Epileptic encephalopathies: an overview

Patients carrying pathogenic SCN8A variants with loss- and gain-of-function effects can be classified into five subgroups exhibiting varying developmental and epileptic components of encephalopathy

OBJECTIVE

Phenotypic heterogeneity presents challenges in providing clinical care to patients with pathogenic SCN8A variants, which underly a wide disease spectrum ranging from neurodevelopmental delays without seizures to a continuum of mild to severe developmental and epileptic encephalopathies (DEEs). An important unanswered question is whether there are clinically important subgroups within this wide spectrum. Using both supervised and unsupervised machine learning (ML) approaches, we previously found statistical support for two and three subgroups associated with loss- and gain- of- function vari-ants, respectively. Here, we test the hypothesis that the unsupervised subgroups (U1-U3) are distinguished by differential contributions of developmental and epileptic components.

METHODS

We predicted that patients in the U1 and U2 subgroups would differ in timing of developmental delay and seizure onset, with earlier and concurrent onset of both features for the U3 subgroup. Standard statistical procedures were used to test these predictions, as well as to investigate clinically relevant associations among all five subgroups.

RESULTS

Two-population proportion and Kruskal-Wallis tests supported the hypothesis of a reversed order of developmental delay and seizure onset for patients in U1 and U2, and nearly synchronous developmental delay/seizure onset for the U3 (termed DEE) subgroup. Association testing identified subgroup variation in treatment response, frequency of initial seizure type, and comorbidities, as well as different median ages of developmental delay onset for all five subgroups.

SIGNIFICANCE

Unsupervised ML approaches discern differential developmental and epileptic components among patients with SCN8A-related epilepsy. Patients in U1 (termed developmental encephalopathy) typically gain seizure control yet rarely experience improvements in development, whereas those in U2 (termed epileptic encephalopathy) have fewer if any developmental impairments despite difficulty in achieving seizure control. This understanding improves prognosis and clinical management and provides a framework to discover mechanisms underlying variability in clinical outcome of patients with SCN8A-related disorders.

Cryo-EM investigation of ryanodine receptor type 3

Ryanodine Receptor isoform 3 (RyR3) is a large ion channel found in the endoplasmic reticulum membrane of many different cell types. Within the hippocampal region of the brain, it is found in dendritic spines and regulates synaptic plasticity. It controls myogenic tone in arteries and is upregulated in skeletal muscle in early development. RyR3 has a unique functional profile with a very high sensitivity to activating ligands, enabling high gain in Ca2+-induced Ca2+ release. Here we solve high-resolution cryo-EM structures of RyR3 in non-activating and activating conditions, revealing structural transitions that occur during channel opening. Addition of activating ligands yields only open channels, indicating an intrinsically high open probability under these conditions. RyR3 has reduced binding affinity to the auxiliary protein FKBP12.6 due to several sequence variations in the binding interface. We map disease-associated sequence variants and binding sites for known pharmacological agents. The N-terminal region contains ligand binding sites for a putative chloride anion and ATP, both of which are targeted by sequence variants linked to epileptic encephalopathy.

Exploring Infantile Epileptic Spasm Syndrome: A Proteomic Analysis of Plasma Using the Data-Independent Acquisition Approach

This study aimed to identify characteristic proteins in infantile epileptic spasm syndrome (IESS) patients' plasma, offering insights into potential early diagnostic biomarkers and its underlying causes. Plasma samples were gathered from 60 patients with IESS and 40 healthy controls. Data-independent acquisition proteomic analysis was utilized to identify differentially expressed proteins (DEPs). These DEPs underwent functional annotation through Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Gene set enrichment analysis (GSEA) was employed for both GO (GSEA-GO) and KEGG (GSEA-KEGG) analyses to examine the gene expression profiles. Receiver operating characteristic (ROC) curves assessed biomarkers' discriminatory capacity. A total of 124 DEPs were identified in IESS patients' plasma, mainly linked to pathways, encompassing chemokines, cytokines, and oxidative detoxification. GSEA-GO and GSEA-KEGG analyses indicated significant enrichment of genes associated with cell migration, focal adhesion, and phagosome pathways. ROC curve analysis demonstrated that the combination of PRSS1 and ACTB, PRSS3, ACTB, and PRSS1 alone exhibited AUC values exceeding 0.7. This study elucidated the significant contribution of cytokines, chemokines, oxidative detoxification, and phagosomes to the IESS pathogenesis. The combination of PRSS1 and ACTB holds promise as biomarkers for the early diagnosis of IESS.

A Comprehensive Review on Current Insights Into Epileptic Encephalopathy: Pathogenesis and Therapeutic Strategies

Epileptic encephalopathy (EE) represents a challenging group of disorders characterized by severe epilepsy and significant cognitive, behavioral, and neurological impairments. This comprehensive review aims to elucidate the current insights into the pathogenesis and therapeutic strategies for these disorders. Pathogenesis involves a complex interplay of genetic factors, neurobiological mechanisms, and environmental influences that contribute to the severity and progression of symptoms. Clinical manifestations are diverse, encompassing various seizure types, cognitive and behavioral impairments, and developmental delays. Current therapeutic strategies include pharmacological treatments, nonpharmacological interventions, and emerging therapies such as gene and stem cell therapy. Despite advancements, significant challenges and limitations remain, highlighting the need for ongoing research and innovation. This review synthesizes existing knowledge, identifies research gaps, and proposes future directions, emphasizing the potential for personalized medicine to improve patient outcomes and quality of life.

