepsy

Background: Vagus nerve stimulation (VNS) is a palliative treatment for medical intractable epileptic syndromes not eligible for resective surgery. Health technology assessment (HTA) represents a modern approach to the analysis of technologies used for healthcare. The purpose of this study is to assess the clinical, organizational, financial, and economic impact of VNS therapy in drug-resistant epilepsies and to establish the congruity between costs incurred and health service reimbursement. Methods: The present study used an HTA approach. It is based on an extensive detailed bibliographic search on databases (Medline, Pubmed, Embase and Cochrane, sites of scientific societies and institutional sites). The HTA study includes the following issues: (a) social impact and costs of the disease; (b) VNS eligibility and clinical results; (c) quality of life (QoL) after VNS therapy; (d) economic impact and productivity regained after VNS; and (e) costs of VNS. Results: Literature data indicate VNS as an effective treatment with a potential positive impact on social aspects and on quality of life. The diagnosis-related group (DRG) financing, both on national and regional levels, does not cover the cost of the medical device. There was an evident insufficient coverage of the DRG compared to the full cost of implanting the device. Conclusions: VNS is a palliative treatment for reducing seizure frequency and intensity. Despite its economic cost, VNS should improve patients' quality of life and reduce care needs.

Can we predict response to vagus nerve stimulation in intractable epilepsy

BACKGROUND

Since vagus nerve stimulation (VNS) was approved by the Food and Drug Administration (FDA). A number of studies show that VNS was effective to reduce seizure frequency. However, there was still some patients treated with VNS having poor or even no clinical effect.

OBJECTIVES

The purpose of the present review was to identify factors predicting the effect of VNS therapy and to select patients suitable for VNS treatment.

METHOD

PubMed and Medline was searched with this terms "epilepsy," "vagus nerve stimulation," "vagal nerve stimulation," "VNS," "intractable," and "refractory".We selected studies by predefining inclusion and exclusion criteria.

RESULTS

the effectiveness of VNA was confirmed by a number of studies. We find many studies exploring the predictive factors to VNS. However there was no any study finding factors correlating clearly with the outcome of VNS. Although, we find these factors, such as post-traumatic epilepsy, temporal lobe epilepsy and focal interictal epileptiform discharges (IEDs), were favorable for the treatment of VNS, while comprehensive IEDs and neuronal migration disorders were indicative of the poor effect. Also, temporal lobe epilepsy was generally effectively controlled by this therapy and yougers seemed to get more benefit from VNS. Additionally, other indexes, such as cytokine profile, slow cortical potential (SCP) shift, preoperative heart rate variability (HRV), EEG reactivity and connectomic profiling, maybe predict the results of VNS.

CONCLUSION

In summary, these conventional and other new factors should be analyzed further by more science and rigorous experimental design to identify the clear correlation with the outcome of VNS therapy.

Efficacy and tolerability of vagus nerve stimulation therapy (VNS) in Slovenian epilepsy patients: younger age and shorter duration of epilepsy might result in better outcome

To review the outcome of vagus nerve stimulation (VNS) therapy in all implanted Slovenian patients with drug-resistant epilepsy, data on 48 patients implanted between 2001 and 2015 were obtained retrospectively from medical records. The outcome was assessed in 2016. Out of 48 patients, 39 responded at follow up. The seizure frequency was reduced in 18 (46.2%) patients; 13 (33.3%) of them reported ≥50% reduction after 12 months of therapy. The responder rate was higher among patients implanted before the age of six years. Ictal severity decreased in 22 (56.4%), seizure duration in 19 (48.7%) and post-ictal recovery time in 22 (56.4%) patients. Favorable effects on the quality of life (QOL) were improved alertness in 33.3%, concentration in 41.0%, energy and mood in 38.5%, and memory in 17.9% of patients. Reduced seizure burden and improved QOL were more often observed in patients implanted at a younger age. Shorter duration of epilepsy was significantly associated with QOL improvement. Adverse effects were transient. Overall positive effects showed VNS to be a safe, well-tolerated and effective adjunctive treatment in most severe drug-resistant epilepsy patients. Implantation at a younger age and shorter duration of epilepsy before implantation could be important predictors of better outcome.

