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

The role of neuromodulation in the management of drug-resistant epilepsy

Drug-resistant epilepsy (DRE) poses significant challenges in terms of effective management and seizure control. Neuromodulation techniques have emerged as promising solutions for individuals who are unresponsive to pharmacological treatments, especially for those who are not good surgical candidates for surgical resection or laser interstitial therapy (LiTT). Currently, there are three neuromodulation techniques that are FDA-approved for the management of DRE. These include vagus nerve stimulation (VNS), deep brain stimulation (DBS), and responsive neurostimulation (RNS). Device selection, optimal time, and DBS and RNS target selection can also be challenging. In general, the number and localizability of the epileptic foci, alongside the comorbidities manifested by the patients, substantially influence the selection process. In the past, the general axiom was that DBS and VNS can be used for generalized and localized focal seizures, while RNS is typically reserved for patients with one or two highly localized epileptic foci, especially if they are in eloquent areas of the brain. Nowadays, with the advance in our understanding of thalamic involvement in DRE, RNS is also very effective for general non-focal epilepsy. In this review, we will discuss the underlying mechanisms of action, patient selection criteria, and the evidence supporting the use of each technique. Additionally, we explore emerging technologies and novel approaches in neuromodulation, such as closed-loop systems. Moreover, we examine the challenges and limitations associated with neuromodulation therapies, including adverse effects, complications, and the need for further long-term studies. This comprehensive review aims to provide valuable insights on present and future use of neuromodulation.

Effectiveness of vagus nerve stimulation for drug-resistant generalized epilepsy in children aged six and younger

BACKGROUND

To explore a novel scoring system to evaluate the efficacy of vagus nerve stimulation (VNS) in children with drug-resistant generalized epilepsy (DRGE) aged six and younger.

BASIC PROCEDURES

The data of twelve children with DRGE under the age of 6 years who accepted VNS and have been followed up for at least 3 years were retrospectively reviewed. The outcome was evaluated with the McHugh Classification System and a novel scoring system we proposed.

MAIN FINDINGS

Based on the McHugh Classification System, the total response rate was 91.67% (11/12) and the rate of Grade I was 41.67% (5/12). A novel scoring system involving seizure frequency, seizure duration and quality of life (QOL) was proposed, by which the outcome was scored from -3 to 11 and graded from IV to I. Based on the novel scoring system, the total response rate was 91.67% (11/12) and the rate of Grade I was 33.33% (4/12). The incidence of complication was 16.67% (2/12). The efficacy of VNS appeared a gradually improving trend with plateau or fluctuation over time. Shorter course of epilepsy prior to VNS may be related to better outcome.

PRINCIPAL CONCLUSIONS

VNS could effectively reduce the seizure frequency and improve the QOL of children with DRGE aged six and younger. The novel scoring system was comprehensive and feasible to evaluate the efficacy of VNS. The time pattern of the long-term efficacy of VNS requires further investigation.

Intracranial neuromodulation with deep brain stimulation and responsive neurostimulation in children with drug-resistant epilepsy: a systematic review

OBJECTIVE

In children with drug-resistant epilepsy (DRE), resective, ablative, and disconnective surgery may not be feasible or may fail. Neuromodulation in the form of deep brain stimulation (DBS) and responsive neurostimulation (RNS) may be viable treatment options, however evidence for their efficacies in children is currently limited. This systematic review aimed to summarize the literature on DBS and RNS for the treatment of DRE in the pediatric population. Specifically, the authors focused on currently available data for reported indications, neuromodulation targets, clinical efficacy, and safety outcomes.

METHODS

PRISMA guidelines were followed throughout this systematic review (PROSPERO no. CRD42020180669). Electronic databases, including PubMed, Embase, Cochrane Library, OpenGrey, and CINAHL Plus, were searched from their inception to February 19, 2021. Inclusion criteria were 1) studies with at least 1 pediatric patient (age < 19 years) who underwent DBS and/or RNS for DRE; and 2) retrospective, prospective, randomized, or nonrandomized controlled studies, case series, and case reports. Exclusion criteria were 1) letters, commentaries, conference abstracts, and reviews; and 2) studies without full text available. Risk of bias of the included studies was assessed using the Cochrane ROBINS-I (Risk of Bias in Non-randomised Studies - of Interventions) tool.

RESULTS

A total of 35 studies were selected that identified 72 and 46 patients who underwent DBS and RNS, respectively (age range 4-18 years). Various epilepsy etiologies and seizure types were described in both cohorts. Overall, 75% of patients had seizure reduction > 50% after DBS (among whom 6 were seizure free) at a median (range) follow-up of 14 (1-100) months. In an exploratory univariate analysis of factors associated with favorable response, the follow-up duration was shorter in those patients with a favorable response (18 vs 33 months, p < 0.05). In the RNS cohort, 73.2% of patients had seizure reduction > 50% after RNS at a median (range) follow-up of 22 (5-39) months. On closer inspection, 83.3% of patients who had > 50% reduction in seizures actually had > 75% reduction, with 4 patients being seizure free.

CONCLUSIONS

Overall, both DBS and RNS showed favorable response rates, indicating that both techniques should be considered for pediatric patients with DRE. However, serious risks of overall bias were found in all included studies. Many research needs in this area would be addressed by conducting high-quality clinical trials and establishing an international registry of patients who have undergone pediatric neuromodulation, thereby ensuring robust prospective collection of predictive variables and outcomes.