Rare X-linked variants carry predominantly male risk in autism, Tourette syndrome, and ADHD

Autism spectrum disorder (ASD), Tourette syndrome (TS), and attention-deficit/hyperactivity disorder (ADHD) display strong male sex bias, due to a combination of genetic and biological factors, as well as selective ascertainment. While the hemizygous nature of chromosome X (Chr X) in males has long been postulated as a key point of "male vulnerability", rare genetic variation on this chromosome has not been systematically characterized in large-scale whole exome sequencing studies of "idiopathic" ASD, TS, and ADHD. Here, we take advantage of informative recombinations in simplex ASD families to pinpoint risk-enriched regions on Chr X, within which rare maternally-inherited damaging variants carry substantial risk in males with ASD. We then apply a modified transmission disequilibrium test to 13,052 ASD probands and identify a novel high confidence ASD risk gene at exome-wide significance (MAGEC3). Finally, we observe that rare damaging variants within these risk regions carry similar effect sizes in males with TS or ADHD, further clarifying genetic mechanisms underlying male vulnerability in multiple neurodevelopmental disorders that can be exploited for systematic gene discovery.

Cannabis: a multifaceted plant with endless potentials

Cannabis sativa, also known as "hemp" or "weed," is a versatile plant with various uses in medicine, agriculture, food, and cosmetics. This review attempts to evaluate the available literature on the ecology, chemical composition, phytochemistry, pharmacology, traditional uses, industrial uses, and toxicology of Cannabis sativa. So far, 566 chemical compounds have been isolated from Cannabis, including 125 cannabinoids and 198 non-cannabinoids. The psychoactive and physiologically active part of the plant is a cannabinoid, mostly found in the flowers, but also present in smaller amounts in the leaves, stems, and seeds. Of all phytochemicals, terpenes form the largest composition in the plant. Pharmacological evidence reveals that the plants contain cannabinoids which exhibit potential as antioxidants, antibacterial agents, anticancer agents, and anti-inflammatory agents. Furthermore, the compounds in the plants have reported applications in the food and cosmetic industries. Significantly, Cannabis cultivation has a minimal negative impact on the environment in terms of cultivation. Most of the studies focused on the chemical make-up, phytochemistry, and pharmacological effects, but not much is known about the toxic effects. Overall, the Cannabis plant has enormous potential for biological and industrial uses, as well as traditional and other medicinal uses. However, further research is necessary to fully understand and explore the uses and beneficial properties of Cannabis sativa.

Perampanel as adjuvant treatment in epileptic encephalopathies: A multicenter study in routine clinical practice

OBJECTIVE

Developmental and epileptic encephalopathies (DEEs) are a heterogeneous group of syndromes, including Lennox-Gastaut syndrome (LGS), which are refractory to multiple therapies. Perampanel efficacy has been reported in LGS but further real-world evidence is needed in DEEs.

METHODS

A multicenter, retrospective, 1-year observational study in patients with DEEs on adjuvant perampanel treatment was conducted to assess perampanel safety and effectiveness in this type of patients in a real-world setting. Seizure types [focal onset seizures (FOS), generalized tonic-clonic seizures (GTCS), tonic seizures (TS), atonic seizures (AtS), atypical absences (AA), and myoclonic seizures (MS)] and seizure clusters were divided in different frequency groups: daily, weekly, and monthly seizures, and absent or seizure freedom. Patients could have more than one seizure type. For each frequency group, group change and seizure freedom were analyzed.

RESULTS

Eighty-seven patients diagnosed with DEEs (45 males) of median age 22 [1-70] years were included. The most frequent DEEs were LGS (35.6%) and Lennox-like syndrome (37.9%). At baseline 20 patients had three to five types of seizures, 36 patients had two types of seizures and 31 patients had one predominant type of seizure. The mean number of seizure types per patient at baseline was 2.12 ± 0.97 which was reduced to 1.62 ± 0.91 at 12 months (p < 0.001). Overall, 51.7% of patients had a significant improvement in at least one seizure type. At baseline, 45 patients had GTCS, 42 FOS, 41 TS, 18 AA, 16 AtS, 11 MS, and 30 seizures clusters. Seizure freedom for each specific type at 12 months was significantly achieved by 35% of patients with GTCS (p < 0.001), 17% (p = 0.016) with TS and 37% with seizure clusters (p < 0.001). Patients achieved seizure freedom from other seizure types but with no statistical significance: 7% FOS-free, 28% AA-free, 6% Ats-free, and 18% MS-free. Regarding changes of group at 12 months, 22% of TS and 19% of FOS improved significantly to a group with lower seizure frequency (p = 0.004 and p = 0.02, respectively). In remaining groups (4% of GTCS, 11% of AA, 18% of Ats, 18% of MS, and 13% of seizure clusters), the improvement was not statistically significant. Twenty-nine patients discontinued perampanel: 18 (21%) due to AEs, 8 (9%) due to lack of efficacy, and 3 (3%) due to seizure worsening. Adverse events, mostly mild or moderate, were reported in 53% of patients, and irritability/mood changes (22%) and somnolence (17%) were the most frequent.

CONCLUSION

This is the first large-scale real-world study with perampanel across different seizure types in patients with DEEs. Perampanel was effective, especially in GTCS, TS, and FOS, as well as in seizure clusters. Perampanel was generally well-tolerated without unexpected AEs.

