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

Integrating the 5-SENSE Score for Patient Selection in Vagus Nerve Stimulation for Drug-Resistant Epilepsy

Addressing the challenge of drug-resistant epilepsy, our study offers a novel perspective by retrospectively applying the 5-SENSE score, initially created for stereoelectroencephalography (SEEG) planning, to evaluate its predictive value in patients undergoing vagus nerve stimulation (VNS) therapy. We conducted a comprehensive preoperative diagnostic work-up, including computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography-CT (PET-CT), video-electroencephalogram (video-EEG), and clinical semiology. We then stratified 76 patients into three groups - low, moderate, and high focality - based on the focality of the seizure-onset zone. Such stratification was made to check the scoring ability in predicting VNS therapy seizure reduction. Our findings demonstrate an association between the extent of focality at the seizure-onset zone and the effectiveness of VNS, which may help to define the role of the 5-SENSE score in patient selection for VNS. This high dispersion of responses in the group with high focality reinforces the idea that outcome estimation is difficult and argues for an individualized strategy in the treatment of drug-resistant epilepsy. A study at the level of the 5-SENSE score indicates the importance of detailed preoperative assessments that may better optimize selection for VNS therapy and further improve clinical outcomes.

Long-Term Outcome in Adult Patients with Drug-Resistant Epilepsy Submitted to Vagus Nerve Stimulation

Epilepsy treatment primarily involves antiseizure medications (ASMs) to eliminate seizures and improve the quality of life, but many patients develop drug-resistant epilepsy (DRE), necessitating alternative interventions. This study aimed to evaluate the long-term efficacy and safety of vagus nerve stimulation (VNS) in managing DRE. We retrospectively analyzed data from 105 adult patients treated at Agostino Gemelli Hospital from 1994 to 2022. Among the 73 patients with follow-up data, 80.8% were responders, experiencing significant reductions in seizure frequency over an average follow-up period of 9.4 years. Although 19.2% were non-responders, many of these patients still opted for generator replacements due to improvements in quality of life, such as fewer falls and shorter post-ictal periods. The overall complication rate was 12.3%, with most complications being mild and manageable. These findings suggest that VNS offers substantial long-term benefits for patients with DRE, improving seizure control and quality of life. This study underscores the importance of VNS as a viable long-term treatment option for DRE, highlighting its potential to significantly enhance patient outcomes and quality of life.

Effect of vagus nerve stimulation against generalized seizure and status epilepticus recurrence

Objective

Vagus nerve stimulation (VNS) is a palliative surgery for drug-resistant epilepsy. The two objectives of this study were to (1) determine the seizure type most responsive to VNS and (2) investigate the preventive effect on status epilepticus (SE) recurrence.

Methods

We retrospectively reviewed 136 patients with drug-resistant epilepsy who underwent VNS implantation. We examined seizure outcomes at 6, 12, and 24 months following implantation of VNS as well as at the last visit to the Juntendo Epilepsy Center. Univariate analysis and multivariate logistic regression models were used to estimate the prognostic factors.

Results

125 patients were followed up for at least 1 year after VNS implantation. The percentage of patients with at least a 50% reduction in seizure frequency compared with prior to VNS implantation increased over time at 6, 12, and 24 months after VNS implantation: 28, 41, and 52%, respectively. Regarding overall seizure outcomes, 70 (56%) patients responded to VNS. Of the 40 patients with a history of SE prior to VNS implantation, 27 (67%) showed no recurrence of SE. The duration of epilepsy, history of SE prior to VNS implantation and seizure type were correlated with seizure outcomes after VNS implantation in univariate analysis (p = 0.05, p < 0.01, and p = 0.03, respectively). In multivariate logistic regression analysis, generalized seizure was associated with VNS response [odds ratio (OR): 4.18, 95% CI: 1.13-15.5, p = 0.03]. A history of SE prior to VNS implantation was associated with VNS non-responders [(OR): 0.221, 95% CI: 0.097-0.503, p < 0.01]. The duration of epilepsy, focal to bilateral tonic-clonic seizure and epileptic spasms were not significantly associated with VNS responders (p = 0.07, p = 0.71, and p = 0.11, respectively).

Conclusion

Following 125 patients with drug-resistant epilepsy for an average of 69 months, 56% showed at least 50% reduction in seizure frequency after VNS implantation. This study suggests that generalized seizure is the most responsive to VNS, and that VNS may reduce the risk of recurrence of SE. VNS was shown to be effective against generalized seizure and also may potentially influence the risk of further events of SE, two marker of disease treatment that can lead to improved quality of life.

