The extracellular matrix (ECM) is composed of proteoglycans and glycoproteins that regulate the external environment surrounding neurons, glia, and the vascular system. The ECM is vital for maintaining the structure and function of the brain and also acts as a reservoir for various signaling molecules and neurotransmitters, modulating synaptic transmission and plasticity. Recent research highlights the important role of ECM proteins in both brain development and various neurological diseases, including epilepsy. Alterations in ECM composition and subsequent remodeling may disrupt physiological network excitability and synaptic connectivity, triggering neuroinflammation with active participation from glial cells, including astrocytes and microglia, and blood-brain barrier function. This influences neuronal function and contributes to the formation of epileptic foci and the development of drug-resistant epilepsy. Understanding the intricate interplay between the ECM and epilepsy may enable the identification of novel biomarkers and development of therapeutic strategies targeting this dynamic microenvironment. In this review, we provide a summary of the discussions held at the XVII Workshop on Neurobiology of Epilepsy (WONOEP), organized in 2023 by the International League Against Epilepsy, on the role of the extracellular space in epilepsy. Specifically, we summarize recent advances in understanding the ECM, its alterations in epilepsy, advanced imaging and omics tools for ECM analysis, and the implications for the development of ECM-based therapeutics and biomarkers for acquired and genetic forms of epilepsy. To complement the material presented at WONOEP, we performed targeted, nonsystematic literature searches in PubMed using topic-specific terms (e.g., "perineuronal nets", "extracellular matrix", "traumatic brain injury", "post-traumatic epilepsy", "chloride") and citation tracking to ensure that key experimental and translational studies relevant to these themes were included.

Postictal deficits are a well-recognized phenomenon, yet their mechanisms and predictors remain poorly understood. Distinguishing postictal deficits from recurring nonconvulsive seizures (NCSz) or nonconvulsive status epilepticus (NCSE), their main differential diagnosis, can be challenging. This study aimed to identify clinical and electrographic features predictive of ongoing or recurrent ictal activity and to explore biomarkers associated with the duration and severity of postictal deficits. We conducted a retrospective case-control study of patients with prolonged (>1 h) postictal deficits at a tertiary medical center between 2017 and 2022. Based on electroencephalographic (EEG) findings, patients were classified as having uncomplicated Todd's palsy or recurring NCSz. Clinical, imaging, and electrographic characteristics were compared between groups, and factors associated with postictal duration were analyzed. Among 112 patients, 86 (77%) had uncomplicated Todd's palsy and 26 (23%) had recurring NCSz. Patients with NCSz were younger (63 vs. 76 years, p = .022) and had longer deficits (2.5 vs. 1.5 days, p = .024). Sporadic epileptiform discharges (73% vs. 22%, p < .001) and rhythmic or periodic discharges on the ictal-interictal continuum (50% vs. 16%, p = .001) were significantly more frequent in the NCSE group, even when limited to short EEGs or the first 30 min of continuous EEG (96% vs. 40%, p < .001). Consequently, 2HELPS2B scores were higher in NCSE patients (2 vs. 1, p = .0065). In the uncomplicated Todd's palsy group, a preceding focal to bilateral tonic-clonic seizure (1.5 vs. 1.0 days, p = .04) and any rhythmic or periodic discharges on EEG (3.0 vs. 1.5 days, p = .003) were associated with longer deficit duration. A notable minority of patients with prolonged postictal deficits have recurring NCSz. In the absence of reliable clinical or imaging predictors, patients with prolonged deficits may benefit from a 30-min EEG followed-when 2HELPS2B score > 1-by extended continuous EEG monitoring.

Balancing the potential benefits and harms of antiseizure medications (ASMs) remains a central challenge in epilepsy care. Although randomized trials routinely report efficacy and adverse-event outcomes, these are typically presented separately, limiting their usefulness for shared decision-making. The Likelihood of Being Helped versus Harmed (LHH)-the ratio of the number needed to harm (NNH) to the number needed to treat (NNT)-offers a simple, intuitive way to integrate these dimensions into a single measure. Using data from a previously published comparative analysis, this brief report illustrates how the LHH can summarize the relative probability of achieving a clinical benefit vs experiencing a treatment-related harm. As an example, an ASM with an LHH of 1.9 would be interpreted as being almost twice as likely to produce a ≥50% seizure reduction as to lead to discontinuation due to adverse effects, whereas an LHH below 1 would indicate that harm is more likely than benefit. These examples demonstrate how the LHH can support clearer communication of benefit-harm trade-offs and complement emerging tools for individualized seizure-risk prediction.

