Vagus nerve stimulation: Outcome and predictors of seizure freedom in long-term follow-up

Vagus nerve stimulation in lesional and Non-Lesional Drug-Resistant focal onset epilepsies

PURPOSE

Drug-resistant epilepsy (DRE) affects one-third of patients with focal epilepsy. A large portion of patients are not candidates for epilepsy surgery, thus alternative options, such as vagus nerve stimulation (VNS), are proposed. Our objective is to study the effect of vagus nerve stimulation on lesional versus non-lesional epilepsies.

METHODS

This is a retrospective cohort study in a single center in London, Ontario, which includes patients with DRE implanted with VNS, implanted between 1997-2018 and the date of analysis is December 2023.

PARTICIPANTS

Patients implanted with VNS were classified by lesional (VNS-L) and non-lesional (VNS-NL) based on their MRI head findings. We further subdivided the VNS groups into patients with VNS alone versus those who also had additional epilepsy surgeries.

RESULTS

A total of 29 patients were enrolled in the VNS-L, compared to 29 in the VNS-NL. The median age of the patients in the study was 31.8 years, 29.31 % were men (N = 17). 41.4 % (n = 12) of the patients were VNS responders (≥50 % seizure reduction) in the VNS-L group compared to 62.0 % (n = 18) in the VNS-NL group (p = 0.03). When other epilepsy surgeries were combined with VNS in the VNS-L group, the median rate of seizure reduction was greater (72.4 (IQR 97.17-45.88) than the VNS-NL group 53.9 (IQR 92.22-27.92); p = 0.27).

CONCLUSIONS

VNS is a therapeutic option for patients with lesional epilepsy, with slightly inferior results compared to patients with non-lesional epilepsy. Patients implanted with VNS showed higher seizure reduction rates if they had previous epilepsy surgeries. This study demonstrates that VNS in lesional epilepsies can be an effective treatment.

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.

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.

Brain-clinical signatures for vagus nerve stimulation response

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Electroencephalogram and heart rate variability features as predictors of responsiveness to vagus nerve stimulation in patients with epilepsy: a systematic review

INTRODUCTION

Vagus nerve stimulation (VNS) is a mainstay treatment in people with medically refractive epilepsy with a growing interest to identify biomarkers that are predictive of VNS efficacy. In this review, we looked at electroencephalography (EEG) and heart rate variability (HRV) parameters as potential biomarkers.

METHODOLOGY

A comprehensive search of several databases limited to the English language and excluding animal studies was conducted. Data was collected from studies that specifically reviewed preoperative EEG and HRV characteristics as predictive factors of VNS outcomes.

RESULTS

Ten out of 1078 collected studies were included in this review, of which EEG characteristics were reported in seven studies; HRV parameters were reported in two studies, and one study reported both. For EEG, studies reported a lower global rate of synchronization in alpha, delta, and gamma waves as predictors of the VNS response. The P300 wave, an evoked response on EEG, had conflicting results. Two studies reported high P300 wave amplitudes in nonresponders and low amplitudes in responders, whereas another study reported high P300 wave amplitudes in responders. For HRV, one study reported high-frequency power as the only parameter to be significantly lower in responders. In contrast, two studies from the same authors showed that HRV parameters were not different between responders and nonresponders.

CONCLUSION

HRV parameters and EEG characteristics including focal seizures and P300 wave have been reported as potential biomarkers for VNS outcomes in people with medically refractive epilepsy. However, the contradictory findings imply a need for validation through clinical trials.

Practical considerations in epilepsy neurostimulation

Neuromodulation is a key therapeutic tool for clinicians managing patients with drug-resistant epilepsy. Multiple devices are available with long-term follow-up and real-world experience. The aim of this review is to give a practical summary of available neuromodulation techniques to guide the selection of modalities, focusing on patient selection for devices, common approaches and techniques for initiation of programming, and outpatient management issues. Vagus nerve stimulation (VNS), deep brain stimulation of the anterior nucleus of the thalamus (DBS-ANT), and responsive neurostimulation (RNS) are all supported by randomized controlled trials that show safety and a significant impact on seizure reduction, as well as a suggestion of reduction in the risk of sudden unexplained death in epilepsy (SUDEP). Significant seizure reductions are observed after 3 months for DBS, RNS, and VNS in randomized controlled trials, and efficacy appears to improve with time out to 7 to 10 years of follow-up for all modalities, albeit in uncontrolled follow-up or retrospective studies. A significant number of patients experience seizure-free intervals of 6 months or more with all three modalities. Number and location of epileptogenic foci are important factors affecting efficacy, and together with comorbidities such as severe mood or sleep disorders, may influence the choice of modality. Programming has evolved-DBS is typically initiated at lower current/voltage than used in the pivotal trial, whereas target charge density is lower with RNS, however generalizable optimal parameters are yet to be defined. Noninvasive brain stimulation is an emerging stimulation modality, although it is currently not used widely. In summary, clinical practice has evolved from those established in pivotal trials. Guidance is now available for clinicians who wish to expand their approach, and choice of neuromodulation technique may be tailored to individual patients based on their epilepsy characteristics, risk tolerance, and preferences.

