Normative modeling is increasingly used to characterize typical growth trajectories and identify atypical neurodevelopment, including early brain development using magnetic resonance imaging (MRI) acquired before birth. Recent work has emphasized the importance of large sample sizes for accurate and robust centile estimation. In this study, we investigate how image quality influences fetal brain normative models, a critical factor in this context where MRI is acquired on a moving fetus in utero. Using a multi-centric cohort of 635 fetal MRI scans, we applied a standardized visual quality control (QC) protocol with continuous quality ratings. We fit normative models for multiple brain structures under progressively relaxed QC stringency, and quantified the deviations in centile estimates relative to a high-quality reference subgroup. Our results showed that including lower-quality data systematically biased normative centiles, with the strongest effects observed in the outer centiles, particularly the lower tail (1st-10th). Bias increased progressively as QC stringency was relaxed and could not be attributed solely to the number of scans used to fit the models. Quality-induced bias was structure dependent, and often not visually apparent at the segmentation level. These findings highlight that image quality is an important source of bias in normative fetal brain modeling, and that increasing sample size at the expense of quality may systematically affect centile estimates, potentially jeopardizing the utility of the model.

Background and ObjectivesDevelopmental and epileptic encephalopathies (DEEs) with early burst-suppression EEG (EIDEE-BS) are among the most severe neonatal epileptic syndromes, typically presenting in the first months of life with refractory seizures and profound neurodevelopmental impairment. Although variants in the KCNQ2, STXBP1, and SCN2A genes are recognized as major causes, the full genetic spectrum remains uncertain. We aimed to delineate the electroclinical characteristics, genetic etiologies, and long-term outcomes in a large MRI-negative EIDEE-BS cohort.MethodsWe retrospectively analyzed 110 patients with BS EEG enrolled from a database of 1,540 individuals with suspected genetic epilepsies (2008-2023). Clinical, EEG, and genetic data were systematically collected. Patients were stratified into 4 groups: KCNQ2, STXBP1, "other pathogenic variants," and "without a genetic diagnosis." EEG traces were reviewed independently, and outcomes were assessed through long-term follow-up.ResultsPathogenic or likely pathogenic variants were identified in 62.7% of patients and involved 23 genes, including 2 copy number variants. KCNQ2 (n = 24) and STXBP1 (n = 16) accounted for one-third of diagnoses, whereas SCN2A (n = 3) and KCNT1 (n = 2) were less frequent. In KCNQ2 cases, seizures and BS onset occurred earlier than in STXBP1 cases: mean 2 days vs 6 weeks for seizures and 3 days vs 2 months for BS, respectively. A typical BS pattern (bursts longer than suppressions) strongly correlated with KCNQ2 and STXBP1 variants. Novel associations were found with DPM1, GRIN2A, KCNT2, PIGO, PURA, WWOX, and candidate genes (KMT2E, SNAP25, and SYT1). Most variants were de novo heterozygous; however, recessive and X-linked inheritance patterns were also observed. Mortality was high (25%), primarily from status epilepticus and complications of severe disability. Most patients (72.5%) had persistent seizures at follow-up (a mean of 6.5 years), as well as profound intellectual disabilities, irrespective of genotype.DiscussionThis large series highlights the strong monogenic basis of EIDEE-BS. KCNQ2, STXBP1, and SCN2A were the most commonly affected genes. Early EEG features, particularly BS timing and morphology, can help anticipate the underlying genotype and guide precision therapy, including the early use of sodium channel blockers in selected cases. These findings support recent ILAE reclassification efforts and underscore the importance of comprehensive genomic testing for improved diagnosis and counseling.

Small nuclear RNAs (snRNAs) are essential components of the spliceosome. De novo variants in snRNA genes RNU4-2 (ReNU syndrome), RNU5B-1 and RNU2-2 have been linked to dominant neurodevelopmental disorders (NDDs), revealing a large unexpected contribution of noncoding RNA genes to genetic diseases. Here, through international collaborations, we analyze systematically 200 potentially functional snRNA genes in a French cohort of 34,329 people with rare disorders. We report RNU2-2 variants in 141 individuals, including 35 with recurrent dominant pathogenic variants and 91 affected members from 73 families with biallelic variants. Recessive RNU2-2 NDD is at least twice as frequent as the dominant form and often involves a de novo variant in trans with an inherited allele, consistent with the high mutability of snRNA genes. Dominant and recessive RNU2-2 NDDs share overlapping clinical features, with frequent epilepsy. Blood transcriptomics and DNA methylation analyses revealed subtle, variant-specific effects on splicing and episignatures. Our results support a gradient-of-impact model bridging dominant and recessive inheritance, and establish RNU2-2 variants as a principal contributor to NDDs, nearly as prevalent as ReNU syndrome.

