Generalized Seizures Research Articles

The Development of Epilepsy Following CNS Viral Infections: Mechanisms.

This review examines the role of different viral infections in epileptogenesis, with a focus on Herpesviruses such as Human Herpesvirus 6 (HHV-6) and Epstein Barr Virus (EBV), Flaviviruses, Picornaviruses, Human Immunodeficiency Virus (HIV), Influenzavirus and Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2). A growing literature on animal models, such as the paradigmatic Theiler's murine encephalomyelitis virus (TMEV) model, and clinical investigations in patients with epilepsy have started to elucidate cellular mechanisms implicated in seizure initiation and development of epilepsy following viral infections. A central role of neuroinflammation has emerged, with evidence of activation of the innate and adaptive immunity, dysregulation of microglial and astrocytic activity and production of multiple cytokines and other inflammatory mediators. Several chronic downstream effects result in increased blood-brain barrier permeability, direct neuronal damage, and modifications of ion channels ultimately leading to altered neuronal excitability and seizure generation. Key findings underscore the complex interplay between initial viral infection, neuroinflammation, and later development of epilepsy. Further research is needed to elucidate these mechanisms and develop targeted interventions.

A review of epilepsy detection and prediction methods based on EEG signal processing and deep learning

Epilepsy is a chronic neurological disorder that poses significant challenges to patients and their families. Effective detection and prediction of epilepsy can facilitate patient recovery, reduce family burden, and streamline healthcare processes. Therefore, it is essential to propose a deep learning method for efficient detection and prediction of epileptic electroencephalography (EEG) signals. This paper reviews several key aspects of epileptic EEG signal processing, focusing on epilepsy detection and prediction. It covers publicly available epileptic EEG datasets, preprocessing techniques, feature extraction methods, and deep learning-based networks used in these tasks. The literature is categorized based on patient independence, distinguishing between patient-independent and non-patient-independent studies. Additionally, the evaluation methods are classified into general classification indicators and specific epilepsy prediction criteria, with findings organized according to the prediction cycles reported in various studies. The review reveals several important insights. Despite the availability of public datasets, they often lack diversity in epilepsy types and are collected under controlled conditions that may not reflect real-world scenarios. As a result, signal preprocessing methods tend to be limited and may not fully represent practical conditions. Feature extraction and network designs frequently emphasize fusion mechanisms, with recent advances in Convolutional Neural Networks (CNNs) and Recurrent Neural Networks (RNNs) showing promising results, suggesting that new network models warrant further exploration. Studies using patient-independent data generally produce better results than those relying on non-patient-independent data. Metrics based on general classification methods typically perform better than those using specific epilepsy prediction criteria, though future research should focus on the latter for more accurate evaluation. Epilepsy prediction cycles are typically kept under 1 h, with most studies concentrating on intervals of 30 min or less.

High-resolution multimodal profiling of human epileptic brain activity via explanted depth electrodes.

The availability and integration of electrophysiological and molecular data from the living brain is critical to understand and diagnose complex human disease. Intracranial stereo electroencephalography (SEEG) electrodes used for identifying the seizure focus on epilepsy patients could enable the integration of such multimodal data. Here, we report MoPEDE (Multimodal Profiling of Epileptic Brain Activity via Explanted Depth Electrodes), a method that recovers extensive protein-coding transcripts, including cell-type markers, DNA methylation and short variant profiles from explanted SEEG electrodes matched with electrophysiological and radiological data allowing for high-resolution reconstructions of brain structure and function. We find gene expression gradients that correspond with the neurophysiology-assigned epileptogenicity index but also outlier molecular fingerprints in some electrodes, potentially indicating seizure generation or propagation zones not detected during electroclinical assessments. Additionally, we identify DNA methylation profiles indicative of transcriptionally permissive or restrictive chromatin states and SEEG-adherent differentially expressed and methylated genes not previously associated with epilepsy. Together, these findings validate that RNA profiles and genome-wide epigenetic data from explanted SEEG electrodes offer high-resolution surrogate molecular landscapes of brain activity. The MoPEDE approach has the potential to enhance diagnostic decisions and deepen our understanding of epileptogenic network processes in the human brain.

