Lennox-Gastaut syndrome and phenotype: secondary network epilepsies

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.

Neuromodulation strategies in developmental and epileptic encephalopathies

Developmental and epileptic encephalopathies (DEEs) are a group of childhood-onset epilepsy syndromes characterized by frequent seizures, severe cognitive and behavioral impairments, and poor long-term outcomes. These conditions are typically refractory to currently available medical therapies, prompting recent exploration of neuromodulation treatments such as deep brain stimulation (DBS) and responsive neurostimulation (RNS), which aim to modulate epileptic networks spanning cortical and subcortical regions. These advances have occurred alongside an improved understanding of syndrome-specific and interictal epileptiform discharge/seizure-specific brain networks. By targeting key nodes within these networks, DBS and RNS hold promise for influencing seizures and associated cognitive and behavioral comorbidities. Initial experiences with centromedian (CM) thalamic DBS for Lennox-Gastaut syndrome (LGS) have shown modest efficacy across multiple seizure types. Reports also indicate the application of DBS and RNS across various genetic and structural etiologies commonly associated with DEEs, with mixed success. Although DBS and RNS are increasingly used in LGS and other DEEs, their mixed efficacy highlights a knowledge gap in understanding why some patients with LGS do not respond and which neuromodulation approach is most effective for other DEEs. To address these issues, this review first discusses recent neuroimaging studies showing similarities and differences in the epileptic brain networks underlying various DEEs, revealing the common involvement of the thalamus and the default-mode network (DMN) across multiple DEEs. We then examine thalamic DBS for LGS to illustrate how such network insights may be used to optimize neuromodulation. Although network-based neuromodulation is still in its infancy, the LGS model may serve as a framework for other DEEs, where optimal treatment necessitates consideration of the underlying epileptic networks. Lastly, the review suggests future research directions, including individualized connectivity assessment and biomarker identification through collaborative efforts, which may enhance the therapeutic potential of neuromodulation for individuals living with DEEs.

Clinical trials for Lennox-Gastaut syndrome: Challenges and priorities

OBJECTIVE

Lennox-Gastaut syndrome (LGS) is a severe, childhood-onset epilepsy that is typically refractory to treatment. We surveyed the current landscape of LGS treatment, aiming to identify challenges to the development of efficacious therapies, and to articulate corresponding priorities toward clinical trials that improve outcomes.

METHODS

The LGS Special Interest Group of the Pediatric Epilepsy Research Consortium integrated evidence from the literature and expert opinion, into a narrative review.

RESULTS

We provide an overview of approved and emerging medical, dietary, surgical and neuromodulation approaches for LGS. We note that quality of care could be improved by standardizing LGS treatment based on expert consensus and empirical data. Whereas LGS natural history is incompletely understood, prospective studies and use of large retrospective datasets to understand LGS across the lifespan would enable clinical trials that address these dynamics. Recent discoveries related to LGS pathophysiology should enable development of disease-modifying therapies, which are currently lacking. Finally, clinical trials have focused chiefly on seizures involving "drops," but should incorporate additional patient-centered outcomes, using emerging measures adapted to people with LGS.

INTERPRETATION

Clinicians and researchers should enact these priorities, with the goal of patient-centered clinical trials that are tailored to LGS pathophysiology and natural history.

A systematic review of electroencephalographic findings in Lennox-Gastaut syndrome

Lennox-Gastaut syndrome (LGS) is a severe form of childhood onset epileptic encephalopathy characterized by multiple drug-resistant seizures, cognitive impairment, and diffuse slow spike and wave (SSW), and generalized paroxysmal fast activity (GPFA) on electroencephalogram (EEG). Systematic review following the Preferred Reporting Items for Systematic Reviews and Meta Analysis (PRISMA) guidelines was done to investigate EEG findings in LGS. PubMed and MEDLINE were systematically searched for English-language studies published until15th may 2023. Original articles and research with patients between age group 1-30 years, and studies with description of EEG findings were included. Search identified 20 studies with 1167 patients. In this analysis 62.6 % of patients were male. The median age was 9.6 years. Etiology was structural abnormality in 42.6 %, genetic in 8.7 % but was unknown in 48.7%. Tonic seizures (74.5 %) were most frequent followed by atypical absences (44.3 %), myoclonic (39.2 %), generalized (38.5 %), atonic (34.8 %), epileptic spasm (15.9 %), focal (11.4 %) and non-convulsive status epilepticus (7.0 %). Out of 20 studies, only 15 studies mentioned GPFA in 46.6 % patients and SSW in 91.7 % patients. Unilateral and focal discharges were more common in patients with unilateral structural abnormalities. Seizure discharges on EEG longer than 10 second duration correlated with seizure diary counts. Combination of atonic, tonic, and atypical absence seizures correlated with SSW, and myoclonic seizures correlated with GPFA. EEG helps in diagnosis and prognosis of LGS. SSW is present in almost all EEG, and GPFA in 46.6 % patients. Longer duration of SSW discharges and disorganized background are associated with poor outcome.

Identification and treatment of surgically-remediable causes of infantile epileptic spasms syndrome

INTRODUCTION

Infantile epileptic spasms syndrome (IESS) is a common developmental and epileptic encephalopathy with poor long-term outcomes. A substantial proportion of patients with IESS have a potentially surgically remediable etiology. Despite this, epilepsy surgery is underutilized in this patient group. Some surgically remediable etiologies, such as focal cortical dysplasia and malformation of cortical development with oligodendroglial hyperplasia in epilepsy (MOGHE), are under-diagnosed in infants and young children. Even when a surgically remediable etiology is recognised, for example, tuberous sclerosis or focal encephalomalacia, epilepsy surgery may be delayed or not considered due to diffuse EEG changes, unclear surgical boundaries, or concerns about operating in this age group.

AREAS COVERED

In this review, the authors discuss the common surgically remediable etiologies of IESS, their clinical and EEG features, and the imaging techniques that can aid in their diagnosis. They then describe the surgical approaches used in this patient group, and the beneficial impact that early epilepsy surgery can have on developing brain networks.

EXPERT OPINION

Epilepsy surgery remains underutilized even when a potentially surgically remediable cause is recognized. Overcoming the barriers that result in under-recognition of surgical candidates and underutilization of epilepsy surgery in IESS will improve long-term seizure and developmental outcomes.

Targeting thalamocortical circuits for closed-loop stimulation in Lennox-Gastaut syndrome

This paper outlines the therapeutic rationale and neurosurgical targeting technique for bilateral, closed-loop, thalamocortical stimulation in Lennox-Gastaut syndrome, a severe form of childhood-onset epilepsy. Thalamic stimulation can be an effective treatment for Lennox-Gastaut syndrome, but complete seizure control is rarely achieved. Outcomes may be improved by stimulating areas beyond the thalamus, including cortex, but the optimal targets are unknown. We aimed to identify a cortical target by synthesizing prior neuroimaging studies, and to use this knowledge to advance a dual thalamic (centromedian) and cortical (frontal) approach for closed-loop stimulation. Multi-modal brain network maps from three group-level studies of Lennox-Gastaut syndrome were averaged to define the area of peak overlap: simultaneous EEG-functional MRI of generalized paroxysmal fast activity, [18F]fluorodeoxyglucose PET of cortical hypometabolism and diffusion MRI structural connectivity associated with clinical efficacy in a previous trial of thalamic deep brain stimulation. The resulting 'hotspot' was used as a seed in a normative functional MRI connectivity analysis to identify connected networks. Intracranial electrophysiology was reviewed in the first two trial patients undergoing bilateral implantations guided by this hotspot. Simultaneous recordings from cortex and thalamus were analysed for presence and synchrony of epileptiform activity. The peak overlap was in bilateral premotor cortex/caudal middle frontal gyrus. Functional connectivity of this hotspot revealed a distributed network of frontoparietal cortex resembling the diffuse abnormalities seen on EEG-functional MRI and PET. Intracranial electrophysiology showed characteristic epileptiform activity of Lennox-Gastaut syndrome in both the cortical hotspot and thalamus; most detected events occurred first in the cortex before appearing in the thalamus. Premotor frontal cortex shows peak involvement in Lennox-Gastaut syndrome and functional connectivity of this region resembles the wider epileptic brain network. Thus, it may be an optimal target for a range of neuromodulation therapies, including thalamocortical stimulation and emerging non-invasive treatments like focused ultrasound or transcranial magnetic stimulation. Compared to thalamus-only approaches, the addition of this cortical target may allow more rapid detections of seizures, more diverse stimulation paradigms and broader modulation of the epileptic network. A prospective, multi-centre trial of closed-loop thalamocortical stimulation for Lennox-Gastaut syndrome is currently underway.