Vagus nerve stimulation for refractory posttraumatic epilepsy: Efficacy and predictors of seizure outcome

Background

Traumatic brain injury (TBI) has been recognized as an important and common cause of epilepsy since antiquity. Posttraumatic epilepsy (PTE) is usually associated with drug resistance and poor surgical outcomes, thereby increasing the burden of the illness on patients and their families. Vagus nerve stimulation (VNS) is an adjunctive treatment for medically refractory epilepsy. This study aimed to determine the efficacy of VNS for refractory PTE and to initially evaluate the potential predictors of efficacy.

Methods

We retrospectively collected the outcomes of VNS with at least a 1-year follow-up in all patients with refractory PTE. Subgroups were classified as responders and non-responders according to the efficacy of VNS (≥50% or <50% reduction in seizure frequency). Preoperative data were analyzed to screen for potential predictors of VNS efficacy.

Results

In total, forty-five patients with refractory PTE who underwent VNS therapy were enrolled. Responders were found in 64.4% of patients, and 15.6% of patients achieved seizure freedom at the last follow-up. In addition, the responder rate increased over time, with 37.8, 44.4, 60, and 67.6% at the 3-, 6-, 12-, and 24-month follow-ups, respectively. After multivariate analysis, generalized interictal epileptic discharges (IEDs) were found to be a negative predictor (OR: 4.861, 95% CI: 1.145–20.632) of VNS efficacy.

Conclusion

The results indicated that VNS therapy was effective in refractory PTE patients and was well tolerated over a 1-year follow-up period. Patients with focal or multifocal IEDs were recognized to have better efficacy after VNS therapy.

Vagus nerve stimulation for conservative therapy-refractive epilepsy and depression

Numerous studies confirm that the vagus nerve stimulation (VNS) is an efficient, indirect neuromodulatory therapy with electrically induced current for epilepsy that cannot be treated by epilepsy surgery and is therapy-refractory and for drug therapy-refractory depression. VNS is an established, evidence-based and in the long-term cost-effective therapy in an interdisciplinary overall concept.Long-term data on the safety and tolerance of the method are available despite the heterogeneity of the patient populations. Stimulation-related side effects like hoarseness, paresthesia, cough or dyspnea depend on the stimulation strength and often decrease with continuing therapy duration in the following years. Stimulation-related side effects of VNS can be well influenced by modifying the stimulation parameters. Overall, the invasive vagus nerve stimulation may be considered as a safe and well-tolerated therapy option.For invasive and transcutaneous vagus nerve stimulation, antiepileptic and antidepressant as well as positive cognitive effects could be proven. In contrast to drugs, VNS has no negative effect on cognition. In many cases, an improvement of the quality of life is possible.iVNS therapy has a low probability of complete seizure-freedom in cases of focal and genetically generalized epilepsy. It must be considered as palliative therapy, which means that it does not lead to healing and requires the continuation of specific medication. The functional principle is a general reduction of the neuronal excitability. This effect is achieved by a slow increase of the effectiveness sometimes over several years. Responders are those patients who experience a 50% reduction of the seizure incidence. Some studies even reveal seizure-freedom in 20% of the cases. Currently, it is not possible to differentiate between potential responders and non-responders before therapy/implantation.The current technical developments of the iVNS generators of the new generation like closed-loop system (cardiac-based seizure detection, CBSD) reduce also the risk for SUDEP (sudden unexpected death in epilepsy patients), a very rare, lethal complication of epilepsies, beside the seizure severity.iVNS may deteriorate an existing sleep apnea syndrome and therefore requires possible therapy interruption during nighttime (day-night programming or magnet use) beside the close cooperation with sleep physicians.The evaluation of the numerous iVNS trials of the past two decades showed multiple positive effects on other immunological, cardiological, and gastroenterological diseases so that additional therapy indications may be expected depending on future study results. Currently, the vagus nerve stimulation is in the focus of research in the disciplines of psychology, immunology, cardiology as well as pain and plasticity research with the desired potential of future medical application.Beside invasive vagus nerve stimulation with implantation of an IPG and an electrode, also devices for transdermal and thus non-invasive vagus nerve stimulation have been developed during the last years. According to the data that are currently available, they are less effective with regard to the reduction of the seizure severity and duration in cases of therapy-refractory epilepsy and slightly less effective regarding the improvement of depression symptoms. In this context, studies are missing that confirm high evidence of effectiveness. The same is true for the other indications that have been mentioned like tinnitus, cephalgia, gastrointestinal complaints etc. Another disadvantage of transcutaneous vagus nerve stimulation is that the stimulators have to be applied actively by the patients and are not permanently active, in contrast to implanted iVNS therapy systems. So they are only intermittently active; furthermore, the therapy adherence is uncertain.

Patient-Specific Characteristics Associated with Favorable Response to Vagus Nerve Stimulation

OBJECTIVE

The expansion in treatments for medically refractory epilepsy heightens the importance of identifying patients who are likely to benefit from vagus nerve stimulation (VNS). Here, we identify predictors with a positive VNS response.

