Dravet syndrome or genetic (generalized) epilepsy with febrile seizures plus?

GABRG2 mutations in genetic epilepsy with febrile seizures plus: structure, roles, and molecular genetics

Genetic epilepsy with febrile seizures plus (GEFS+) is a genetic epilepsy syndrome characterized by a marked hereditary tendency inherited as an autosomal dominant trait. Patients with GEFS+ may develop typical febrile seizures (FS), while generalized tonic-clonic seizures (GTCSs) with fever commonly occur between 3 months and 6 years of age, which is generally followed by febrile seizure plus (FS+), with or without absence seizures, focal seizures, or GTCSs. GEFS+ exhibits significant genetic heterogeneity, with polymerase chain reaction, exon sequencing, and single nucleotide polymorphism analyses all showing that the occurrence of GEFS+ is mainly related to mutations in the gamma-aminobutyric acid type A receptor gamma 2 subunit (GABRG2) gene. The most common mutations in GABRG2 are separated in large autosomal dominant families, but their pathogenesis remains unclear. The predominant types of GABRG2 mutations include missense (c.983A → T, c.245G → A, p.Met199Val), nonsense (R136*, Q390*, W429*), frameshift (c.1329delC, p.Val462fs*33, p.Pro59fs*12), point (P83S), and splice site (IVS6+2T → G) mutations. All of these mutations types can reduce the function of ion channels on the cell membrane; however, the degree and mechanism underlying these dysfunctions are different and could be linked to the main mechanism of epilepsy. The γ2 subunit plays a special role in receptor trafficking and is closely related to its structural specificity. This review focused on investigating the relationship between GEFS+ and GABRG2 mutation types in recent years, discussing novel aspects deemed to be great significance for clinically accurate diagnosis, anti-epileptic treatment strategies, and new drug development.

SCN1A-Characterization of the Gene's Variants in the Polish Cohort of Patients with Dravet Syndrome: One Center Experience

The aim of this study was to characterize the genotype and phenotype heterogeneity of patients with SCN1A gene mutations in the Polish population, fulfilling the criteria for the diagnosis of Dravet syndrome (DRVT). Particularly important was the analysis of the clinical course, the type of epileptic seizures and the co-occurrence of additional features such as intellectual disability, autism or neurological symptoms such as ataxia or gait disturbances. Based on their results and the available literature, the authors discuss potential predictors for DRVT. Identifying these early symptoms has important clinical significance, affecting the course and disease prognosis. 50 patients of the Pediatric Neurology Clinic of the Institute of Mother and Child in Warsaw clinically diagnosed with DRVT and carriers of SCN1A pathogenic variants were included. Clinical data were retrospectively collected from caregivers and available medical records. Patients in the study group did not differ significantly in parameters such as type of first seizure and typical epileptic seizures from those described in other studies. The age of onset of the first epileptic seizure was 2-9 months. The co-occurrence of intellectual disability was confirmed in 71% of patients and autism in 18%. The study did not show a correlation between genotype and phenotype, considering the severity of the disease course, clinical symptoms, response to treatment, the presence of intellectual disability, autism symptoms or ataxia. From the clinical course, a significant problem was the differentiation between complex febrile convulsions and symptoms of DRVT. The authors suggest that parameters such as the age of the first seizure, less than one year of age, the onset of a seizure up to 72 h after vaccination and the presence of more than two features of complex febrile seizures are more typical of DRVT, which should translate into adequate diagnostic and clinical management. The substantial decrease in the age of genetic verification of the diagnosis, as well as the decline in the use of sodium channel inhibitors, underscores the growing attention of pediatric neurologists in Poland to the diagnosis of DRVT.

Generation of iPSC lines (KAIMRCi003A, KAIMRCi003B) from a Saudi patient with Dravet syndrome carrying homozygous mutation in the CPLX1 gene and heterozygous mutation in SCN9A

The most prevalent form of epileptic encephalopathy is Dravet syndrome (DRVT), which is triggered by the pathogenic variant SCN1A in 80% of cases. iPSCs with different SCN1A mutations have been constructed by several groups to model DRVT syndrome. However, no studies involving DRVT-iPSCs with rare genetic variants have been conducted. Here, we established two DRVT-iPSC lines harboring a homozygous mutation in the CPLX1 gene and heterozygous mutation in SCN9A gene. Therefore, the derivation of these iPSC lines provides a unique cellular platform to dissect the molecular mechanisms underlying the cellular dysfunctions consequent to CPLX1 and SCN9A mutations.

Impact of variant subtype on electro-clinical phenotype of Dravet syndrome- a South Indian cohort study

OBJECTIVE

We aimed to compare the electroclinical correlates of truncating and missense variants of SCN1A variants in children with Dravet syndrome (DS) and to determine phenotypic features in relation to variants identified and seizure outcomes.