Sigma-1 is a chaperone protein that serves as a key homeostatic regulator, implicated in neuronal excitability and seizure control. Positive allosteric modulators offer a use-dependent means to enhance Sigma-1 activity, potentially with favorable tolerability compared to direct agonists. This study examined the role of sigma-1 in ictogenesis, seizure spread, and termination, and evaluated whether sigma-1 targeting could modify progression in the amygdala kindling model. Using the mouse amygdala kindling paradigm, we assessed the effects of subchronic administration of the sigma-1 positive allosteric modulator E1R and of the antiseizure medication fenfluramine on seizure thresholds, severity, duration, and progression of kindling. Tolerability, behavioral outcomes, and potential disease-modifying effects were evaluated. Additional experiments investigated the influence of sigma-1 antagonism (NE-100) and genetic sigma-1 deficiency on E1R efficacy and seizure development. E1R delayed kindling acquisition, increased seizure thresholds in both naïve and kindled animals, and reduced seizure duration without evidence of tolerance or significant adverse effects. Subchronic E1R exposure slowed or prevented progression to generalized seizures, although effects did not persist after drug withdrawal. Sigma-1 deficiency prolonged seizure duration, supporting a role in the termination of endogenous seizures. High-dose NE-100 partially antagonized E1R effects, whereas genetic deficiency did not, possibly due to compensatory mechanisms. Fenfluramine did not affect kindling progression in this model. Positive allosteric modulation of sigma-1 attenuates ictogenesis and seizure severity and appears to contribute to endogenous seizure-termination mechanisms. Although E1R influences seizure generation in response to repeated stimulation, it does not produce sustained disease-modifying effects after discontinuation. These findings support a functional role of sigma-1 positive allosteric modulators as promising candidates for seizure management in the model used. The absence of persistent effects after withdrawal argues against disease modification under the current conditions and warrants further investigation in chronic epilepsy models evaluating long-term therapeutic, disease-modifying, or preventive potential.

This study was undertaken to characterize the functional impact of novel SLC12A5 variants in two unrelated patients with early onset developmental and epileptic encephalopathy (DEE) and to investigate the mechanisms underlying KCC2 dysfunction. Clinical, genetic, and functional analyses were performed in two patients (Cases A and B) with DEE. SLC12A5 encodes two KCC2 splice isoforms (KCC2a and KCC2b). Functional effects of the identified variants on KCC2b ion transport, phosphorylation, mRNA processing, and KCC2-dependent synaptogenesis were assessed using invitro assays in heterologous expression systems and primary neurons, supported by in silico structural modeling. Both patients developed severe neonatal onset DEE characterized by developmental delay, axial hypotonia, extrapyramidal features, and bilateral migratory seizures within 24 h of birth. Both cases resulted in early mortality (Case A at 9 years; Case B at 6 months). Sequencing revealed distinct biallelic compound heterozygous SLC12A5 variants in both individuals, each inherited from one unaffected parent. Functional analyses demonstrated that in Case A, one variant markedly reduced KCC2-mediated ion transport, whereas the second variant preserved transport activity but exhibited an altered phosphorylation profile at Ser940, located on the intracellular C-terminal region. This variant also disrupted wild-type (WT) KCC2-dependent excitatory synapse formation in immature rat hippocampal neurons. In Case B, one variant disrupted normal mRNA transcript processing consistent with loss of expression, and the second variant exhibited reduced ion transport activity. These data demonstrate that SLC12A5-related DEE can result from combined impairment of KCC2-dependent chloride homeostasis and disruption of chloride-independent KCC2 functions critical for early neuronal development. This work expands the mutational and mechanistic spectrum of SLC12A5-DEE and highlights the importance of KCC2 regulatory roles in early brain development, providing new knowledge and tools for basic research and potential avenues for targeted precision therapies.

