Brain

We conducted the largest PSP GWAS of the Iberian population to date (522 cases from 22 Spanish and Portuguese institutions). We independently replicated seven known PSP risk variants, and unveiled a novel locus in NFASC/CNTN2 after meta-analysing our results with a newly available Dutch cohort and publicly available summary statistics. These findings highlight the importance of neuron-oligodendrocyte interactions in PSP etiopathology.

Mild malformation of cortical development with oligodendroglial hyperplasia in epilepsy (MOGHE) is a recently discovered histopathological lesion entity. Approximately half of affected individuals carry a pathogenic brain mosaicism in the X-linked SLC35A2 gene, and all suffer from epilepsy. In this work, we extended the search for genetic alterations of MOGHE by investigating sex chromosome copy number alterations in 29 brain tissue samples from 19 males and 10 females with histopathologically confirmed MOGHE. Twenty individuals carried pathogenic SLC35A2 variants, while no genetic alteration was identified in nine individuals using targeted deep panel sequencing. Interestingly, DNA methylation-derived copy number variation (CNV) plots revealed significant gains of the Y chromosome in 16/19 males (84.2%) and in 5/10 females (50%). These findings were validated by chromogenic and fluorescent in situ hybridisation (ISH), PCR amplification of Y-specific sequences, and microscopic localisation of cells with Y-chromosomal gain in clusters of oligodendroglial hyperplasia. PCR and ISH demonstrated lesion-restricted Y-chromosome gains, absent in the overlying non-lesional neocortex. Together with pathogenic variants in the X-chromosomal SLC35A2 gene, Y-chromosomal sequences detected in phenotypic females and mosaic Y chromosome gains in males provide a genomic correlate for all cases of MOGHE. Based on SLC35A2 mutational status and Y-chromosome copy number changes, we stratified the cohort into three subgroups: SLC35A2-mutant without Y gain (SLC+/Y-, n = 8), SLC35A2-mutant with Y gain (SLC+/Y+, n = 12), and SLC35A2-wild type with Y gain (SLC-/Y+, n = 9). These genetically defined subgroups also differed in their clinical presentation, with individuals from group 2 having the earliest disease onset and the largest lesion volume on MRI. These findings expand the genetic spectrum of epileptogenic cortical malformations and highlight a potentially overlooked role of sex chromosome biology in this focal epilepsy.

Focal Cortical Dysplasia Type II (FCDII) is a subtype of cortical malfunction and is the primary cause of drug-resistant epilepsy in children. Although somatic mosaicism and clonal expansion of brain cells have been identified as crucial factors in FCD cases, the overall genetic landscape and clinical implications of FCDII remain largely unclear due to a significant gap in translating genetic data to inform surgical approaches and prognostic evaluations of individual cases. We carried out deep exome sequencing and deep amplicon validation of surgical biopsies and matched blood samples from 14 FCDII patients with confirmed neuropathology. We further performed multiscale pathogenic validations and took advantage of existing single-nucleus RNA sequencing and spatial maps from developing human cortices to explore the functionality of potential pathogenic somatic variants. We identified novel somatic variants in several functional categories, like neurotransmission (TAAR2, GRM6, ZACN), structural regulation (TUBB2A, PLEC, COL18A1), cellular maintenance (IDO2, PARP4, P2RX5), and RNA processing (RBMX), mapping the expression of these genes back to the developing human brain demonstrated significant enrichment in neuronal cell types, especially excitatory neurons, further confirming their contributions in early brain development and phenotypic functions in dysmorphic neurons. Combining these genetic findings with clinical phenotypes, we found brain-specific mosaic variants with very high mosaic fractions (fraction of mosaic cells, MF, up to 99.5% on P2RX5) associated with different clinical phenotypes. FCDIIB, a more severe subtype that contains balloon cells, had higher MFs (>40%) for variants within resectable cortical layers (excitatory neurons in Layers 5 and 6). This allows potentially targeted resection and achieves better clinical outcome (87.5 % with Engel score I). FCDIIA subtype, on the other hand, displayed lower MFs (<5%) with diffuse distribution, and required hemispherectomy, with poor surgical outcomes (Engel score II/III). Our results suggest MF thresholds are high-definition biomarkers of surgical outcome estimate, with MF > 40% predicting viable focal resection and MF < 5% indicating network dysfunction that necessitates broad-spectrum resection. Combining genetic mapping with cellular localization thus offers a coherent solution to precision surgery in FCDII, translating molecular diagnosis to clinical practice.