CNSC-45. EXTRINSIC ELECTRICAL MODULATION IMPACTS GLIOBLASTOMA TUMOR GROWTH BY DISRUPTING ITS INTERCELLULAR COMMUNICATION

Abstract Glioblastoma (GBM) is an incurable primary malignant neoplasm of the central nervous system. GBM as an electrically active neoplasm diffusely colonizes healthy brain tissues, disrupting the neurotransmission balance and causing glioma-related epilepsy (GRE) in up to 50% of patients. Interestingly, GRE is an independent favorable prognostic factor for survival in GBM. The therapeutic induction of seizure may have a previously unexplored oncologic value in GBM. We have previously reported in CT-2A-bearing mice subjected to daily extrinsic electrical modulation (EEM) diminished tumor progression and increased overall survival relative to sham-treated mice, but the mechanism by which EEM produces its anti-tumor effect remains uncertain. Therefore, GBM-bearing mice (CT-2A cells xenografted into 5-7 weeks old C57BL/6 female mice, n=5/group) received either a single EEM of 2.0 millicoulombs (mC) or sham treatment. The mice were terminated at 3 hours, 24 hours, 4, 7, and 10 days post-EEM, and tumors and contralateral brain cortex were analyzed using bulk RNA-sequencing and Sequential immunofluorescence (SeqIFTM). SeqIFTM revealed how EEM activates neuronal activity via cFOS expression and induces tumor-specific cell damage through cleaved caspase-3 expression, without affecting healthy brain tissue. Furthermore, RNA-seq performed post-EEM revealed gene expression changes of not only synapse organization markers but also of several tumor-tumor and tumor-neuron connectivity key markers, such as growth-associated protein 43 (GAP43), neuroligin-3 (NLGN3), and glutamate receptors such as GRIA4 and GRIN1 between others. However, the expression of these markers diminished significantly 96h after-EEM, indicating a reduction in intercellular electrical communication by the inhibition of the neoplasm cells electrical integration with neuronal circuits by downregulating glutamatergic receptor expression, blocking the synapse-forming protein NLGN3, and the network-connecting protein GAP43. Taken together, our findings reveal how by the disruption of these critical interactions within the tumor microenvironment though EEM impacts on GBM growth making it more susceptible to therapeutic interventions.

IMMU-44. EXTRINSIC ELECTRICAL MODULATION OF THE GLIOBLASTOMA TUMOR MICROENVIRONMENT

Abstract BACKGROUND Approximately 30 to 50% of patients with glioblastoma (GBM) present with glioma-related epilepsy (GRE). Despite morbidity associated with seizures, GRE constitutes an independent positive predictive predictor for survival in GBM. Our prior results showed that repeated seizure induction through extrinsic electrical modulation (EEM, a technique in which an electrical stimulus sufficient to produce a therapeutic seizure is applied) slows intracranial tumor growth and prolongs overall survival in immunocompetent CT-2A glioma-bearing mice. However, the overall survival advantage following EEM treatment was diminished in immunocompromised mice bearing human patient derived xenografts. We hypothesized that EEM induces immune-related tumor microenvironment (TME) changes that prolong survival in mice. METHODS C57BL/6J mice were orthotopically implanted with CT-2A xenografts and subjected to EEM of 2.0 millicoulombs or sham treatment. Quantitative reverse transcription polymerase chain reaction (RT-qPCR) was performed at 3 and 24 hours to determine mRNA level of inflammatory cytokines. Immunohistochemistry (IHC) and bulk RNA sequencing analysis were utilized to assess CD3+ T-cell infiltration and identify immune-related secreted genes, respectively. Flow cytometry at 3 and 96 hours was utilized to characterize tumor-infiltrating immune cell populations. Samples were subjected to Percoll gradient enrichment of immune cell populations and stained for extracellular (CD45, CD4, CD8, CD11b, F4/80, CD80, Ly6G, Ly6C, and CX3CR1) and intracellular (TNF-a, Il-1b, CCL2, and Arg1) antigens. RESULTS RT-qPCR showed an increase in pro-inflammatory cytokines TNF-α (P = 0.0087) and IL-1β (P = 0.000349). IHC analysis demonstrated an increase in intratumoral CD3+ T-cells in EEM-treated samples (P = 0.0171). From 1855 upregulated genes, 3 immune-related secreted genes (C1QTNF4, FAM19A4, and GREM2) were identified. Flow cytometric analysis showed a significant increase in CD11b+, CX3RC1+ microglia (P = 0.0306) and CD45+, CD11b+ tumor-associated myeloid cells (TAMCs) (P = 0.0192) at 3 hours post-EEM. CONCLUSIONS EEM treatment promotes an inflammatory TME with increased intratumoral microglia, TAMCs and T-cell infiltration. These inflammatory changes may prolong survival of CT-2A glioma-bearing mice.