Vagus Nerve Stimulation for Drug Resistant Epilepsy: Clinical Outcome, Adverse Events, and Potential Prognostic Factors in a Single Center Experience

OBJECTIVE

Vagus nerve stimulation (VNS) has been used for adjunctive treatment in drug resistant epilepsy (DRE) for decades. Nevertheless, information is lacking on possible potential prognostic factors. Our study presents the efficacy and safety of VNS with a focus on prognostic factors in 45 patients with DRE.

METHODS

We retrospectively evaluated the clinical outcome of 45 consecutive patients with DRE undergoing VNS implantation in The First Affiliated Hospital of Anhui Medical University between November 2016 and August 2021. Medical records were aggregated across all patient visits. Cox proportional hazards regression was used to estimate the prognostic factors.

RESULTS

Significant decrease in seizure frequency was observed after intermittent stimulation of the vagus nerve. According to the modified McHugh classification, 11 patients (24.4%) were Class I, 11 patients (24.4%) were Class II, four patients (8.9%) were Class III, 10 patients (22.2%) were Class IV, and nine patients (20.0%) were Class V. Notably, 22 patients (48.9%) were responders and four patients (8.9%) were seizure-free at the final follow-up. No significant prognostic factors were found in this cohort. Furthermore, 37 patients reported improved quality of life. Of the patients, 22 (48.9%) experienced adverse events after surgery; hoarseness, discomfort at the surgical site, and coughing were the most common.

CONCLUSION

The results confirmed the efficacy and safety of VNS. No prognostic factors were identified.

Neurostimulation in People with Drug-Resistant Epilepsy: Systematic Review and Meta-Analysis from the ILAE Surgical Therapies Commission

OBJECTIVE

Summarize the current evidence on efficacy and tolerability of vagus nerve stimulation (VNS), responsive neurostimulation (RNS), and deep brain stimulation (DBS) through a systematic review and meta-analysis.

METHODS

We followed the PRISMA reporting standards and searched Ovid Medline, Ovid Embase, and the Cochrane Central Register of Controlled Trials. We included published randomized controlled trials (RCT) and their corresponding open-label extension studies, as well as prospective case series, with ≥ 20 participants (excluding studies limited to children). Our primary outcome was the mean (or median when unavailable) percentage decrease in frequency, as compared to baseline, of all epileptic seizures at last follow-up. Secondary outcomes included proportion of treatment responders and proportion with seizure freedom.

RESULTS

We identified 30 eligible studies, six of which were RCTs. At long-term follow-up (mean 1.3 years), five observational studies for VNS reported a pooled mean percentage decrease in seizure frequency of 34.7% (95% CI: -5.1, 74.5). In the open-label extension studies for RNS, the median seizure reduction was 53%, 66%, and 75% at two, five, and nine years of follow-up, respectively. For DBS, the median reduction was 56%, 65%, and 75% at two, five, and seven years, respectively. The proportion of individuals with seizure freedom at last follow-up increased significantly over time for DBS and RNS while a positive trend was observed for VNS. Quality of life was improved in all modalities. The most common complications included hoarseness, cough and throat pain for VNS and implant site pain, headache, and dysesthesia for DBS and RNS.

SIGNIFICANCE

Neurostimulation modalities are an effective treatment option for drug resistant epilepsy, with improving outcomes over time and few major complications. Seizure reduction rates among the three therapies were similar during the initial blinded phase. Recent long-term follow-up studies are encouraging for RNS and DBS but are lacking for VNS.

Impact of COVID-19 public health measures on myelin oligodendrocyte glycoprotein IgG-associated disorders in children

BACKGROUND

Despite better characterization of the spectrum of MOG-IgG-associated disorders (MOGAD) in children, the role of infection in its pathophysiology remains unclear. The goal of this study was to evaluate if public health measures put in place to prevent the spread of SARS-CoV-2 in March 2020 in Ontario (Canada) have been associated with a change in the incidence of MOGAD and other neuroinflammatory disorders in children.

METHODOLOGY

We reviewed a single-centre cohort of children referred for a suspicion of neuroinflammatory disorder between January 2015 and March 2021. Age, date, sex, diagnosis, MOG-IgG antibodies status and detected pathogens at presentation were identified. Comparative statistical analysis was performed based on diagnosis between years and seasons using Pearson's Chi-squared test or Fisher's exact test for categorical variables and using ANOVA or Kruskal-Wallis test for continuous variables, as appropriate. We compared the post-lockdown period (March 17th, 2020, to March 31st, 2021) to previous calendar years (2015 to 2019) alone and to previous calendar years and the pre-lockdown 2020 period (January 1st, 2020, to March 16th, 2020). A p-value of < 0.05 was considered significant. Post-hoc pairwise comparisons between the post-lockdown period and previous years were performed on significant results. A false discovery rate adjustment with an adjusted p-value (q-value) < 0.05 was computed. We hypothesized that the number of new MOGAD would be significantly lower in the post-lockdown period compared to previous years due to decreased regional pathogen transmission.