Network hypersynchrony is emerging as an important system-level mechanism underlying seizures, as well as cognitive and behavioural impairments, in children with structural brain abnormalities. We investigated patterns of single neuron action potential behaviour in 206 neurons recorded from tubers, transmantle tails of tubers and normal looking cortex in 3 children with tuberous sclerosis. The patterns of neuronal firing, on a neuron-by-neuron (autocorrelation) basis did not reveal any differences as a function of anatomy. However, at the level of functional networks (cross-correlation), there is a much larger propensity towards hypersynchrony of tuber-tuber neurons that in neurons from any other anatomical site. This suggests that tubers are the primary drivers of adverse outcomes in children with tuberous sclerosis.

The PTPN11 gene was recently described as a novel lesional epilepsy gene by extensive exome-wide sequencing studies. However, germline mutations of PTPN11 and other RAS-/MAP-Kinase signaling pathway genes cause Noonan syndrome, a multisystem disorder characterized by abnormal facial features, developmental delay, and sporadically, also brain tumors. Herein, we performed a deep phenotype-genotype analysis of a comprehensive series of ganglioglioma (GG) with brain somatic alterations of the PTPN11 gene compared to GG with other common MAP-Kinase signaling pathway alterations. Seventy-two GG were submitted to whole exome sequencing and genotyping and 86 low grade epilepsy associated tumors (LEAT) to DNA-methylation analysis. Clinical data were retrieved from hospital files including postsurgical disease onset, age at surgery, brain localization, and seizure outcome. A comprehensive histopathology staining panel was available in all cases. We identified eight GG with PTPN11 alterations, copy number variant (CNV) gains of chromosome 12, and the commonality of additional CNV gains in FGFR4, RHEB, NF1, KRAS as well as BRAFV600E alterations. Histopathology revealed an atypical and complex glio-neuronal phenotype with subpial tumor spread and large, pleomorphic, and multinuclear cellular features. Only three out of eight patients with GG and PTPN11 alterations were free of disabling-seizures two years after surgery (38% Engel I). This was remarkably different from our series of GG with BRAFV600E mutations (85% Engel I). Our data point to a subgroup of GG with cellular atypia in glial and neuronal cell components, adverse postsurgical outcome, and genetically characterized by PTPN11 and other Noonan syndrome-related alterations of the RAS-/MAP-Kinase signaling pathway. These findings need prospective validation in clinical practice as they argue for an adapted WHO grading system in developmental, glio-neuronal tumors associated with early-onset focal epilepsy. These findings also open avenues for targeted medical treatment.

One striking clinical hallmark in patients with autoantibodies to leucine-rich glioma inactivated 1 (LGI1) is the very frequent focal seizure semiologies, including faciobrachial dystonic seizures (FBDS), in addition to the amnesia. Polyclonal serum IgGs have successfully modelled the cognitive changes in vivo but not seizures. Hence, it remains unclear whether LGI1-autoantibodies are sufficient to cause seizures. We tested this with the molecularly precise monoclonal antibodies directed against LGI1 (LGI1-mAbs), derived from patient circulating B cells. These were directed towards both major domains of LGI1, LRR (n=5) and EPTP (n=5) and infused intracerebroventricularly over 7 days into juvenile male Wistar rats using osmotic pumps. Continuous wireless EEG was recorded from a depth electrode placed in hippocampal CA3 plus behavioural tests for memory and hyperexcitability were performed. Following infusion completion (Day 9), post-mortem brain slices were studied using electrophysiology and immunostaining. By comparison to control-mAb injected rats (n=6), video-EEG analysis over 9 days revealed convulsive and non-convulsive seizure activity in rats infused with LGI1-mAbs, with a significant number of ictal events (245{+/-}83 vs. 7.8{+/-}7.8 in controls; p=0.002). Memory was not impaired in the novel object recognition test. Local field potential recordings from postmortem brain slices showed spontaneous ictal-like spike activity in the CA3 region (p=0.03). The LGI1-mAbs bound most strongly in the hippocampal CA3 region and induced a significant reduction in Kv1.1 cluster number in this subfield (6 controls; 7 LGI1-mAbs; p=0.01) Peripherally-derived human LGI1-mAbs infused into rodent CSF provide strong evidence of direct in vivo epileptogenesis with molecular correlations. These findings fulfill criteria for LGI1-antibodies in seizure causation.