Role of inflammasomes and neuroinflammation in epilepsy.

Epilepsy is a brain disorder characterized by recurrent seizures, which are brief episodes of abnormal electrical activity in the brain and involuntary movement that can lead to physical injury and loss of consciousness. Seizures are canonically accompanied by increased inflammatory cytokine production that promotes neuroinflammation, brain pathology, and seizure propagation. Understanding the source of pro-inflammatory cytokines which promote seizure pathogenesis could be a gateway to precision epilepsy drug design. This review discusses the inflammasome in epilepsy including its role in seizure propagation and negative impacts on brain health. The inflammasome is a multiprotein complex that coordinates IL-1β and IL-18 production in response to tissue damage, cellular stress, and infection. Clinical evidence for inflammasome signaling in epileptogenesis is reviewed followed by a discussion of emerging strategies to modulate inflammasome activity in epilepsy.

Whole exome sequencing-based testing of adult epilepsy in a Polish population.

Genetic panel testing in paediatric and mixed adult and children populations has demonstrated clinical utility and provided a diagnostic yield of 18-40%. The data on adult epilepsies is limited. We aimed to investigate the diagnostic yield and analyse genetic diagnoses in whole exome sequenced adult patients with epilepsies in Poland. We recruited 151 patients from 42 clinical centres across Poland. The patients had a diagnosis of epilepsy/ seizures, were 18 or older at the time of the genetic testing, and did not have a genetic diagnosis. All patients were tested with whole exome sequencing after an initial testing with a panel of 47 epilepsy-related genes. We reached a diagnostic yield when considering pathogenic/probably pathogenic variants according to ClinVar of 8.6% (n = 13) and 17% (n = 26) when applying the American College of Medical Genetics (ACMG) criteria. Most patients had a pathogenic/probably pathogenic variant in epilepsy-related genes (54%), followed by potential epilepsy-related genes (19%), and neurodevelopment-associated epilepsy genes (15%). Our study shows that whole exome sequencing-based testing reaches a slightly higher diagnostic yield that the traditional 300 gene panel. Genes related to childhood onset neurodevelopmental disorders and epilepsy should be considered as well. Clinical implications/future directions. Patients may have had a diagnosis related to a childhood syndrome, but due to limited diagnostic possibilities, it was not possible to diagnose them in childhood. We would consider testing adult patients with epilepsy with whole exome or genome sequencing (or if not possible with a panel) in cases of a diagnosis of epilepsy with no hints suggesting secondary epilepsy, and especially with clinical features indicating a genetic epilepsy diagnosis, such as neurodevelopmental delay and early onset of seizures.

Propagation effect of the thalamic feed-forward and feed-back inhibition in multi-type coupling models.

Seizure waves of epilepsy can propagate in a coupled thalamocortical model, which typically occurs in malfunctioning neuronal networks. However, it remains unclear whether thalamic feed-forward inhibition (FFI) and feed-back inhibition (FBI), the two most important microcircuits in this network, have propagation effects. In this study, we first investigated the importance of the pyramidal neuronal population-thalamic reticular nucleus and specific relay nucleus-thalamic reticular nucleus pathways in the Taylor model for seizure control as FFI and FBI, respectively. Subsequently, using the FBI as a crucial parameter, we constructed 2- and 3-compartment coupling models and evaluated their impact on seizure propagation in other chambers by varying the degree of coupling strength. Finally, we replicated the above study in a 10-compartment model to ensure the robustness of the findings. We confirmed that FBI is more effective by analyzing the combined effect of FFI and FBI, and the pathology state does advance as the coupling strength is increased. These findings elucidate the roles that these two pathways play in the propagation of epileptic seizures and may offer fresh perspectives on the clinical management of epilepsy.

Subcortical Alterations in Newly Diagnosed Epilepsy and Associated Changes in Brain Connectivity and Cognition.