Molecular Dynamics of CYFIP2 Protein and Its R87C Variant Related to Early Infantile Epileptic Encephalopathy

The CYFIP2 protein (cytoplasmic FMR1-interacting protein 2) is part of the WAVE regulatory complex (WRC). CYFIP2 was recently correlated to neurological disorders by the association of the R87C variant with early infantile epileptic encephalopathy (EIEE) patients. In this set of syndromes, the epileptic spasms and seizures since early childhood lead to impaired neurological development in children. Inside the WRC, the variant residue is at the CYFIP2 and WAVE1 protein interface. Thus, the hypothesis is that the R87C modification weakens this interaction, allowing the WRC complex's constant activation. This work aimed to investigate the impacts of the mutation on the structure of the WRC complex through molecular dynamics simulation. For that, we constructed WRC models containing WAVE1-NCKAP1 proteins complexed with WT or R87C CYFIP2. Our simulations showed a flexibilization of the loop comprising residues 80-110 due to the loss of contacts between internal residues in the R87C CYFIP2 as well as the key role of residues R/C87, E624, and E689 in structural modification. These data could explain the mechanism by which the mutation impairs the stability and proper regulation of the WRC.

EEG biomarkers for the diagnosis and treatment of infantile spasms

Early diagnosis and treatment are critical for young children with infantile spasms (IS), as this maximizes the possibility of the best possible child-specific outcome. However, there are major barriers to achieving this, including high rates of misdiagnosis or failure to recognize the seizures, medication failure, and relapse. There are currently no validated tools to aid clinicians in assessing objective diagnostic criteria, predicting or measuring medication response, or predicting the likelihood of relapse. However, the pivotal role of EEG in the clinical management of IS has prompted many recent studies of potential EEG biomarkers of the disease. These include both visual EEG biomarkers based on human visual interpretation of the EEG and computational EEG biomarkers in which computers calculate quantitative features of the EEG. Here, we review the literature on both types of biomarkers, organized based on the application (diagnosis, treatment response, prediction, etc.). Visual biomarkers include the assessment of hypsarrhythmia, epileptiform discharges, fast oscillations, and the Burden of AmplitudeS and Epileptiform Discharges (BASED) score. Computational markers include EEG amplitude and power spectrum, entropy, functional connectivity, high frequency oscillations (HFOs), long-range temporal correlations, and phase-amplitude coupling. We also introduce each of the computational measures and provide representative examples. Finally, we highlight remaining gaps in the literature, describe practical guidelines for future biomarker discovery and validation studies, and discuss remaining roadblocks to clinical implementation, with the goal of facilitating future work in this critical area.

Detection of Deregulated miRNAs in Childhood Epileptic Encephalopathies

The term "epileptic encephalopathy" is used to describe a possible relationship between epilepsy and developmental delay. The pathogenesis of developmental encephalopathies, independent of epilepsy, can be defined by genetic control mechanisms. The aim of this study was to investigate the use of miRNAs as serum biomarkers for the determination and discrimination of epileptic encephalopathies. Whole blood samples obtained from 54 individuals in 2 groups designated as epileptic encephalopathy patients' group (n = 24) and healthy controls (n = 30) were included in this study. The expression levels of 10 miRNAs were determined using qRT-PCR. After the determination of expression levels, the correlation of upregulated miRNA levels and Ki67 index was calculated using Pearson correlation test. The comparison of epileptic encephalopathy patients' group with healthy controls revealed the upregulation of one miRNAs (hsa-miR-324-5p) and downregulation of three miRNAs (hsa-miR-146a-5p, hsa-miR-138-5p, hsa-miR-187-3p). It has been determined that miRNAs with altered expression are an important factor in the formation of epileptic seizures and seizure-induced neuronal death. The fact that processes that play a key role in epiloptogenesis are under the control of miRNAs causes miRNAs to become meta-controllers of gene expression in the brain. We thought that further studies are needed to prove that especially hsa-miR-146a-5p, hsa-miR-138-5p, and hsa-miR-187-3p can be used as epileptic encephalopathy biomarkers. The detection of disease-specific miRNAs could contribute to the development of precision treatments.

Genetic analysis using targeted exome sequencing of 53 Vietnamese children with developmental and epileptic encephalopathies

Developmental and epileptic encephalopathies (DEE) refers to a group of rare and severe neurodevelopmental disorders where genetic etiologies can play a major role. This study aimed to elucidate the genetic etiologies of a cohort of 53 Vietnamese patients with DEE. All patients were classified into known electroclinical syndromes where possible. Exome sequencing (ES) followed by a targeted analysis on 294 DEE-related genes was then performed. Patients with identified causative variants were followed for 6 months to determine the impact of genetic testing on their treatment. The diagnostic yield was 38.0% (20/53), which was significantly higher in the earlier onset group (<12 months) than in the later onset group (≥12 months). The 19 identified variants belonged to 11 genes with various cellular functions. Genes encoding ion channels especially sodium voltage-gated channel were the most frequently involved. Most variants were missense variants and located in key protein functional domains. Four variants were novel and four had been reported previously but in different phenotypes. Within 6 months of further follow-up, treatment changes were applied for six patients based on the identified disease-causing variants, with five patients showing a positive impact. This is the first study in Vietnam to analyze the genetics of DEE. This study confirms the strong involvement of genetic etiologies in DEE, especially early onset DEE. The study also contributes to clarify the genotype-phenotype correlations of DEE and highlights the efficacy of targeted ES in the diagnosis and treatment of DEE.

Psychosocial impact of genetic testing on parents of children with developmental and epileptic encephalopathy

Aim

To investigate the psychosocial impact of genetic testing for childhood‐onset developmental and epileptic encephalopathies (DEEs) in order to identify parents’ information and support needs.