Hyperpolarization-activated cyclic nucleotide-gated 1 channels (HCN1) mediate the Ih cationic current and play a central role in regulating neuronal excitability and synaptic integration. HCN1 is predominantly expressed in the neocortex and hippocampus. Pathogenic variants in HCN1 have been increasingly identified in individuals presenting with a broad spectrum of epileptic disorders, ranging from severe developmental and epileptic encephalopathy (DEE) to milder epilepsies. Here, we used patch-clamp electrophysiology in combination with confocal imaging in HEK293 cells to functionally characterize 43 HCN1 variants found in patients presenting with neurodevelopmental disorders, with or without epilepsy. Based on their biophysical properties, we defined four functional classes: (I) low or no current, (II) hyperpolarizing (i.e. left) shift in voltage dependence, (III) depolarizing (i.e. right) shift in voltage dependence, and (IV) generation of an instantaneous current. Integration of this functional classification with detailed clinical data from a cohort of 49 patients revealed a striking genotype-phenotype correlation. Loss-of-function variants were strongly enriched among individuals without epilepsy or with milder generalized phenotypes, whereas gain-of-function and mixed variants were predominantly associated with epilepsy, including all cases of DEE. Notably, non-epileptic cases clustered within a subgroup of loss-of-function variants affecting the selectivity filter. We further show that allosteric modulators, including the peptides NB6 and TRIP8bnano and the small molecule J&J12e, normalize the functional properties of mutant HCN1 channels in three classes. These findings establish a clinically relevant framework for interpreting HCN1 gain- and loss-of-function variants suggesting that the direction of channel dysfunction is a major determinant of epilepsy risk and severity.

Hyperpolarization activated Cyclic Nucleotide (HCN) gated channels are crucial for various neurophysiological functions, including learning and sensory functions, and their dysfunction are responsible for brain disorders, such as epilepsy. To date, HCN2 variants have only been associated with mild epilepsy and recently, one monoallelic missense variant has been linked to developmental and epileptic encephalopathy. Here, we expand the phenotypic spectrum of HCN2-related disorders by describing twenty-one additional individuals from fifteen unrelated families carrying HCN2 variants. Seventeen individuals had developmental delay/intellectual disability (DD/ID), two had borderline DD/ID, and one had borderline DD. Ten individuals had epilepsy with DD/ID, with median age of onset of 10 months, and one had epilepsy with normal development. Molecular diagnosis identified thirteen different pathogenic HCN2 variants, including eleven missense variants affecting highly conserved amino acids, one frameshift variant, and one in-frame deletion. Seven variants were monoallelic of which five occurred de novo, one was not maternally inherited, one was inherited from a father with mild learning disabilities, and one was of unknown inheritance. The remaining six variants were biallelic, with four homozygous and two compound heterozygous variants. Functional studies using two-electrode voltage-clamp recordings in Xenopus laevis oocytes were performed on three monoallelic variants, p.(Arg324His), p.(Ala363Val), and p.(Met374Leu), and three biallelic variants, p.(Leu377His), p.(Pro493Leu) and p.(Gly587Asp). The p.(Arg324His) variant induced a strong increase of HCN2 conductance, while p.(Ala363Val) and p.(Met374Leu) displayed dominant negative effects, leading to a partial loss of HCN2 channel function. By confocal imaging, we found that the p.(Leu377His), p.(Pro493Leu) and p.(Gly587Asp) pathogenic variants impaired membrane trafficking, resulting in a complete loss of HCN2 elicited currents in Xenopus oocytes. Structural 3D-analysis in depolarized and hyperpolarized states of HCN2 channels, revealed that the pathogenic variants p.(His205Gln), p.(Ser409Leu), p.(Arg324Cys), p.(Asn369Ser) and p.(Gly460Asp) modify molecular interactions altering HCN2 function. Taken together, our data broadens the clinical spectrum associated with HCN2 variants, and disclose that HCN2 is involved in developmental encephalopathy with or without epilepsy.

