Deep Brain Stimulation of the Centromedian Nucleus of the Thalamus for Lennox-Gastaut Syndrome: A Systematic Review and Individual Patient Data Analysis

Neuromodulation Strategies in Lennox-Gastaut Syndrome: Practical Clinical Guidance from the Pediatric Epilepsy Research Consortium

Lennox-Gastaut syndrome (LGS) is a severe developmental and epileptic encephalopathy characterized by multiple drug-resistant seizure types, cognitive impairment, and distinctive electroencephalographic patterns. Neuromodulation techniques, including vagus nerve stimulation (VNS), deep brain stimulation (DBS), and responsive neurostimulation (RNS), have emerged as important treatment options for patients with LGS who do not respond adequately to antiseizure medications. This review, developed with input from the Pediatric Epilepsy Research Consortium (PERC) LGS Special Interest Group, provides practical guidance for clinicians on the use of these neuromodulation approaches in patients with LGS. We discuss patient selection criteria, expected seizure and non-seizure outcomes, potential complications, and device management considerations for each technique. The review also covers initiation and titration strategies, ongoing care requirements, and emerging data on combining multiple neuromodulation modalities. While all three approaches can reduce seizure frequency in patients with LGS, with commonly reported responder rates ranging from 50 % to 60 %, their impacts on cognition, behavior and quality of life are more variable. Careful patient selection, individualized programming, and long-term follow-up are essential to optimize outcomes with neuromodulation in this challenging patient population. Further research is needed to identify optimal candidates, determine the ideal timing during patients' clinical course to consider neuromodulation, develop standardized outcome measures, and evaluate the comparative effectiveness and cost-effectiveness of different neuromodulation techniques for LGS.

Stereoelectroencephalographic exploration and surgical outcome in Lennox-Gastaut syndrome

OBJECTIVE

Lennox-Gastaut syndrome (LGS) is typically characterized by drug-resistant epilepsy and subsequent cognitive deterioration. Surgery is a rare but viable option for the control of seizures in a subset of patients with LGS. This study aimed to describe the organization of the epileptogenic zone network (EZN) in patients with LGS using stereoelectroencephalography (SEEG) and to report the outcome of post-SEEG treatment.

METHODS

A quantitative SEEG signal analysis was conducted in 14 consecutive patients with LGS, in whom a potentially localized EZN was suggested based on a comprehensive noninvasive evaluation. The EZN and the irritative zone network were identified using relevant biomarkers during ictal (epileptogenicity index and connectivity epileptogenicity index) and interictal (spikes and high-frequency oscillations) recordings. The applied post-SEEG treatments were assessed, including SEEG-guided radiofrequency thermocoagulation (RF-TC), surgery, and neurostimulation.

RESULTS

The seizure onset patterns showed some specificity by seizure type, with 84% of tonic seizures involving low-voltage fast activity. The EZN of patients with LGS was often, but not always, complex and extensive, involving two or more lobes (79%) and both hemispheres (64%). The lateral neocortical structures, particularly the lateral premotor and dorsolateral prefrontal cortices, were identified as being most frequently involved in the EZN. Among the explored subcortical structures, only the pulvinar, central-lateral thalamic nucleus, and hypothalamic hamartoma belonged to the EZN. Twelve patients (86%) underwent SEEG-guided RF-TC, with 50% experiencing a >50% reduction in baseline seizure frequency. Four patients (29%) underwent curative surgery for significant involvement of a lesion in the EZN, and one case achieved an Engel class I outcome.

SIGNIFICANCE

This is the first quantitative SEEG study in patients with LGS to demonstrate the utility of SEEG in identifying patients who may benefit from surgery and to perform SEEG-guided RF-TC. Nevertheless, the indications for SEEG should be carefully assessed, as localized EZN is uncommon in LGS.

Promising therapeutic strategies for Lennox-Gastaut syndrome: what's new?