Magnetic resonance imaging of fetal and neonatal brains reveals rapid neurodevelopment marked by substantial anatomical changes unfolding within days. Studying this critical stage of the developing human brain, therefore, requires accurate brain models—referred to as atlases—of high spatial and temporal resolution. To meet these demands, established traditional atlases and recently proposed deep learning-based methods rely on large and comprehensive datasets. This poses a major challenge for studying brains in the presence of pathologies for which data remains scarce. We address this limitation with CINeMA (Conditional Implicit Neural Multi-Modal Atlas), a novel framework for creating high-resolution, spatio-temporal, multimodal brain atlases, suitable for low-data settings. Unlike established methods, CINeMA operates in latent space, avoiding compute-intensive image registration and reducing atlas construction times from days to minutes. Furthermore, it enables flexible conditioning on anatomical features including gestational age, birth age, and pathologies like agenesis of the corpus callosum and ventriculomegaly of varying degree. CINeMA supports downstream tasks such as tissue segmentation and age prediction whereas its generative properties enable synthetic data creation and anatomically informed data augmentation. Surpassing state-of-the-art methods in accuracy, efficiency, and versatility, CINeMA represents a powerful tool for advancing brain research. We release the code and atlases at https://github.com/m-dannecker/CINeMA.

Aminoacyl-tRNA synthetases (aaRSs) are multi-domain enzymes that, in addition to their catalytic and tRNA-anticodon-binding domains, may include clade-specific extra regions conferring unique properties. These extra domains are poorly characterized in mitochondrial aaRSs (ARS2), complicating genetic diagnosis. ARS2 enzymes are essential for mitochondrial translation, broadly expressed, and pathogenic variants in any domain can cause varied neurological disorders. Here, we show how diagnosis challenge leads to a fundamental discovery. PARS2 deficiency, caused by pathogenic variantsin the nuclear gene encoding mitochondrial prolyl-tRNA synthetase (ProRS), was reported in few patients. Here, we describe two unrelated patients with epileptic encephalopathy who carry biallelic PARS2 variants including one novel variant predicted as "likely benign" due to poor interspecies conservation of the impacted region.First, through thorough phenotypic evaluation, we confirmed that both patients' clinical features match those of a cohort of 22 patients previously reported with PARS2 deficiency. Next, using comparative protein-structure modeling and a detailed clade-specific analysis of sequence conservation, we discovered that this variant actually falls within a previously unrecognized zinc-binding domain (ZBD), structurally similar to the well-characterized and essential ZBD found in cytosolic ProRS. Our findings underscore the limitations of existing tools for predicting the pathogenicity of ARS2 variants and demonstrate the value of integrating structural modeling with evolutionary conservation analysis. In conclusion, this work not only reveals a critical ZBD in PARS2, offering new insights into its structural and functional properties but also expands the genotypic spectrum of PARS2-related disorders and provides a comprehensive description of the associated phenotypes.

De novo mutations in the Stxbp1 gene lead to Munc18.1 haploinsufficiency and are a major cause of neurodevelopmental disorders. Because Munc18.1 is essential for vesicular exocytosis, most electrophysiological investigations have focused on synaptic transmission and much less on intrinsic neuronal properties. In addition the potential developmental dependence of these effects is unknown. Here, using acute brain slices from neonatal and juvenile Stxbp1 heterozygous mice, we examined the intrinsic excitability of CA1 hippocampal and motor cortical layers II/III pyramidal neurons as well as spontaneous and evoked glutamatergic and GABAergic synaptic transmission recorded in these cells. In neonatal mice, Munc18.1 haploinsufficiency leads to a marked increase in intrinsic excitability in both hippocampal and neocortical pyramidal neurons. In juvenile mice, intrinsic properties appear largely normalized, but evoked synaptic transmission is impacted with a higher sensitivity of glutamatergic synapses than of GABAergic synapses to high-frequency electrical stimulation. In contrast, spontaneous synaptic activity mediated by glutamate and GABA receptors remains unchanged at both developmental stages, suggesting that basal synaptic drive is preserved. We also performed western blot analysis and show that Munc18.1 deficiency is associated with a reduction of t-SNARE protein expression in the hippocampus and neocortex of juvenile, but not neonatal mice. Together, these findings indicate that Munc18.1 deficiency induces stage dependent electrophysiological and biochemical alterations. We hypothesize that early changes involve disrupted of certain ion channels function/expression and that the later reduction of t-SNARE proteins in juvenile may play a role in the normalization of neuronal excitability.