Atypical absence seizures and gene variants: A gene-based review of etiology, electro-clinical features, and associated epilepsy syndrome

Atypical absence seizures are generalized non-convulsive seizures that often occur in children with cognitive impairment. They are common in refractory epilepsy and have been recognized as one of the hallmarks of developmental epileptic encephalopathies. Notably, pathogenic variants associated with AAS, such as GABRG2, GABRG3, SLC6A1, CACNB4, SCN8A, and SYNGAP1, are also linked to developmental epileptic encephalopathies. Atypical absences differ from typical absences in that they are frequently drug-resistant and the prognosis is dependent on the etiology or related epileptic syndromes. To improve clinicians' understanding of atypical absences and provide novel perspectives for clinical treatment, we have reviewed the electro-clinical characteristics, etiologies, treatment, and prognosis of atypical absences, with a focus on the etiology of advancements in gene variants, shedding light on potential avenues for improved clinical management.

Brain network reconstruction of abnormal functional connectivity in Lennox-Gastaut syndrome according to drug responsiveness: A retrospective study

OBJECTIVE

Functional network effects of resective or palliative epilepsy surgery in Lennox-Gastaut syndrome (LGS) patients are different according to the seizure outcome. This study aimed to clarify whether the response to antiseizure medications (ASM) can affect to alteration of brain network connectivity.

METHODS

In this retrospective study, 37 patients with LGS who underwent 1st electroencephalography (EEG) and 40 healthy controls were enrolled. Among them, 24 LGS patients had follow-up EEG data and were classified as drug responders and non-responders according to the ASM response. Graphical theoretical analysis was used to assess functional connectivity using resting-state EEG.

RESULTS

The 1st EEG showed a decreased radius in patients with LGS compared with that in healthy controls (3.987 vs. 4.279, P = 0.003). Follow-up EEG data of patients with LGS revealed significant differences in functional connectivity depending on the ASM response. On follow-up EEG, non-responders (n = 11) demonstrated significant increases in global network parameters, whereas responders (n = 13) showed no significant difference in functional connectivity compared with healthy controls.

CONCLUSIONS

The functional connectivity patterns in patients with LGS differed from those in healthy controls. Functional connectivity in drug-responsive patients with LGS tended to preserve the network of brain connections in a pattern similar to that in healthy controls, whereas non-responders showed more disrupted functional connectivity.

Neurostimulation for Generalized Epilepsy: Should Therapy be Syndrome-specific?

Current applications of neurostimulation for generalized epilepsy use a one-target-fits-all approach that is agnostic to the specific epilepsy syndrome and seizure type being treated. The authors describe similarities and differences between the 2 "archetypes" of generalized epilepsy-Lennox-Gastaut syndrome and Idiopathic Generalized Epilepsy-and review recent neuroimaging evidence for syndrome-specific brain networks underlying seizures. Implications for stimulation targeting and programming are discussed using 5 clinical questions: What epilepsy syndrome does the patient have? What brain networks are involved? What is the optimal stimulation target? What is the optimal stimulation paradigm? What is the plan for adjusting stimulation over time?

A scoping review of the functional magnetic resonance imaging-based functional connectivity of focal cortical dysplasia-related epilepsy

Focal cortical dysplasia (FCD) is the most frequent etiology of operable pharmacoresistant epilepsy in children. There is burgeoning evidence that FCD-related epilepsy is a disorder that involves distributed brain networks. Functional magnetic resonance imaging (fMRI) is a tool that allows one to infer neuronal activity and to noninvasively map whole-brain functional networks. Despite its relatively widespread availability at most epilepsy centers, the clinical application of fMRI remains mostly task-based in epilepsy. Another approach is to map and characterize cortical functional networks of individuals using resting state fMRI (rsfMRI). The focus of this scoping review is to summarize the evidence to date of investigations of the network basis of FCD-related epilepsy, and to highlight numerous potential future applications of rsfMRI in the exploration of diagnostic and therapeutic strategies for FCD-related epilepsy. There are numerous studies demonstrating a global disruption of cortical functional networks in FCD-related epilepsy. The underlying pathological subtypes of FCD influence overall functional network patterns. There is evidence that cortical functional network mapping may help to predict postsurgical seizure outcomes, highlighting the translational potential of these findings. Additionally, several studies emphasize the important effect of FCD interaction with cortical networks and the expression of epilepsy and its comorbidities.

Frontoparietal 18F-FDG-PET hypo-metabolism in Lennox-Gastaut syndrome: further evidence highlighting the key network

INTRODUCTION

Lennox Gastaut syndrome (LGS) can be conceptualised as a "secondary network epilepsy", in which the shared electroclinical manifestations reflect epileptic recruitment of a common brain network, despite a range of underlying aetiologies. We aimed to identify the key networks recruited by the epileptic process of LGS using interictal 2-deoxy-2-(¹⁸F)fluoro-D-glucose positron emission tomography (¹⁸F-FDG-PET).

METHODS

Group analysis of cerebral ¹⁸F-FDG-PET, comparing 21 patients with LGS (mean age = 15 years) and 18 pseudo-controls (mean age = 19 years), studied at Austin Health Melbourne, between 2004 and 2015. To minimise the influence of individual patient lesions in the LGS group, we only studied brain hemispheres without structural MRI abnormalities. The pseudo-control group consisted of age- and sex-matched patients with unilateral temporal lobe epilepsy, using only the hemispheres contralateral to the side of epilepsy. Voxel-wise permutation testing compared ¹⁸F-FDG-PET uptake between groups. Associations were explored between areas of altered metabolism and clinical variables (age of seizure onset, proportion of life with epilepsy, and verbal/nonverbal ability). Penetrance maps were calculated to explore spatial consistency of altered metabolic patterns across individual patients with LGS.

RESULTS

Although not always readily apparent on visual inspection of individual patient scans, group analysis revealed hypometabolism in a network of regions including prefrontal and premotor cortex, anterior and posterior cingulate, inferior parietal lobule, and precuneus (p < 0.05, corrected for family-wise error). These brain regions tended to show a greater reduction in metabolism in non-verbal compared to verbal LGS patients, although this difference was not statistically significant. No areas of hypermetabolism were detected on group analysis, although ∼25 % of individual patients showed increased metabolism (relative to pseudo-controls) in the brainstem, putamen, thalamus, cerebellum, and pericentral cortex.

DISCUSSION

Interictal hypometabolism in frontoparietal cortex in LGS is compatible with our previous EEG-fMRI and SPECT studies showing that interictal bursts of generalised paroxysmal fast activity and tonic seizures recruit similar cortical regions. This study provides further evidence that these regions are central to the electroclinical expression of LGS.

Paediatric epilepsy and cognition

Cognitive comorbidities are more frequent in children with epilepsy than in the general population. The cognitive function of children with epilepsy should be appropriately screened, and when there is an impairment, it must be diagnosed and managed. Several factors contribute to the occurrence of this comorbidity. The underlying aetiology and epilepsy syndrome are the major risk factors. Other factors also play a role, such as seizure recurrence, antiseizure medication, and interictal abnormalities. Recent evidence also suggested that cognitive involvement is an ongoing process that interacts with the normal maturation of cognitive function in children with epilepsy. Furthermore, some patients experience rapid cognitive deterioration related to epileptic activity, resulting in epileptic encephalopathy. Further research is needed to better understand how to prevent or modify factors that affect cognitive function in children with epilepsy. WHAT THIS PAPER ADDS: Cognitive comorbidities are more frequent in children with epilepsy than in the general population. The risk factors for cognitive impairment are the underlying aetiology/syndrome, seizure recurrence, antiseizure medication, and interictal abnormalities. Advanced genetic and neuroimaging studies are useful tools to better understand cognitive impairment in children with epilepsy.