INTRODUCTION

The seizures in Lennox-Gastaut syndrome are typically resistant to treatment. Seven antiseizure medications (ASMs) in the US (six in the UK/EU) are licensed for the treatment of seizures in LGS: lamotrigine, topiramate, rufinamide, clobazam, felbamate (not licensed in the UK/EU), cannabidiol and fenfluramine. Other options include neurostimulation, corpus callosotomy and dietary therapies, principally the ketogenic diet and its variants. New treatments and therapeutic strategies are needed to improve management of both seizures and cognitive/behavioral comorbidities in LGS.

AREAS COVERED

Embase and Medline were searched for articles published between 1 January 2014 and 21 August 2024 reporting efficacy data for pharmacological, neurostimulation, surgical and dietary interventions in individuals with LGS focusing on recent advances. Ongoing and prospective studies were identified from the National Library of Medicine register of clinical trials.

EXPERT OPINION

LGS remains a difficult-to-treat epilepsy. Although no major breakthroughs have been reported, several established and novel ASMs, some surgical strategies and other treatment approaches are of benefit or are showing promise. Progress remains incremental but any improvements in the management of this resistant epilepsy syndrome are worthwhile.

Understanding the Burden of Lennox-Gastaut Syndrome: Implications for Patients, Caregivers, and Society in High and Low Resource Settings: A Narrative Review

BACKGROUND

Lennox-Gastaut syndrome (LGS) poses significant challenges in diagnosis, management, and treatment due to its rare nature, diverse presentation, and drug-resistant seizures. While classical features aid diagnosis, challenges persist, impacting patient care and outcomes. Understanding the syndrome's burden is essential for improving healthcare policies and interventions.

AIM

This literature review aimed to comprehensively analyze clinical symptom burden, comorbidities, care requirements, quality of life (QoL), economic burden, caregiver burden, and treatment burden to pinpoint knowledge gaps for future research and intervention development, ultimately aiming to enhance the well-being of patients and caregivers.

METHODS

A comprehensive literature review was conducted using electronic databases and manual searches to analyze clinical symptom burden, comorbidities, care requirements, QoL, economic burden, caregiver burden, and treatment burden associated with LGS.

RESULTS

LGS significantly impacts the QoL for patients, with seizures, cognitive impairment, and social challenges affecting various aspects of daily living. Caregivers, particularly mothers, face significant stress and exhaustion, impacting their own health and well-being. Healthcare resource utilization is substantial, with elevated costs for LGS patients compared to controls. Cognitive impairment is prevalent and worsens over time, influencing educational and social outcomes. Prognosis varies based on factors like age of onset, underlying cause, and genetic factors, with limited treatment options available.

CONCLUSION

Managing LGS requires tailored approaches addressing seizures, comorbidities, and caregiver needs. While advancements in treatments and surgical techniques offer hope, challenges persist in achieving optimal outcomes and reducing the societal burden. The management of LGS involves a combination of pharmacological and nonpharmacological therapies, tailored to the individual patient's needs and response to treatment. Regular follow-up with a neurologist specialized in epilepsy is crucial for ongoing management, including annual reassessment of the diagnosis and treatment plan. The primary focus should always be on optimizing the patient's QoL, including learning and behavioral management, as complete seizure remission is rare.

Utilizing Centromedian Thalamus Connectivity to Personalize Noninvasive Neuromodulation Targets

INTRODUCTION

The centromedian nucleus (CM) of the thalamus is essential for arousal, attention, sensory processing, and motor control. Neuromodulation targeting CM dysfunction has shown efficacy in various neurological disorders. However, its individualized precise transcranial magnetic stimulation (TMS) remains unreported. Using resting-state functional MRI, we mapped CM-based functional connectivity (CM-FC) to develop a personalized TMS scheme for neurological conditions.

METHODS

We first analyzed the CM-FC patterns of healthy subjects via 10 scanning sessions in three MRI scanners spanning two subject groups: one from the Human Connectome Project (n = 20, four sessions) dataset and the other from Hangzhou Normal University (n = 20, three sessions of 3 T MRI and three sessions of 1.5 T MRI). Pearson's correlation was used for CM-FC evaluation. Then, we proposed an overlapping index ranging from 1 to 10, and group-level clusters with the highest overlapping index located 4 cm beneath the scalp were identified. In the individual CM-FC map, watershed image segmentation was used to obtain an individual cluster. The peak voxel with the highest FC value within the individual cluster was defined as a potential individualized target for future TMS.