BACKGROUND AND OBJECTIVES:Developmental and epileptic encephalopathies (DEEs) with early burst-suppression EEG (EIDEE-BS) are among the most severe neonatal epileptic syndromes, typically presenting in the first months of life with refractory seizures and profound neurodevelopmental impairment. Although variants in the KCNQ2, STXBP1, and SCN2A genes are recognized as major causes, the full genetic spectrum remains uncertain. We aimed to delineate the electroclinical characteristics, genetic etiologies, and long-term outcomes in a large MRI-negative EIDEE-BS cohort. METHODS:We retrospectively analyzed 110 patients with BS EEG enrolled from a database of 1,540 individuals with suspected genetic epilepsies (2008-2023). Clinical, EEG, and genetic data were systematically collected. Patients were stratified into 4 groups: KCNQ2, STXBP1, "other pathogenic variants," and "without a genetic diagnosis." EEG traces were reviewed independently, and outcomes were assessed through long-term follow-up. RESULTS:Pathogenic or likely pathogenic variants were identified in 62.7% of patients and involved 23 genes, including 2 copy number variants. KCNQ2 (n = 24) and STXBP1 (n = 16) accounted for one-third of diagnoses, whereas SCN2A (n = 3) and KCNT1 (n = 2) were less frequent. In KCNQ2 cases, seizures and BS onset occurred earlier than in STXBP1 cases: mean 2 days vs 6 weeks for seizures and 3 days vs 2 months for BS, respectively. A typical BS pattern (bursts longer than suppressions) strongly correlated with KCNQ2 and STXBP1 variants. Novel associations were found with DPM1, GRIN2A, KCNT2, PIGO, PURA, WWOX, and candidate genes (KMT2E, SNAP25, and SYT1). Most variants were de novo heterozygous; however, recessive and X-linked inheritance patterns were also observed. Mortality was high (25%), primarily from status epilepticus and complications of severe disability. Most patients (72.5%) had persistent seizures at follow-up (a mean of 6.5 years), as well as profound intellectual disabilities, irrespective of genotype. DISCUSSION:This large series highlights the strong monogenic basis of EIDEE-BS. KCNQ2, STXBP1, and SCN2A were the most commonly affected genes. Early EEG features, particularly BS timing and morphology, can help anticipate the underlying genotype and guide precision therapy, including the early use of sodium channel blockers in selected cases. These findings support recent ILAE reclassification efforts and underscore the importance of comprehensive genomic testing for improved diagnosis and counseling.

Pathogenic KCNQ2 variants are the most common genetic cause of neonatal-onset epilepsies, with phenotypes ranging from self-limited (familial) neonatal epilepsy (SeL(F)NE) to severe developmental and epileptic encephalopathy (KCNQ2-DEE). Sodium channel blockers (SCBs) have shown promise for seizure control in these disorders, but their impact on neurodevelopmental outcomes and possible relationship with timing of initiation remain incompletely understood. We leveraged a large, multicentre international cohort comprising 282 individuals with pathogenic KCNQ2 variants to retrospectively assess the effectiveness of antiseizure medications (ASMs), particularly SCBs, on seizure control and neurodevelopment. Individuals were grouped according to the predicted variant-specific functional effects: loss-of-function (LOF) variants known to be associated with SeL(F)NE or DEE respectively, and gain-of-function (GOF) variants. Epilepsy course, ASM effectiveness, and neurodevelopmental milestones were systematically collected and analysed, including time-to-event and adjusted outcome analyses. SCBs, especially carbamazepine (CBZ) and oxcarbazepine (OXC), emerged as the most effective ASMs in both LOF groups. In LOF KCNQ2-DEE, time-to-event analyses showed that early SCB initiation (≤1 month) was associated with earlier seizure offset. Early SCB initiation was also associated with significantly more favourable neurodevelopmental outcomes, including higher rates of attaining major motor milestones. This association remained significant after adjustment for seizure control by 1 month and total ASM burden. Considerable phenotypic variability persisted, with some individuals experiencing severe impairment despite early seizure control and SCB initiation, suggesting that variant severity and additional genetic or biological modifiers contribute to outcome heterogeneity.Our results support the use of SCBs, particularly CBZ and OXC, as first-line therapy in (LOF) KCNQ2-DEE and SeL(F)NE. Earlier SCB initiation was associated with earlier seizure offset and more favourable developmental outcomes, underscoring the importance of early genetic diagnosis and timely SCB therapy. We however emphasise that early treatment is not universally transformative and further prospective work, including exploration of targeted therapies and standardised neurodevelopmental assessments, is needed to optimise long-term outcomes in this heterogeneous population.