Method

In this mixed‐methods study, we conducted in‐depth semi‐structured interviews with parents (n=25) of children, recruited from the Sydney Children’s Hospital Network, Australia, who had received genetic testing. Thematic saturation was reached; interviews were transcribed, deidentified, line‐by‐line coded, and thematically analysed by three coders, using an inductive approach. We also quantitatively assessed the impact of genetic testing on quality of life outcomes and parents’ satisfaction with genetics services.

Results

Qualitative and quantitative analysis revealed that compassionate genetic counselling and consistent clinician–parent partnerships facilitated parents’ capacity to process their child’s genetic diagnosis. Parents believed that a sparsity of diagnosis‐specific information to contextualize their child’s genetic DEE, combined with limited psychosocial resources to support coping with ongoing prognostic uncertainty, contributed to chronic psychological stress. Access to diagnosis‐specific resources and peer support was considered necessary to support parents in communicating their child’s genetic DEE and to reduce social isolation.

Interpretation

Integrated psychosocial resources, including tailored psychological supports, diagnosis‐specific information, and peer‐to‐peer supports, are priority areas to complement genetic services.

Imprecision in Precision Medicine: Differential Response of a Disease-Linked GluN2A Mutant to NMDA Channel Blockers

Mutations in N-methyl-d-aspartate receptors (NMDAR) subunits have been implicated in a growing number of human neurodevelopmental disorders. Previously, a de novo mutation in GRIN2A, encoding the GluN2A subunit, was identified in a patient with severe epilepsy and developmental delay. This missense mutation, which leads to GluN2A-P552R, produces significant dendrotoxicity in transfected rodent cortical neurons, as evidenced by pronounced dendritic blebbing. This injurious process can be prevented by treatment with the NMDA antagonist memantine. Given the increasing use of FDA approved NMDA antagonists to treat patients with GRIN mutations, who may have seizures refractory to traditional anti-epileptic drugs, we investigated whether additional NMDA antagonists were effective in attenuating neurotoxicity associated with GluN2A-P552R expression. Intriguingly, we found that while treatment with memantine can effectively block GluN2A-P552R-mediated dendrotoxicity, treatment with ketamine does not, despite the fact that both drugs work as open NMDAR channel blockers. Interestingly, we found that neurons expressing GluN2A-P552R were more vulnerable to an excitotoxic insult-an effect that, in this case, could be equally rescued by both memantine and ketamine. These findings suggest that GluN2A-P552R induced dendrotoxicity and increased vulnerability to excitotoxic stress are mediated through two distinct mechanisms. The differences between memantine and ketamine in halting GluN2A-P552R dendrotoxicity could not be explained by NMDA antagonist induced changes in MAP or Src kinase activation, previously shown to participate in NMDA-induced excitotoxicity. Our findings strongly suggest that not all NMDA antagonists may be of equal clinical utility in treating GRIN2A-mediated neurological disorders, despite a shared mechanism of action.

Efficacy of Fenfluramine and Norfenfluramine Enantiomers and Various Antiepileptic Drugs in a Zebrafish Model of Dravet Syndrome

Dravet syndrome (DS) is a rare genetic encephalopathy that is characterized by severe seizures and highly resistant to commonly used antiepileptic drugs (AEDs). In 2020, FDA has approved fenfluramine (FFA) for treatment of seizures associated with DS. However, the clinically used FFA is a racemic mixture (i.e. (±)-FFA), that is substantially metabolized to norfenfluramine (norFFA), and it is presently not known whether the efficacy of FFA is due to a single enantiomer of FFA, or to both, and whether the norFFA enantiomers also contribute significantly. In this study, the antiepileptic activity of enantiomers of FFA (i.e. (+)-FFA and (−)-FFA) and norFFA (i.e. (+)-norFFA and (−)-norFFA) was explored using the zebrafish scn1Lab^−/− mutant model of DS. To validate the experimental conditions used, we assessed the activity of various AEDs typically used in the fight against DS, including combination therapy. Overall, our results are highly consistent with the treatment algorithm proposed by the updated current practice in the clinical management of DS. Our results show that (+)-FFA, (−)-FFA and (+)-norFFA displayed significant antiepileptic effects in the preclinical model, and thus can be considered as compounds actively contributing to the clinical efficacy of FFA. In case of (−)-norFFA, the results were less conclusive. We also investigated the uptake kinetics of the enantiomers of FFA and norFFA in larval zebrafish heads. The data show that the total uptake of each compound increased in a time-dependent fashion. A somewhat similar uptake was observed for the (+)-norFFA and (−)-norFFA, implying that the levo/dextrotation of the structure did not dramatically affect the uptake. Significantly, when comparing (+)-FFA with the less lipophilic (+)-norFFA, the data clearly show that the nor-metabolite of FFA is taken up less than the parent compound.

A Wide Spectrum of Genetic Disorders Causing Severe Childhood Epilepsy in Taiwan: A Case Series of Ultrarare Genetic Cause and Novel Mutation Analysis in a Pilot Study

BACKGROUND

Pediatric epileptic encephalopathy and severe neurological disorders comprise a group of heterogenous diseases. We used whole-exome sequencing (WES) to identify genetic defects in pediatric patients.

METHODS

Patients with refractory seizures using ≥2 antiepileptic drugs (AEDs) receiving one AED and having neurodevelopmental regression or having severe neurological or neuromuscular disorders with unidentified causes were enrolled, of which 54 patients fulfilled the inclusion criteria, were enrolled, and underwent WES.

