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Normal brain functioning is presumed to depend upon interacting regions within large-scale neuronal networks. Increasing evidence exists that interictal network alterations in focal epilepsy are associated with cognitive and behavioral deficits. Nevertheless, the reported network alterations are inconclusive and prone to low statistical power due to small sample sizes as well as modest effect sizes. We therefore systematically reviewed the existing literature and conducted a meta-analysis to characterize the changes in whole-brain interictal focal epilepsy networks at sufficient power levels. We focused on the two most commonly used metrics in whole-brain networks: average path length and average clustering coefficient. Twelve studies were included that reported whole-brain network average path length and average clustering coefficient characteristics in patients and controls. The overall group difference, quantified as the standardized mean average path length difference between epilepsy and control groups, corresponded to a significantly increased average path length of 0.29 (95% confidence interval (CI): 0.12 to 0.45, p = 0.0007) in the epilepsy group. This suggests a less integrated interictal whole-brain network. Similarly, a significantly increased standardized mean average clustering coefficient of 0.35 (CI: 0.05 to 0.65, p = 0.02) was found in the epilepsy group in comparison with controls, pointing towards a more segregated interictal network. Sub-analyses revealed similar results for functional and structural networks in terms of effect size and directionality for both metrics. In addition, we found individual network studies to be prone to low power due to the relatively small group differences in average path length and average clustering coefficient in combination with small sample sizes. The pooled network characteristics support the hypothesis that focal epilepsy has widespread detrimental effects, that is, reduced integration and increased segregation, on whole brain interictal network organization, which may relate to the co-morbid cognitive and behavioral impairments often reported in patients with focal epilepsy.

Background Developmental and epileptic encephalopathy with spike wave activation in sleep (DEE-SWAS) and epileptic encephalopathy with spike wave activation in sleep (EE-SWAS) are rare but well-known childhood epileptic disorders. Steroids are one of the first line treatment options, but a variety of steroid regimens exists. The aim of this survey was to evaluate the practices of steroid therapy in the treatment of (D)EE-SWAS across European centers. Methods An online survey was conducted (via ‘SurveyMonkey’ Europe) among European epilepsy centers. Questions asked included: characteristics of replying center, applied definition of DEE-SWAS, existence of regional/national guidelines regarding diagnostic and therapeutic management. Particular attention was paid to the indication/contraindication of steroids and treatment regimens used. Results Responses were obtained from 60 centers across 18 countries. Only 15% of centers reported the availability of national guidelines for the management of (D)EE-SWAS. There were variations in definition of (D)EE-SWAS, with Spike-Wave- Index (SWI) > 85 (irrespective of cognitive status) and SWI > 50% with concurrent neurodevelopmental regression being the most prevalent, reported in 36% and 50%, respectively. Steroids and clobazam were considered the predominant treatment options, with the primary indication for steroids being neurodevelopmental arrest (52%) and failure of clobazam treatment (51%). Treatment goals of steroid treatment primarily focused on neurodevelopmental improvement (95%), and reduction of SWI (66%). Methylprednisolone and prednisone were the most frequently used steroids, although other steroid types were also reported. Pulse therapy was utilized exclusively in 47% of centers. The most commonly used steroid regimen was intravenous/oral methylprednisolone pulse therapy (20 mg/kg/day for 3 days, either monthly or weekly), although a broad variety of different regimens were reported. Criteria influencing decisions about steroid treatment were largely based on personal experience, with scientific publications playing a role in decision-making in only 14% of centers. Conclusion Steroids are part of the first line therapy of (D)EE-SWAS across Europe, but heterogeneity in formulations, dosages, and regimens persists due to limited guideline availability. The absence of comparative studies and the discordant definitions of (D)EE-SWAS further hinder comparisons of treatment efficacy. We recommend that harmonizing steroid treatment strategies is imperative for optimizing (D)EE-SWAS management.