Abstract Objective The ongoing conflict in Ukraine has created a severe humanitarian crisis, disproportionately affecting vulnerable populations such as children with chronic conditions. We set out to determine information about mental health in children with epilepsy in Ukraine affected by the conflict. Methods Mental health outcomes in 213 Ukrainian children with epilepsy during the conflict were screened using standardized instruments for post‐traumatic stress disorder (PTSD; Harvard Trauma Questionnaire), anxiety (7 item Generalized Anxiety Disorder module, GAD‐7), depression (Patient Health Questionnaire‐9, PHQ‐9), and epilepsy severity (Global Assessment of Severity of Epilepsy scale, GASE). Data were collected between February and June 2023 through self‐ or proxy‐completed surveys. Results Participants (14.6%) screened positive for PTSD symptoms, with girls significantly more affected than boys. A high proportion screened positive for symptoms of anxiety and depression, with 22% in the range for severe anxiety and 55% in the moderate‐to‐severe depression range. Epilepsy severity strongly correlated with mental health burden. Access to care was severely disrupted: 76% reported difficulty obtaining antiseizure medications, and 51% struggled to access medical services, contributing to increased seizure frequency in 56% of cases. Regression analyses identified epilepsy severity and barriers to medical care as key predictors of adverse mental health outcomes. Significance These findings underscore the compounded impact of war and chronic illness on children's psychological well‐being and highlight the urgent need for trauma‐informed, multilevel interventions, and improved access to health care for this vulnerable population.

To delineate morphometric similarity network (MSN) topological abnormalities and their underlying spatial transcriptomics in the normal-appearing cortex of unilateral mesial temporal lobe epilepsy with hippocampal sclerosis (mTLE-HS). High-resolution T1-weighted magnetic resonance imaging (MRI) from 109 unilateral mTLE-HS patients (64 left, 45 right) and 90 matched controls were analyzed to construct individual-level MSNs by integrating five cortical morphometric features. Graph-theoretical analysis quantified global and local network topology, and machine-learning models assessed their values in patient identification and epileptogenic lateralization, with performance further evaluated in an independent validation dataset. Further connectome-transcriptome association analyses linked these macroscale topological abnormalities to the microscale substrates in specific gene expressions, biological pathways, cellular compositions, and neurodevelopmental windows. Patients exhibited global small-worldness increase and local nodal reorganizations, with hyper-connectivity in default mode and limbic networks and hypo-connectivity in temporo-occipital cortex. These MSN-topology abnormalities enabled accurate patient classification (77.4%) and epileptogenic lateralization (83.2%), driven predominantly by features from limbic network (40.0% and 41.1%, respectively). These performances were reproducible in an independent validation dataset (classification accuracy = 75.4%, lateralization accuracy = 77.1%). Spatial transcriptomics mapped the MSN-topology alterations to expression of genes enriched in RNA processing and mitochondrial energy metabolism, including key epilepsy risk genes such as DNM1 and PPFIA3. These genes showed enriched expression in excitatory neurons, astrocytes, and oligodendrocytes, peaking during neurodevelopment in early-fetal striatum and neonatal-to-childhood cortex. MSN topology delineates the pattern of cortical network reorganization in mTLE-HS, aiding in patient identification and lateralization. The convergence of these macroscale connectomic alterations with microscale transcriptomic profiles points to an RNA-metabolic interplay that shapes cortical vulnerability of mTLE-HS in a progressive way.

To estimate the incidence and determine the consequences of status epilepticus (SE) associated with idiopathic generalized epilepsy (IGE) in adults. Based on International Classification of Diseases, Tenth Revision (ICD-10) codes we extracted patients with IGE in the period from January 1, 2005 to December 31, 2018, and divided them into two groups: patients with and without a hospitalization with SE before the end of the study. Each patient was matched with 10 normal population controls from the Danish National Patient Register based on age, sex, and geography. Survival, drug resistance, medical history, and surrogate markers for social status were compared. We identified 6295 IGE patients and 62 950 normal population controls with slight female preponderance (3338 female; 55.5%). At least one admission with SE was documented for 4.5% (n = 283 patients), of which 57.2% (n = 162) had two or more admissions with SE. The comparison of patients with and without SE before first-time admission for SE showed higher age, surrogate markers for lower social status (affiliation with the labour market, household income, marital status), indicators of more severe IGE (number of antiseizure medications tried, prescription patterns suggestive for drug resistance), and higher psychiatric comorbidity in patients with SE than without. It is important to note that an episode of SE only transiently and slightly affected markers for social status. All-cause mortality was increased in IGE patients with SE (17.7%) as compared to 6.2% in age-matched population controls. SE in IGE has a high rate of occurrence and is associated with drug-resistant IGE, poor social status, and psychiatric comorbidity already before the first episode of SE. Although the social impact of SE in the short term remains limited, all-cause mortality after SE is increased.