Progressive supranuclear palsy (PSP) is a heterogeneous neurodegenerative disease characterised by the accumulation of misfolded 4-repeat tau within neurones and glial cells. There is limited longitudinal data on pathologically confirmed PSP patients with phenotypes other than classical Richardsons syndrome (RS), and the pathomechanisms responsible for the broad variability in clinical phenotype and progression are not well understood. An unresolved question in this context is whether distinct spatiotemporal patterns of tau pathology propagation exist within the clinicopathological spectrum of PSP. We identified 241 consecutive, pathologically confirmed patients with PSP from the Queen Square Brain Bank for Neurological Disorders (2010-2022). Phenotyping was performed based on clinical features present within the first 3 years from symptom onset according to the Movement Disorder Society (MDS) criteria, and specific clinical features and disease milestones were recorded. Genotyping was performed using Illumina NeuroBooster and NeuroChip arrays and MAPT haplotype, APOE genotype, TRIM11 rs564309, and SLC2A13 rs2242367 single nucleotide polymorphism status were collated from imputed data. Tissue sections from eight brain regions, mounted on glass slides, were immunostained for hyperphosphorylated tau and digitised using whole-slide scanning. Forty-one anatomical regions of interest were manually segmented, and total tau pathology burden was quantified using an automated, machine learning-based algorithm. The associations between survival and both clinicogenetic features and regional tau pathology burden were modelled using Cox regression and generalised linear models, respectively, and the Subtype and Stage Inference (SuStaIn) algorithm was used to identify subgroups with distinct progression patterns. We have identified: 1) several clinical predictors of survival in PSP and the relationship between regional tau pathology burden and survival; 2) novel anatomical reference standards for the expected distribution of tau pathology across MDS-defined PSP phenotypes, emphasising region-specific white matter involvement in patients with corticobasal syndrome and speech/language variants; 3) associations linking biological sex, MAPT haplotype, and TDP-43 co-pathology to clinical phenotype and regional tau pathology burden; 4) patterns of covariance in regional tau pathology implicating inter-regional connectivity in tau spreading; and 5) three distinct spatiotemporal patterns of tau pathology progression: one characterised by initial involvement of subcortical grey matter followed by rostral spread to frontal white matter and other cortical regions, and two characterised by early, simultaneous involvement of subcortical grey matter and frontal white matter. Taken together, these results indicate that PSP clinicopathological heterogeneity is mediated by propagation of tau pathology along anatomically connected networks, and via cell- autonomous mechanisms influenced by sex, genetic factors and possibly co-pathology.

Declarative memory deficits represent considerable challenges to adequate functioning and wellbeing in temporal lobe epilepsy (TLE) and frontal lobe epilepsy (FLE), two of the most common pharmaco-resistant epilepsies. TLE and FLE are impacted differently however, with TLE affecting primarily episodic, and mildly semantic memory, while FLE presenting with overall lesser declarative impairments and a greater involvement of language processes. Although functional magnetic resonance imaging (fMRI) studies are overall compatible with differential disruptions of medial temporal and fronto-limbic networks in both syndromes, direct comparisons of brain activity and connectivity remain scarce. The current study investigated how alterations in intrinsic functional brain organization, as mapped with resting-state connectivity (rsFC), shapes altered brain network activations in both episodic and semantic memory states. To this end, we acquired task- and rs-fMRI data in 28 TLE patients and 17 FLE patients and 87 age- and sex-matched healthy controls (HCs). We used activity flow mapping (AFM), a generative machine learning technique that derives plausible task activation patterns via individualized rsFC as well as normative task activation data. Previous studies in HC as well as patient populations have shown that this technique has been effective in identifying mechanisms contributing to atypical functional organization across different context. Overall, AFM reliably predicted task activations across HC, TLE, and FLE, but prediction accuracy was consistently reduced in both patient groups, indicating impaired propagation of task-relevant signals. These reductions co-occurred with abnormal episodic and semantic task activation patterns, atypical rsFC, and behavioral profiles marked by preserved semantic but impaired episodic memory performance in both patient groups. Importantly, although neither task-evoked abnormalities nor rsFC disruptions alone were associated with clinical variables, lower AFM accuracy in patients robustly tracked poorer episodic and semantic memory performance and longer disease duration. Prediction accuracy was driven more by intrinsic functional than structural network features, suggesting that altered network communication, rather than gross anatomy, constrains AFM in pharmaco-resistant epilepsy. Our work revealed syndrome-specific yet convergent disruptions in paralimbic and heteromodal association systems, linking intrinsic dysconnectivity to a shared episodic vulnerability and semantic resilience across TLE and FLE. By modelling how intrinsic connectivity shapes task-evoked responses, AFM provides a mechanistic account of imbalanced memory-state activations and isolates network-flow pathways as targets for intervention and rehabilitation.