Surgically Remediable Secondary Network Epileptic Encephalopathies With Continuous Spike Wave in Sleep: Lesions May Not Be Visible on Brain Magnetic Resonance Imaging (MRI)

BACKGROUND

Continuous spike wave in sleep (CSWS) is an electroencephalogram (EEG) pattern associated with developmental and epileptic encephalopathy with spike-and-wave activation in sleep (DEE-SWAS). This etiologically heterogeneous syndrome may occur because of genetic factors and congenital or acquired brain lesions. We studied the pattern of clinical presentation and underlying etiologies in patients with DEE-SWAS that respond to resective surgery.

METHODS

We reviewed our clinical and research databases for patients who had resolution of CSWS following surgical resection of a focal lesion.

RESULTS

We identified 5 patients meeting inclusion criteria. In 3 of 5, an epileptogenic structural abnormality was not apparent on brain magnetic resonance imaging (MRI). In all 3 patients, focal cortical dysplasia was identified through intracranial EEG monitoring.

SIGNIFICANCE

DEE-SWAS may be a secondary bilateral network epilepsy syndrome, which can be treated with resection of the inciting focal lesion. In patients with drug-resistant CSWS, clinicians should consider a complete epilepsy presurgical workup, including intracranial EEG monitoring.

Wearable OPM-MEG: A changing landscape for epilepsy

Magnetoencephalography with optically pumped magnometers (OPM-MEG) is an emerging and novel, cost-effective wearable system that can simultaneously record neuronal activity with high temporal resolution ("when" neuronal activity occurs) and spatial resolution ("where" neuronal activity occurs). This paper will first outline recent methodological advances in OPM-MEG compared to conventional superconducting quantum interference device (SQUID)-MEG before discussing how OPM-MEG can become a valuable and noninvasive clinical support tool in epilepsy surgery evaluation. Although OPM-MEG and SQUID-MEG share similar data features, OPM-MEG is a wearable design that fits children and adults, and it is also robust to head motion within a magnetically shielded room. This means that OPM-MEG can potentially extend the application of MEG into the neurobiology of severe childhood epilepsies with intellectual disabilities (e.g., epileptic encephalopathies) without sedation. It is worth noting that most OPM-MEG sensors are heated, which may become an issue with large OPM sensor arrays (OPM-MEG currently has fewer sensors than SQUID-MEG). Future implementation of triaxial sensors may alleviate the need for large OPM sensor arrays. OPM-MEG designs allowing both awake and sleep recording are essential for potential long-term epilepsy monitoring.

Clinical Usefulness of Simultaneous Electroencephalography and Functional Magnetic Resonance Imaging in Children With Focal Epilepsy

Background and Purpose

The current study analyzed the interictal epileptiform discharge (IED)-related hemodynamic response and aimed to determine the clinical usefulness of simultaneous electroencephalography and functional magnetic resonance imaging (EEG-fMRI) in defining the epileptogenic zone (EZ) in children with focal epilepsy.

Methods

Patients with focal epilepsy showing IEDs on conventional EEG were evaluated using EEG-fMRI. Statistical analyses were performed using the times of spike as events modeled with multiple hemodynamic response functions. The area showing the most significant t-value for blood-oxygen-level-dependent (BOLD) changes was compared with the presumed EZ. Moreover, BOLD responses between -9 and +9 s around the spike times were analyzed to track the hemodynamic response patterns over time.

Results

Half (n=13) of 26 EEG-fMRI investigations of 19 patients were successful. Two patients showed 2 different types of spikes, resulting in 15 analyses. The maximum BOLD response was concordant with the EZ in 11 (73.3%) of the 15 analyses. In 10 (66.7%) analyses, the BOLD response localized the EZs more specifically. Focal BOLD responses in the EZs occurred before IEDs in 11 analyses and were often widespread after IEDs. Hemodynamic response patterns were consistent in the same epilepsy syndrome or when repeating the investigation in the same patients.

Conclusions

EEG-fMRI can provide additional information for localizing the EZ in children with focal epilepsy, and also reveal the pathogenesis of pediatric epilepsy by evaluating the patterns in the hemodynamic response across time windows of IEDs.

EEG-fMRI of epileptiform discharges: non-invasive investigation of the whole brain

Simultaneous EEG-fMRI is a unique and non-invasive method for investigating epileptic activity. Interictal epileptiform discharge-related EEG-fMRI provides cortical and subcortical blood oxygen level-dependent (BOLD) signal changes specific to epileptic discharges. As a result, EEG-fMRI has revealed insights into generators and networks involved in epileptic activity in different types of epilepsy, demonstrating-for instance-the implication of the thalamus in human generalized spike and wave discharges and the role of the Default Mode Network (DMN) in absences and focal epilepsy, and proposed a mechanism for the cortico-subcortical interactions in Lennox-Gastaut syndrome discharges. EEG-fMRI can find deep sources of epileptic activity not available to scalp EEG or MEG and provides critical new information to delineate the epileptic focus when considering surgical treatment or electrode implantation. In recent years, methodological advances, such as artifact removal and automatic detection of events have rendered this method easier to implement, and its clinical potential has since been established by evidence of the impact of BOLD response on clinical decision-making and of the relationship between concordance of BOLD responses with extent of resection and surgical outcome. This review presents the recent developments in EEG-fMRI methodology and EEG-fMRI studies in different types of epileptic disorders as follows: EEG-fMRI acquisition, gradient and pulse artifact removal, statistical analysis, clinical applications, pre-surgical evaluation, altered physiological state in generalized genetic epilepsy, and pediatric EEG-fMRI studies.

Characterization of cortical activity in juvenile myoclonic epilepsy by gradient magnetic field topography

OBJECTIVE

Gradient magnetic field topography (GMFT) illustrates the magnetic field gradients of epileptic spike or polyspikes (S/PS) activities on a volume-rendered brain surface. The purpose is to characterize cortical activation in juvenile myoclonic epilepsy (JME).

METHODS

We compared interictal S/PS activities in 10 patients with JME to five patients with Lennox-Gastaut syndrome (LGS). We defined areas with gradients exceeding 300fT/cm as activated zones (AZs) on GMFT. We defined the hemisphere where an AZ initially appeared as the "preceding hemisphere". We localized the foci where AZs arose and evaluated their spatiotemporal changes.

RESULTS

In JME, the localization of S/PS in the preceding hemisphere was frontal in 18 activities (28%), parietal in 10 (15%), and frontal/parietal in 33 (51%), and in the contralateral hemisphere it was frontal in 14 (32%), parietal in 6 (14%), and frontal/parietal in 19 (43%). In LGS, AZs arose in every lobe of the brain. The median interhemispheric time difference was 7 ms (range: 0-20) in JME, which was significantly shorter than the 19 ms (1-50) observed among patients with LGS (p < 0.0001).

CONCLUSIONS

AZs are localized within the bilateral frontal and parietal regions. AZs arose serially from foci with small time differences.

SIGNIFICANCE

These results are consistent with regional network involvement in JME.