METHODS

We present a retrospective analysis of 158 patients with medically refractory epilepsy. Patients were categorized as VNS responders or nonresponders. Baseline characteristics and time to VNS response were recorded. Univariate and multivariate Cox regression were used to identify predictors of response. Recursive partitioning analysis was used to identify likely VNS responders.

RESULTS

Eighty-nine (56.3%) patients achieved ≥50% seizure frequency reduction. Left-hand dominance (hazard ratio [HR] 1.703, P = 0.038), age at epilepsy onset ≥15 years (HR 2.029, P = 0.005), duration of epilepsy ≥8 years (HR 1.968, P = 0.007) and age at implantation ≥35 years (HR 1.809, P = 0.020), and baseline seizure frequency <5/month (HR 1.569, P = 0.044) were significant univariate predictors of VNS response. Following multivariate Cox regression, left-hand dominance, age at epilepsy onset ≥15 years, and duration of epilepsy ≥8 years remained significant. With recursive partitioning analysis, patients with either age at epilepsy onset ≥15 years, left-hand dominance, or baseline seizure frequency <5/month were stratified into Group A and had a 73.9% responder rate; the remaining patients stratified into Group B had a 43.8% responder rate.

CONCLUSIONS

Patients with age at epilepsy onset ≥15 years, left-hand dominance, or baseline seizure frequency <5/month are ideal candidates for VNS.

Efficacy and potential predictors of vagus nerve stimulation therapy in refractory postencephalitic epilepsy

BACKGROUND

Vagus nerve stimulation (VNS) is a therapeutic approach for patients with refractory postencephalitic epilepsy (PEE), which is characterized by drug resistance and disappointing surgical outcomes. However, the efficacy of VNS has not yet been studied in patients with refractory PEE. The present study aimed to demonstrate the efficacy of VNS and evaluate potential clinical predictors in patients with refractory PEE.

METHODS

We retrospectively collected the outcomes of VNS with at least a 1-year follow-up in all patients with refractory PEE. Subgroups were classified as responders and non-responders according to the efficacy of VNS (⩾50% or < 50% reduction in seizure frequency). Preoperative data were analyzed to screen for potential predictors of VNS responsiveness.

RESULTS

A total of 42 refractory PEE patients who underwent VNS therapy were enrolled, with an average age of 21.13 ± 9.70 years. Seizure frequency was reduced by more than 50% in 64.25% of patients, and 7.14% of patients achieved seizure-free events after VNS therapy. In addition, the response rates increased over time, with 40.5%, 50.0% and 57.1%, respectively at 6 months, 12 months, and 24 months after VNS therapy. Preoperative duration of epilepsy, monthly seizure frequency, and spatial distribution of interictal epileptic discharges (IEDs) were correlated with responders (p < 0.05) in the univariate analysis. Further multivariate regression analysis demonstrated that refractory PEE patients with high monthly seizure frequency or Focal IEDs (focal or multifocal epileptiform discharges) achieved better efficacy on VNS (p = 0.010, p = 0.003, respectively).

CONCLUSION

VNS is an effective palliative therapy for patients with refractory PEE. Focal IEDs (focal or multifocal epileptiform discharges) and high seizure frequency were potential preoperative predictors of effectiveness after VNS therapy.

Patient Characteristics Associated with Seizure Freedom after Vagus Nerve Stimulation in Pediatric Intractable Epilepsy: An Analysis of “Super-Responders”

Clinical responses to vagus nerve stimulation (VNS) therapy for intractable epilepsy can be unpredictable, and factors that predict response to therapy are elusive. Minority of children undergoing VNS achieve seizure freedom. The current study aimed to characterize this exceptional patient population, defined as “super-responders” (SRs). Retrospective data were collected from 150 children who underwent VNS at a single pediatric institution. The patients' mean age at VNS device implantation was 12.0 years (range, 3.09–17.9 years). Ten SRs (6.7%) were identified who achieved and maintained seizure freedom for longer than 1 year following implantation. The interval between epilepsy onset and VNS device implantation was significantly shorter in SRs than in the other children (mean epilepsy duration 5.72 vs. 8.44 years, respectively; p = 0.032). SRs also had a significantly shorter proportion of life with epilepsy compared with the other children (mean ratio of epilepsy duration to age at implantation 0.52 vs. 0.71, respectively; p = 0.023). SRs reported their seizure freedom relatively early (six patients within 6 months and all patients within 12 months after implantation) at relatively low device settings (mean output current 0.81 mA at their last follow-up). Compared with conventional models, responsive VNS models with autostimulation features did not increase the ratio of SRs. No other clinical or imaging characteristic difference between SRs and the other children was found in this cohort. The current study showed a significant association between shorter epilepsy duration and shorter proportion of life with epilepsy and seizure freedom after VNS.