In N-methyl-D-aspartate receptor (NMDAR) antibody encephalitis, NMDAR-autoantibodies are hypothesised to cause prominent neuropsychiatric symptoms by internalizing NMDARs. However, supporting evidence comes chiefly from in vitro and rodent data with scant direct evidence from affected humans. Here, we used in vivo positron emission tomography (PET) with [18F]GE-179 to show a mean 30% reduction of the density of open, activated NMDARs in grey matter of persistently NMDAR-autoantibody seropositive patients following NMDAR-antibody encephalitis compared to healthy controls. The reduction was most prominent in the anterior temporal and superior parietal cortices. These patients had normal structural MRIs and mild residual symptoms. In contrast, one symptom-free patient who recovered from NMDAR-antibody encephalitis and was not NMDAR-autoantibody seropositive had normal density of active NMDARs. These findings reveal a functional deficit of open, activated NMDARs in humans with NMDAR-autoantibodies. Moreover, we observed a functional NMDAR deficit for up to 8 months following the disease peak, despite only mild residual symptoms, highlighting the considerable compensatory capacity of the human brain. One Sentence SummaryReductions of activated NMDA receptors detected in vivo in female patients following NMDA-receptor-antibody encephalitis.

Dementia in Lewy body diseases (LBD) is common and arises through heterogeneous and incompletely understood pathways. Evidence suggests contributions from genetic factors, including APOE {varepsilon}4 genotype, co-pathology including concomitant Alzheimers disease pathology and hypoperfusion related to orthostatic hypotension. However, the relative impact of these factors remains unclear. To address this, we analysed 399 post-mortem brains from LBD cases comprising Parkinsons disease, Parkinsons disease dementia and dementia with Lewy bodies, and controls, integrating APOE genotype, clinical data and assessment of ischaemic pathology alongside large-scale digital pathology quantification. We established an image analysis pipeline utilising machine learning to enable automated, standardised measurement of -synuclein, amyloid-{beta}, and phosphorylated tau burden across multiple brain regions. Quantitative pathology strongly correlated with semi-quantitative ratings and outperformed conventional staging in predicting dementia. Across multiple analytical approaches, APOE {varepsilon}3 and {varepsilon}4 carriers showed distinct dementia risk profiles. APOE {varepsilon}3 carriers developed dementia at lower quantitative -synuclein and amyloid-{beta} thresholds than {varepsilon}4 carriers, although overall dementia risk was dominated by {varepsilon}4 genotype, consistent with {varepsilon}4 both promoting greater pathology accumulation and modifying the threshold for dementia onset. Orthostatic hypotension and ischaemic pathology increased dementia risk only in {varepsilon}3 carriers with low Lewy and Alzheimers proteinopathy burden, while male sex further modulated dementia risk for this subgroup. A data-driven progression model (SuStaIn) identified four trajectories of Lewy pathology: two corresponding to recognised patterns, one brainstem-first and the other with early amygdala involvement, and two representing novel cortical-onset patterns, one with early cingulate cortex involvement and the other starting in neocortex before limbic and brainstem involvement. Co-pathology progression modelling identified subtypes with early predominance of amyloid-{beta}, phosphorylated tau, or -synuclein, and showed that Lewy subtypes follow two propagation trajectories in opposite directions. Together, these findings demonstrate that integrating quantitative pathology with genotype and clinical data uncovers distinct yet overlapping pathways to dementia in LBD, refining disease progression models and providing a basis for genotype- and pathology-informed patient stratification in therapeutic trials.