RESULTS

Genetic diagnoses were confirmed in 24 patients. In the seizure group, KCNQ2, SCN1A, TBCID 24, GRIN1, IRF2BPL, MECP2, OSGEP, PACS1, PIGA, PPP1CB, SMARCA4, SUOX, SZT2, UBE3A, 16p13.11 microdeletion, [4p16.3p16.1(68,345-7,739,782)X1, 17q25.1q25.3(73,608,322-81,041,938)X3], and LAMA2 were identified. In the nonseizure group, SCN2A, SPTBN2, DMD, and FBN1 were identified. Ten novel mutations were identified. The recurrent genes included SCN1A, KCNQ2, and TBCID24. Male pediatric patients had a significantly higher (57% vs. 29%; p < 0.05, odds ratio = 3.18) yield than their female counterparts. Seventeen genes were identified from the seizure groups, of which 82% were rare genetic etiologies for childhood seizure and did not appear recurrently in the case series.

CONCLUSIONS

Wide genetic variation was identified for severe childhood seizures by WES. WES had a high yield, particularly in male infantile patients.

Survival of a male patient harboring CASK Arg27Ter mutation to adolescence

Background

CASK is an X‐linked gene in mammals and its deletion in males is incompatible with life. CASK heterozygous mutations in female patients associate with intellectual disability, microcephaly, pontocerebellar hypoplasia, and optic nerve hypoplasia, whereas CASK hemizygous mutations in males manifest as early infantile epileptic encephalopathy with a grim prognosis. Here, we report a rare case of survival of a male patient harboring a CASK null mutation to adolescent age.

Methods

Trio whole exome sequencing analysis was performed from blood genomic DNA. Magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), and electroencephalogram (EEG) analyses were performed to determine anomalies in brain development, metabolite concentrations, and electrical activity, respectively.

Results

Trio‐WES analysis identified a de novo c.79C>T (p.Arginine27Ter) mutation in CASK causing a premature translation termination at the very N‐terminus of the protein. The 17‐years, and 11‐month‐old male patient displayed profound intellectual disability, microcephaly, dysmorphism, ponto‐cerebellar hypoplasia, and intractable epilepsy. His systemic symptoms included overall reduced somatic growth, dysautonomia, ventilator and G tube dependence, and severe osteopenia. Brain MRI revealed a severe cerebellar and brain stem hypoplasia with progressive cerebral atrophy. EEG spectral analysis revealed a global functional defect with generalized background slowing and delta waves dominating even in the awake state.

Conclusion

This case study is the first to report survival of a male patient carrying a CASK loss‐of‐function mutation to adolescence and highlights that improved palliative care could extend survival. Moreover, the genomic position encoding Arg27 in CASK may possess an increased susceptibility to mutations.

GRIN2D/GluN2D NMDA receptor: Unique features and its contribution to pediatric developmental and epileptic encephalopathy

N-methyl-d-aspartate receptors (NMDARs), a subset of ligand-gated ionotropic glutamate receptors, are critical for learning, memory, and neuronal development. However, when NMDAR subunits are mutated, a host of neuropathological conditions can occur, including epilepsy. Recently, genetic variation within the GRIN2D gene, which encodes the GluN2D subunit of the NMDAR, has been associated with a set of early-onset neurological diseases, notably developmental and epileptic encephalopathy (DEE). Importantly, patients with GRIN2D variants are largely refractory to conventional anti-epileptic drug (AED) treatment, highlighting the need to further understand the distinctive characteristics of GluN2D in neurological and pathological functions. In this review, we first summarize GluN2D's unique spatial and temporal expression patterns, electrophysiological profiles, and contributions to both pre- and postsynaptic signaling. Next, we review thirteen unique case studies from DEE patients harboring ten different causal GRIN2D variants. These patients are highly heterogenous, manifesting multiple seizure types, electroencephalographic recordings, and neurological and developmental outcomes. Lastly, this review concludes by highlighting the difficulty in treating patients with DEE-associated GRIN2D variants, and stresses the need for selective therapeutic agents delivered within a precise time window.

Epilepsy in Children with Autistic Spectrum Disorder

The comorbidity of autistic spectrum disorder (ASD) and epilepsy has been widely discussed but many questions still remain unanswered. The aim of this study was to establish the occurrence of epilepsy among children with ASD to define the type of epileptic seizures and syndromes, the age of onset of epilepsy, EEG abnormalities, the used antiepileptic drugs and the therapeutic responses for seizures and autistic behavior, as well as to find some correlations between epilepsy and gender, etiology and intellectual disability (ID). A retrospective study of medical files of 59 patients (aged 1–18 years) with ASD during a 5-year period was performed. ASD diagnosis was based on the DSM-5 diagnostic criteria. The patients were examined with a detailed medical history, physical and neurological examination, as well as some additional functional, imaging, laboratory and genetic investigations ASD etiology was syndromic in 9, probable syndromic in 9, and idiopathic in 41 children. ID was established in 90% of ASD children, and epilepsy in 44.4%. The onset of epilepsy prevailed before 7 years of age. The most common seizure types were focal with or without secondary generalization (53.4%). Focal epileptiform EEG abnormalities prevailed. Therapeutic response to seizures was good: 58% were seizure-free, while 27% had >50% seizure reduction but no improvement in autistic behavior. There was no correlation between epilepsy and either occurrence or degree of ID. There was a correlation between the frequency of epileptic seizures and the degree of ID. There was no significant difference among epilepsy rates in different etiologic, gender, and ID groups, probably because of the high percentage of ID and because this was a hospital-based study. Our study showed a significant percentage of epilepsy in ASD population and more than 1/4 were of symptomatic etiology. Those could be managed with specific treatments based on the pathophysiology of the gene defect.