METHODS

A single center prospective study was carried out on a South Indian cohort. Patients below 18 years of age who met the clinical criteria for DS who had undergone genetic testing and completed a minimum of one year follow up were included. We compared the differences in clinical profile, seizure outcome, developmental characteristics and anti-seizure medication (ASM) responsiveness profiles between patients with missense and truncating variants.

RESULTS

Out of a total of 3967 children with drug-resistant epilepsy during the period 2015-2021, 49 patients who fulfilled the inclusion criteria were studied. Thirty-seven had positive genetic tests, out of which 29 were SCN1A variants and 9 were other novel variants. The proportion of missense (14; 48.3%) and truncating SCN1A variants (15; 51.7%) was similar. A significant trend for developing multiple seizure types was noted among children with truncating variants (p = 0.035) and seizure freedom was more likely among children with missense variants (p = 0.042). All patients with truncating variants had ASM resistant epilepsy (p = 0.020). Developmental outcomes did not differ between the variant subtypes.

CONCLUSION

Our results show that children harbouring missense variants demonstrated a significantly lower propensity for multiple seizure subtypes and a higher proportion with seizure freedom. However developmental implications appear to be independent of variant subtype.

An SCN1A gene missense variant in a Chinese Tujia ethnic family with genetic epilepsy with febrile seizures plus

Genetic epilepsy with febrile seizures plus (GEFSP) is a familial epileptic syndrome that is genetically heterogeneous and inherited in an autosomal dominant form in most cases. To date, at least seven genes have been reported to associate with GEFSP. This study aimed to identify the disease-causing variant in a Chinese Tujia ethnic family with GEFSP by using whole exome sequencing, Sanger sequencing, and in silico prediction. A heterozygous missense variant c.5725A>G (p.T1909A) was identified in the sodium voltage-gated channel alpha subunit 1 gene (SCN1A) coding region. The variant co-segregated with the GEFSP phenotype in this family, and it was predicted as disease-causing by multiple in silico programs, which was proposed as the genetic cause of GEFSP, further genetically diagnosed as GEFSP2. These findings expand the genetic and phenotypic spectrum of GEFSP and should contribute to genetic diagnoses, personalized therapies, and prognoses.

A Retrospective Study of the Profile and Outcome of Children with Dravet Syndrome in a Tertiary Care Hospital of Southern India

Objective Dravet syndrome (DS) is an epileptic syndrome that shares similarities with febrile seizures (FS), especially before 1 year of age, making it challenging to differentiate the two. We describe the profile of DS, with emphasis on the first year of life that can aid in early diagnosis.

Methods The clinical, investigative, treatment, and outcome profiles of DS patients presenting to the outpatient department (OPD) between October 2016 and December 2021 in a single tertiary care center in South India were analyzed.

Results Seventeen children were studied, with median age at presentation of 30 (interquartile range [IQR] 10, 47) months. The median age at seizure onset was 5 (IQR 3, 6) months. First seizure semiology were generalized tonic-clonic (GTCS) (35.3%), focal (52.9%), and myoclonic (11.8%). Fever preceding first seizure was seen in 76.5%. Status epilepticus (SE; ≥30 minutes) and prolonged seizures (>10 minutes) were seen in 41.2% each, and >5 seizures were seen in 82.4% in the first year of life. The most frequent subsequent seizure types were focal seizures (76.5%) and GTCS (76.5%). Other seizure triggers included vaccination (52.9%), light (17.6%), and Hot-bath (5.8%). Delayed developmental milestones for age were found in 52.9% at diagnosis. Magnetic resonance imaging (MRI) brain and electroencephalogram were normal in 76.4% each. Pathogenic/likely pathogenic variants in SCN1A gene were seen in 64.7%. Average of 3.9 anti-seizure medications were used. After optimization of treatment seizure frequency reduced in 40% and 4/15 (26.6%) had SE.

Conclusion In addition to characteristic clinical profile of DS we observed atypical presentations: an earlier age of seizure onset and afebrile seizure at onset. Delayed diagnosis was noted. Seizure control improved and SE reduced on optimal treatment.

Current and promising therapeutic options for Dravet syndrome

INTRODUCTION

Dravet Syndrome (DS) is a developmental and epileptic encephalopathy carrying high-level psychobehavioral burdens. Although the disease has been known for almost 4 decades, and despite significant progress in the understanding of its physiopathology and natural course, the pharmacological treatment leaves patients and caregivers with significant unmet needs. This review provides a summary of the current and promising therapeutic options for DS.