Epileptic seizures exhibit marked phenotypic heterogeneity that reflects distinct underlying network mechanisms, yet these differences are incompletely captured by current clinical classifications. Computational models offer a principled approach to infer latent excitation-inhibition dynamics from intracranial EEG, enabling mechanism-informed seizure characterization. We analyzed 205 seizures from 15 patients with drug-resistant epilepsy from the European Epilepsy Database, covering seven clinically annotated seizure onset patterns. Using the Wendling neural mass model, we fitted five-second iEEG segments by optimizing synaptic excitation and inhibition parameters across four temporal windows spanning 60 s before to 25 s after seizure onset. Model-derived excitation-inhibition changes distinguished seizure types significantly above chance. Classification performance was strongest when combining excitation and inhibition parameters, with peridendritic inhibition being the single most discriminative parameter. Seizure-type-specific signatures were detectable not only during seizure onset and within seizure onset zones, but already during interictal periods and in non-onset channels, indicating that seizure mechanisms are preconfigured tens of seconds before clinical onset and extend beyond focal onset regions. Although all seizure types showed increases in both excitation and inhibition during seizure transition, their timing and magnitude differed systematically. In particular, our study supports and extends prior evidence that high-amplitude slow (HAS) seizures are driven by localized hyperexcitation within the seizure onset zone, whereas low-amplitude fast (LAF) seizures arise from inhibition-driven network mechanisms. Excitation-inhibition signatures were further linked to individual patient characteristics and surgical outcomes, highlighting their potential clinical relevance.

Hippocampal sclerosis is a frequent finding in pediatric epilepsy surgery and has traditionally been regarded as an acquired lesion. It commonly co-occurs with focal cortical dysplasia (FCD IIIa), yet whether hippocampal injury is secondary to seizures or reflects a shared underlying etiology remains unresolved. Here we identified somatic variants activating the RAS-MAPK pathway in 40% of patients with hippocampal sclerosis, but in none with non-sclerotic hippocampus. Gain-of-function variants in PTPN11 were the most common finding, with mutations present in both cortex and hippocampus and enriched in hippocampal neurons, consistent with a shared developmental origin. In mice, Ptpn11D61Y mutants developed profound hippocampal degeneration and gliosis following subthreshold kainic acid exposure, whereas wild-type controls were unaffected. p38-dependent stress pathways were upregulated in patients and mice, suggesting a mechanism through which ERK-p38 crosstalk lowers the threshold for seizure-induced injury. These results provide a genetic explanation for FCD IIIa, elucidate the role of somatic mutations within the RAS-MAPK pathway in driving hippocampal sclerosis, and provide a target for pathway-specific interventions for intractable seizures.

Parkinson s Disease (PD) is heritable, however how genetic risk confers vulnerability remains mostly unknown. Here we use genetic and neuroimaging measures from 20,000 healthy adults from the UK Biobank to show that PD polygenic risk score (PRS) is associated with cortical thinning in a pattern that resembles cortical atrophy seen in PD. Conversely, PD PRS is associated with a global increase in cortical surface area. We also show that the genetically determined cortical thinning profile overlaps with the expression of genes associated with synaptic signaling, is dependent on anatomical connectivity and on regional expression of the most significant PD risk genes. Despite identical PRS distributions in males and females, only males show the associated brain features, possibly explaining the sex disparity in PD. We discuss potential mechanisms linking genetic risk to cortical thickness and surface area, and suggest that the divergent effects may reflect separate routes of genetic vulnerability.

Seizures are a prominent feature in N-Methyl-D-Aspartate receptor antibody (NMDAR-Ab) encephalitis, a distinct neuro-immunological disorder in which specific human autoantibodies bind and crosslink the surface of NMDAR proteins thereby causing internalization and a state of NMDAR hypofunction. To further understand ictogenesis in this disorder, and to test a novel treatment compound, we developed an NMDAR-Ab mediated rat seizure model that displays spontaneous epileptiform activity in vivo and in vitro. Using a combination of electrophysiological and dynamic causal modelling techniques we show that, contrary to expectation, reduction of synaptic excitatory, but not inhibitory, neurotransmission underlies the ictal events through alterations in the dynamical behaviour of microcircuits in brain tissue. Moreover, in vitro application of an NMDAR-specific neurosteroid, pregnenolone sulfate, that upregulates NMDARs, reduced established ictal activity. This proof-of-concept study highlights the complexity of circuit disturbances that may lead to seizures and the potential use of receptor-specific treatments in antibody-mediated seizures and epilepsy.