Lennox-Gastaut Syndrome: In a Nutshell

Lennox-Gastaut syndrome is one of the rare childhood-onset epileptic encephalopathies, characterized by multiple type seizure disorder, the typical pattern on electroencephalogram and intellectual disability. Tonic-type seizures are most commonly seen in these patients. Behavioral disturbances and cognitive decline are gradual-onset and last long after the first episode of epileptiform activity. In most cases, there is some identifiable cause that has led to the clinical presentation of the patient. Various pharmacological and surgical procedures have been proposed for the treatment of Lennox-Gastaut syndrome and many more to come in the very near future to overcome the drug resistance and to avoid the patient forming a life-long dependency.

Efficacy, Retention, and Tolerability of Brivaracetam in Patients With Epileptic Encephalopathies: A Multicenter Cohort Study From Germany

Objective: To evaluate the efficacy and tolerability of brivaracetam (BRV) in a severely drug refractory cohort of patients with epileptic encephalopathies (EE).

Method: A multicenter, retrospective cohort study recruiting all patients treated with EE who began treatment with BRV in an enrolling epilepsy center between 2016 and 2017.

Results: Forty-four patients (27 male [61%], mean age 29 years, range 6 to 62) were treated with BRV. The retention rate was 65% at 3 months, 52% at 6 months and 41% at 12 months. A mean retention time of 5 months resulted in a cumulative exposure to BRV of 310 months. Three patients were seizure free during the baseline. At 3 months, 20 (45%, 20/44 as per intention-to-treat analysis considering all patients that started BRV including three who were seizure free during baseline) were either seizure free (n = 4; 9%, three of them already seizure-free at baseline) or reported at least 25% (n = 4; 9%) or 50% (n = 12; 27%) reduction in seizures. An increase in seizure frequency was reported in two (5%) patients, while there was no change in the seizure frequency of the other patients. A 50% long-term responder rate was apparent in 19 patients (43%), with two (5%) free from seizures for more than six months and in nine patients (20%, with one [2 %] free from seizures) for more than 12 months. Treatment-emergent adverse events were predominantly of psychobehavioural nature and were observed in 16%.

Significance: In this retrospective analysis the rate of patients with a 50% seizure reduction under BRV proofed to be similar to those seen in regulatory trials for focal epilepsies. BRV appears to be safe and relatively well tolerated in EE and might be considered in patients with psychobehavioral adverse events while on levetiracetam.

A De Novo Mutation in the Sodium-Activated Potassium Channel KCNT2 Alters Ion Selectivity and Causes Epileptic Encephalopathy

Early infantile epileptic encephalopathies (EOEE) are a debilitating spectrum of disorders associated with cognitive impairments. We present a clinical report of a KCNT2 mutation in an EOEE patient. The de novo heterozygous variant Phe240Leu SLICK was identified by exome sequencing and confirmed by Sanger sequencing. Phe240Leu rSlick and hSLICK channels were electrophysiologically, heterologously characterized to reveal three significant alterations to channel function. First, [Cl^-]_i sensitivity was reversed in Phe240Leu channels. Second, predominantly K⁺-selective WT channels were made to favor Na⁺ over K⁺ by Phe240Leu. Third, and consequent to altered ion selectivity, Phe240Leu channels had larger inward conductance. Further, rSlick channels induced membrane hyperexcitability when expressed in primary neurons, resembling the cellular seizure phenotype. Taken together, our results confirm that Phe240Leu is a "change-of-function" KCNT2 mutation, demonstrating unusual altered selectivity in K_Na channels. These findings establish pathogenicity of the Phe240Leu KCNT2 mutation in the reported EOEE patient.

Integrating exome sequencing into a diagnostic pathway for epileptic encephalopathy: Evidence of clinical utility and cost effectiveness

Background

Epileptic encephalopathies are a devastating group of neurological conditions in which etiological diagnosis can alter management and clinical outcome. Exome sequencing and gene panel testing can improve diagnostic yield but there is no cost‐effectiveness analysis of their use or consensus on how to best integrate these tests into clinical diagnostic pathways.

Methods

We conducted a retrospective cost‐effectiveness study comparing trio exome sequencing with a standard diagnostic approach, for a well‐phenotyped cohort of 32 patients with epileptic encephalopathy, who remained undiagnosed after “first‐tier” testing. Sensitivity analysis was included with a range of commercial exome and multigene panels.

Results

The diagnostic yield was higher for the exome sequencing (16/32; 50%) than the standard arm (2/32; 6.2%). The trio exome sequencing pathway was cost‐effective compared to the standard diagnostic pathway with a cost saving of AU$5,236 (95% confidence intervals $2,482; $9,784) per additional diagnosis; the standard pathway cost approximately 10 times more per diagnosis. Sensitivity analysis demonstrated that the majority of commercial exome sequencing and multigene panels studied were also cost‐effective. The clinical utility of all diagnoses was reported.

Conclusion

Our study supports the integration of exome sequencing and gene panel testing into the diagnostic pathway for epileptic encephalopathy, both in terms of cost effectiveness and clinical utility. We propose a diagnostic pathway that integrates initial rapid screening for treatable causes and comprehensive genomic screening. This study has important implications for health policy and public funding for epileptic encephalopathy and other neurological conditions.