The Present and Future of Vagus Nerve Stimulation

Epilepsy is one of the major chronic neurological diseases affecting many patients. Resection surgery is the most effective therapy for medically intractable epilepsy, but it is not feasible in all patients. Vagus nerve stimulation (VNS) is an adjunctive neuromodulation therapy that was approved in 1997 for the alleviation of seizures; however, efforts to control epilepsy by stimulating the vagus nerve have been studied for over 100 years. Although its exact mechanism is still under investigation, VNS is thought to affect various brain areas. Hence, VNS has a wide indication for various intractable epileptic syndromes and epilepsyrelated comorbidities. Moreover, recent studies have shown anti-inflammatory effects of VNS, and the indication is expanding beyond epilepsy to rheumatoid arthritis, chronic headaches, and depression. VNS yields a more than 50% reduction in seizures in approximately 60% of recipients, with an increase in reduction rates as the follow-up duration increases. The complication rate of VNS is 3–6%, and infection is the most important complication to consider. However, revision surgery was reported to be feasible and safe with appropriate measures. Recently, noninvasive VNS (nVNS) has been introduced, which can be performed transcutaneously without implantation surgery. Although more clinical trials are being conducted, nVNS can reduce the risk of infection and subsequent device failure. In conclusion, VNS has been demonstrated to be beneficial and effective in the treatment of epilepsy and various diseases, and more development is expected in the future.

Vagus nerve stimulation for pediatric patients with intractable epilepsy between 3 and 6 years of age: study protocol for a double-blind, randomized control trial

BACKGROUND

Recent clinical observations have reported the potential benefit of vagus nerve stimulation (VNS) as an adjunctive therapy for pediatric epilepsy. Preliminary evidence suggests that VNS treatment is effective for seizure reduction and mental development in young participants between 3 and 6 years of age who suffer from intractable epilepsy. However, robust clinical evidence for quantifying the difference of the efficacy and safety of VNS treatment in this specific patient population has yet to be reported.

METHODS/DESIGN

A two-armed, multicenter, randomized, double-blind, prospective trial will be carried out to evaluate whether VNS is beneficial and safe for pediatric epilepsy. Pediatric participants aged between 3 to 6 years old with intractable epilepsy will be recruited and randomly assigned to experimental and control groups with a 1:1 allocation using a computer-generating randomization schedule. Before enrollment, informed consent will be signed by the parents of the participants and the study researchers. Participants in the experimental group will receive electrical stimulation over 24 weeks under standard stimulation parameters. Participants in the control group will not receive any stimulation during the 12 weeks of the double-blind period. The guardians of the participants are required to keep a detailed diary to record seizure activity. Outcome assessments including seizure frequency, Gesell Mental Developmental Scale scores, use of antiepileptic drugs and dosages, and adverse events will be collected at baseline, 6, 12, 18 and/or 24 weeks after electrical stimulation is initiated. The effects of treatment will be analyzed with time and treatment group comparisons.

DISCUSSION

This trial will evaluate quantitative differences in efficacy and safety with/without VNS treatment for pediatric participants aged between 3 to 6 years with intractable epilepsy and will explore whether the current age range of VNS therapy can be expanded.

TRIAL REGISTRATION

ClinicalTrials.gov, ID: NCT03062514 , Registered on 23 February 2017.

Use of Vagus Nerve Stimulator on Children With Primary Generalized Epilepsy

OBJECTIVE

To describe the response to vagus nerve stimulator (VNS) in otherwise neurotypical children with medically intractable primary generalized epilepsy.

METHODS

Retrospective chart review of patients who underwent vagus nerve stimulator surgery between January 2011 and December 2015.

RESULTS

Eleven patients were identified. Median follow-up duration was 2.5 years (1.2-8.4 years). Prior to vagus nerve stimulator surgery, all patients had at least 1 seizure per week, and 7/11 (64%) had daily seizures. At 1-year follow-up after vagus nerve stimulator, 7/11 (64%) reported improved seizure frequency and 6/11 (55%) reported fewer than 1 seizure per month. Three patients (27%) reported complications related to vagus nerve stimulator surgery, and no patients required device removal.

SIGNIFICANCE

In children with medically intractable primary generalized epilepsy, vagus nerve stimulator is well tolerated and appears to lead to improvement in seizure frequency. Improvement was not attributable to epilepsy classification, age at vagus nerve stimulator implantation, output current, duty cycle, or follow-up duration.

Treatment Strategies for Dravet Syndrome

Dravet syndrome (DS) is a medically refractory epilepsy that onsets in the first year of life with prolonged seizures, often triggered by fever. Over time, patients develop other seizure types (myoclonic, atypical absences, drops), intellectual disability, crouch gait and other co-morbidities (sleep problems, autonomic dysfunction). Complete seizure control is generally not achievable with current therapies, and the goals of treatment are to balance reduction of seizure burden with adverse effects of therapies. Treatment of co-morbidities must also be addressed, as they have a significant impact on the quality of life of patients with DS. Seizures are typically worsened with sodium-channel agents. Accepted first-line agents include clobazam and valproic acid, although these rarely provide adequate seizure control. Benefit has also been noted with stiripentol, topiramate, levetiracetam, the ketogenic diet and vagal nerve stimulation. Several agents presently in development, specifically fenfluramine and cannabidiol, have shown efficacy in clinical trials. Status epilepticus is a recurring problem for patients with DS, particularly in their early childhood years. All patients should be prescribed a home rescue therapy (usually a benzodiazepine) but should also have a written seizure action plan that outlines when rescue should be given and further steps to take in the local hospital if the seizure persists despite home rescue therapy.