Impaired consciousness is a debilitating and unpredictable outcome of mesial temporal lobe seizures whose mechanisms to date remain unclear. Moreover, questions about the relationship between impaired consciousness and lateralization, hemispheric spread and electrophysiological characteristics of seizures are yet to be answered. To address these gaps, we conducted in-depth investigation of behavioral and intracranial EEG data from 186 mesial temporal lobe seizures of 51 patients with intractable mesial temporal lobe epilepsy. We found that bilateral mesial temporal spread of seizures is not a necessary condition for impaired consciousness, although seizures with bilateral mesial temporal involvement were significantly more likely to have impaired consciousness than unilateral seizures. Contrary to prior belief, we found no relationship between the onset side (left vs. right temporal lobe or language dominant vs. non-dominant lobe) of seizures and the probability of impaired consciousness. Lastly, we established that widespread increases in slow-wave activity (delta band) in extratemporal cortical areas, as well as increases in fast activity (beta band) in the temporal lobes were both robust markers of seizures with impaired consciousness and could predict ictal impairment with up to 86% accuracy. Our findings shed new light on networks that underlie impaired consciousness in temporal lobe epilepsy and may help guide deep brain stimulation of such systems (e.g. via thalamic nuclei) as a potential intervention to improve consciousness during seizures.

Magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy is an established thermoablative treatment for tremor. Although outcomes in Essential Tremor approach those of deep brain stimulation, efficacy in tremor-dominant Parkinsons disease (TDPD) is often less durable, with tremor relapse reported in 30-50% of cases. Previous associations with lesion size or age remain descriptive and do not explain why anatomically similar lesions yield divergent long-term outcomes. We retrospectively analyzed 20 patients with TDPD who underwent unilateral MRgFUS. Lesions were used as seeds for normative structural and functional connectivity analyses. Durable tremor control was associated with lesion showing stronger functional connectivity to primary motor (M1), primary somatosensory (S1), and supplementary motor areas, as well as inferior frontal and occipital cortices. In contrast, relapse was linked to greater connectivity with cerebellar motor and associative regions. Structurally, optimal lesions converged at the triangular interface of the nuclei ventralis intermedius, ventralis oralis, and ventro caudalis. Streamlines associated with better outcomes projected posteriorly towards S1, with M1 delineating an anterior functional boundary beyond which outcomes declined. Structural fingerprints emphasized posterior sensorimotor areas as critical therapeutic outputs. Findings define a connectivity-based substrate of durable tremor suppression and support the development of individualized, network-guided targeting strategies for MRgFUS in TDPD

Epilepsy is increasingly conceptualized as a network disorder. In this cross-sectional mega-analysis, we integrated neuroimaging and connectome analysis to identify network associations with atrophy patterns in 1,021 adults with epilepsy compared to 1,564 healthy controls from 19 international sites. In temporal lobe epilepsy, areas of atrophy co-localized with highly interconnected cortical hub regions, whereas idiopathic generalized epilepsy showed preferential subcortical hub involvement. These morphological abnormalities were anchored to the connectivity profiles of distinct disease epicenters, pointing to temporo-limbic cortices in temporal lobe epilepsy and fronto-central cortices in idiopathic generalized epilepsy. Indices of progressive atrophy further revealed a strong influence of connectome architecture on disease progression in temporal lobe, but not idiopathic generalized, epilepsy. Our findings were reproduced across individual sites and single patients, and were robust across different analytical methods. Through worldwide collaboration in ENIGMA-Epilepsy, we provided novel insights into the macroscale features that shape the pathophysiology of common epilepsies.

Epilepsy is associated with genetic risk factors and cortico-subcortical network alterations, but associations between neurobiological mechanisms and macroscale connectomics remain unclear. This multisite ENIGMA-Epilepsy study examined whole-brain structural covariance networks in patients with epilepsy and related findings to postmortem co-expression patterns of epilepsy risk genes. Brain network analysis included 578 adults with temporal lobe epilepsy (TLE), 288 adults with idiopathic generalized epilepsy (IGE), and 1,328 healthy controls from 18 centres worldwide. Graph theoretical analysis of structural covariance networks revealed increased clustering and path length in orbitofrontal and temporal regions in TLE, suggesting a shift towards network regularization. Conversely, people with IGE showed decreased clustering and path length in fronto-temporo-parietal cortices, indicating a random network configuration. Syndrome-specific topological alterations reflected expression patterns of risk genes for hippocampal sclerosis in TLE and for generalized epilepsy in IGE. These imaging-genetic signatures could guide diagnosis, and ultimately, tailor therapeutic approaches to specific epilepsy syndromes.