Abstract Objective In KCNQ2-related disorders ( KCNQ2 -RD), neurodevelopmental outcome remains variable despite established genotype-phenotype correlations. Our aim is to improve counselling, by developing and internally validating models predicting neurodevelopmental outcomes based on early clinical and genetic features, universally available to clinicians. Methods We conducted a multicentric retrospective cohort study including 277 individuals carrying a (likely) pathogenic variant in the KCNQ2 gene, with a minimum follow-up age of three years. Mosaic variants were excluded. The cohort was randomly split into training (70%) and validation (30%) sets. Ten expert selected parameters with minimal missing data were used to train random forest models to predict (i) dichotomous outcomes and (ii) three-category outcomes for cognition, language, and gross motor milestones. Results Models incorporated seven clinical (neonatal hypotonia, EEG characteristics, age at seizure onset, seizure type, and seizure frequency at onset, prematurity, and sex) and three genetic variables ( de novo status, exon localisation, and position within known KCNQ2 -developmental and epileptic encephalopathy (DEE) hotspot regions). Dichotomous models showed the highest predictive performance, with accuracies of 0.83 for normal vs. mild-profound intellectual disability (ID), 0.83 for achievement of first words, and 0.86 for achievement of independent walking. Three-category models remained clinically informative: accuracies were 0.79 for normal vs. mild vs. moderate-profound ID, 0.70 for first words ≤16 months vs. >16 months vs. never, and 0.71 for independent walking ≤18 months vs. >18 months vs. never. The strongest predictors for adverse neurodevelopmental outcomes were presence of hypotonia at birth, seizure onset within the first day of life, multiple seizures per day at onset, tonic seizures at onset, a burst-suppression pattern on EEG at onset, the presence of a de novo variant, and variant location within exons 6-7. Significance These prediction models demonstrate the feasibility of early prognostication in KCNQ2 -RD and support future prospective external validation. They enable more accurate individualised counselling by integrating clinical and genetic information readily available at time of genetic diagnosis and provide an objective foundation for early intervention planning and future precision medicine trial stratification.