Case Report: Late-Onset Lennox-Gastaut Syndrome Treated With Stereotactic Electroencephalography-Guided Radiofrequency Thermocoagulation Before Craniotomy

The onset of Lennox-Gastaut syndrome (LGS), a severe epilepsy syndrome, is typically before 8 years of age. Late-onset LGS (with onset in adolescence and adulthood) is relatively rare clinically and has some differences from classical LGS. Herein, we describe the case of a patient with late-onset LGS and provide a literature review of such cases. The patient had focal epilepsy onset at 8 years of age. After a 9-year evolution, he suffered seizures of different types and had a diagnosis of late-onset LGS. Drug treatment was ineffective. Nothing was found on stereotactic electroencephalography (SEEG) and magnetic resonance imaging (MRI) during the course of the disease. After the second presurgical evaluation, we found a suspicious focus on high-resolution structural MRI which was verified by SEEG at last. After SEEG-guided radiofrequency thermocoagulation (RFTC), his seizures were controlled, and his cognitive function and quality of living clearly improved. However, his seizures recurred 2 years later, and he underwent left occipital resection. Thereafter, his seizures have been controlled until now. This case emphasizes the importance of high-resolution structural MRI in the treatment of LGS. Furthermore, it suggests that late-onset LGS may be caused by focal lesions and evolve from focal epilepsy. Thus, characterizing the clinical symptoms and performing individualized electroencephalographic follow-up are both very important. Additionally, the clinical outcome in this case implies the value and limitations of RFTC in patients with epilepsy and a clear focal lesion. Moreover, this case further supports differences between late-onset and classical LGS in terms of clinical manifestation, cognitive changes, prognosis, and treatment.

Gastrointestinal and Autonomic Symptoms—How to Improve the Diagnostic Process in Panayiotopoulos Syndrome?

One of the most common epileptic disorders in the pediatric population is Panayiotopoulos syndrome. Clinical manifestations of this idiopathic illness include predominantly autonomic symptoms and dysfunction of the cardiorespiratory system. Another feature constitutes prolonged seizures that usually occur at sleep. It is crucial to differentiate the aforementioned disease from other forms of epilepsy, especially occipital and structural epilepsy and non-epileptic disorders. The diagnostic process is based on medical history, clinical examination, neuroimaging and electroencephalography—though results of the latter may be unspecific. Patients with Panayiotopoulos syndrome (PS) do not usually require treatment, as the course of the disease is, in most cases, mild, and the prognosis is good. The purpose of this review is to underline the role of central autonomic network dysfunction in the development of Panayiotopoulos syndrome, as well as the possibility of using functional imaging techniques, especially functional magnetic resonance imaging (fMRI), in the diagnostic process. These methods could be crucial for understanding the pathogenesis of PS. More data arerequired to create algorithms that will be able to predict the exposure to various complications of PS. It also concerns the importance of electroencephalography (EEG) as a tool to distinguish Panayiotopoulos syndrome from other childhood epileptic syndromes and non-epileptic disorders.

Neuroimaging and thalamic connectomics in epilepsy neuromodulation

Neuromodulation is an increasingly utilized therapy for the treatment of people with drug-resistant epilepsy. To date, the most common and effective target has been the thalamus, which is known to play a key role in multiple forms of epilepsy. Neuroimaging has facilitated rapid developments in the understanding of functional targets, surgical and programming techniques, and the effects of thalamic stimulation. In this review, the role of neuroimaging in neuromodulation is explored. First, the structural and functional changes of the thalamus in common epilepsy syndromes are discussed as the rationale for neuromodulation of the thalamus. Next, methods for imaging different thalamic nuclei are presented, as well as rationale for the need of direct surgical targeting rather than reliance on traditional stereotactic coordinates. Lastly, we discuss the potential role of neuroimaging in assessing the effects of thalamic stimulation and as a potential biomarker for neuromodulation outcomes.

Age at onset in patients with Lennox-Gastaut syndrome: Correlations with clinical manifestations

The aim of the current study was to investigate the age at onset in patients with Lennox-Gastaut Syndrome (LGS). We also investigated the clinical and EEG characteristics of these patients in different age groups. This was a retrospective study. All patients with a diagnosis of LGS were recruited at the outpatient epilepsy clinic at Shiraz University of Medical Sciences, Shiraz, Iran, from 2008 through 2020. 300 patients had LGS. Age at onset was 3.3 ± 4.1 years (minimum = 0 and maximum = 21 years). In 10 patients (3%) LGS started at age 14 years or above. Epileptic spasms were more often observed in those with an age at onset below one year (8%) compared with those with an age at onset of 1 to 8 years (0.7%) [Odds Ratio (OR) = 10.32]. Intellectual disability was less frequently observed in those with an age at onset of 8 years and above (68%) compared with those with an age at onset of 1 to 8 years (90%) (OR = 0.33). Tonic-clonic seizures were more often observed in those with an age at onset of 8 years and above (83%) compared with those with an age at onset of 1 to 8 years (55%) (OR = 2.87). While age at onset of LGS in the majority of patients is below 8 years, in some patients the syndrome begins in their late childhood or even during adolescence. Age at onset of LGS has significant correlations with the clinical manifestations of the syndrome.

The optimal target and connectivity for DBS in Lennox‐Gastaut syndrome

Objective

Deep brain stimulation (DBS) can reduce seizures in Lennox–Gastaut syndrome (LGS). However, little is known about the optimal target and whether efficacy depends on connectivity of the stimulation site. Using outcome data from the ESTEL trial, we aimed to determine the optimal target and connectivity for DBS in LGS.

Methods

A total of 20 patients underwent bilateral DBS of the thalamic centromedian nucleus (CM). Outcome was percentage seizure reduction from baseline after 3 months of DBS, defined using three measures (monthly seizure diaries, 24‐hour scalp electroencephalography [EEG], and a novel diary‐EEG composite). Probabilistic stimulation mapping identified thalamic locations associated with higher/lower efficacy. Two substitute diffusion MRI datasets (a normative dataset from healthy subjects and a “disease‐matched” dataset from a separate group of LGS patients) were used to calculate structural connectivity between DBS sites and a map of areas known to express epileptic activity in LGS, derived from our previous EEG‐fMRI research.

Results

Results were similar across the three outcome measures. Stimulation was most efficacious in the anterior and inferolateral “parvocellular” CM border, extending into the ventral lateral nucleus (posterior subdivision). There was a positive association between diary‐EEG composite seizure reduction and connectivity to areas of a priori EEG‐fMRI activation, including premotor and prefrontal cortex, putamen, and pontine brainstem. In contrast, outcomes were not associated with baseline clinical variables.

Interpretation

Efficacious CM‐DBS for LGS is linked to stimulation of the parvocellular CM and the adjacent ventral lateral nucleus, and is associated with connectivity to, and thus likely modulation of, the “secondary epileptic network” underlying the shared electroclinical manifestations of LGS. ANN NEUROL 2022;92:61–74

Involvement of brain structures in childhood epilepsy with centrotemporal spikes

BACKGROUND

We aimed to investigate electroencephalography (EEG)-functional magnetic resonance imaging (fMRI) findings to elucidate the interictal epileptiform discharge (IED)-related functional alterations in deep brain structures and the neocortex in childhood epilepsy with centrotemporal spikes (CECTS).

METHODS

Ten children with CECTS (median age 8.2 years), referred to our hospital within a year of onset, were eligible for inclusion. They underwent EEG-fMRI recording during sleep. Llongitudinal evaluations, including medical examinations, intelligence tests, and questionnaires about developmental disabilities, were performed. The initial evaluation was performed at the same time as the EEG-fMRI, and the second evaluation was performed over 2 years after the initial evaluation.

RESULTS

Three children were unable to maintain sleep during the EEG-fMRI recording, and the remaining seven children were eligible for further assessment. All patients showed unilateral-dominant centrotemporal spikes during scans. One patient had only positive hemodynamic responses, while the others had both positive and negative hemodynamic responses. All patients showed IED-related hemodynamic responses in the bilateral neocortex. For deep brain structures, IED-related hemodynamic responses were observed in the cingulate gyrus (n = 4), basal ganglia (n = 3), thalamus (n = 2), and default mode network (n = 1). Seizure frequencies at the second evaluation were infrequent or absent, and the longitudinal results of intelligence tests and questionnaires were within normal ranges.

CONCLUSIONS

We demonstrated that IEDs affect broad brain areas, including deep brain structures such as the cingulate gyrus, basal ganglia, and thalamus. Deep brain structures may play an important role in the pathophysiology of CECTS.