AREAS COVERED

PubMed and ClinicalTrials.gov were screened using 'Dravet Syndrome' OR 'DS,' AND 'pharmacotherapy,' AND 'treatments.' Randomized clinical trials, structured reviews, and meta-analyses were selected for in-human application of well-known anti-seizure medications; while in-vivo experiments on models of DS were selected to evaluate the potential of new therapeutic strategies.

EXPERT OPINION

The search for new pharmacological treatment options is led by the need for care and defeat of the natural course of the disease, an aspect still largely neglected by the available therapeutic strategies. Yet, the last 6 years have led to a climate of increased interest and availability of clinical trials. Particularly, gene therapy could hopefully prevent DS evolution by directly relieving the specific genetic defect, although the possibility of off-target editing, and the uneasy administration route have still largely prevented its use.

Mechanism of the promotion of GEFS+ by the STAT3-mediated expression of interleukin-6

BACKGROUND

Genetic epilepsy with febrile seizures plus (GEFS+) is generally considered an ion channelopathy. To date, there have been few studies on inflammation associated with various types of epilepsy, and it remains unclear whether the inflammatory mechanism plays a key role in epilepsy.

METHODS

In order to explore the role of the regulatory mechanism of immune factor expression in the pathogenesis of GEFS+, the present study detected the expression level of relevant immune factors such as interleukin-6 (IL-6) in peripheral blood of GEFS+ mice.

RESULTS

The cluster of differentiation 4⁺/cluster of differentiation 8⁺ (CD4⁺/CD8⁺) ratio in the GEFS+ mice was decreased, while the signal transducer and activator of transcription 3 (STAT3) was also activated and the IL-6 was upregulated. Inhibit of STAT3 can lead to the GEFS+ asymptomatically due to the downregulated IL-6, IL-1β, and complement factor H (CFH) levels. Suppression of STAT3 can also inhibited the epileptic seizures, the CD8⁺ T cells were declined after the IL-6 was neutralized.

CONCLUSIONS

The purpose of this study was to analyze and compare the effect of STAT3 expression and activation differences on GEFS+ attack, and to clarify the relationship between various cytokines and GEFS+ outbreak. Inhibiting the expression of pro-inflammatory factors can further prevent GEFS+ attack, which supports that IL-6 is one of the important factors that aggravate the clinical symptoms of GEFS+. We expected to provide a theoretical basis for immunosuppressive therapy of GEFS+ and a new way for its clinical treatment.

Whole exome sequencing and co-expression analysis identify an SCN1A variant that modifies pathogenicity in a family with genetic epilepsy and febrile seizures plus

OBJECTIVE

Family members carrying the same SCN1A variant often exhibit differences in the clinical severity of epilepsy. This variable expressivity suggests that other factors aside from the primary sodium channel variant influence the clinical manifestation. However, identifying such factors has proven challenging in humans.

METHODS

We perform whole exome sequencing (WES) in a large family in which an SCN1A variant (p.K1372E) is segregating that is associated with a broad spectrum of phenotypes ranging from lack of epilepsy, to febrile seizures and absence seizures, to Dravet syndrome. We assessed the hypothesis that the severity of the SCN1A-related phenotype was affected by alternate alleles at a modifier locus (or loci).

RESULTS

One of our top candidates identified by WES was a second variant in the SCN1A gene (p.L375S) that was shared exclusively by unaffected carriers of the K1372E allele. To test the hypothesized that L375S variant nullifies the loss-of-function effect of K1372E, we transiently expressed Nav1.1 carrying the two variants in HEK293T cells and compared their biophysical properties with the wild-type (WT) variant, and then co-expressed WT with K1372E or L375S with K1372E in equal quantity and tested the functional consequence. The data demonstrated that co-expression of the L375S and K1372E alleles reversed the loss-of-function property brought by the K1372E variant, whereas WT-K1372E co-expression remained partial loss-of-function.

SIGNIFICANCE

These results support the hypothesis that L375S counteracts the loss-of-function effect of K1372E such that individuals carrying both alleles in trans do not present epilepsy-related symptoms. We demonstrate that monogenic epilepsies with wide expressivity can be modified by additional variants in the disease gene, providing a novel framework for the gene-phenotype relationship in genetic epilepsies.