Patients with chronic focal epilepsy commonly exhibit subcortical atrophy, particularly of the thalamus. The timing of these alterations remains uncertain, though preliminary evidence suggests that observable changes may already be present at diagnosis. It is also not yet known how these morphological changes are linked to the coherence of white matter pathways throughout the brain, or to neuropsychological function often compromised before antiseizure medication treatment. This study investigates localized atrophy in subcortical regions using surface shape analysis in individuals with newly diagnosed focal epilepsy (NDfE) and assesses their implications on brain connectivity and cognitive function. We collected structural (T1w) and diffusion-weighted MRI and neuropsychological data from 104 patients with NDfE and 45 healthy controls (HCs) matched for age, sex, and education. A vertex-based shape analysis was performed on subcortical structures to compare patients with NDfE and HC, adjusting for age, sex, and intracranial volume. The mean deformation of significance areas (pcor < 0.05) was used to identify white matter pathways associated with overall shape alterations in patients relative to controls using correlational tractography. Additionally, the relationship between significant subcortical shape values and neuropsychological outcomes was evaluated using a generalized canonical correlation approach. Shape analysis revealed bilateral focal inward deformation (a proxy for localized atrophy) in anterior areas of the right and left thalamus and right pallidum in patients with NDfE compared to HC (FWE corrected). No structures showed areas of outward deformation in patients. The connectometry analysis revealed that fractional anisotropy (FA) was positively correlated with thalamic and pallidal shape deformation, that is, reduced FA was associated with inward deformation in tracts proximal to and or connecting with the thalamus including the fornix, frontal, parahippocampal, and corticothalamic pathways. Thalamic and pallidal shape changes were also related to increased depression and anxiety and reduced memory and cognitive function. These findings suggest that atrophy of the thalamus, which has previously been associated with the generation and maintenance of focal seizures, may present at epilepsy diagnosis and relate to alterations in both white matter connectivity and cognitive performance. We suggest that at least some alterations in brain structure and consequent impact on cognitive and affective processes are the result of early epileptogenic processes rather than exclusively due to the chronicity of longstanding epilepsy, recurrent seizures, and treatment with antiseizure medication.

Association of LONP1 gene with epilepsy and the sub-regional effect

The LONP1 gene encodes Lon protease, which is responsible for degrading damaged or misfolded proteins and binding mitochondrial DNA. Previously, LONP1 variants have been identified in patients with cerebral, ocular, dental, auricular, and skeletal anomalies (CODAS syndrome) and mitochondrial diseases. Seizures were occasionally observed. However, the association between LONP1 and epilepsy remains elusive. In this study, we performed trio-based whole-exome sequencing in a cohort of 450 patients with unexplained epilepsy and identified four pairs of compound heterozygous LONP1 variants in four unrelated cases. All patients exhibited good responses to anti-seizure medications and demonstrated no developmental delay or intellectual disabilities. The variant allele frequencies observed in this study were absent or low in the general population and were significantly lower than those of benign variants. At least one variant in each biallelic pair affected hydrogen bonding and/or altered protein stability. The CODAS syndrome-associated variants were concentrated in the AAA+ module, especially the α domain. Four of the five mitochondrial disease-associated variants were located in the AAA + domain and the NTD5H and NTD3H subdomains. In contrast, each of the biallelic variants from the patients with pure epilepsy had one variant located in the linker domain, and the other variant located in the mitochondrial targeting sequence or P domain. This study suggested that LONP1 gene is potentially a novel candidate gene for pure epilepsy. The phenotypic variation is associated with the sub-regional effects of variants.

Somatic variant analysis of resected brain tissue in epilepsy surgery patients.

We studied the distribution of germline and somatic variants in epilepsy surgery patients with (suspected) malformations of cortical development (MCD) who underwent surgery between 2015 and 2020 at University Medical Center Utrecht (the Netherlands) and pooled our data with four previously published cohort studies. Tissue analysis yielded a pathogenic variant in 203 of 663 (31%) combined cases. In 126 of 379 (33%) focal cortical dysplasia (FCD) type II cases and 23 of 37 (62%) hemimegalencephaly cases, a pathogenic variant was identified, mostly involving the mTOR signaling pathway. Pathogenic variants in 10 focal epilepsy genes were found in 48 of 178 (27%) FCDI/mild MCD/mMCD with oligodendroglial hyperplasia and epilepsy cases; 36 of these (75%) were SLC35A2 variants. Six of 69 (9%) patients without a histopathological lesion had a pathogenic variant in SLC35A2 (n = 5) or DEPDC5 (n = 1). A germline variant in blood DNA was confirmed in all cases with a pathogenic variant in tissue, with a variant allele frequency (VAF) of ~50%. In seven of 114 patients (6%) with a somatic variant in tissue, mosaicism in blood was detected. More than half of pathogenic somatic variants had a VAF < 5%. Further analysis of the correlation between genetic variants and surgical outcomes will improve patient counseling and may guide postoperative treatment decisions.