Epilepsy Surgery is a Viable Treatment for Lennox Gastaut Syndrome

Lennox Gastaut Syndrome (LGS) is a severe developmental epileptic encephalopathy with onset in childhood characterized by multiple seizure types and characteristic electroencephalogram findings. The majority of patients develop drug resistant epilepsy, defined as failure of 2 appropriate anti-seizure medications used at adequate doses. Epilepsy surgery can reduce seizure burden, in some cases leading to seizure freedom, and improve neuro-developmental outcomes and quality of life. Epilepsy surgery should be considered for all patients with drug resistant LGS. Herein, we review current surgical treatment options for patients with LGS, both definitive and palliative, including: focal cortical resection, vagus nerve stimulation and corpus callosotomy. Newer neuromodulation techniques will be explored, as well as the concept of LGS as a secondary network disorder.

Recent Advances in Neuroimaging of Epilepsy

Human neuroimaging has had a major impact on the biological understanding of epilepsy and the relationship between pathophysiology, seizure management, and outcomes. This review highlights notable recent advancements in hardware, sequences, methods, analyses, and applications of human neuroimaging techniques utilized to assess epilepsy. These structural, functional, and metabolic assessments include magnetic resonance imaging (MRI), positron emission tomography (PET), and magnetoencephalography (MEG). Advancements that highlight non-invasive neuroimaging techniques used to study the whole brain are emphasized due to the advantages these provide in clinical and research applications. Thus, topics range across presurgical evaluations, understanding of epilepsy as a network disorder, and the interactions between epilepsy and comorbidities. New techniques and approaches are discussed which are expected to emerge into the mainstream within the next decade and impact our understanding of epilepsies. Further, an increasing breadth of investigations includes the interplay between epilepsy, mental health comorbidities, and aberrant brain networks. In the final section of this review, we focus on neuroimaging studies that assess bidirectional relationships between mental health comorbidities and epilepsy as a model for better understanding of the commonalities between both conditions.

Automatic detection of generalized paroxysmal fast activity in interictal EEG using time-frequency analysis

OBJECTIVE

Markup of generalized interictal epileptiform discharges (IEDs) on EEG is an important step in the diagnosis and characterization of epilepsy. However, manual EEG markup is a time-consuming, subjective, and the specialized task where the human reviewer needs to visually inspect a large amount of data to facilitate accurate clinical decisions. In this study, we aimed to develop a framework for automated detection of generalized paroxysmal fast activity (GPFA), a generalized IED seen in scalp EEG recordings of patients with the severe epilepsy of Lennox-Gastaut syndrome (LGS).

METHODS

We studied 13 children with LGS who had GPFA events in their interictal EEG recordings. Time-frequency information derived from manually marked IEDs across multiple EEG channels was used to automatically detect similar events in each patient's interictal EEG. We validated true positives and false positives of the proposed spike detection approach using both standalone scalp EEG and simultaneous EEG-functional MRI (EEG-fMRI) recordings.

RESULTS

GPFA events displayed a consistent low-high frequency arrangement in the time-frequency domain. This 'bimodal' spectral feature was most prominent over frontal EEG channels. Our automatic detection approach using this feature identified EEG events with similar time-frequency properties to the manually marked GPFAs. Brain maps of EEG-fMRI signal change during these automatically detected IEDs were comparable to the EEG-fMRI brain maps derived from manual IED markup.

CONCLUSION

GPFA events have a characteristic bimodal time-frequency feature that can be automatically detected from scalp EEG recordings in patients with LGS. The validity of this time-frequency feature is demonstrated by EEG-fMRI analysis of automatically detected events, which recapitulates the brain maps we have previously shown to underlie generalized IEDs in LGS.

SIGNIFICANCE

This study provides a novel methodology that enables a fast, automated, and objective inspection of generalized IEDs in LGS. The proposed framework may be extendable to a wider range of epilepsy syndromes in which monitoring the burden of epileptic activity can aid clinical decision-making and faster assessment of treatment response and estimation of future seizure risk.

Epilepsy surgery for pediatric patients with mild malformation of cortical development

PURPOSE

The observation of mild malformation of cortical development (mMCD) has yet to have a major clinical impact due to the lack of clinical and research data. We characterized the clinical features, surgical outcomes, and postoperative seizure control patterns in pediatric patients with mMCD.

METHODS

We examined 40 patients with isolated mMCD who underwent resective surgery during a 10-year period.

RESULTS

The median age at seizure onset was 1.2 years, and the median age at surgery was 7.9 years. Twenty-seven patients (67.5%) presented with childhood-onset epileptic encephalopathy (21 Lennox-Gastaut syndrome, 6 West syndrome), and 13 patients (32.5%) presented with intractable focal epilepsy (10 extratemporal lesions, 3 temporal lesions). Twenty-one patients (52.5%) showed "suspected focal cortical malformation" on MRI, whereas 16 patients (40.0%) and 3 patients (7.5%) showed normal MRI findings or mild brain atrophy, respectively. The most common surgical procedures were two lobar resections (18 patients, 45.0%), followed by unilobar resections (12 patients, 30.0%) and resections exceeding two lobar boundaries (10 patients, 25.0%). As a final surgical outcome, 24 patients (60.0%) were ILAE Class 1-3. Discontinuation of all AEDs was possible for 36.8% of ILAE Class 1 patients. Regarding the seizure control pattern, fluctuating seizure control was observed most frequently (21 patients, 52.5%).

CONCLUSION

Our results suggest that mMCD is an important pathological finding in children related to a significant degree of epileptogenicity, and resective surgery can have positive outcomes. However, these patients showed unstable postoperative seizure control patterns with a high rate of late recurrence, suggesting difficulties in the surgical treatment of intractable epilepsy.

Asymmetric Slow-Spike-Wave Patterns with Maximal Discharges Contralateral to MRI Lesions Predict Better Surgical Prognosis in Symptomatic Lennox-Gastaut Syndrome or Lennox-Gastaut Phenotypes

INTRODUCTION

Lennox-Gastaut syndrome (LGS) is a severe subtype of childhood-onset epileptic encephalopathy with drug-resistant and poor surgical prognosis. However, electroencephalogram (EEG) patterns of symptomatic LGS or LG phenotypes with structural brain lesions including focal abnormalities or asymmetric slow-spike-wave (SSW) patterns remain largely unknown. Due to the contradictory lateralization difference between MRI lesions and EEG pattern in symptomatic LGS or LG phenotypes, it is difficult to determine the precise lateralization of epileptic lesions, which is crucial to better surgical prognosis. This study is aim to ascertain the clinical characteristics of the EEG patterns, and its relationship with MRI lesions and to evaluate its prognostic value of surgical treatment in symptomatic LGS or LG phenotypes.

METHODS

Twenty-four symptomatic LGS cases with asymmetric EEG SSW patterns and contralaterally independent or contralaterally dominant MRI lesions were collected, and their clinical features were analyzed retrospectively.

RESULTS

In this cohort, most of lesions were perinatal or acquired during the first 6 months of life. The most common etiology was intracerebral hemorrhage. The LGS patients with both asymmetric SSW and focal sporadic epileptic waves (SEW) patterns showed the best surgical outcome with Engel class I level. Asymmetric SSW patterns with maximal discharges contralateral to MRI lesions were frequently observed in most of symptomatic LGS or LG phenotypes. Predominantly diffuse destructive lesions led to an attenuated voltage of ipsilateral scalp EEG producing an asymmetric SSW pattern in those patients with symptomatic LGS or LG phenotypes.

CONCLUSIONS

Our study reveals a special SEW EEG pattern in symptomatic LG patients with asymmetric SSW and MRI lesions contralateral to the dominant EEG patterns. Contradictory lateralization difference between MRI and EEG probably arises from the relative voltage attenuation presenting in EEG ipsilateral to huge destructive lesions from early life. Our study suggests that the independent focal SEW activity remaining ipsilateral to the MRI lesion can potentially predict better surgical prognosis in symptomatic LGS or LG phenotypes.

Alteration of the anatomical covariance network after corpus callosotomy in pediatric intractable epilepsy

PURPOSE

This study aimed to use graph theoretical analysis of anatomical covariance derived from structural MRI to reveal how the gray matter connectivity pattern is altered after corpus callosotomy (CC).