Background: Pathogenic KCNQ2 variants are the most common genetic cause of neonatal-onset epilepsies, with phenotypes ranging from self-limited (familial) neonatal epilepsy (SeL(F)NE) to severe developmental and epileptic encephalopathy (KCNQ2-DEE). Sodium channel blockers (SCBs) have shown promise for seizure control in these disorders, but their impact on neurodevelopmental outcomes and possible relationship with timing of initiation remain incompletely understood. Methods: We leveraged a large, multicentre international cohort comprising 282 individuals with KCNQ2 pathogenic variants to retrospectively assess the effectiveness of antiseizure medications (ASMs), particularly SCBs, on seizure control and neurodevelopment. Individuals were grouped according to the predicted variant-specific functional effects: loss-of-function (LOF) variants known to be associated with SeL(F)NE or DEE respectively, and gain-of-function (GOF) variants. Epilepsy course, ASM effectiveness, and neurodevelopmental milestones were systematically collected and analysed. Results: SCBs, especially carbamazepine (CBZ) and oxcarbazepine (OXC), emerged as the most effective ASMs in both LOF groups. In LOF KCNQ2-DEE, early SCB initiation within the first month of life was associated with significantly more favourable neurodevelopmental trajectories, including higher rates of achievement of major motor milestones. Early seizure freedom itself was a strong predictor of improved neurodevelopment, with the positive effect of SCBs likely mediated by their ability to control seizures. However, considerable phenotypic variability persisted, with some individuals experiencing severe impairment despite early seizure control and SCB initiation. Variant severity and possible genetic modifiers likely contribute to this heterogeneity, underscoring the need for precision therapies beyond nonspecific ASM approaches. Conclusion: Our results strongly support the use of SCBs as first-line therapy in (LOF) KCNQ2-DEE and SeL(F)NE due to their high effectiveness. Moreover, SCBs appear most beneficial when initiated during the neonatal period, with earlier treatment linked to earlier seizure offset and better developmental outcomes. These results highlight the importance of early genetic diagnosis and timely SCB therapy, and support CBZ or OXC as first-line agents. We however emphasise that early treatment is not universally transformative, and further work, including exploration of targeted therapies but also standardised neurodevelopmental assessments, is needed to optimise long-term outcomes in this heterogeneous population. ### Competing Interest Statement S.W. received consultancy fees from UCB, Xenon Pharmaceuticals, Lundbeck, Knopp Biosciences, Encoded Therapeutics, Angelini Pharma, and Roche. C.F. has served on scientific advisory board for longboard pharmaceuticals and biocodex and has received speaker honoraria from Nutricia, UCB, and Jazz Pharmaceuticals. S.A. is Deputy Editor for Epilepsia. He has received personal fees for lectures or advice from: Biocodex, Eisai, Encoded, GRIN therapeutics, Jazz Pharmaceuticals, Longboard, Lundbeck, Neuraxpharm, Nutricia, Mosaica, Proveca, Servier, Stoke, Stream neuroscience, UCB Pharma. He has been investigators for: Eisai, Lundbeck, Proveca, Takeda, UCB Pharma. I.E.S. has served on scientific advisory boards for Biocodex, BioMarin, CAMP4 Therapeutics, Chiesi, Eisai, Encoded Therapeutics, Knopp Biosciences, Longboard Pharmaceuticals, Mosaica Therapeutics, Takeda Pharmaceuticals, UCB; has received speaker honoraria from Akumentis, Biocodex, BioMarin, Chiesi, Eisai, GlaxoSmithKline, Liva Nova, Nutricia, Stoke Therapeutics, Zuellig Pharma; has received funding for travel from Biocodex, BioMarin, Eisai, Encoded Therapeutics, GlaxoSmithKline, Stoke Therapeutics, UCB; has served as an investigator for Anavex Life Sciences, Biohaven Ltd, Bright Minds Biosciences, Cerebral Therapeutics, Cerecin Inc, Cereval Therapeutics, Encoded Therapeutics, EpiMinder Inc, ES-Therapeutics, GW Pharma, Longboard Pharmaceuticals, Marinus, Neuren Pharmaceuticals, Neurocrine BioSciences, Ovid Therapeutics, Praxis Precision Medicines, Shanghai Zhimeng Biopharma, SK Life Science, Supernus Pharmaceuticals, Takeda Pharmaceuticals, UCB, Ultragenyx, Xenon Pharmaceuticals, Zogenix, Zynerba; and has consulted for Atheneum Partners, Biohaven Pharmaceuticals, Care Beyond Diagnosis, Cerecin Inc, Eisai, Epilepsy Consortium, Longboard Pharmaceuticals, Praxis, Stoke Therapeutics, UCB, Zynerba Pharmaceuticals; and is a Non-Executive Director of Bellberry Ltd and a Director of the Australian Academy of Health and Medical Sciences. She may accrue future revenue on pending patent WO61/010176 (filed: 2008): Therapeutic Compound; has a patent for SCN1A testing held by Bionomics Inc and licensed to various diagnostic companies; has a patent molecular diagnostic/theranostic target for benign familial infantile epilepsy (BFIE) [PRRT2] 2011904493 & 2012900190 and PCT/AU2012/001321 (TECH ID:2012-009). The remaining authors report no competing interests. ### Funding Statement C.M. received funding from University of Antwerp-BOF (FFB200262). S.W. received funding from Fonds Wetenschappelijk Onderzoek (FWO 1861424N), GSKE - UCB Award, European Partnership for Personalized Medicine (EPPerMed BEATKCNQ), KCNQ2e.v. L.V. and S.W. received funding from the European Joint Programme on Rare Disease JTC 2020 (TreatKCNQ). L.V. recieved funding from the Agence Nationale de la Recherche (ANR 19-CE17-0018-02). M.M. was supported by Aix Marseille Univ, Agence Nationale de la Recherche (ANR 19‐CE17‐0018‐02). A.T.G.C received funding from the National Health and Medical Research Council (NHMRC) Postgraduate Scholarship, Australia. E.C.C. received funding from the Jack Pribaz Foundation, the KCNQ2 Cure Alliance, the Miles Family Fund, and the parents of Raz Fisher. This work was supported by funding from the Australian National Health and Medical Research Council (GNT1091593, GNT1172897, GNT2006841, GNT2010562, GNT2033247) and Medical Research Future Fund Australia (GNT2007707). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Informed consent for participation and publication was obtained from all parents or legal guardians according to the Declaration of Helsinki. The study was approved by the Human Research Ethics Committees of the University Hospital of Antwerp (Belgium, number: 20/50/683) and the Committee for the Protection of Persons (Comite de Protection des Personnes Sud-Est III, France, IDRCB: 2020-A01363-36). Data are reported in line with the Strengthening Reporting of Observational Studies in Epidemiology (STROBE) statement. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data supporting the findings of this study are available to those eligible upon request to the corresponding author.