RESULTS

The spatial FC patterns were remarkably similar between the left and right CMs. CMs have widespread positive connectivity with cortical areas, including the sensorimotor cortex, supplementary motor area, middle frontal cortex, medial temporal cortex, and middle cingulate. Among the group-level FC patterns of the left and right CMs, only the left CM had a group cluster in the left primary sensorimotor cortex (PSMC, cluster size = 51) with an overlapping index of 10, that is, 10 sessions showed significant CM-FC.

CONCLUSIONS

The left PSMC exhibited reproducible FC with the left CM. The individual peak FC location in the left PSMC could be used as a TMS target for indirect modulation of CM activity and aid in the treatment of CM-related neurological disorders.

Deep brain stimulation targets in drug-resistant epilepsy: Systematic review and meta-analysis of effectiveness and predictors of response

PURPOSE

Anterior nucleus of the thalamus (ANT) is the only deep brain stimulation (DBS) target that is approved by the FDA for treatment of drug-resistant epilepsy (DRE). Hippocampus (HC) and centromedian nucleus (CMN) have been reported as potential DBS targets for DRE. This study aimed to assess the effectiveness and predictors of response among DRE patients treated with DBS in general and among ANT, HC and CMN DBS-targets.

METHODS

A systematic search was executed on PubMed, SCOPUS and the Cochrane Central Register of Controlled Trials (CENTRAL) electronic databases between Jan 1, 2000 and June 29, 2020. Patients with DRE who underwent DBS treatment with at least three months of follow-up were included. Individual patient data (IPD) meta-analysis was conducted on DBS studies with available IPD. Response was defined as ≥50 % reduction in seizures frequency. Responders group was compared with non-responders group in terms of demographics, epilepsy/seizure characteristics, MRI findings, and DBS targets and duration of use. Subsequently, predictors of response to different DBS targets were investigated.

RESULTS

Thirty-nine studies with a total of 296 patients (ANT: 69 %, HC: 11 %, CMN: 21 %) were included. The responders group constituted of 209 patients (70.6 %). The response was significantly higher in patients with generalized seizures compared to those with focal seizures (93.2% vs 63.9 %; p < 0.001). Response was significantly higher with CMN (83.9 %) and HC (77.4 %) compared with ANT (65.5 %) as DBS targets (p = 0.014). Response was also significantly associated with longer duration of DBS use (p = 0.008). The responder rate was higher among the patients with lesional MRIs (76.7 %) than those with non-lesional MRIs (66.7 %), but with no statistically significant difference (p = 0.134). Age, gender, epilepsy etiology, onset zone of focal seizures, and previous use of VNS had no significant differences between the responders and non-responders. A binary logistic regression including the seizure type, MRI findings, DBS targets, and DBS duration showed, after controlling for confounders, that the duration of DBS use was the only significant predictor of response (adjusted OR 1.061; 95 % CI 1.019-1.106; p = 0.005). Regarding DBS targets, the response rate in patients with symptomatic etiology was significantly higher with HC or CMN targets than the ANT (p = 0.003). In patients with non-lesional MRI, response rate was significantly higher with the CMN target compared to the other two targets (p = 0.008).

CONCLUSION

DBS proves to be effective in DRE, with progressive success upon longer treatment and possibility of improving quality of life. In addition to focal seizures, DBS has potential for treating generalized seizures as well. While the ANT stands as the most utilized and only approved DBS target for DRE, CMN and HC are alternative targets with high seizure control potential. Patients with symptomatic etiology showed significant seizure reduction when HC or CMN were targeted. Studies revealed noticeable effectiveness of CMN-DBS in treating patients with non-lesional MRI. Despite ANT prominence in research, our findings suggest promising outcomes with CMN and HC, emphasizing the need for future larger-scale comparative clinical trials to better understand the efficacy of different DBS targets.