MATERIALS AND METHODS

We recruited 21 patients with epilepsy who had undergone CC. Enrollment criteria were applied: (1) no lesion identified on brain MRI; (2) no history of other brain surgery; and (3) age not younger than 3 years and not older than 18 years at preoperative MRI evaluation. The most common epilepsy syndrome was Lennox-Gastaut syndrome (11 patients). For voxel-based morphometry, the normalized gray matter images of pre-CC and post-CC patients were analyzed with SPM12 (voxel-level threshold of p<0.05 [familywise error-corrected]). Secondly, the images of both groups were subjected to graph theoretical analysis using the Graph Analysis Toolbox with SPM8. Each group was also compared with 32 age- and sex-matched control patients without brain diseases.

RESULTS

Comparisons between the pre- and post-CC groups revealed a significant reduction in seizure frequency with no change in mean intelligence quotient/developmental quotient levels. There was no relationship among the three groups in global network metrics or in targeted attack. A regional comparison of betweenness centrality revealed decreased connectivity to and from the right middle cingulate gyri and medial side of the right superior frontal gyrus and a partial shift in the distribution of betweenness centrality hubs to the normal location. Significantly lower resilience to random failure was found after versus before CC and versus controls (p = 0.0450 and p = 0.0200, respectively).

CONCLUSION

Graph theoretical analysis of anatomical covariance derived from structural imaging revealed two neural network effects of resection associated with seizure reduction: the reappearance of a structural network comparable to that in healthy children and reduced connectivity along the median line, including the middle cingulate gyrus.

The epileptic network of Lennox-Gastaut syndrome

Objective

To identify brain regions underlying interictal generalized paroxysmal fast activity (GPFA), and their causal interactions, in children and adults with Lennox-Gastaut syndrome (LGS).

Methods

Concurrent scalp EEG-fMRI was performed in 2 separately analyzed patient groups with LGS: 10 children (mean age 8.9 years) scanned under isoflurane-remifentanil anesthesia and 15 older patients (mean age 31.7 years) scanned without anesthesia. Whole-brain event-related analysis determined GPFA-related activation in each group. Results were used as priors in a dynamic causal modeling (DCM) analysis comparing evidence for different neuronal hypotheses describing initiation and propagation of GPFA between cortex, thalamus, and brainstem.

Results

A total of 1,045 GPFA events were analyzed (cumulative duration 1,433 seconds). In both pediatric and older groups, activation occurred in distributed association cortical areas, as well as the thalamus and brainstem (p < 0.05, corrected for family-wise error). Activation was similar across individual patients with structural, genetic, and unknown etiologies of epilepsy, particularly in frontoparietal cortex. In both groups, DCM revealed that GPFA was most likely driven by prefrontal cortex, with propagation occurring first to the brainstem and then from brainstem to thalamus.

Conclusions

We show reproducible evidence of a cortically driven process within the epileptic network of LGS. This network is present early (in children) and late (in older patients) in the course of the syndrome and across diverse etiologies of epilepsy, suggesting that LGS reflects shared “secondary network” involvement. A cortical-to-subcortical hierarchy is postulated whereby GPFA rapidly propagates from prefrontal cortex to the brainstem via extrapyramidal corticoreticular pathways, whereas the thalamus is engaged secondarily.

Hemiconvulsion-hemiplegia-epilepsy evolving to contralateral hemi-Lennox-Gastaut-like phenotype

BACKGROUND

Hemiconvulsion-hemiplegia-epilepsy (HHE) involves infantile-onset acute hemiconvulsive febrile status epilepticus with subsequent unilateral cerebral atrophy and hemiparesis. Chronic epilepsy later develops, typically involving refractory focal seizures; however, the underlying pathophysiology of this epilepsy is not well understood.

PATIENT

We present a boy who had a typical acute presentation of HHE at 23 months, but an unusual evolution to chronic epilepsy in which the initially unaffected hemisphere was significantly abnormal. His initial acute presentation was right-sided hemiconvulsive febrile status epilepticus, with subsequent left cerebral hemiatrophy and hemiparesis affecting the right face, arm and leg. Focal seizures began at 5 years and were refractory to medical treatment. At 9 years, video EEG monitoring showed a striking pattern of interictal slow spike-wave and paroxysmal fast activity, maximal over the right, initially unaffected, hemisphere. He had primarily focal tonic seizures involving left-sided stiffening, also appearing to originate from the right hemisphere. Following left functional hemispherotomy he became seizure-free and parents reported improved cognitive function, attention and quality of life.

DISCUSSION

This boy had classic features of Lennox-Gastaut syndrome, but expressed almost exclusively over the right hemisphere, which was initially unaffected in his acute presentation of HHE. His evolution to "hemi-Lennox-Gastaut-like phenotype" illustrates the importance of monitoring chronic epilepsy in patients with HHE; early surgical intervention might prevent pathologic recruitment of bilateral secondary networks leading to the refractory seizures and cognitive impairment associated with Lennox-Gastaut syndrome.

Generalized seizures presurgically in a cohort of children with hemispherectomy: Predictors and a potential link to surgical outcome?

PURPOSE

Generalized seizures were often thought to be contraindications for hemispherectomy. However, few studies had investigated this issue comprehensively, as well as the predictors for generalized seizures in hemispheric lesion. We studied the predictors of generalized seizures and their potential link to seizure outcomes in a cohort of children who underwent hemispherectomy.

METHODS

A cohort of 76 children with hemispherectomy were reviewed and dichotomized into two groups with and without generalized seizures confirmed by vEEG presurgically. All preoperative evaluation data correlated to generalized seizures and postoperative prognosis were collected and analysed.

RESULTS

Of 76 patients, 11 (14.5%) cases were documented with various generalized seizures, including atypical absence (54.5%, 6/11), myoclonic (45.5%, 5/11), atonic (36.4%, 4/11), myoclonic-atonic (18.2%, 2/11), myoclonic-absence (9.1%, 1/11) and spasms (9.1%). Electrical status epilepticus during sleep (ESES) was recorded in 3 patients (27.3%, 3/11). At last follow-up, 72.7% (8/11) patients remained seizure-free. ESES was a predictor of generalized seizures (χ² = 4.69, P = 0.043). No correlation was found between generalized seizures and unfavourable postoperative seizure outcome (P = 0.153). For different seizure types, focal to bilateral tonic-clonic seizures (P = 0.020) and myoclonic-atonic seizures (P = 0.002) might correlate with unfavourable outcomes.

CONCLUSION

Generalized seizures were not an absolute contraindication for hemispherectomy. Those patients with ESES might experience generalized seizures presurgically. Focal to bilateral tonic-clonic seizures and myoclonic-atonic seizures pre-surgery may indicate unfavourable post-operative seizure outcomes.

Lennox-Gastaut syndrome in adulthood: Long-term clinical follow-up of 38 patients and analysis of their recorded seizures

Lennox-Gastaut syndrome (LGS) is a severe epileptic encephalopathy with childhood onset that usually continues through adolescence and into adulthood. In the long term, patients with this condition still have intractable seizures, intellectual disability, behavioral problems, and physical comorbidities. The aim of this study was to describe the clinical and EEG characteristics of a group of adults with Lennox-Gastaut syndrome. We identified 38 (22 females, 16 males) patients with LGS older than age 18years at their last evaluation, with mean age of 43.3±10.6years. Median follow-up was 14.4years (range: 2-40). All of our patients had 3 or more seizure types during their clinical history. The most prevalent seizure types at follow-up were atypical absences (28/38), tonic (28/38), generalized tonic-clonic (17/38), focal (11/38), and myoclonic seizures (9/38). All patients had drug-resistant seizures. Besides epilepsy, intellectual disability and behavioral problems were prominent features. Surprisingly, paroxysmal nonepileptic seizures were reported in 3 patients. Our observations confirm the poor outcome of Lennox-Gastaut syndrome through adulthood, regardless of age at seizure onset, etiology, and history of previous West syndrome.