Factors Affecting Vagus Nerve Stimulation Outcomes in Epilepsy

Epilepsy as a common neurological disease is mostly managed effectively with antiepileptic medications. One-third of patients do not respond to medical treatments requiring alternative therapies. Vagus nerve stimulation (VNS) has been used in the last decades for the treatment of medically resistant epilepsy. Despite the extensive use of VNS in these patients, factors associated with clinical outcomes of VNS remain to be elucidated. In this study, we evaluated factors affecting VNS outcomes in epileptic patients to have a better understanding of patients who are better candidates for VNS therapy. Several databases including PubMed, Scopus, and Google Scholar were searched through June 2020 for relevant articles. The following factors were assessed in this review: previous surgical history, age at implantation and gender, types of epilepsy, duration of epilepsy, age at epilepsy onset, frequency of attacks, antiepileptic drugs, VNS parameters, EEG findings, MRI findings, and biomarkers. Literature data show that nonresponder rates range between 25% and 65%. Given the complexity and diversity of factors associated with response to VNS, more clinical studies are needed to establish better paradigm for selection of patients for VNS therapy.

Vagus Nerve Stimulation and Seizure Outcomes in Pediatric Refractory Epilepsy: Systematic Review and Meta-analysis

OBJECTIVE

We synthesized evidence for effectiveness of vagus nerve stimulation (VNS) as adjuvant therapy in pediatric drug-resistant epilepsy (DRE) by obtaining pooled estimates for seizure outcomes and analyzing their determinants.

METHODS

MEDLINE, EMBASE, and Cochrane databases were searched up to July 2019 for original research on VNS in pediatric (≤18 years of age) epilepsy. The primary outcome was 50% responder rate (50% RR), the proportion of patients with ≥50% seizure reduction, at the last reported follow-up. Other outcomes included a 50% RR and proportion of seizure-free patients at additional reported time points. A random-effects meta-analysis with restricted maximum likelihood estimation was performed to obtain pooled effect estimates. Meta-regression using multiple linear models was performed to obtain determinants of seizure outcomes and sources of heterogeneity.

RESULTS

A total of 101 studies were included. The pooled prevalence estimates for a 50% RR and seizure freedom at last follow-up (mean 2.54 years) were 56.4% (95% confidence intervals [CIs] 52.4, 60.4) and 11.6% (95% CI 9.6, 13.9), respectively. Fewer antiseizure medications (ASMs) tried before VNS and later age at onset of seizures were associated with better seizure outcomes following VNS implantation. An effect of sex distribution of studies on long-term outcomes and a potential publication bias for short-term outcomes were also observed.

CONCLUSION

Pooled evidence supports possible effectiveness of VNS in pediatric DRE, although complete seizure freedom is less common. Early referral (fewer trials of ASMs) may be a modifiable factor for desirable seizure outcomes with VNS from a clinical perspective.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

Long-term effects of vagus nerve stimulation in refractory pediatric epilepsy: A single-center experience

INTRODUCTION

Vagus nerve stimulation (VNS) has been used as an adjunctive therapy for both children and adults with refractory epilepsy, over the last two decades. In this study, we aimed to evaluate the long-term effects and tolerability of VNS in the pediatric drug-resistant epilepsy (DRE) and to identify the predictive factors for responsiveness to VNS.

METHODS

We retrospectively reviewed the medical records of pediatric patients who underwent VNS implantation between 1997 and 2018. Patients with ≥50% reduction of seizure frequency compared with the baseline were defined as "responders". The clinical characteristics of responders and nonresponders were compared.

RESULTS

A total of 58 children (male/female: 40/18) with a mean follow-up duration of 5.7 years (3 months to 20 years) were included. The mean age at implantation was 12.4 years (4.5 to 18.5 years). Approximately half (45%) of our patients were responders, including 3 patients (5.8%) who achieved seizure freedom during follow-up. The age of seizure-onset, duration of epilepsy, age at implantation, and etiologies of epilepsy showed no significant difference between responders and nonresponders. Responders were more likely to have focal or multifocal epileptiform discharges (63%) on interictal electroencephalogram (EEG), when compared to nonresponders (36%) (p = .07). Vocal disturbances and paresthesias were the most common side effects, and in two patients, VNS was removed because of local reaction.

CONCLUSION

Our series had a diverse etiological profile and patients with transition to adult care. Long-term follow-up showed that VNS is an effective and well-tolerated treatment modality for refractory childhood onset epilepsy. Age at implantation, duration of epilepsy and underlying etiology are not found to be predictors of responsiveness to VNS. Higher response rates were observed for a subset of patients with focal epileptiform discharges.

Vagus nerve stimulation: a pre-hospital case report

Introduction:

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

Case:

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

Conclusion:

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

Biomarkers of seizure response to vagus nerve stimulation: A scoping review

Although vagus nerve stimulation (VNS) is a common procedure, seizure outcomes are heterogeneous, with few available means to preoperatively identify the ideal surgical candidate. Here, we perform a scoping review of the literature to identify biomarkers of VNS response in patients with drug-resistant epilepsy. Several databases (Ovid MEDLINE, Ovid Embase, BIOSIS Previews, and Web of Science) were searched for all relevant articles that reported at least one biomarker of VNS response following implantation for intractable epilepsy. Patient demographics, seizure data, and details related to biomarkers were abstracted from all studies. From the 288 records screened, 28 articles reporting on 16 putative biomarkers were identified. These were grouped into four categories: network/connectomic-based biomarkers, electrophysiological signatures, structural findings on neuroimaging, and systemic assays. Differences in brain network organization, connectivity, and electrophysiological synchronicity demonstrated the most robust ability to identify VNS responders. Structural findings on neuroimaging yielded inconsistent associations with VNS responsiveness. With regard to systemic biomarkers, heart rate variability was shown to be an independent marker of VNS response, whereas inflammatory markers were not useful. There is an unmet need to preoperatively identify candidates who are likely to benefit from VNS. Several biomarkers demonstrate promise in predicting seizure responsiveness to VNS, particularly measures of brain network connectivity. Further efforts are required to validate existing biomarkers to inform clinical decision-making.