Experimental studies suggest that increased resting-state power of gamma oscillations is associated with autism spectrum disorder (ASD). To extend the clinical applicability of this finding, we retrospectively investigated routine electroencephalography (EEG) recordings of 19 patients with ASD and 19 age- and gender-matched controls. Relative resting-state condition gamma spectral power was variable, but on average significantly increased in children with ASD. This effect remained when excluding electrodes associated with myogenic gamma activity. These findings further indicate that increased resting-state gamma activity characterizes a subset of ASD and may also be detected by routine EEG as a clinically accessible and well-tolerated investigation.

Abstract Tuberous sclerosis complex (TSC) is a monogenetic disease that arises due to mutations in either the TSC1 or TSC2 gene and affects multiple organ systems. One of the hallmark manifestations of TSC are cortical malformations referred to as cortical tubers. These tubers are frequently associated with treatment-resistant epilepsy. Some of these patients are candidates for epilepsy surgery. White matter abnormalities, such as loss of myelin and oligodendroglia, have been described in a small subset of resected tubers but mechanisms underlying this phenomenon are unclear. Herein, we analyzed a variety of neuropathologic and immunohistochemical features in gray and white matter areas of resected cortical tubers from 46 TSC patients using semi-automated quantitative image analysis. We observed divergent amounts of myelin basic protein as well as numbers of oligodendroglia in both gray and white matter when compared with matched controls. Analyses of clinical data indicated that reduced numbers of oligodendroglia were associated with lower numbers on the intelligence quotient scale and that lower amounts of myelin-associated oligodendrocyte basic protein were associated with the presence of autism-spectrum disorder. In conclusion, myelin pathology in cortical tubers extends beyond the white matter and may be linked to cognitive dysfunction in TSC patients.

Tuberous Sclerosis Complex (TSC) is a genetic hamartoma syndrome frequently associated with severe intractable epilepsy. In some TSC patients epilepsy surgery is a promising treatment option provided that the epileptogenic zone can be precisely delineated. TSC brain lesions (cortical tubers) contain dysmorphic neurons, brightly eosinophilic giant cells and white matter alterations in various proportions. However, a histological classification system has not been established for tubers. Therefore, the aim of this study was to define distinct histological patterns within tubers based on semi-automated histological quantification and to find clinically significant correlations. In total, we studied 28 cortical tubers and seven samples of perituberal cortex from 28 TSC patients who had undergone epilepsy surgery. We assessed mammalian target of rapamycin complex 1 (mTORC1) activation, the numbers of giant cells, dysmorphic neurons, neurons, and oligodendrocytes, and calcification, gliosis, angiogenesis, inflammation, and myelin content. Three distinct histological profiles emerged based on the proportion of calcifications, dysmorphic neurons and giant cells designated types A, B, and C. In the latter two types we were able to subsequently associate them with specific features on presurgical MRI. Therefore, these histopathological patterns provide consistent criteria for improved definition of the clinico-pathological features of cortical tubers identified by MRI and provide a basis for further exploration of the functional and molecular features of cortical tubers in TSC.

Precision treatments for monogenic epilepsies, i.e. treatments that can at least partially reverse the biochemical consequences of a pathogenic gene variant, have been gradually emerging over the years. To date, however, information on the efficacy of these treatments is mostly based on case-reports and retrospective studies. As a result, utilisation of precision treatments often lack consistency and a pre-defined outcome monitoring plan. N-of-1 strategies in clinical care are pre-defined, individually tailored, repeated challenge-withdrawal therapeutic trials designed to assess the value of a treatment of interest for an individual. Despite their potential to improve clinical decision-making, N-of-1 strategies have been hampered by limited guidance on their implementation and lack of consensus on oversight procedures. To improve treatment selection for rare monogenic epilepsies, the PINPOINT initiative (Precision Treatments In MoNogenic EPilepsies: Observational Registry And N-of-1 Trial Recommendations) was set up as a collaborative effort within the European Reference Network for Rare and Complex Epilepsies. PINPOINT aims to develop recommendations for the design of N-of-1 strategies with off-label precision treatments for monogenic epilepsies. Using available N-of-1 trial manuals, different components of N-of-1 design were tailored to the context of epilepsy and oversight procedures were outlined. These efforts resulted in this guidance document—or blueprint for N-of-1 strategies for monogenic epilepsies in clinical care. This blueprint defines the characteristics of treatments and patients that would be suitable for N-of-1 strategies. Key principles for outcome measure selection, period duration and statistical analysis are defined. Consideration is given to interim assessment rules, which establish whether proceeding onto an additional treatment cycle is likely to provide significant advantages. Procedures for ethical oversight are proposed. This blueprint for N-of-1 strategies can be used as a basis for master protocols to optimise individualised clinical care in a standardised and consistent manner. We are confident that this document will provide physicians with the building blocks needed to elevate precision treatments for rare monogenic epilepsies out of their current landscape of inadequate evidence.