CTNNB1 monoallelic pathogenic variants account for up to 4% of genetically determined cerebral palsy cases, yet their phenotypic spectrum remains poorly defined. We retrospectively analyzed 25 individuals with pathogenic CTNNB1 variants using medical records and a questionnaire. Data included genetic variants, perinatal history, developmental milestones, behavioral characteristics, head growth, feeding, sleep difficulties, neurological and ophthalmological assessments. Brain MRIs were reviewed by expert neuroradiologists. Twenty-two distinct heterozygous variants were identified. Microcephaly occurred in 16/22 patients. All exhibited global developmental delay, independent walking was achieved at a mean age of 2.1 years, with regression in 4/16 independent walkers. Behavioral disorders were frequent, as were oral sensorimotor disorders (21/25) and sleep disturbances (13/21). Lower limb hypertonia was present in 22/25 patients [spastic (8) and/or dystonic (11)]. Unstable gait were common among ambulatory patients. Exaggerated startle reactions, often since birth, were reported in 16/21. Exudative vitreoretinopathy was identified in 3/5 patients with retinal angiography. Brain MRI (19 patients) showed: thickening of anterior commissure (8), frontal lobe hypoplasia (9), widening of superior vermian sulci (10) and corpus callosum anomalies (7). This study broadens the spectrum of CTNNB1-related syndrome, reporting a complex motor phenotype combining (i) gait disturbances related to dystonic or non-dystonic hypertonia and unsteadiness, sometimes associated to dystonia in other body parts (ii) possible deterioration of motor achievements over the course of the disease (iii) an exaggerated startle reflex. New non-specific brain anomalies are precisely described. Our work underscores the need for registries and longitudinal studies to refine characterization and guide future therapies.

ObjectiveCarbamazepine is the first line treatment for patients affected by KCNQ2 developmental and epileptic encephalopathy. It is efficient to reduce or stop seizures in this context. However, its effect on the neurodevelopmental outcomes is debated. The aim of this study was to evaluate the efficacy of long-term oral administration of carbamazepine in a mouse model of Kcnq2 dysfunction.MethodsMice were treated at weaning and during 70 days. The impact on seizures was measured, and blood samples were collected every week. At 3 months of age, all mice were tested using the Water T-maze and Barnes maze tests to evaluate their cognitive abilities. Brain tissue was collected to measure carbamazepine and carbamazepine-epoxide concentrations.ResultsAfter 70 days of carbamazepine treatment, the impact on seizures was strong in the Kcnq2-DEE mice, with 1 out of 12 treated knock-in mice having a seizure compared to 8 out of 13 mice receiving the vehicle. Carbamazepine efficacy on seizures was progressive and correlated to an accumulation of carbamazepine-epoxide in the brain. The cognitive abilities of treated knock-in mice at 3 months of age were similar to those of wild-type mice.SignificanceIn addition to validating this knock-in model as a model of anticonvulsant efficacy, these results reveal that carbamazepine-epoxide accumulates in the brain when given over a long period of time. They also show that chronic treatment with carbamazepine strongly impacts cognitive abilities in a mouse model of Kcnq2-DEE, questioning current treatment strategies in human patients.Plain Language SummaryThis study evaluated the long-term effects of a treatment with an antiepileptic drug called carbamazepine (CBZ). It was performed in a mouse model of a severe form of genetic epilepsy. The results showed that a chronic treatment with CBZ effectively reduced seizures. Treated mice also showed improved cognitive abilities. An accumulation of a modified form of CBZ was measured in the brain of the treated animals. These findings call for a reevaluation of the long-term effects of CBZ treatment in humans, as the animal data suggest potential beneficial effects that may not yet be fully appreciated in clinical practice.