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.

Vagus Nerve Stimulation-Induced Laryngeal Motor Evoked Potentials: A Possible Biomarker of Effective Nerve Activation

Vagus nerve stimulation (VNS) therapy is associated with laryngeal muscle activation and induces voice modifications, well-known side effects of the therapy resulting from co-activation of the recurrent laryngeal nerve. In this study, we describe the non-invasive transcutaneous recording of laryngeal motor evoked potentials (LMEPs), which could serve as a biomarker of effective nerve activation and individual titration in patients with drug-resistant epilepsy. We recruited drug-resistant epileptic patients treated for at least 6 months with a VNS. Trains of 600-1200 VNS pulses were delivered with increasing current outputs. We placed six skin electrodes on the ventral surface of the neck, in order to record LMEPs whenever the laryngeal muscular threshold was reached. We studied the internal consistency and the variability of LMEP recordings, and compared different methods for amplitude calculation. Recruitment curves were built based on the stimulus-response relationship. We also determined the electrical axis of the LMEPs dipole in order to define the optimal electrode placement for LMEPs recording in a clinical setting. LMEPs were successfully recorded in 11/11 patients. The LMEPs threshold ranged from 0.25 to 1 mA (median 0.50 mA), and onset latency was between 5.37 and 8.77 ms. The signal-to-noise ratio was outstanding in 10/11 patients. In these cases, excellent reliability (Intraclass correlation coefficient, ICC > 0.90 across three different amplitude measurements) was achieved with 10 sample averages. Moreover, our recordings showed very good internal consistency (Cronbach's alpha > 0.95 for 10 epochs). Area-under-the-curve and peak-to-peak measurement proved to be complementary methods for amplitude calculation. Finally, we determined that an optimal derivation requires only two recording electrodes, aligned on a horizontal axis around the laryngeal prominence. In conclusion, we describe here an optimal methodology for the recording of VNS-induced motor evoked responses from the larynx. Although further clinical validation is still necessary, LMEPs might be useful as a non-invasive marker of effective nerve activation, and as an aid for the clinician to perform a more rational titration of VNS parameters.

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.

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.

New Techniques and Progress in Epilepsy Surgery

While open surgical resection for medically refractory epilepsy remains the gold standard in current neurosurgical practice, modern techniques have targeted areas for improvement over open surgical resection. This review focuses on how a variety of these new techniques are attempting to address these various limitations. Stereotactic electroencephalography offers the possibility of localizing deep epileptic foci, improving upon subdural grid placement which limits localization to neocortical regions. Laser interstitial thermal therapy (LITT) and stereotactic radiosurgery can minimally or non-invasively ablate specific regions of interest, with near real-time feedback for laser interstitial thermal therapy. Finally, neurostimulation offers the possibility of seizure reduction without needing to ablate or resect any tissue. However, because these techniques are still being evaluated in current practice, there are no evidence-based guidelines for their use, and more research is required to fully evaluate their proper role in the current management of medically refractory epilepsy.

[Invasive stimulation procedures and EEG diagnostics in epilepsy]

Stimulation has been performed experimentally and in small case series to treat epilepsy since the 1970s. Since the introduction of vagus nerve stimulation in 1997 and intracranial stimulation methods in 2011 into patient care, invasive stimulation has become a rapidly developing but infrequently used therapeutic option in Europe. Whereas vagus nerve stimulation is frequently used, particularly in the USA, intracranial stimulation differs in its regional availability. In order to improve the efficacy of stimulation, develop criteria for its use and assure low complication rates, a concentration on experienced centers and multicenter data acquisition and sharing are needed.Invasive electroencephalographic (EEG) monitoring with subdural electrodes and especially with stereotactically implanted depth electrodes have been used increasingly more often for presurgical evaluation in recent years. They are applied when non-invasive diagnostics show insufficient results to exactly identify the location and extent of the epileptogenic zone or cannot be adequately distinguished from eloquent cortex areas. Complications include intracranial hemorrhage, infections and increased intracranial pressure but lasting deficits or even death are rare (≤2 %). The outcome of invasive monitoring is inferior to non-invasive monitoring because of the higher degree of complexity of the cases; however, it is far superior to the seizure-free rates achieved by anticonvulsant drug treatment alone.