Background Tuberous sclerosis complex (TSC) is an autosomal dominant disease that affects multiple organs including the brain. TSC is strongly associated with broad neurodevelopmental disorders, including autism spectrum disorder symptomatology. Preclinical TSC studies have indicated altered neuronal chloride homeostasis affecting the polarity of γ-aminobutyric acid (GABA) ergic transmission as a potential treatment target. Bumetanide, a selective NKCC1 chloride importer antagonist, may attenuate depolarizing GABA action, and in that way reduce disease burden. In this open-label pilot study, we tested the effect of bumetanide on a variety of neurophysiological, cognitive, and behavioral measures in children with TSC. Methods Participants were treated with bumetanide (2dd 0.5–1.0 mg) for 13 weeks in an open-label trial. The Aberrant Behavior Checklist-Irritability (ABC-I) subscale was chosen as the primary endpoint. Secondary endpoints included other behavioral questionnaires in addition to event-related potentials (ERP) and neuropsychological tests if tolerated. Additionally, the treatment effect on seizure frequency and quality of life was assessed. Endpoint data were collected at baseline, after 91 days of treatment and after a 28-day wash-out period. Results Fifteen patients (8–21-years old) with TSC were included of which 13 patients completed the study. Treatment was well-tolerated with only expected adverse events due to the diuretic effects of bumetanide. Irritable behavior (ABC-I) showed significant improvement after treatment in 11 out of 13 patients ( t (12) = 4.41, p = .001, d = .773). A favorable effect was also found for social behavior (Social Responsiveness Scale) ( t (11) = 4.01, p = .002, d = .549) and hyperactive behavior (ABC-hyperactivity subscale) (t (12) = 3.65, p = .003, d = .686). Moreover, patients rated their own health-related quality of life higher after treatment. At baseline, TSC patients showed several atypical ERPs versus typically developing peers of which prepulse inhibition was significantly decreased in the TSC group. Neuropsychological measurements showed no change and bumetanide had no effect on seizure frequency. Limitations The sample size and open-label design of this pilot study warrant caution when interpreting outcome measures. Conclusions Bumetanide treatment is a potential treatment to alleviate the behavioral burden and quality of life associated with TSC. More elaborate trials are needed to determine the application and effect size of bumetanide for the TSC population. Trial registration EU Clinical Trial Register, EudraCT 2016-002408-13 ( www.clinicaltrialsregister.eu/ctr-search/trial/2016-002408-13/NL ). Registered 25 July 2016.

