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

A predictive model combining connectomics and entropy biomarkers to discriminate long-term vagus nerve stimulation efficacy for pediatric patients with drug-resistant epilepsy

AIMS

To predict the vagus nerve stimulation (VNS) efficacy for pediatric drug-resistant epilepsy (DRE) patients, we aim to identify preimplantation biomarkers through clinical features and electroencephalogram (EEG) signals and thus establish a predictive model from a multi-modal feature set with high prediction accuracy.

METHODS

Sixty-five pediatric DRE patients implanted with VNS were included and followed up. We explored the topological network and entropy features of preimplantation EEG signals to identify the biomarkers for VNS efficacy. A Support Vector Machine (SVM) integrated these biomarkers to distinguish the efficacy groups.

RESULTS

The proportion of VNS responders was 58.5% (38/65) at the last follow-up. In the analysis of parieto-occipital α band activity, higher synchronization level and nodal efficiency were found in responders. The central-frontal θ band activity showed significantly lower entropy in responders. The prediction model reached an accuracy of 81.5%, a precision of 80.1%, and an AUC (area under the receiver operating characteristic curve) of 0.838.

CONCLUSION

Our results revealed that, compared to nonresponders, VNS responders had a more efficient α band brain network, especially in the parieto-occipital region, and less spectral complexity of θ brain activities in the central-frontal region. We established a predictive model integrating both preimplantation clinical and EEG features and exhibited great potential for discriminating the VNS responders. This study contributed to the understanding of the VNS mechanism and improved the performance of the current predictive model.

Analysis of factors influencing the efficacy of vagus nerve stimulation for the treatment of drug-resistant epilepsy in children and prediction model for efficacy evaluation

Objective

Vagus nerve stimulation (VNS) has been widely used in the treatment of drug-resistant epilepsy (DRE) in children. We aimed to explore the efficacy and safety of VNS, focusing on factors that can influence the efficacy of VNS, and construct a prediction model for the efficacy of VNS in the treatment of DRE children.

Methods

Retrospectively analyzed 45 DRE children who underwent VNS at Qilu Hospital of Shandong University from June 2016 to November 2022. A ≥50% reduction in seizure frequency was defined as responder, logistic regression analyses were performed to analyze factors affecting the efficacy of VNS, and a predictive model was constructed. The predictive model was evaluated by receiver operating characteristic curve (ROC), calibration curves, and decision curve analyses (DCA).

Results

A total of 45 DRE children were included in this study, and the frequency of seizures was significantly reduced after VNS treatment, with 25 responders (55.6%), of whom 6 (13.3%) achieved seizure freedom. There was a significant improvement in the Quality of Life in Childhood Epilepsy Questionnaire (15.5%) and Seizure Severity Score (46.2%). 16 potential factors affecting the efficacy of VNS were included, and three statistically significant positive predictors were ultimately screened: shorter seizure duration, focal seizure, and absence of intellectual disability. We developed a nomogram for predicting the efficacy of VNS in the treatment of DRE children. The ROC curve confirmed that the predictive model has good diagnostic performance (AUC = 0.864, P < 0.05), and the nomogram can be further validated by bootstrapping for 1,000 repetitions, with a C-index of 0.837. Besides, this model showed good fitting and calibration and positive net benefits in decision curve analysis.

Conclusion

VNS is a safe and effective treatment for DRE children. We developed a predictive nomogram for the efficacy of VNS, which provides a basis for more accurate selection of VNS patients.

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.

Long-term outcomes and prognosis factors of vagus nerve stimulation in patients with refractory epilepsy

Background

Vagus nerve stimulation (VNS) is an effective treatment for patients with refractory epilepsy, yet with varied predictive factors and heterogeneous long-term outcomes. Adjustment of VNS parameters is critical for obtaining favorable efficacy. In this study, we aimed to investigate the long-term outcomes and the possible predictive factors of VNS in patients with refractory epilepsy.