Enhancing non-invasive pre-surgical evaluation through functional connectivity and graph theory in drug-resistant focal epilepsy

BackgroundEpilepsy, characterized as a network disorder, involves widely distributed areas following seizure propagation from a limited onset zone. Accurate delineation of the epileptogenic zone (EZ) is crucial for successful surgery in drug-resistant focal epilepsy. While visual analysis of scalp electroencephalogram (EEG) primarily elucidates seizure spreading patterns, we employed brain connectivity techniques and graph theory principles during the pre-ictal to ictal transition to define the epileptogenic network. MethodCortical sources were reconstructed from 40-channel scalp EEG in five patients during pre-surgical evaluation for focal drug-resistant epilepsy. Temporal Granger connectivity was estimated ten seconds before seizure and at seizure onset. Results have been analyzed using some centrality indices taken from Graph theory (Outdegree, Hubness). A new lateralization index is proposed by taking into account the sum of the most relevant hubness values across left and right regions of interest. ResultsIn three patients with positive surgical outcomes, analysis of the most relevant Hubness regions closely aligned with clinical hypotheses, demonstrating consistency in EZ lateralization and location. In one patient, the method provides unreliable results due to the abundant movement artifacts preceding the seizure. In a fifth patient with poor surgical outcome, the proposed method suggests a wider epileptic network compared with the clinically suspected EZ, providing intriguing new indications beyond those obtained with traditional electro-clinical analysis. ConclusionsThe proposed method could serve as an additional tool during pre-surgical non-invasive evaluation, complementing data obtained from EEG visual inspection. It represents a first step toward a more sophisticated analysis of seizure onset based on connectivity imbalances, electrical propagation, and graph theory principles.

Allopregnanolone and progesterone in relation to a single electroconvulsive therapy seizure and subsequent clinical outcome: an observational cohort study

BackgroundElectroconvulsive therapy (ECT) is an important treatment for several severe psychiatric conditions, yet its precise mechanism of action remains unknown. Increased inhibition in the brain after ECT seizures, mediated by γ-aminobutyric acid (GABA), has been linked to clinical effectiveness. Case series on epileptic patients report a postictal serum concentration increase of the GABAA receptor agonist allopregnanolone. Serum allopregnanolone remains unchanged after a full ECT series, but possible transient effects directly after a single ECT seizure remain unexplored. The primary aim was to measure serum concentrations of allopregnanolone and its substrate progesterone after one ECT seizure. Secondary aims were to examine whether concentrations at baseline, or postictal changes, either correlate with seizure generalization or predict clinical outcome ratings after ECT.MethodsA total of 130 participants (18–85 years) were included. Generalization parameters comprised peak ictal heart rate, electroencephalographic (EEG) seizure duration, and prolactin increase. Outcome measures were ratings of clinical global improvement, perceived health status and subjective memory impairment. Non-parametric tests were used for group comparisons and correlations. The prediction analyses were conducted with binary logistic and simple linear regression analyses.ResultsAllopregnanolone and progesterone remained unchanged and correlated neither with seizure generalization nor with clinical outcome. In men (n = 50), progesterone increased and allopregnanolone change correlated negatively with EEG seizure duration. In a subgroup analysis (n = 62), higher baseline allopregnanolone and progesterone correlated with postictal EEG suppression.ConclusionsECT seizures have different physiologic effects than generalized seizures in epilepsy. Progesterone might have implications for psychiatric illness in men.

A spike is a spike: On the universality of spike features in four epilepsy models.