Effectiveness of vagal nerve stimulation in medication-resistant epilepsy. Comparison between patients with and without medication changes

BACKGROUND

Vagal nerve stimulation (VNS) response is not immediate. A progressive decline in seizure frequency is usually found during a period of 12-18 months after implantation. During this time, the patient's medication is usually modified, which can create doubts about whether their clinical improvement is due to medication changes or to VNS itself. Our goal is to compare two groups of patients treated with VNS, with and without changes in their medication.

METHODS

We prospectively analyze 85 patients who were treated with VNS in our hospital between 2005 and 2014. In 43 patients, changes in the antiepileptic drugs (EAD) were not allowed during the postoperative follow-up and they were compared with 42 patients who were left at the option of neurologist make changes in medication. We analyzed the clinical situation at 18 months and compared the two groups.

RESULTS

Overall, 54.1% of patients had a reduction in seizures of 50% or higher (responders). In the group with no changes in medication, responders reached 63%, while in the group in which changes in medication were allowed, 45.2% were responders. Between responders and non-responders, there were no statistical differences in type of epilepsy, frequency, previous surgery, or intensity of stimulation.

CONCLUSIONS

We did not find a statistical difference in seizure frequency reduction between patients with or without changes in medication during their follow-up, so changes in medication did not improve the outcome. Furthermore, the absence of changes in AED can help to optimize the parameters of the stimulator in order to improve its effectiveness.

An interictal EEG can predict the outcome of vagus nerve stimulation therapy for children with intractable epilepsy

PURPOSE

This study aimed to evaluate the long-term efficacy of vagus nerve stimulation (VNS) in children and adolescents with intractable epilepsy and identify predictive factors for responsiveness to VNS.

METHODS

Medical records of pediatric patients who underwent VNS implantation at two Korean tertiary centers were reviewed. At 0.5, 1, 3, and 5 years post-VNS implantation, the frequency of the most disabling seizures in each patient was assessed. Responders were defined as showing an overall 50 % reduction from baseline seizure frequency during follow-up. The clinical characteristics of responders and non-responders were compared.

RESULTS

Among 58 patients, approximately half (29/58) were responders. The mean age at implantation was 10.9 years (range, 2.7-20.9) and the mean follow-up duration after VNS implantation was 8.4 years (range, 1-15.5). At 0.5, 1, 3, and 5 years after implantation, 43.1, 50.0, 56.9, and 58.1 % of patients exhibited ≥50 % seizure frequency reduction disabling seizures. The patients with focal or multifocal epileptiform discharges were more likely to be responders than those with generalized epileptiform activities by video or conventional EEG at the time of VNS implantation (Pearson's and χ ² test, p = 0.001). No other clinical variables were found to be associated with seizure outcomes. Wound infections caused VNS removal in two cases. All other adverse events, including cough and hoarseness, were tolerable.

CONCLUSION

VNS is a well-tolerated and effective adjuvant therapy in pediatric patients with intractable epilepsy. Notably, patients with focal epileptiform discharges alone rather than those with generalized epileptiform discharges maybe better candidates for VNS.

Quality-of-life metrics with vagus nerve stimulation for epilepsy from provider survey data

OBJECTIVE

Drug-resistant epilepsy is a devastating disorder associated with diminished quality of life (QOL). Surgical resection leads to seizure freedom and improved QOL in many epilepsy patients, but not all individuals are candidates for resection. In these cases, neuromodulation-based therapies such as vagus nerve stimulation (VNS) are often used, but most VNS studies focus exclusively on reduction of seizure frequency. QOL changes and predictors with VNS remain poorly understood.

METHOD

Using the VNS Therapy Patient Outcome Registry, we examined 7 metrics related to QOL after VNS for epilepsy in over 5000 patients (including over 3000 with ≥12months follow-up), as subjectively assessed by treating physicians. Trends and predictors of QOL changes were examined and related to post-operative seizure outcome and likelihood of VNS generator replacement.

RESULTS

After VNS therapy, physicians reported patient improvement in alertness (58-63%, range over follow-up period), post-ictal state (55-62%), cluster seizures (48-56%), mood change (43-49%), verbal communication (38-45%), school/professional achievements (29-39%), and memory (29-38%). Predictors of net QOL improvement included shorter time to implant (odds ratio [OR], 1.3; 95% confidence interval [CI], 1.1-1.6), generalized seizure type (OR, 1.2; 95% CI, 1.0-1.4), female gender (OR, 1.2; 95% CI, 1.0-1.4), and Caucasian ethnicity (OR, 1.3; 95% CI, 1.0-1.5). No significant trends were observed over time. Patients with net QOL improvement were more likely to have favorable seizure outcomes (chi square [χ²]=148.1, p<0.001) and more likely to undergo VNS generator replacement (χ²=68.9, p<0.001) than those with worsened/unchanged QOL.

SIGNIFICANCE

VNS for drug-resistant epilepsy is associated with improvement on various QOL metrics subjectively rated by physicians. QOL improvement is associated with favorable seizure outcome and a higher likelihood of generator replacement, suggesting satisfaction with therapy. It is important to consider QOL metrics in neuromodulation for epilepsy, given the deleterious effects of seizures on patient QOL.