Epilepsy surgery in developmental and epileptic encephalopathies

Developmental and epileptic encephalopathies (DEEs) present significant treatment challenges due to frequent, drug-resistant seizures and comorbidities that impact quality of life. DEEs include both developmental encephalopathy from underlying pathology and epileptic encephalopathy where seizures exacerbate cognitive and behavioral impairments. Classification by syndrome and etiology is essential for therapy and prognosis, with common syndromes like infantile epileptic spasms syndrome and Dravet syndrome having specific first-line treatments. Etiologies are predominantly genetic, structural, or combined, with targeted therapies increasingly available. Surgery aims to improve seizure control but also may improve development, if the epileptic encephalopathy can be ameliorated. Timely intervention can reduce seizures and epileptiform discharges, maximizing developmental potential and allowing reduction in antiseizure medication. In cases requiring extensive resections, new deficits may be offset by developmental gains. Studies indicate that parents are generally willing to accept some deficits for significant seizure reduction.

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.

Predictors of therapeutic response following thalamic neuromodulation for drug-resistant pediatric epilepsy: A systematic review and individual patient data meta-analysis

We sought to perform a systematic review and individual participant data meta-analysis to identify predictors of treatment response following thalamic neuromodulation in pediatric patients with medically refractory epilepsy. Electronic databases (MEDLINE, Ovid, Embase, and Cochrane) were searched, with no language or data restriction, to identify studies reporting seizure outcomes in pediatric populations following deep brain stimulation (DBS) or responsive neurostimulation (RNS) implantation in thalamic nuclei. Studies featuring individual participant data of patients with primary or secondary generalized drug-resistant epilepsy were included. Response to therapy was defined as >50% reduction in seizure frequency from baseline. Of 417 citations, 21 articles reporting on 88 participants were eligible. Mean age at implantation was 13.07 ± 3.49 years. Fifty (57%) patients underwent DBS, and 38 (43%) RNS. Sixty (68%) patients were implanted in centromedian nucleus and 23 (26%) in anterior thalamic nucleus, and five (6%) had both targets implanted. Seventy-four (84%) patients were implanted bilaterally. The median time to last follow-up was 12 months (interquartile range = 6.75-26.25). Sixty-nine percent of patients achieved response to treatment. Age, target, modality, and laterality had no significant association with response in univariate logistic regression. Until thalamic neuromodulation gains widespread approval for use in pediatric patients, data on efficacy will continue to be limited to small retrospective cohorts and case series. The inherent bias of these studies can be overcome by using individual participant data. Thalamic neuromodulation appears to be a safe and effective treatment for epilepsy. Larger, prolonged prospective, multicenter studies are warranted to further evaluate the efficacy of DBS over RNS in this patient population where resection for curative intent is not a safe option.

Current and emerging pharmacotherapy for the treatment of Lennox-Gastaut syndrome

INTRODUCTION

Lennox-Gastaut syndrome (LGS) is a severe childhood-onset epileptic encephalopathy, characterized by multiple seizure types, generalized slow spike-and-wave complexes in the EEG, and cognitive impairment. Seizures in LGS are typically resistant to treatment with antiseizure medications (ASMs). Tonic/atonic ('drop') seizures are of particular concern, due to their liability to cause physical injury.

AREAS COVERED

We summarize evidence for current and emerging ASMs for the treatment of seizures in LGS. The review focuses on findings from randomized, double-blind, placebo-controlled trials (RDBCTs). For ASMs for which no double-blind trials were identified, lower quality evidence was considered. Novel pharmacological agents currently undergoing investigation for the treatment of LGS are also briefly discussed.

EXPERT OPINION

Evidence from RDBCTs supports the use of cannabidiol, clobazam, felbamate, fenfluramine, lamotrigine, rufinamide, and topiramate as adjunct treatments for drop seizures. Percentage decreases in drop seizure frequency ranged from 68.3% with high-dose clobazam to 14.8% with topiramate. Valproate continues to be considered the first-line treatment, despite the absence of RDBCTs specifically in LGS. Most individuals with LGS will require treatment with multiple ASMs. Treatment decisions should be individualized and take into account adverse effects, comorbidities, general quality of life, and drug interactions, as well as individual efficacy.