Frequency properties of the EEG characteristics of different seizure types including absence seizures have been described for various rodent models of epilepsy. However, little attention has been paid to the frequency properties of individual spike-wave complexes (SWCs), the constituting elements characterizing the different generalized seizure types. Knowledge of their properties is not only important for understanding the mechanisms underlying seizure generation but also for the identification of epileptiform activity in various seizure types. Here, we compared the frequency properties of SWCs in different epilepsy models. A software package was designed and used for the extraction and frequency analysis of SWCs from long-term EEG of four spontaneously seizing, chronic epilepsy models: a post-status epilepticus model of temporal lobe epilepsy, a lateral fluid percussion injury model of post-traumatic epilepsy, and two genetic models of absence epilepsy-GAERS and rats of the WAG/Rij strain. The SWCs within the generalized seizures were separated into fast (three-phasic spike) and slow (mostly containing the wave) components. Eight animals from each model were used (32 recordings, 104 510 SWCs in total). A limitation of our study is that the recordings were hardware-filtered (high-pass), which could affect the frequency composition of the EEG. We found that the three-phasic spike component was similar in all animal models both in time and frequency domains, their amplitude spectra showed a single expressed peak at 18-20 Hz. The slow component showed a much larger variability across the rat models. Despite differences in the morphology of the epileptiform activity in different models, the frequency composition of the spike component of single SWCs is identical and does not depend on the particular epilepsy model. This fact may be used for the development of universal algorithms for seizure detection applicable to different rat models of epilepsy. There is a large variety between people with epilepsy regarding the clinical manifestations and the electroencephalographic (EEG) phenomena accompanying the epileptic seizures. Here, we show that one of the EEG signs of epilepsy, an epileptic spike, is universal, since it has the same shape and frequency characteristics in different animal models of generalized epilepsies, despite differences in recording sites and location.

Exploration of epileptic networks in temporal lobe encephaloceles with stereotactic EEG: Electroclinical characteristics and surgical outcomes.

Temporal lobe encephaloceles (TLEN) have been implicated as a cause of temporal lobe epilepsy (TLE), the treatment which is primarily surgical; however, there is no clear consensus on the optimal surgical approach, because it is unclear whether TLE related to TLEN can be addressed by a restricted encephalocele resection or if a more extensive resection is required. The aim of the current article is to report the clinical and electrophysiological profile of patients with TLE secondary to TLEN who underwent stereotactic electroencephalography (SEEG) implantation to identify the epileptogenic network. A retrospective review was performed of patients with TLE related to TLEN who underwent SEEG implantation. Medical charts were reviewed for demographic data, the results of noninvasive and invasive investigations, and operative details. Surgical outcomes were based on Engel classification with at least 6 months follow-up. Nine patients were identified. The mean age at epilepsy onset was 28 years (range, 15-41 years), and 7/9 patients were female. Scalp EEG revealed interictal epileptiform activity most often maximum in the frontotemporal and/or temporal regions. A discrete TLEN was often not identified on initial imaging, but was identified during re-review or at the time of surgery. Seizure onset zones during SEEG were localized to the mesial temporal structures, the temporal pole, or both. One patient became seizure-free following SEEG and another refused further surgery. Of the 7 patients who underwent epilepsy surgery, 5/7 underwent an anterior temporal lobectomy-surgical outcomes were favorable, with 5/7 achieving Engel I outcomes. Invasive SEEG monitoring demonstrated ictal onsets may not be restricted to the TLEN, and often the temporal pole and mesial structures are involved at seizure onset. Ictal propagation patterns vary significantly, which may be related to the underlying pathology and explain the variability in semiology. These findings may inform surgical treatment options. Temporal lobe encephaloceles can cause intractable epilepsy, although their presence may be missed on routine imaging. The management of encephaloceles is primarily surgical; however, the optimal surgical approach can be unclear. Invasive monitoring with SEEG may help characterize the epileptogenic network and result in more optimal surgical outcomes.

Explaining slow seizure propagation with white matter tractography.