Predictors of response to vagus nerve stimulation in childhood-onset medically refractory epilepsy

This study explored predictors of response to vagus nerve stimulation in childhood-onset epilepsy. This retrospective chart review included all patients with new vagus nerve stimulator insertion between January 1, 2006, and December 31, 2011. Primary outcome was change in seizure frequency classified on the International League Against Epilepsy scale. Overall, 67.4% (95% confidence limits 53.3%-81.6%) of the patients had outcome of class 4 or better, and 4 patients (9.3%, 95% confidence interval 0.5%-18.1%) achieved complete seizure freedom (mean follow-up 3.5 y). Absence of magnetic resonance imaging (MRI) lesion (odds ratio 6.068, 95% confidence interval 1.214-30.329, P = .028) and duration of epilepsy before implantation (odds ratio 1.291, 95% confidence interval 1.015-1.642, P = .038) were found to be statistically significant predictors of good outcome and provided a sufficient fit to the data (area under the receiver operating characteristic curve .80, Hosmer-Lemeshow goodness of fit P = .92). This study provides preliminary evidence that nonlesional patients are significantly more likely to have better outcome with vagus nerve stimulation.

Clinical utility of implantable neurostimulation devices as adjunctive treatment of uncontrolled seizures

About one third of patients with epilepsy are refractory to medical treatment. For these patients, alternative treatment options include implantable neurostimulation devices such as vagus nerve stimulation (VNS), deep brain stimulation (DBS), and responsive neurostimulation systems (RNS). We conducted a systematic literature review to assess the available evidence on the clinical efficacy of these devices in patients with refractory epilepsy across their lifespan. VNS has the largest evidence base, and numerous randomized controlled trials and open-label studies support its use in the treatment of refractory epilepsy. It was approved by the US Food and Drug Administration in 1997 for treatment of partial seizures, but has also shown significant benefit in the treatment of generalized seizures. Results in adult populations have been more encouraging than in pediatric populations, where more studies are required. VNS is considered a safe and well-tolerated treatment, and serious side effects are rare. DBS is a well-established treatment for several movement disorders, and has a small evidence base for treatment of refractory epilepsy. Stimulation of the anterior nucleus of the thalamus has shown the most encouraging results, where significant decreases in seizure frequency were reported. Other potential targets include the centromedian thalamic nucleus, hippocampus, cerebellum, and basal ganglia structures. Preliminary results on RNS, new-generation implantable neurostimulation devices which stimulate brain structures only when epileptic activity is detected, are encouraging. Overall, implantable neurostimulation devices appear to be a safe and beneficial treatment option for patients in whom medical treatment has failed to adequately control their epilepsy. Further large-scale randomized controlled trials are required to provide a sufficient evidence base for the inclusion of DBS and RNS in clinical guidelines.

[Treatment of epilepsy: peripheral and central stimulation techniques]

The efficacy of electrical stimulation in the treatment of epileptic seizures was demonstrated experimentally even in the 1970s. Clinical studies have proven the efficacy of vagus nerve stimulation and in recent years also of stimulation of the trigeminal nerve, the anterior nucleus of the thalamus and of the epileptic focus in treating focal epilepsy. Mechanisms of action depend on the stimulation site and parameters and include activation of endogenous antiepileptic nuclei, modulation of propagation of epileptic activity and suppression of ictal activity at the site of generation. Based on available data the tolerability of peripheral and central brain stimulation appears to be good but experiences from wider clinical use are still lacking.

Vagus nerve stimulation in refractory epilepsy: new indications and outcome assessment

Although vagus nerve stimulation (VNS) is an effective alternative option for patients with refractory epilepsy unsuitable for conventional resective surgery, predictors of a better control of seizure frequency and severity are still unavailable. This prospective study reports on 39 patients, including 4 children affected by epilepsia partialis continua (EPC), who underwent VNS for refractory epilepsy. The overall seizure frequency outcome was classified into three groups according to reduction rate: ≥75%, ≥50%, and <50%. Engel and McHugh classifications were also used. The median follow-up period was 36months. A seizure reduction rate ≥50% or EPC improvement was observed in 74% of the patients. Twenty-one out of 35 cases (60%) resulted in Engel classes II and III. Outcome, as defined by the McHugh scale, showed a responder rate of 71%. These results suggest that younger patient age and focal or multifocal epilepsy are related to a better seizure control and cognitive outcome. Vagus nerve stimulation could also be considered as an effective procedure in severe conditions, such as drug-refractory EPC.

Emerging devices for epilepsy

About 30% of people with epilepsy continue to have seizures despite a growing array of antiseizure drugs. For some of these people, surgical resection of brain tissue is an effective therapeutic option. For others, the likelihood of seizure freedom is low, and has not improved much despite the introduction of several new antiseizure drugs. The vagus nerve stimulator is the only device approved by the Food and Drug Administration (FDA), but it rarely results in freedom from seizures. Recently, 2 approaches to electrical stimulation of the brain have been reported. One device has been approved for use in Canada and in Europe, and it seems likely that one or more such devices will be approved for use in the United States. We examine some of the data from these studies in the context of the current FDA-approved drugs and devices.