[Genetics and treatment of early infantile epileptic encephalopathies]

Epileptic encephalopathies (EE) are the group of progressive conditions with various etiologies that can produce neurocognitive deficit both per se and due to constant epileptiform discharges. Epileptic encephalopathies constitute about 15% of epilepsy in childhood and 40% of all seizures occurring in the first 3 years of life. Ten syndrome forms of EE are identified. Genetic factors contribute to 70-80% of all epileptic diseases and approximately 40% of idiopathic epilepsies have a monogenic mode of inheritance. Thirty-five genes of EE have been identified and the search is still continuing. The marked genetic heterogeneity of early EE, including 16 with autosomal-dominant-, 13 with autosomal-recessive-, 4 with X-linked recessive- and 2 with X-linked autosomal inheritance, was shown. The article describes differentiated approaches to the treatment of certain EE syndromes. Recent publications record the effectiveness of targeted therapy for certain forms of monogenic early EE (stiripentol in SCN1A mutations, diphenine in SCN8A mutations, levetiracetam in STXBP1 mutations). These results indicate the necessity for accurate diagnosis of genetic variants in early infantile EE for preventive actions in burdened families and for increasing the effectiveness of treatment.

Mutations in BRAT1 cause autosomal recessive progressive encephalopathy: Report of a Spanish patient

We describe a 4-year-old male child born to non-consanguineous Spanish parents with progressive encephalopathy (PE), microcephaly, and hypertonia. Whole exome sequencing revealed compound heterozygous BRAT1 mutations [c.1564G > A (p.Glu522Lys) and c.638dup (p.Val214Glyfs*189)]. Homozygous and compound heterozygous BRAT1 mutations have been described in patients with lethal neonatal rigidity and multifocal seizure syndrome (MIM# 614498). The seven previously described patients suffered from uncontrolled seizures, and all of those patients died in their first months of life. BRAT1 acts as a regulator of cellular proliferation and migration and is required for mitochondrial function. The loss of these functions may explain the cerebral atrophy observed in this case of PE. This case highlights the extraordinary potential of next generation technologies for the diagnosis of rare genetic diseases, including PE. Making a prompt diagnosis of PE is important for genetic counseling and disease management.

Early-onset epileptic encephalopathies and the diagnostic approach to underlying causes

Early-onset epileptic encephalopathies are one of the most severe early onset epilepsies that can lead to progressive psychomotor impairment. These syndromes result from identifiable primary causes, such as structural, neurodegenerative, metabolic, or genetic defects, and an increasing number of novel genetic causes continue to be uncovered. A typical diagnostic approach includes documentation of anamnesis, determination of seizure semiology, electroencephalography, and neuroimaging. If primary biochemical investigations exclude precipitating conditions, a trial with the administration of a vitaminic compound (pyridoxine, pyridoxal-5-phosphate, or folinic acid) can then be initiated regardless of presumptive seizure causes. Patients with unclear etiologies should be considered for a further workup, which should include an evaluation for inherited metabolic defects and genetic analyses. Targeted next-generation sequencing panels showed a high diagnostic yield in patients with epileptic encephalopathy. Mutations associated with the emergence of epileptic encephalopathies can be identified in a targeted fashion by sequencing the most likely candidate genes. Next-generation sequencing technologies offer hope to a large number of patients with cryptogenic encephalopathies and will eventually lead to new therapeutic strategies and more favorable long-term outcomes.

Vagal Nerve Stimulation in the Treatment of Drug-Resistant Epileptic Encephalopathies in Inborn Errors of Metabolism: Report of 2 Cases

Patients affected by inborn errors of metabolism can develop catastrophic epilepsies ineligible for resective surgery. Few reports concerning vagal nerve stimulation in patients with epileptic encephalopathy in the context of metabolic diseases have been published in the literature. Drug-resistant epilepsies in metabolic disease could be a specific target for vagal nerve stimulation, although the efficacy of this technique in these patients still needs to be proved. The authors report our experience in treating refractory epilepsy with vagal nerve stimulation in 2 patients affected by inborn errors of metabolism. The first patient is a 23-year-old patient affected by glutaric aciduria type II, the other one is a 16-month-old child with nonketotic hyperglycinemia. Vagal nerve stimulation reduced seizures up to 50% in the first case and up to 90% in the second one.

Epileptic encephalopathies: new genes and new pathways

Epileptic encephalopathies represent a group of devastating epileptic disorders that occur early in life and are often characterized by pharmaco-resistant epilepsy, persistent severe electroencephalographic abnormalities, and cognitive dysfunction or decline. Next generation sequencing technologies have increased the speed of gene discovery tremendously. Whereas ion channel genes were long considered to be the only significant group of genes implicated in the genetic epilepsies, a growing number of non-ion-channel genes are now being identified. As a subgroup of the genetically mediated epilepsies, epileptic encephalopathies are complex and heterogeneous disorders, making diagnosis and treatment decisions difficult. Recent exome sequencing data suggest that mutations causing epileptic encephalopathies are often sporadic, typically resulting from de novo dominant mutations in a single autosomal gene, although inherited autosomal recessive and X-linked forms also exist. In this review we provide a summary of the key features of several early- and mid-childhood onset epileptic encephalopathies including Ohtahara syndrome, Dravet syndrome, Infantile spasms and Lennox Gastaut syndrome. We review the recent next generation sequencing findings that may impact treatment choices. We also describe the use of conventional and newer anti-epileptic and hormonal medications in the various syndromes based on their genetic profile. At a biological level, developments in cellular reprogramming and genome editing represent a new direction in modeling these pediatric epilepsies and could be used in the development of novel and repurposed therapies.