Tuberous Sclerosis Complex (TSC) is a rare genetic disorder that results from a mutation in the TSC1 or TSC2 genes leading to constitutive activation of the mechanistic target of rapamycin complex 1 (mTORC1). TSC is associated with autism, intellectual disability and severe epilepsy. Cortical tubers are believed to represent the neuropathological substrates of these disabling manifestations in TSC. In the presented study we used high-throughput RNA sequencing in combination with systems-based computational approaches to investigate the complexity of the TSC molecular network. Overall we detected 438 differentially expressed genes and 991 differentially expressed small non-coding RNAs in cortical tubers compared to autopsy control brain tissue. We observed increased expression of genes associated with inflammatory, innate and adaptive immune responses. In contrast, we observed a down-regulation of genes associated with neurogenesis and glutamate receptor signaling. MicroRNAs represented the largest class of over-expressed small non-coding RNA species in tubers. In particular, our analysis revealed that the miR-34 family (including miR-34a, miR-34b and miR-34c) was significantly over-expressed. Functional studies demonstrated the ability of miR-34b to modulate neurite outgrowth in mouse primary hippocampal neuronal cultures. This study provides new insights into the TSC transcriptomic network along with the identification of potential new treatment targets.

Electroencephalogram (EEG) acquisition is routinely performed to support an epileptic origin of paroxysmal events in patients referred with a possible diagnosis of epilepsy. However, in children with partial epilepsies the interictal EEGs are often normal. We aimed to develop a multivariable diagnostic prediction model based on electroencephalogram functional network characteristics. Routinely performed interictal EEG recordings at first presentation of 35 children diagnosed with partial epilepsies, and of 35 children in whom the diagnosis epilepsy was excluded (control group), were used to develop the prediction model. Children with partial epilepsy were individually matched on age and gender with children from the control group. Periods of resting-state EEG, free of abnormal slowing or epileptiform activity, were selected to construct functional networks of correlated activity. We calculated multiple network characteristics previously used in functional network epilepsy studies and used these measures to build a robust, decision tree based, prediction model. Based on epileptiform EEG activity only, EEG results supported the diagnosis of with a sensitivity and specificity of 0.77 and 0.91 respectively. In contrast, the prediction model had a sensitivity of 0.96 [95% confidence interval: 0.78-1.00] and specificity of 0.95 [95% confidence interval: 0.76-1.00] in correctly differentiating patients from controls. The overall discriminative power, quantified as the area under the receiver operating characteristic curve, was 0.89, defined as an excellent model performance. The need of a multivariable network analysis to improve diagnostic accuracy was emphasized by the lack of discriminatory power using single network characteristics or EEG's power spectral density. Diagnostic accuracy in children with partial epilepsy is substantially improved with a model combining functional network characteristics derived from multi-channel electroencephalogram recordings. Early and accurate diagnosis is important to start necessary treatment as soon as possible and inform patients and parents on possible risks and psychosocial aspects in relation to the diagnosis.

Malformations of cortical development are manifestations of mTORopathies, including tubers in context of Tuberous Sclerosis Complex (TSC) cortical tubers and Focal Cortical Dysplasia (FCD), and are associated with epilepsy, often accompanied by comorbidities such as autism spectrum disorder (ASD). This study aims to investigate the cell-type-specific transcriptional alterations and disrupted intercellular communication networks in mTORopathies, focusing on their implications for cortical network dysfunction. Using single-cell RNA sequencing, we identified 33 transcriptionally distinct cell clusters across control and pathological samples, including neuronal, glial, and endothelial populations. Our analysis revealed disease-specific changes, such as the loss of certain glutamatergic and microglial clusters in cortical tubers (TSC), MTOR_FCD and DEPDC5_FCD, and the presence of a unique endothelial cluster in pathological samples. Pathway enrichment analysis highlighted the critical role of synaptic signaling, axonogenesis, and neuroimmune regulation in these disorders. Additionally, cell–cell communication network analysis demonstrated disrupted interactions between neuron-astrocyte, astrocyte-OPC, and microglia-neuron across mTORopathies. We found that the neurexins-neuroligins (NRXN-NLGN) signaling pathway, crucial for synapse formation and stability, was altered in both glutamatergic and GABAergic neurons, reflecting dysregulated synaptic plasticity and impaired neuron-glia communication. These findings provide novel insights into the molecular underpinnings of mTORopathies and suggest potential therapeutic targets to restore cellular communication and synaptic function in these disorders.