Closed-loop neural stimulation for pentylenetetrazole-induced seizures in zebrafish

Neural stimulation can reduce the frequency of seizures in persons with epilepsy, but rates of seizure-free outcome are low. Vagus nerve stimulation prevents seizures by continuously activating noradrenergic projections from the brainstem to the cortex. Cortical norepinephrine then increases GABAergic transmission and increases seizure threshold. Another approach, responsive nervous stimulation, prevents seizures by reactively shocking the seizure onset zone in precise synchrony with seizure onset. The electrical shocks abort seizures before they can spread and manifest clinically. The goal of this study was to determine whether a hybrid platform in which brainstem activation triggered in response to impending seizure activity could prevent seizures. We chose the zebrafish as a model organism for this study because of its ability to recapitulate human disease, in conjunction with its innate capacity for tightly controlled high-throughput experimentation. We first set out to determine whether electrical stimulation of the zebrafish hindbrain could have an anticonvulsant effect. We found that pulse train electrical stimulation of the hindbrain significantly increased the latency to onset of pentylenetetrazole-induced seizures, and that this apparent anticonvulsant effect was blocked by noradrenergic antagonists, as is also the case with rodents and humans. We also found that the anticonvulsant effect of hindbrain stimulation could be potentiated by reactive triggering of single pulse electrical stimulations in response to impending seizure activity. Finally, we found that the rate of stimulation triggering was directly proportional to pentylenetetrazole concentration and that the stimulation rate was reduced by the anticonvulsant valproic acid and by larger stimulation currents. Taken as a whole, these results show that that the anticonvulsant effect of brainstem activation can be efficiently utilized by reactive triggering, which suggests that alternative stimulation paradigms for vagus nerve stimulation might be useful. Moreover, our results show that the zebrafish epilepsy model can be used to advance our understanding of neural stimulation in the treatment of epilepsy.

Seizure freedom in epilepsia partialis continua (EPC) through vagus nerve stimulation (VNS) therapy: A case report

Vagus nerve stimulation (VNS) is generally considered as a palliative treatment for patients with drug-resistant partial-onset epilepsy. We report a case in which a patient with drug-resistant epilepsia partialis continua (EPC), became seizure-free for 15 months with VNS combined with antiepileptic medication regimens. To our knowledge, similar cases have not been reported previously.

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.

Therapeutic devices for epilepsy

Therapeutic devices provide new options for treating drug-resistant epilepsy. These devices act by a variety of mechanisms to modulate neuronal activity. Only vagus nerve stimulation (VNS), which continues to develop new technology, is approved for use in the United States. Deep brain stimulation of anterior thalamus for partial epilepsy recently was approved in Europe and several other countries. Responsive neurostimulation, which delivers stimuli to 1 or 2 seizure foci in response to a detected seizure, recently completed a successful multicenter trial. Several other trials of brain stimulation are in planning or underway. Transcutaneous magnetic stimulation (TMS) may provide a noninvasive method to stimulate cortex. Controlled studies of TMS are split on efficacy, which may depend on whether a seizure focus is near a possible region for stimulation. Seizure detection devices in the form of shake detectors via portable accelerometers can provide notification of an ongoing tonic-clonic seizure, or peace of mind in the absence of notification. Prediction of seizures from various aspects of electroencephalography (EEG) is in early stages. Prediction appears to be possible in a subpopulation of people with refractory seizures, and a clinical trial of an implantable prediction device is underway. Cooling of neocortex or hippocampus reversibly can attenuate epileptiform EEG activity and seizures, but engineering problems remain in its implementation. Optogenetics is a new technique that can control excitability of specific populations of neurons with light. Inhibition of epileptiform activity has been demonstrated in hippocampal slices, but use in humans will require more work. In general, devices provide useful palliation for otherwise uncontrollable seizures, but with a different risk profile than with most drugs. Optimizing the place of devices in therapy for epilepsy will require further development and clinical experience.

Vagal nerve stimulation for the treatment of medically refractory epilepsy: a review of the current literature

Object

The authors conducted a study to evaluate the published results of vagal nerve stimulation (VNS) for medically refractory seizures according to evidence-based criteria.

Methods

The authors performed a review of available literature published between 1980 and 2010. Inclusion criteria for articles included more than 10 patients evaluated, average follow-up of 1 or more years, inclusion of medically refractory epilepsy, and consistent preoperative surgical evaluation. Articles were divided into 4 classes of evidence according to criteria established by the American Academy of Neurology.

Results

A total of 70 publications were reviewed, of which 20 were selected for review based on inclusion and exclusion criteria. There were 2 articles that provided Class I evidence, 7 that met criteria for Class II evidence, and 11 that provided Class III evidence.

The majority of evidence supports VNS usage in partial epilepsy with a seizure reduction of 50% or more in the majority of cases and freedom from seizure in 6%–27% of patients who responded to stimulation. High stimulation with a gradual increase in VNS stimulation over the first 6 weeks to 3 months postoperatively is well supported by Class I and II data. Predictors of positive response included absence of bilateral interictal epileptiform activity and cortical malformations.

Conclusions

Vagal nerve stimulation is a safe and effective alternative for adult and pediatric populations with epilepsy refractory to medical and other surgical management.