Lennox-Gastaut syndrome: a comprehensive review

Lennox-Gastaut syndrome (LGS) is considered an epileptic encephalopathy and is defined by a triad of multiple drug-resistant seizure types, a specific EEG pattern showing bursts of slow spike-wave complexes or generalized paroxysmal fast activity, and intellectual disability. The prevalence of LGS is estimated between 1 and 2% of all patients with epilepsy. The etiology of LGS is often divided into two groups: identifiable (genetic-structural-metabolic) in 65 to 75% of the patients and LGS of unknown cause in others. Lennox-Gastaut syndrome may be considered as secondary network epilepsy. The seizures in LGS are usually drug-resistant, and complete seizure control with resolution of intellectual and psychosocial dysfunction is often not achievable. Reduction in frequency of the most incapacitating seizures (e.g., drop attacks and tonic-clonic seizures) should be the major objective. Valproate, lamotrigine, and topiramate are considered to be the first-line drugs by many experts. Other effective antiepileptic drugs include levetiracetam, clobazam, rufinamide, and zonisamide. The ketogenic diet is an effective and well-tolerated treatment option. For patients with drug resistance, a further therapeutic option is surgical intervention. Corpus callosotomy is a palliative surgical procedure that aims at controlling the most injurious seizures. Finally, vagus nerve stimulation offers reasonable seizure improvement. The long-term outcome for patients with LGS is generally poor. This syndrome is often associated with long-term adverse effects on intellectual development, social functioning, and independent living.

Thalamocortical functional connectivity in Lennox-Gastaut syndrome is abnormally enhanced in executive-control and default-mode networks

OBJECTIVE

To identify abnormal thalamocortical circuits in the severe epilepsy of Lennox-Gastaut syndrome (LGS) that may explain the shared electroclinical phenotype and provide potential treatment targets.

METHODS

Twenty patients with a diagnosis of LGS (mean age = 28.5 years) and 26 healthy controls (mean age = 27.6 years) were compared using task-free functional magnetic resonance imaging (MRI). The thalamus was parcellated according to functional connectivity with 10 cortical networks derived using group-level independent component analysis. For each cortical network, we assessed between-group differences in thalamic functional connectivity strength using nonparametric permutation-based tests. Anatomical locations were identified by quantifying spatial overlap with a histologically informed thalamic MRI atlas.

RESULTS

In both groups, posterior thalamic regions showed functional connectivity with visual, auditory, and sensorimotor networks, whereas anterior, medial, and dorsal thalamic regions were connected with networks of distributed association cortex (including the default-mode, anterior-salience, and executive-control networks). Four cortical networks (left and right executive-control network; ventral and dorsal default-mode network) showed significantly enhanced thalamic functional connectivity strength in patients relative to controls. Abnormal connectivity was maximal in mediodorsal and ventrolateral thalamic nuclei.

SIGNIFICANCE

Specific thalamocortical circuits are affected in LGS. Functional connectivity is abnormally enhanced between the mediodorsal and ventrolateral thalamus and the default-mode and executive-control networks, thalamocortical circuits that normally support diverse cognitive processes. In contrast, thalamic regions connecting with primary and sensory cortical networks appear to be less affected. Our previous neuroimaging studies show that epileptic activity in LGS is expressed via the default-mode and executive-control networks. Results of the present study suggest that the mediodorsal and ventrolateral thalamus may be candidate targets for modulating abnormal network behavior underlying LGS, potentially via emerging thalamic neurostimulation therapies.

Electroencephalography Network Effects of Corpus Callosotomy in Patients with Lennox-Gastaut Syndrome

OBJECTIVES

This study aimed to investigate the functional network effects of corpus callosotomy (CC), a well-recognized palliative surgical therapy for patients with Lennox-Gastaut syndrome (LGS). Specifically, we sought to gain insight into the effects of CC on LGS remission, based on brain networks in LGS by calculating network metrics and evaluating by network measures before and after surgery.

METHODS

Electroencephalographic recordings made during preoperative and 3-month postoperative states in 14 patients with LGS who had undergone successful CC were retrospectively analyzed. First, undirected correlation matrices were constituted for the mathematical expression of functional networks. Then, we plotted these networks to analyze the effects of CC on connectivity. In addition, conventional local and global network measures were applied to evaluate differences in network topology between preoperative and postoperative states.

RESULTS

In the preoperative state, hubs were mainly distributed around the paramedian regions. After CC, the hubs moved from the paramedian regions to the dual-hemisphere and even the lateral regions. Thus, the general connectivity state became more homogeneous, which was verified by network plots and statistical analysis of local measures. The results of global network measures indicated a decreased clustering coefficient in the delta band, decreased characteristic path length in both the delta and gamma bands, and increased global efficiency in the gamma band.

CONCLUSION

Our results showed a consistent variation in the global brain network that converted to a small-world topology with an optimal balance of functional integration and segregation of the network. Such changes were positively correlated with satisfactory surgery results, which could be interpreted as being indicative of LGS recovery process after CC. For patients with refractory LGS along with no focal epileptogenic zone findings, which were not suitable for the resective surgical therapy, our results verified that CC could work as an effective surgical treatment option.

Age-related "Sleep/nocturnal" tonic and tonic clonic seizure clusters are underdiagnosed in patients with Dravet Syndrome

OBJECTIVES

To describe the semiology and EEG characteristics of the age-related pattern of sleep/nocturnal (S/N) seizures in patients with Dravet Syndrome (DS).

METHODS

We retrospectively analysed the clinical and EEG data of DS patients followed at our reference centre for Rare Epilepsies. We included patients aged two years and older who fulfilled clinical and EEG criteria of DS (ILAE 1989). Genetic testing for SCN1A was done in all, followed by PCDH19 if this was negative. Patients showing a genetic abnormality in PCDH19 were excluded. Of 73 DS patients followed at our centre, 26 (15 males and 11 females), called the S/N group, experienced a switch in the circadian rhythm of seizures, from mainly awake/diurnal to mainly S/N seizures. We retrospectively analysed their clinical, EEG and genetic data. We have compared them to a second group of 7 patients (4 males and 3 females), aged more than 11years, the non-S/N group, who did not develop S/N seizures.

RESULTS

We observed a pattern of S/N seizures concomitant with a decrease of awake seizures between 4 and 11years (median 6years 6months). S/N seizures were brief but often occurred in clusters of 2-15 per night. Seizures were mostly focal (26) with frontal-central onset (25) and tonic or tonic-vibratory in semiology. S/N seizure clusters were difficult to control despite many AEDs trials. Benzodiazepines reduced seizure recurrence within a cluster in some patients. While no significant differences were found between groups regarding clinical features, the presence of frontal and central anomalies on wake and sleep EEG was significantly associated with the presence of the S/N pattern.

CONCLUSIONS

Patients with DS often develop a characteristic clinical and EEG pattern with S/N tonic and tonic clonic seizures that is often underdiagnosed. Seizure semiology and EEG pattern differ from LGS but may worsen the quality of sleep of such patients and their families. The possible role of this pattern in SUDEP occurring mainly during sleep and at the same age should be further explored. Current AEDs have limited efficacy and specific drug trials should be proposed.

Dynamic coupling between fMRI local connectivity and interictal EEG in focal epilepsy: A wavelet analysis approach

Simultaneous scalp EEG-fMRI recording is a noninvasive neuroimaging technique for combining electrophysiological and hemodynamic aspects of brain function. Despite the time-varying nature of both measurements, their relationship is usually considered as time-invariant. The aim of this study was to detect direct associations between scalp-recorded EEG and regional changes of hemodynamic brain connectivity in focal epilepsy through a time-frequency paradigm. To do so, we developed a voxel-wise framework that analyses wavelet coherence between dynamic regional phase synchrony (DRePS, calculated from fMRI) and band amplitude fluctuation (BAF) of a target EEG electrode with dominant interictal epileptiform discharges (IEDs). As a proof of concept, we applied this framework to seven patients with focal epilepsy. The analysis produced patient-specific spatial maps of DRePS-BAF coupling, which highlight regions with a strong link between EEG power and local fMRI connectivity. Although we observed DRePS-BAF coupling proximate to the suspected seizure onset zone in some patients, our results suggest that DRePS-BAF is more likely to identify wider 'epileptic networks'. We also compared DRePS-BAF with standard EEG-fMRI analysis based on general linear modelling (GLM). There was, in general, little overlap between the DRePS-BAF maps and GLM maps. However, in some subjects the spatial clusters revealed by these two analyses appeared to be adjacent, particularly in medial posterior cortices. Our findings suggest that (1) there is a strong time-varying relationship between local fMRI connectivity and interictal EEG power in focal epilepsy, and (2) that DRePS-BAF reflect different aspects of epileptic network activity than standard EEG-fMRI analysis. These two techniques, therefore, appear to be complementary. Hum Brain Mapp 38:5356-5374, 2017. © 2017 Wiley Periodicals, Inc.