RESULTS

Among 491 referred cases, we identified 415 new cases of neuroinflammatory disorder between January 2015 and March 2021. The number of new neuroinflammatory disorder diagnoses did not change between years. We noted significantly fewer new MOGAD diagnoses in 2020 compared to previous years, with no MOGAD patients presenting in 2020 after the spring lockdown (q=0.0009). In addition, there were significantly fewer parainfectious neuroinflammatory cases (q=0.04) and pathogen detected (q=0.04) in the post-lockdown period. The number of new multiple sclerosis (MS) and aquaporin-4 neuromyelitis optica spectrum disorders (AQP4-NMOSD) cases remained stable despite the lockdown (q=0.185 and 0.693 respectively).

INTERPRETATION

Enhanced population-based infection control strategies may have a role in modulating the incidence of MOGAD and parainfectious neuroinflammatory disorders, but not MS or AQP4-NMOSD.

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.

Review of the treatment options for epilepsy in tuberous sclerosis complex: towards precision medicine

Tuberous sclerosis complex (TSC) is a rare genetic disorder caused by mutations in the TSC1 or TSC2 genes, which encode proteins that antagonise the mammalian isoform of the target of rapamycin complex 1 (mTORC1) - a key mediator of cell growth and metabolism. TSC is characterised by the development of benign tumours in multiple organs, together with neurological manifestations including epilepsy and TSC-associated neuropsychiatric disorders (TAND). Epilepsy occurs frequently and is associated with significant morbidity and mortality; however, the management is challenging due to the intractable nature of the seizures. Preventative epilepsy treatment is a key aim, especially as patients with epilepsy may be at a higher risk of developing severe cognitive and behavioural impairment. Vigabatrin given preventatively reduces the risk and severity of epilepsy although the benefits for TAND are inconclusive. These promising results could pave the way for evaluating other treatments in a preventative capacity, especially those that may address the underlying pathophysiology of TSC, including everolimus, cannabidiol and the ketogenic diet (KD). Everolimus is an mTOR inhibitor approved for the adjunctive treatment of refractory TSC-associated seizures that has demonstrated significant reductions in seizure frequency compared with placebo, improvements that were sustained after 2 years of treatment. Highly purified cannabidiol, recently approved in the US as Epidiolex® for TSC-associated seizures in patients ⩾1 years of age, and the KD, may also participate in the regulation of the mTOR pathway. This review focusses on the pivotal clinical evidence surrounding these potential targeted therapies that may form the foundation of precision medicine for TSC-associated epilepsy, as well as other current treatments including anti-seizure drugs, vagus nerve stimulation and surgery. New future therapies are also discussed, together with the potential for preventative treatment with targeted therapies. Due to advances in understanding the molecular genetics and pathophysiology, TSC represents a prototypic clinical syndrome for studying epileptogenesis and the impact of precision medicine.

Resective epilepsy surgery in tuberous sclerosis complex: a nationwide multicentre retrospective study from China

At least 50% of patients with tuberous sclerosis complex present with intractable epilepsy; for these patients, resective surgery is a treatment option. Here, we report a nationwide multicentre retrospective study and analyse the long-term seizure and neuropsychological outcomes of epilepsy surgery in patients with tuberous sclerosis complex. There were 364 patients who underwent epilepsy surgery in the study. Patients' clinical data, postoperative seizure outcomes at 1-, 4-, and 10-year follow-ups, preoperative and postoperative intelligence quotients, and quality of life at 1-year follow-up were collected. The patients' ages at surgery were 10.35 ± 7.70 years (range: 0.5-47). The percentage of postoperative seizure freedom was 71% (258/364) at 1-year, 60% (118/196) at 4-year, and 51% (36/71) at 10-year follow-up. Influence factors of postoperative seizure freedom were the total removal of epileptogenic tubers and the presence of outstanding tuber on MRI at 1- and 4-year follow-ups. Furthermore, monthly seizure (versus daily seizure) was also a positive influence factor for postoperative seizure freedom at 1-year follow-up. The presence of an outstanding tuber on MRI was the only factor influencing seizure freedom at 10-year follow-up. Postoperative quality of life and intelligence quotient improvements were found in 43% (112/262) and 28% (67/242) of patients, respectively. Influence factors of postoperative quality of life and intelligence quotient improvement were postoperative seizure freedom and preoperative low intelligence quotient. The percentage of seizure freedom in the tuberectomy group was significantly lower compared to the tuberectomy plus and lobectomy groups at 1- and 4-year follow-ups. In conclusion, this study, the largest nationwide multi-centre study on resective epilepsy surgery, resulted in improved seizure outcomes and quality of life and intelligence quotient improvements in patients with tuberous sclerosis complex. Seizure freedom was often achieved in patients with an outstanding tuber on MRI, total removal of epileptogenic tubers, and tuberectomy plus. Quality of life and intelligence quotient improvements were frequently observed in patients with postoperative seizure freedom and preoperative low intelligence quotient.