Seizures are among the most common symptoms of cerebral arteriovenous malformations (AVMs). Although the main goal of AVM treatment remains complete obliteration, seizure control has become an important treatment aspect in recent years. Thus, we analyzed seizure control following Gamma Knife Radiosurgery (GKRS) treatment at our department in patients with AVMs. We analyzed 130 patients with AVMs who had at least one seizure before treatment with GKRS at our tertiary referral center between 1992 and 2022. We analyzed predictors for treatment success, including AVM size, Virginia Radiosurgery AVM Scale, Radiosurgery-Based AVM Score, Spetzler-Ponce class, Spetzler-Martin grade, localization, and identified independent predictors of seizure persistence. Median follow-up was 9.7 years. Improved seizure control was documented for 89% of patients. Seizure-free status after radiosurgery was achieved for 78% of patients. Spetzler-Ponce class C (odds ratio [OR] = 4.6) and having multiple seizures before the first GKRS treatment (OR = 3.5) were independent predictors for seizure persistence. Still, 72% of patients with multiple seizures prior to AVM treatment were seizure-free at last follow-up. Among patients with multiple seizures, having a high-grade AVM was identified as an independent predictor of seizure persistence (OR = 12.1). GKRS, as a stand-alone management option or in combination with endovascular therapy, is an effective treatment option in AVM management, not only to achieve AVM obliteration but also to control AVM-related seizures. The Spetzler-Ponce class is a powerful predictor of seizure persistence at last follow-up, especially in patients with multiple seizures prior to treatment.

Nonconvulsive epileptic activity is common after acute brain injury and contributes to neuronal injury and poor outcomes. Although intracranial electroencephalography (iEEG) improves detection compared with surface EEG (suEEG), it currently relies on focal recordings of epileptic dynamics. We prospectively evaluated multielectrode iEEG strategies designed to achieve large-scale cortical and deep brain coverage in critically ill patients. In a prospective cohort of adults with acute brain injury requiring invasive neuromonitoring, we implemented four depth electrode-based iEEG techniques: three electrocorticographic approaches (open subdural, burr hole subdural, and foramen ovale) and one stereotactic (transcortical) approach. The primary objective was to establish and quantify the extent and durability of cortical recordings. Additional assessments included safety, feasibility, and management impact. Electrode localization was performed in MNI305 space, and recording longevity was assessed using Kaplan-Meier and Cox proportional hazards models. Thirty patients with severe brain injury underwent implantation of 64 electrodes (772 contacts), yielding 361 total iEEG recording days across heterogeneous etiologies and surgical settings. Multielectrode implantation enabled distributed sampling spanning multilobar frontoparietotemporal cortical clusters. Overall, 72% of electrodes sampled cortical convexity alone, whereas 28% incorporated deep targets, including mesial temporal and orbitofrontal regions. Recording durability differed by implantation strategy (log-rank p = .0002), with a mean combined iEEG-suEEG monitoring duration of 14.5 days per patient. Implantation was successful in >95% of electrodes, monitoring started within 24 h postoperatively in 88%, and the per-electrode risk of a causally related adverse event was 3.1%, without hemorrhagic complications. iEEG influenced treatment initiation or escalation in 32% of monitored patients. Multielectrode iEEG strategies enable durable, large-scale cortical sampling in acute brain injury while remaining feasible and safe in the intensive care unit. By shifting from focal to distributed spatial sampling, these approaches provide a conceptual framework for improving detection of epileptic activity in critically ill patients.