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

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

Comparison of traditional and closed loop vagus nerve stimulation for treatment of pediatric drug-resistant epilepsy: A propensity-matched retrospective cohort study

OBJECTIVE

For epilepsy patients with drug-resistant, unresectable epilepsy, vagus nerve stimulation (VNS) is an option for seizure control. Approximately 40-70% of patients will achieve ≥50% seizure reduction with VNS. New closed loop VNS models detect ictal tachycardia and responsively stimulate the vagus nerve. The effectiveness of closed loop VNS compared to traditional VNS for pediatric epilepsy is unknown.

METHODS

An 11-year retrospective electronic medical record review at Children's Hospital of Pittsburgh was performed. Patients with drug-resistant epilepsy who underwent VNS implantation were included. Patients were divided into groups based on VNS model: traditional versus closed loop. Those who transitioned from traditional to closed loop VNS were excluded. Given potential for selection bias, propensity scores matching was utilized to compare traditional to closed loop VNS patients. Patients with focal versus generalized epilepsy were also separately analyzed. The primary outcome was "VNS response", defined as at least 50% seizure frequency reduction from baseline.

RESULTS

A total of 320 patients were included in this sample. The percentage of matched patients (total n = 220: n = 179 traditional VNS, n = 41 closed loop VNS) who responded to VNS after one year of therapy was 43% for traditional VNS and 39% for closed loop VNS (p = 0.64). After two years of therapy, a higher proportion of closed loop VNS patients than traditional VNS patients responded to VNS among all subgroups, though no differences were statistically significant (p>0.05). Notably, for those with generalized epilepsy, 73% of closed loop patients responded to VNS compared to only 46% of traditional patients (p = 0.10). After two years of VNS therapy, patients were taking approximately the same quantity of antiseizure medications as baseline (change of +0.074 +/- 0.90 ) with no difference between VNS models (p = 0.87).

SIGNIFICANCE

Among pediatric patients with drug-resistant epilepsy, closed loop VNS trends towards a higher rate of VNS response after two years of treatment, especially among generalized epilepsy patients. Neither model of VNS allows patients to reduce antiseizure medication quantity after two years.

Grey and white matter microstructure changes in epilepsy patients with vagus nerve stimulators

OBJECTIVES

Vagus nerve stimulation (VNS) has been widely used as an effective treatment for patients with drug-resistant epilepsy (DRE). However, little is known about grey matter (GM) and white matter (WM) microstructure changes caused by VNS. This study aimed to detect consistent GM and WM alterations in epilepsy patients with vagus nerve stimulators.

METHODS

The diffusion tensor imaging data was acquired from 15 patients who underwent VNS implantation. The voxel-based morphometry (VBM) and tract-based spatial statistics (TBSS) were used to detect group differences in GM and WM microstructure and explore their correlation with postoperative seizure reduction.

RESULTS

After 3 months of stimulation, GM density reduced in right cerebellum, left superior temporal gyrus, right inferior temporal gyrus and left thalamus, and increased in left cerebellum, left inferior parietal lobule, left middle occipital gyrus and left gyrus rectus. No significant volume changes had been found in 14 subcortical nuclei. The fractional anisotropy (FA) values reduced in left superior longitudinal fasciculus and left corticospinal tract, and increased in bilateral cingulum and body of corpus callosum. The mean diffusivity (MD) values reduced in right retrolenticular part of internal capsule, right posterior corona radiata and right superior longitudinal fasciculus. The seizure reduction had positive correlation trends with the volume reduction in left nucleus accumbens and right amygdala, and MD reduction in right medial lemniscus and right posterior corona radiata.

CONCLUSIONS

The results showed that VNS could cause changes of GM density, WM FA and MD values in epilepsy patients. The volume and MD reduction in some subcortical structures might participate in the seizure frequency reduction of VNS.

Advances in Epilepsy Surgery

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Role of Neuromodulation for Treatment of Drug-Resistant Epilepsy

The choice of neuromodulation techniques has greatly increased over the past two decades. While vagal nerve stimulation (VNS) has become established, newer variations of VNS have been introduced. Following the SANTE's trial, deep brain stimulation (DBS) is now approved for clinical use. In addition, responsive neurostimulation (RNS) has provided exciting new opportunities for treatment of drug-resistant epilepsy. While neuromodulation mostly offers only a 'palliative' measure, it still provides a significant reduction of frequency and intensity of epilepsy. We provide an overview of all the techniques of neuromodulation which are available, along with long-term outcomes. Further research is required to delineate the exact mechanism of action, the indications and the stimulation parameters to extract the maximum clinical benefit from these techniques.

Vagus nerve stimulation in brain diseases: Therapeutic applications and biological mechanisms

Brain diseases, including neurodegenerative, cerebrovascular and neuropsychiatric diseases, have posed a deleterious threat to human health and brought a great burden to society and the healthcare system. With the development of medical technology, vagus nerve stimulation (VNS) has been approved by the Food and Drug Administration (FDA) as an alternative treatment for refractory epilepsy, refractory depression, cluster headaches, and migraines. Furthermore, current evidence showed promising results towards the treatment of more brain diseases, such as Parkinson's disease (PD), autistic spectrum disorder (ASD), traumatic brain injury (TBI), and stroke. Nonetheless, the biological mechanisms underlying the beneficial effects of VNS in brain diseases remain only partially elucidated. This review aims to delve into the relevant preclinical and clinical studies and update the progress of VNS applications and its potential mechanisms underlying the biological effects in brain diseases.