Epileptic seizures recorded with stereo-EEG can take a fraction of a second or several seconds to propagate from one region to another. What explains such propagation patterns? We combine tractography and stereo-EEG to determine the relationship between seizure propagation and the white matter architecture and to describe seizure propagation mechanisms. Patient-specific spatiotemporal seizure propagation maps were combined with tractography from diffusion imaging of matched subjects from the Human Connectome Project. The onset of seizure activity was marked on a channel-by-channel basis by two board-certified neurologists for all channels involved in the seizure. We measured the tract connectivity (number of tracts) between regions-of-interest pairs among the seizure onset zone, regions of seizure spread and non-involved regions. We also investigated how tract-connected the seizure onset zone is to regions of early seizure spread compared with regions of late spread. Comparisons were made after correcting for differences in distance. Sixty-nine seizures were marked across 26 patients with drug-resistant epilepsy; 11 were seizure free after surgery (Engel IA) and 15 were not (Engel IB-Engel IV). The seizure onset zone was more tract-connected to regions of seizure spread than to non-involved regions (P < 0.0001); however, regions of seizure spread were not differentially tract-connected to other regions of seizure spread compared with non-involved regions. In seizure-free patients only, regions of seizure spread were more tract-connected to the seizure onset zone than to other regions of spread (P < 0.0001). Over the temporal evolution of a seizure, the seizure onset zone was significantly more tract-connected to regions of early spread compared with regions of late spread in seizure-free patients only (P < 0.0001). By integrating information on structure, we demonstrate that seizure propagation is likely to be mediated by white matter tracts. The pattern of connectivity between seizure onset zone, regions of spread and non-involved regions demonstrates that the onset zone might be largely responsible for seizures propagating throughout the brain, rather than seizures propagating to intermediate points, from which further propagation takes place. Our findings also suggest that seizure propagation over seconds might be the result of a continuous bombardment of action potentials from the seizure onset zone to regions of spread. In non-seizure-free patients, the paucity of tracts from the presumed seizure onset zone to regions of spread suggests that the onset zone was missed. Fully understanding the structure-propagation relationship might eventually provide insight into selecting the correct targets for epilepsy surgery.

Heterozygous variants in USP25 cause genetic generalized epilepsy.

USP25 encodes ubiquitin-specific protease 25, a key member of the deubiquitinating enzyme family that is involved in neural fate determination. Although abnormal expression in Down's syndrome was reported previously, the specific role of USP25 in human diseases has not been defined. In this study, we performed trio-based whole exome sequencing in a cohort of 319 cases (families) with generalized epilepsy of unknown aetiology. Five heterozygous USP25 variants, including two de novo and three co-segregated variants, were determined in eight individuals affected by generalized seizures and/or febrile seizures from five unrelated families. The frequency of USP25 variants showed a significantly high aggregation in this cohort compared with the East Asian population and all populations in the gnomAD database. The mean age at onset of febrile and afebrile seizures were 10 months (infancy) and 11.8 years (juvenile), respectively. The patients achieved seizure freedom, except that one had occasional nocturnal seizures at the last follow-up. Two patients exhibited intellectual disability. Usp25 was expressed ubiquitously in mouse brain with two peaks, on embryonic Days 14-16 and postnatal Day 21, respectively. In human brain, likewise, USP25 is expressed in the fetus/early childhood stage and with a second peak at ∼12-20 years old, consistent with the seizure onset age in patients during infancy and in juveniles. To investigate the functional impact of USP25 deficiency in vivo, we established Usp25 knockout mice, which showed increased seizure susceptibility compared with wild-type mice in a pentylenetetrazol-induced seizure test. To explore the impact of USP25 variants, we used multiple functional detections. In HEK293 T cells, the variant associated with a severe phenotype (p.Gln889Ter) led to a significant reduction of mRNA and protein expressions but formed stable truncated dimers with an increment of deubiquitinating enzyme activities and abnormal cellular aggregations, indicating a gain-of-function effect. The p.Gln889Ter and p.Leu1045del variants increased neuronal excitability in mouse brain, with a higher firing ability in p.Gln889Ter. These functional impairments align with the severity of the observed phenotypes, suggesting a genotype-phenotype correlation. Hence, a moderate association between USP25 and epilepsy was noted, indicating that USP25 is potentially a predisposing gene for epilepsy. Our results from Usp25 null mice and the patient-derived variants indicated that USP25 would play an epileptogenic role via loss-of-function or gain-of-function effects. The truncated variant p.Gln889Ter would have a profoundly different effect on epilepsy. Together, our results underscore the significance of USP25 heterozygous variants in epilepsy, thereby highlighting the critical role of USP25 in the brain.

Subject-based assessment of large-scale integration dynamics in epileptic brain networks: insights from the intrinsic ignition framework.