Cognitive network reorganization following surgical control of seizures in Lennox-Gastaut syndrome

We previously observed that adults with Lennox-Gastaut syndrome (LGS) show abnormal functional connectivity among cognitive networks, suggesting that this may contribute to impaired cognition. Herein we report network reorganization following seizure remission in a child with LGS who underwent functional magnetic resonance imaging (fMRI) before and after resection of a cortical dysplasia. Concurrent electroencephalography (EEG) was acquired during presurgical fMRI. Presurgical and postsurgical functional connectivity were compared using (1) graph theoretical analyses of small-world network organization and node-wise strength; and (2) seed-based analyses of connectivity within and between five functional networks. To explore the specificity of these postsurgical network changes, connectivity was further compared to nine children with LGS who did not undergo surgery. The presurgical EEG-fMRI revealed diffuse activation of association cortex during interictal discharges. Following surgery and seizure control, functional connectivity showed increased small-world organization, stronger connectivity in subcortical structures, and greater within-network integration/between-network segregation. These changes suggest network improvement, and diverged sharply from the comparison group of nonoperated children. Following surgery, this child with LGS achieved seizure control and showed extensive reorganization of networks that underpin cognition. This case illustrates that the epileptic process of LGS can directly contribute to abnormal network organization, and that this network disruption may be reversible.

Brainstem dysfunction in patients with late-onset Lennox-Gastaut syndrome: Voxel-based morphometry and tract-based spatial statistics study

Background:

There have been a few reports of patients who developed Lennox–Gastaut syndrome (LGS) in the second decades of their life.

Objectives:

The aim of this study was to investigate electroclinical presentation in patients with late-onset LGS. In addition, we evaluated structural abnormalities of the brain, which may give some clue about the common pathogenic pathway in LGS.

Materials and Methods:

We enrolled the patients with late-onset LGS. We collected electroclinical characteristics of the patients and evaluated structural abnormalities using voxel-based morphometry (VBM) and tract-based spatial statistics (TBSS) analysis.

Results:

The three subjects were diagnosed with late-onset LGS. The patients have no mental retardation and normal background activities on electroencephalography (EEG), and they had generalized paroxysmal fast activities on EEG, especially during sleep. The TBSS analysis revealed that fractional anisotropy values in the patients were significantly reduced in the white matter of brainstem compared with normal controls. However, VBM analysis did not show any significant difference between the patients and normal controls.

Conclusions:

Patients with late-onset LGS have different clinical and EEG characteristics from those with early-onset LGS. In addition, we demonstrated that brainstem dysfunction might contribute to the pathogenesis of late-onset LGS.

Resective surgery combined with corpus callosotomy for children with non-focal lesional Lennox-Gastaut syndrome

BACKGROUND

The first prospective trial for resective surgery combined with corpus callosotomy (CCT) was performed to investigate the outcomes of the combined surgery in children with Lennox-Gastaut syndrome (LGS) without focal lesion on brain MRI.

METHODS

This study enrolled 68 children with LGS and without focal lesion on brain MRI, of which 25 received medicine (medicine group) and 43 underwent surgery (surgery group), including 20 with exclusively resective surgery (exclusively resection subgroup) and 23 with resective surgery combined with CCT (combined CCT subgroup). All patients were followed for 3-5 years.

RESULTS

Significant differences in seizure control were observed between the medicine group and the exclusively resection subgroup and combined CCT subgroup at the 1-year, 3-year, and 5-year follow-ups. There was a trend that the children with resection combined with CCT had better seizure control than those with exclusively resection at the three follow-ups, but this could not be verified by the statistical method used. Furthermore, significant differences were not observed in seizure control between children with different MRI findings, age at surgery, or pathology in the surgery group. The percentage of long-term seizure-free did not remain as high as the percentage of early stage seizure-free at 1-year follow-up. However, the children with combined CCT surgery demonstrated more postoperative improvement than the children with resective surgery alone based on the mean QOL score (10.78 vs. 5.75, p = 0.0152) and full-scale IQ (7.91 vs. 4.55, p = 0.0446).

CONCLUSIONS

Resective surgery combined with CCT can provide favorable seizure control and obvious improvements in QOL and IQ in children with LGS. This combined approach can be performed in carefully selected LGS children without focal lesions and can localize the epileptogenic zone following a comprehensive preoperative evaluation.

Surgical Management of Pediatric Epilepsy: Decision-Making and Outcomes

First-line treatment for epilepsy is antiepileptic drug and requires an interdisciplinary approach and enduring commitment and adherence from the patient and family for successful outcome. Despite adherence to antiepileptic drugs, refractory epilepsy occurs in approximately 30% of children with epilepsy, and surgical treatment is an important intervention to consider. Surgical management of pediatric epilepsy is highly effective in selected patients with refractory epilepsy; however, an evidence-based protocol, including best methods of presurgical imaging assessments, and neurodevelopmental and/or behavioral health assessments, is not currently available for clinicians. Surgical treatment of epilepsy can be critical to avoid negative outcomes in functional, cognitive, and behavioral health status. Furthermore, it is often the only method to achieve seizure freedom in refractory epilepsy. Although a large literature base can be found for adults with refractory epilepsy undergoing surgical treatment, less is known about how surgical management affects outcomes in children with epilepsy. The purpose of the review was fourfold: (1) to evaluate the available literature regarding presurgical assessment and postsurgical outcomes in children with medically refractory epilepsy, (2) to identify gaps in our knowledge of surgical treatment and its outcomes in children with epilepsy, (3) to pose questions for further research, and (4) to advocate for a more unified presurgical evaluation protocol including earlier referral for surgical candidacy of pediatric patients with refractory epilepsy. Despite its effectiveness, epilepsy surgery remains an underutilized but evidence-based approach that could lead to positive short- and long-term outcomes for children with refractory epilepsy.

Managing drug-resistant epilepsy: challenges and solutions

Despite the development of new antiepileptic drugs (AEDs), ~20%-30% of people with epilepsy remain refractory to treatment and are said to have drug-resistant epilepsy (DRE). This multifaceted condition comprises intractable seizures, neurobiochemical changes, cognitive decline, and psychosocial dysfunction. An ongoing challenge to both researchers and clinicians alike, DRE management is complicated by the heterogeneity among this patient group. The underlying mechanism of DRE is not completely understood. Many hypotheses exist, and relate to both the intrinsic characteristics of the particular epilepsy (associated syndrome/lesion, initial response to AED, and the number and type of seizures prior to diagnosis) and other pharmacological mechanisms of resistance. The four current hypotheses behind pharmacological resistance are the "transporter", "target", "network", and "intrinsic severity" hypotheses, and these are reviewed in this paper. Of equal challenge is managing patients with DRE, and this requires a multidisciplinary approach, involving physicians, surgeons, psychiatrists, neuropsychologists, pharmacists, dietitians, and specialist nurses. Attention to comorbid psychiatric and other diseases is paramount, given the higher prevalence in this cohort and associated poorer health outcomes. Treatment options need to consider the economic burden to the patient and the likelihood of AED compliance and tolerability. Most importantly, higher mortality rates, due to comorbidities, suicide, and sudden death, emphasize the importance of seizure control in reducing this risk. Overall, resective surgery offers the best rates of seizure control. It is not an option for all patients, and there is often a significant delay in referring to epilepsy surgery centers. Optimization of AEDs, identification and treatment of comorbidities, patient education to promote adherence to treatment, and avoidance of triggers should be periodically performed until further insights regarding causative pathology can guide better therapies.