Interregional metabolic connectivity of 2-deoxy-2[18 F]fluoro-D-glucose positron emission tomography in vagus nerve stimulation for pediatric patients with epilepsy: A retrospective cross-sectional study

OBJECTIVE

With the recognition of epilepsy as a network disease that disrupts the organizing ability of resting-state brain networks, vagus nerve stimulation (VNS) may control epileptic seizures through modulation of functional connectivity. We evaluated preoperative 2-deoxy-2[¹⁸ F]fluoro-D-glucose (FDG) positron emission tomography (PET) in VNS-implanted pediatric patients with refractory epilepsy to analyze the metabolic connectivity of patients and its prognostic role in seizure control.

METHODS

Preoperative PET data of 66 VNS pediatric patients who were followed up for a minimum of 1 year after the procedure were collected for the study. Retrospective review of the patients' charts was performed, and five patients with inappropriate PET data or major health issues were excluded. We conducted an independent component analysis of FDG-PET to extract spatial metabolic components and their activities, which were used to perform cross-sectional metabolic network analysis. We divided the patients into VNS-effective and VNS-ineffective groups (VNS-effective group, ≥50% seizure reduction; VNS-ineffective group, <50% reduction) and compared metabolic connectivity differences between groups using a permutation test.

RESULTS

Thirty-four (55.7%) patients showed >50% seizure reduction from baseline frequency 1 year after VNS. A significant difference in metabolic connectivity evaluated by preoperative FDG-PET was noted between groups. Relative changes in glucose metabolism were strongly connected among the areas of brainstem, cingulate gyrus, cerebellum, bilateral insula, and putamen in patients with <50% seizure control after VNS.

SIGNIFICANCE

This study shows that seizure outcome of VNS may be influenced by metabolic connectivity, which can be obtained from preoperative PET imaging. This study of metabolic connectivity analysis may contribute in further understanding of the mechanism of VNS in intractable seizures.

Vagus Nerve Stimulation for Pediatric and Adult Patients with Pharmaco-resistant Epilepsy

Background:

Over past two decades, vagus nerve stimulation (VNS) has been widely used and reported to alleviate seizure frequency worldwide, however, so far, only hundreds of patients with pharmaco-resistant epilepsy (PRE) have been treated with VNS in mainland China. The study aimed to evaluate the effectiveness of VNS for Chinese patients with PRE and compare its relationship with age cohort and gender.

Methods:

We retrospectively assessed the clinical outcome of 94 patients with PRE, who were treated with VNS at Beijing Fengtai Hospital and Beijing Tiantan Hospital between November 2008 and April 2014 from our database of 106 consecutive patients. The clinical data analysis was retrospectively examined.

Results:

Seizure frequency significantly decreased with VNS therapy after intermittent stimulation of the vagus nerve. At last follow-up, we found McHugh classifications of Class I in 33 patients (35.1%), Class II in 27 patients (28.7%), Class III in 20 patients (21.3%), Class IV in 3 patients (3.2%), and Class V in 11 patients (11.7%). Notably, 8 (8.5%) patients were seizure-free while ≥50% seizure frequency reduction occurred in as many as 60 patients (63.8%). Furthermore, with regard to the modified Engel classification, 12 patients (12.8%) were classified as Class I, 11 patients (11.7%) were classified as Class II, 37 patients (39.4%) were classified as Class III, 34 patients (36.2%) were classified as Class IV. We also found that the factors of gender or age are not associated with clinical outcome.

Conclusions:

This comparative study confirmed that VNS is a safe, well-tolerated, and effective treatment for Chinese PRE patients. VNS reduced the seizure frequency regardless of age or gender of studied patients.

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.