Methods

Eighty-six patients (59 males and 27 females) who underwent VNS implantation for treatment of refractory epilepsy between May 2016 and May 2017 at five Epilepsy Centers were enrolled. The clinical data, including sex, age at epilepsy onset, VNS implantation, epilepsy duration, seizure type, MRI findings, history of neurosurgical operations, and responder rate (responders were those with ≥50% seizure reduction), were analyzed.

Results

Four-year follow-up data were available for 76 patients (53 males and 23 females). The mean current intensity at the last follow-up was 1.8 ± 0.3 mA (range: 0.75–2.5 mA). The mean seizure reduction was 36.2% at 6 months, 38.5% at 1 year, 69.4% at 3 years, and 56.7% at 4 years. A favorable outcome of ≥50% reduction in seizure frequency occurred in 40.0% of the patients at 6 months, 55.9% at 1 year with 4 patients being seizure-free, 63.2% at 3 years with 5 patients being seizure-free, and 68.4% at 4 years with 5 patients being seizure-free. Earlier onset age (P < 0.001) and shorter duration (P = 0.042) were associated with favorable prognosis. Compared with generalized tonic-clonic seizures, tonic seizures had a favorable outcome (P = 0.026). Twenty-three patients underwent neurosurgical operations before VNS implantation, and the responder rate was 60.9% at the last follow-up.

Conclusions

VNS is an adjunctive and effective treatment for patients with refractory epilepsy who are not good candidates for surgical resection or have failed to respond to surgical treatment. The stimulation efficacy increases over time after implantation, and earlier exposure to VNS improves the prognosis.

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.

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.

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.

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.

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.

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.

Invasive Neuromodulation for the Treatment of Pediatric Epilepsy

Neuromodulatory strategies are increasingly adopted for the treatment of intractable epilepsy in children. These encompass a wide range of treatments aimed at externally stimulating neural circuitry in order to decrease seizure frequency. In the current review, the authors discuss the evidence for invasive neuromodulation, namely vagus nerve and deep brain stimulation in affected children. Putative mechanisms of action and biomarkers of treatment success are explored and evidence of the efficacy of invasive neuromodulation is highlighted.

The vagus afferent network: emerging role in translational connectomics

Vagus nerve stimulation (VNS) is increasingly considered for the treatment of intractable epilepsy and holds potential for the management of a variety of neuropsychiatric conditions. The emergence of the field of connectomics and the introduction of large-scale modeling of neural networks has helped elucidate the underlying neurobiology of VNS, which may be variably expressed in patient populations and related to responsiveness to stimulation. In this report, the authors outline current data on the underlying neural circuitry believed to be implicated in VNS responsiveness in what the authors term the “vagus afferent network.” The emerging role of biomarkers to predict treatment effect is further discussed and important avenues for future work are highlighted.

Ictal heart rate changes and the effects of vagus nerve stimulation for patients with refractory epilepsy

Vagus nerve stimulation (VNS) shows long-term efficiency worldwide in most pharmacoresistant patients with epilepsy; however, there are still a small number of patients who are non-responders to VNS therapy. It has been shown that VNS treatment outcomes for drug-resistant epilepsy may be predicted by preoperative heart-rate variability measurements and that patients with epilepsy with ictal tachycardia (IT) during seizures have good responses to VNS. However, few studies have reported the efficacy of VNS in patients with epilepsy with ictal bradycardia (IB) or normal heart rate (HR), and none have explored the possible mechanisms of VNS efficacy based on different HR types. HR during seizures varies, and we presume that different HRs during seizures may impact the effects of VNS. It has been shown that blood pressure in the human body needs to be maintained through the arterial baroreflex (ABR). VNS efficacy in patients with epilepsy with IT, IB, and normal HR during seizures may be related to ABR. Mechanical signals generated by VNS are similar to the autonomic nerve pathways and, thus, we propose the hypothesis that different HRs during seizures can predict VNS efficacy in patients. If VNS is highly efficient in patients with IT during seizures, VNS in patients with a normal HR during seizures may be less efficient, and may even be inefficient in patients with IB during seizures.