This study examined the dynamic properties of brain regions involved in the genesis and spread of seizures in 10 individuals diagnosed with pharmacoresistant focal epilepsy. The patients and 30 healthy controls underwent resting-state functional magnetic resonance imaging scans and the brain's functional network dynamics were analyzed using the intrinsic ignition framework. Comparative statistical analyses examined the differences in the integration and metastability measures in both groups in the whole brain and specific local brain regions. Invasive electroencephalography evaluations validated the findings of significant global and regional changes in the patient's brain network dynamics. There was a marked increase in global integration and metastability across the brain, reflecting substantial alterations in the overall connectivity and flexibility of the functional networks. Specific brain regions exhibited paradoxical dynamics within the seizure onset zone, with decreased intrinsic ignition and increased metastability. Increased intrinsic ignition was observed in remote brain regions, suggesting a reorganization of the brain network hubs and potential pathways for seizure propagation. Using the intrinsic ignition framework provided insights into dynamic alterations in the brain networks of patients with epilepsy. These have increased our understanding of the mechanisms underlying epileptic seizures and may guide the development of diagnostic biomarkers and targeted therapeutic interventions.

The causal association between epilepsy and amyotrophic lateral sclerosis: A two-sample Mendelian randomization study.

Epilepsy and amyotrophic lateral sclerosis (ALS) are common neurological disorders. The association between the two disorders has been raised in observational studies. However, it is uncertain to what extent they have mutual causal effects. In this study, we aimed to investigate their causal association using a two-sample Mendelian randomization (MR) method. We performed a two-sample bidirectional MR analysis to evaluate the causal association of epilepsy with the risk of ALS. Publicly published genome-wide association study statistics for epilepsy and ALS were used in the study. The primary analysis included genetic variants with a p value of less than 1 × 10-5 as instrumental variables. We applied several alternative methods, including inverse variance weighting, weighted median, simple mode, weighted mode, MR-Egger regression and MR pleiotropy residual sum and outlier, and statistical graphs to assess the associations of epilepsy and its subtype with the risk of ALS. Reverse MR analyses were also performed to examine the association of ALS with the risk of epilepsy. The primary MR analysis found no causal effect of epilepsy on risk of ALS (odds ration [OR]: 1.133, 95% confidence interval [CI]: 0.964-1.332, p=.130). Among subtypes of epilepsy, it also failed to observe any causal association between general epilepsy and ALS (OR: 1.036, 95% CI: 0.969-1.108, P=.300). However, focal epilepsy contributed to an increase in the risk of ALS (OR: 1.177, 95% CI: 1.027-1.348, p=.019). Moreover, the investigation of reverse causalities did not reveal significant results. The current study supports a causal influence of focal epilepsy on ALS risk. Future studies are needed to explore its potential role in ALS.

Kindling Models of Epileptogenesis for Developing Disease-Modifying Drugs for Epilepsy.

Kindling models are widely used animal models to study the pathobiology of epilepsy and epileptogenesis. These models exhibit distinctive features whereby sub-threshold stimuli instigate the initial induction of brief focal seizures. Over time, the severity and duration of these seizures progressively increase, leading to a fully epileptic state, which is marked by consistent development of generalized tonic-clonic seizures. Kindling involves focal stimulation via implanted depth electrodes or repeated administration of chemoconvulsants such as pentylenetetrazol. Comparative analysis of preclinical and clinical findings has confirmed a high predictive validity of fully kindled animals for testing novel antiseizure medications. Thus, kindling models remain an essential component of anticonvulsant drug development programs. This article provides a comprehensive guide to working protocols, testing of therapeutic drugs, outcome parameters, troubleshooting, and data analysis for various electrical and chemical kindling epileptogenesis models for new therapeutic development and optimization. The use of pharmacological agents or genetically modified mice in kindling experiments is valuable, offering insights into the impact of a specific target on various aspects of seizures, including thresholds, initiation, spread, termination, and the generation of a hyperexcitable network. These kindling epileptogenesis paradigms are helpful in identifying mechanisms and disease-modifying interventions for epilepsy. © 2024 The Author(s). Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Hippocampal kindling Basic Protocol 2: Amygdala kindling Basic Protocol 3: Rapid hippocampal kindling Basic Protocol 4: Chemical kindling.