BACKGROUND:Children with complex congenital heart disease (CCHD) are at high risk for early neurodevelopmental delays across all domains. Neuromotor delay often emerges first and may impact broader development. Identifying early biomarkers of motor function could capture a critical window for intervention. We assessed the prognostic value of neuron-specific enolase (NSE) and S100B in predicting 4-month motor outcomes in newborns undergoing cardiac surgery with cardiopulmonary bypass (CPB). METHODS:Between December 2021 and October 2024, we conducted a prospective, single-centre study including term neonates with (CCHD) who required cardiac surgery within the first two months of life. NSE and S100B levels were measured at five perioperative time points. Blinded Alberta Infant Motor Scale (AIMS) assessment at four months evaluated motor outcomes. RESULTS:Of 35 newborns, 27 completed follow-up. Preoperative NSE levels were significantly higher in infants with AIMS scores below the 10th percentile (32.7 vs. 20.9 ng/mL, p = 0.044) and negatively correlated with AIMS percentiles (ρ = -0.617, p = 0.006. There was no significant association between motor outcomes, MRI findings or S100B levels. CONCLUSIONS:Higher preoperative NSE levels predict poor early motor outcomes in CCHD and may be a marker for early risk stratification and intervention. IMPACT:Neuron-specific enolase (NSE) may serve as an early biomarker of neuromotor development in newborns with complex congenital heart disease (CCHD). Elevated preoperative NSE levels were associated with poorer motor outcomes at four months. NSE may serve as an additional biomarker within a multimodal risk stratification strategy, complementing clinical, imaging, and electrophysiological assessments to refine prognostic evaluation. These findings highlight the prognostic value of perioperative biomarkers for predicting early motor outcomes and support earlier identification of at-risk newborns, enabling targeted neurodevelopmental interventions. This work adds new evidence to limited literature on biological predictors of motor development after neonatal cardiac surgery.

Variants in spliceosomal small nuclear RNA (snRNA) genes RNU4-2 (ReNU syndrome), RNU5B-1, and RNU2-2 have recently been linked to dominant neurodevelopmental disorders (NDDs), revealing a major, previously overlooked role for noncoding snRNAs in human disease. Here, we systematically analysed 200 potentially functional snRNA genes in a French cohort comprising 26,911 individuals with rare disorders and through international collaborations. We identify de novo and biallelic variants in RNU2-2 associated with both dominant and recessive NDDs in 126 individuals from 108 unrelated families. Recessive RNU2-2 NDD is at least twice as frequent as the dominant NDD caused by n.4G>A and n.35A>G, and often arises from a de novo variant in trans with an inherited allele, reflecting the high mutability of snRNA genes. Dominant and recessive RNU2-2-NDDs share overlapping clinical features with frequent epilepsy. Blood transcriptomics and DNA methylation analyses revealed subtle, variant-specific effects on splicing and episignatures. Our findings support a gradient-of-impact model and a continuum between dominant and recessive inheritance, establishing RNU2-2 variants as a frequent cause of NDDs, nearly as prevalent as ReNU syndrome.