Reduced distractor interference during vagus nerve stimulation

Suppressing irrelevant information in decision making is an essential everyday skill. We studied whether this ability could be improved in epileptic patients during vagus nerve stimulation (VNS). VNS is known to increase norepinephrine (NE) in the brain. NE is thought to improve several aspects of cognitive control, including the suppression of irrelevant information. Nineteen epileptic VNS patients executed the Eriksen flanker task twice, both during on and off stimulation. Distractor interference was indexed by the congruency effect, a standard empirical marker of cognitive control. We found a reduced congruency effect during stimulation, which indicates an improved ability to suppress distractor interference. This effect was only found in patients that are clinically determined VNS-responders (n = 10). As VNS increases NE in VNS-responders, our finding suggests a beneficial role of NE in cognitive control. At the same time, it suggests that VNS does not only reduce seizure frequency in epileptic patients, but also improves cognitive control.

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

Expert Opinion on the Management of Lennox-Gastaut Syndrome: Treatment Algorithms and Practical Considerations

Lennox–Gastaut syndrome (LGS) is a severe epileptic and developmental encephalopathy that is associated with a high rate of morbidity and mortality. It is characterized by multiple seizure types, abnormal electroencephalographic features, and intellectual disability. Although intellectual disability and associated behavioral problems are characteristic of LGS, they are not necessarily present at its outset and are therefore not part of its diagnostic criteria. LGS is typically treated with a variety of pharmacological and non-pharmacological therapies, often in combination. Management and treatment decisions can be challenging, due to the multiple seizure types and comorbidities associated with the condition. A panel of five epileptologists met to discuss consensus recommendations for LGS management, based on the latest available evidence from literature review and clinical experience. Treatment algorithms were formulated. Current evidence favors the continued use of sodium valproate (VPA) as the first-line treatment for patients with newly diagnosed de novo LGS. If VPA is ineffective alone, evidence supports lamotrigine, or subsequently rufinamide, as adjunctive therapy. If seizure control remains inadequate, the choice of next adjunctive antiepileptic drug (AED) should be discussed with the patient/parent/caregiver/clinical team, as current evidence is limited. Non-pharmacological therapies, including resective surgery, the ketogenic diet, vagus nerve stimulation, and callosotomy, should be considered for use alongside AED therapy from the outset of treatment. For patients with LGS that has evolved from another type of epilepsy who are already being treated with an AED other than VPA, VPA therapy should be considered if not trialed previously. Thereafter, the approach for a de novo patient should be followed. Where possible, no more than two AEDs should be used concomitantly. Patients with established LGS should undergo review by a neurologist specialized in epilepsy on at least an annual basis, including a thorough reassessment of their diagnosis and treatment plan. Clinicians should always be vigilant to the possibility of treatable etiologies and alert to the possibility that a patient’s diagnosis may change, since the seizure types and electroencephalographic features that characterize LGS evolve over time. To date, available treatments are unlikely to lead to seizure remission in the majority of patients and therefore the primary focus of treatment should always be optimization of learning, behavioral management, and overall quality of life.

From psychological moments to mortality: A multidisciplinary synthesis on heart rate variability spanning the continuum of time

Heart rate variability (HRV) indexes functioning of the vagus nerve, arguably the most important nerve in the human body. The Neurovisceral Integration Model has provided a structural framework for understanding brain-body integration, highlighting the role of the vagus in adaptation to the environment. In the present paper, we emphasise a temporal framework in which HRV may be considered a missing, structural link between psychological moments and mortality, a proposal we label as Neurovisceral Integration Across a Continuum of Time (or NIACT). This new framework places neurovisceral integration on a dimension of time, highlighting implications for lifespan development and healthy aging, and helping to bridge the gap between clearly demarcated disciplines such as psychology and epidemiology. The NIACT provides a novel framework, which conceptualizes how everyday psychological moments both affect and are affected by the vagus in ways that have long-term effects on mortality risk. We further emphasize that a longitudinal approach to understanding change in vagal function over time may yield novel scientific insights and important public health outcomes.

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.