Epilepsy and mental retardation restricted to females: X-linked epileptic infantile encephalopathy of unusual inheritance

Epilepsy in females with mental retardation (EFMR) is a rare early infantile epileptic encephalopathy (EIEE), phenotypically resembling Dravet syndrome (DS). It is characterised by a variable degree of intellectual deficits and epilepsy. EFMR is caused by heterozygous mutations in the PCDH19 gene (locus Xq22.1) encoding protocadherin-19, a protein that is highly expressed during brain development. The protein is involved in cell adhesion and probably plays an important role in neuronal migration and formation of synaptic connections. EFMR is considered X-linked of variable mutations' penetrance. Mutations in the PCDH19 gene mainly arise de novo, but if inherited, they show a unique pattern of transmission. Females with heterozygous mutations are affected, while hemizygous males are not, regardless of mutation carriage. This singular mode might be explained by cell interference as a pathogenic molecular mechanism leading to neuronal dysfunction. Recently, PCDH19-related EIEE turned out to be more frequent than initially thought, contributing to around 16% of cases (25% in female groups) in the SCN1A-negative DS-like patients. Therefore, the PCDH19 gene is now estimated to be the second, after SCN1A, most clinically relevant gene in epilepsy.

The sodium leak channel, NALCN, in health and disease

Ion channels are crucial components of cellular excitability and are involved in many neurological diseases. This review focuses on the sodium leak, G protein-coupled receptors (GPCRs)-activated NALCN channel that is predominantly expressed in neurons where it regulates the resting membrane potential and neuronal excitability. NALCN is part of a complex that includes not only GPCRs, but also UNC-79, UNC-80, NLF-1 and src family of Tyrosine kinases (SFKs). There is growing evidence that the NALCN channelosome critically regulates its ion conduction. Both in mammals and invertebrates, animal models revealed an involvement in many processes such as locomotor behaviors, sensitivity to volatile anesthetics, and respiratory rhythms. There is also evidence that alteration in this NALCN channelosome can cause a wide variety of diseases. Indeed, mutations in the NALCN gene were identified in Infantile Neuroaxonal Dystrophy (INAD) patients, as well as in patients with an Autosomal Recessive Syndrome with severe hypotonia, speech impairment, and cognitive delay. Deletions in NALCN gene were also reported in diseases such as 13q syndrome. In addition, genes encoding NALCN, NLF- 1, UNC-79, and UNC-80 proteins may be susceptibility loci for several diseases including bipolar disorder, schizophrenia, Alzheimer's disease, autism, epilepsy, alcoholism, cardiac diseases and cancer. Although the physiological role of the NALCN channelosome is poorly understood, its involvement in human diseases should foster interest for drug development in the near future. Toward this goal, we review here the current knowledge on the NALCN channelosome in physiology and diseases.

Attention deficit associated with early life interictal spikes in a rat model is improved with ACTH

Children with epilepsy often present with pervasive cognitive and behavioral comorbidities including working memory impairments, attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder. These non-seizure characteristics are severely detrimental to overall quality of life. Some of these children, particularly those with epilepsies classified as Landau-Kleffner Syndrome or continuous spike and wave during sleep, have infrequent seizure activity but frequent focal epileptiform activity. This frequent epileptiform activity is thought to be detrimental to cognitive development; however, it is also possible that these IIS events initiate pathophysiological pathways in the developing brain that may be independently associated with cognitive deficits. These hypotheses are difficult to address due to the previous lack of an appropriate animal model. To this end, we have recently developed a rat model to test the role of frequent focal epileptiform activity in the prefrontal cortex. Using microinjections of a GABA(A) antagonist (bicuculline methiodine) delivered multiple times per day from postnatal day (p) 21 to p25, we showed that rat pups experiencing frequent, focal, recurrent epileptiform activity in the form of interictal spikes during neurodevelopment have significant long-term deficits in attention and sociability that persist into adulthood. To determine if treatment with ACTH, a drug widely used to treat early-life seizures, altered outcome we administered ACTH once per day subcutaneously during the time of the induced interictal spike activity. We show a modest amelioration of the attention deficit seen in animals with a history of early life interictal spikes with ACTH, in the absence of alteration of interictal spike activity. These results suggest that pharmacological intervention that is not targeted to the interictal spike activity is worthy of future study as it may be beneficial for preventing or ameliorating adverse cognitive outcomes.

Electroencephalogram of age-dependent epileptic encephalopathies in infancy and early childhood

Epileptic encephalopathy syndromes are disorders in which the epileptiform abnormalities are thought to contribute to a progressive cerebral dysfunction. Characteristic electroencephalogram findings have an important diagnostic value in classification of epileptic encephalopathy syndromes. In this paper, we focus on electroencephalogram findings of childhood epileptic encephalopathy syndromes and provide sample illustrations.

The role of epilepsy surgery in the treatment of childhood epileptic encephalopathy

Children with epileptic encephalopathy often have global impairment of brain function and frequent intractable seizures, which contribute further to their developmental disability. Many of these children have identifiable brain lesion on neurological imaging. In such cases, epilepsy surgery may be considered as a treatment option despite the lack of localized epileptic pattern on electroencephalogram (EEG). In this paper, we summarize the clinical features of epileptic encephalopathy syndromes and review the reported literature on the surgical approach to some of these disorders.