Pathogenic variants in gamma-aminobutyric acid type A (GABAA) receptor subunit genes are increasingly associated with epilepsy and neurodevelopmental disorders. Pathogenic variants in GABRA2, encoding the alpha-2 subunit of GABAA receptors, have been recently reported. This study aims to better delineate the phenotypic spectrum of GABRA2 pathogenic variants. We conducted a retrospective multicenter study, analyzing six new patients with GABRA2 pathogenic variants identified through a French national collaboration. Clinical, electroencephalographic (EEG), and genetic data were reviewed alongside a literature analysis of eight previously reported cases. Two distinct electroclinical phenotypes were identified. The most severe, in four of six patients, featured early infantile developmental and epileptic encephalopathy with an EEG pattern of rapid rhythms suggestive of GABAergic hyperactivity. The milder phenotype, in two of six patients, included later onset, drug-responsive epilepsy with moderate developmental delay. A literature review confirmed these phenotypes and supported genotype-phenotype correlations, with transmembrane domain variants more frequently associated with severe phenotypes. This study refines the phenotypic spectrum of GABRA2-related disorders, highlighting two distinct electroclinical phenotypes. The identification of a recognizable EEG pattern of unusual rapid rhythms for age may be a biomarker for early diagnosis of a severe phenotype and suggests a potential underlying gain-of-function mechanism, to be confirmed by functional studies.

BACKGROUND:Epileptic disorders are a heterogeneous group of neurological conditions, with many cases linked to monogenic causes, particularly in developmental and epileptic encephalopathies (DEE). Identifying pathogenic variants aids treatment, prognosis, and family planning. In France, genetic testing is coordinated through the EpiGene network. METHODS:We analyzed clinical and genetic data from 2563 epilepsy patients referred to four diagnostic labs (2016-2023). Epilepsy syndromes were classified via pre-test questionnaires, and genotyping used various gene panels, including a 68-gene core panel. Multivariate logistic regression assessed diagnostic rates and genotype-phenotype correlations. RESULTS:Overall, 27.0% of patients had pathogenic/likely pathogenic variants, mainly within the core panel (24%). SCN1A and KCNQ2 were the most frequently mutated genes. Diagnostic yield varied by syndrome, with Dravet Syndrome Spectrum (DSS) and early-infantile DEE (EIDEE) showing the highest rates (41% and 34%, respectively). Genetic heterogeneity differed across syndromes, from DSS (predominantly SCN1A) to Infantile Epileptic Spasms Syndrome (IESS, 12%), involving ≥ 26 genes. Outside DEE, self-limited neonatal epilepsy (SeLNE) had the highest yield (50%). Earlier seizure onset was associated with a higher likelihood of a positive molecular diagnosis, whereas intellectual disability severity and drug resistance were not independently predictive of diagnostic outcome. Genotype-phenotype correlations highlighted that objective clinical data (e.g., age of onset) can outperform syndrome labels (e.g., EIDEE) in predicting diagnosis. CONCLUSION:This large cohort study refines the genetic landscape of epilepsy, informs classification challenges, and enhances genetic testing strategies, ultimately improving patient care and future research directions.

BACKGROUND:Leigh syndrome or subacute necrotizing encephalomyelopathy was first recognized as a neuropathological entity in 1951. It is a progressive neurological disease characterized by neuroradiological lesions, particularly in the brainstem and basal ganglia. Leigh's syndrome is a pan-ethnic disorder with onset usually in infancy or early childhood. Over the last six decades, this complex neurodegenerative disorder has been shown to comprise >100 separate monogenic disorders associated with enormous clinical and biochemical heterogeneity. This article reviews clinical, radiological, biochemical and genetic aspects of the disorder. OBJECTIVES:this overview provides a better understanding of this rare mitochondrial disease by identifying its clinical, radiological and genetic manifestations in order to improve early diagnosis, patient follow-up and genetic counseling. METHODOLOGY:systematic literature review RESULTS: Leigh syndromes present with childhood developmental regression, a loss of previously achieved developmental milestones. Numerous non-neurological manifestations of Leigh syndrome have been reported, many of which are related to the underlying genetic defects. These include cardiomyopathy, renal tubulopathy, gastrointestinal and endocrine dysfunction, and liver disease. Known genetic causes, including defects in 16 mitochondrial DNA (mtDNA) genes and nearly 100 nuclear genes, are categorized into disorders of subunits and assembly factors of the five oxidative phosphorylation enzymes, disorders of pyruvate metabolism and vitamin and cofactor transport and metabolism, disorders of mtDNA maintenance, and defects in mitochondrial gene expression, protein quality control, lipid remodeling, dynamics and toxicity. An approach to diagnosis is presented, together with known treatable causes and an overview of current supportive management options and emerging therapies on the horizon CONCLUSION: Management of mitochondrial diseases must be multidisciplinary, and in collaboration with a center of reference (CRMR) or a center of competence (CCMR) with expertise in mitochondrial diseases.

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.