Adjuvant Treatment for Protocadherin 19 (PCDH19) Syndrome

Protocadherin 19 (PCDH19) syndrome is inherited as an X-linked pattern and affects mainly females. This syndrome is caused by a mutation in the PCDH19 gene encoding for the protocadherin protein. It is characterized by refractory seizures during febrile episodes with neuropsychiatric manifestations. There is no consensus on the treatment of PCDH19. We conducted a literature review to investigate the main drugs used for this syndrome, and to evaluate the best possible course of adjuvant treatment for these patients. We used an advanced PubMed search strategy with the following inclusion criteria: a) full-text papers, b) English Language, and c) studies conducted in humans. Exclusion criteria: a) literature reviews, b) systematic reviews, and c) metanalysis. We gathered 26 observational papers to conduct this literature review on clobazam and bromide which have been shown to reduce seizures by 50%. Corticosteroids improved neurological symptoms during the episodes in a few patients. Nevertheless, they recurred after a few months. Preliminary results of ganaxolone, which is still under study, demonstrated a reduction of 60% in seizure episodes. A ketogenic diet has been studied to treat several refractory epilepsies, including PCDH19; it has promising results as effective adjuvant therapy in the resolution of status epilepticus, suggesting it could be used as part of the treatment in early childhood. Stiripentol was given as adjuvant therapy in a patient with PCDH19 epilepsy resulting in the most extended period of seizure-free episodes, but more studies must be performed to assess its efficacy.

Genetic Landscape of SCN1A Variants in a Turkish Cohort with GEFS+ Spectrum and Dravet Syndrome

Introduction

The α subunit of voltage-gated sodium channels in mammals is encoded by 9 different genes, and variations in the SCN1A, SCN2A, SCN3A, and SCN8A genes highly expressed in the CNS have been associated with epilepsy phenotypes. This study aimed at investigating the frequency of SCN1A gene variations in Dravet syndrome (DS) and GEFS+ spectrum phenotype cases and discussing the molecular results in the context of genotype-phenotype correlation.

Methods

Fifteen patients diagnosed with DS and 54 patients meeting the GEFS+ spectrum criteria were included in this study. All patients were evaluated by next-generation sequencing and multiplex ligation-dependent probe amplification using an SCN1A gene commercial kit.

Results

A total of 17 different variants were detected in 18 index cases (26%), of which 7 were novel variations (p.M1R, p.M147T, p.I767L, p.N1391Ifs*5, p.R1886G, p.E1915G, p.R1933Q). Of the 18 cases with variation in the SCN1A gene, 12 had DS and 6 had GEFS+ phenotype. The variations were de novo in all DS cases and in 1 case with a GEFS+ phenotype; in 5 GEFS+ cases, the variant was inherited from the affected parent.

Discussion

This study contributes to the variation spectrum in cases with DS and GEFS+ phenotype with the novel variants detected. SCN1A genetic analysis can help in determining whether antiseizure medication should be selected or avoided in cases with variations. The elucidation of the molecular etiology makes it possible to provide the family with effective genetic counseling for future pregnancies.

Genetic therapeutic advancements for Dravet Syndrome

Dravet Syndrome is a genetic epileptic syndrome characterized by severe and intractable seizures associated with cognitive, motor, and behavioral impairments. The disease is also linked with increased mortality mainly due to sudden unexpected death in epilepsy. Over 80% of cases are due to a de novo mutation in one allele of the SCN1A gene, which encodes the α-subunit of the voltage-gated ion channel Na_V1.1. Dravet Syndrome is usually refractory to antiepileptic drugs, which only alleviate seizures to a small extent. Viral, non-viral genetic therapy, and gene editing tools are rapidly enhancing and providing new platforms for more effective, alternative medicinal treatments for Dravet syndrome. These strategies include gene supplementation, CRISPR-mediated transcriptional activation, and the use of antisense oligonucleotides. In this review, we summarize our current knowledge of novel genetic therapies that are currently under development for Dravet syndrome.

Human iPSC Modeling of Genetic Febrile Seizure Reveals Aberrant Molecular and Physiological Features Underlying an Impaired Neuronal Activity

Mutations in SCN1A gene, encoding the voltage-gated sodium channel (VGSC) NaV1.1, are widely recognized as a leading cause of genetic febrile seizures (FS), due to the decrease in the Na+ current density, mainly affecting the inhibitory neuronal transmission. Here, we generated induced pluripotent stem cells (iPSCs)-derived neurons (idNs) from a patient belonging to a genetically well-characterized Italian family, carrying the c.434T > C mutation in SCN1A gene (hereafter SCN1AM145T). A side-by-side comparison of diseased and healthy idNs revealed an overall maturation delay of SCN1AM145T cells. Membranes isolated from both diseased and control idNs were injected into Xenopus oocytes and both GABA and AMPA currents were successfully recorded. Patch-clamp measurements on idNs revealed depolarized action potential for SCN1AM145T, suggesting a reduced excitability. Expression analyses of VGSCs and chloride co-transporters NKCC1 and KCC2 showed a cellular “dysmaturity” of mutated idNs, strengthened by the high expression of SCN3A, a more fetal-like VGSC isoform, and a high NKCC1/KCC2 ratio, in mutated cells. Overall, we provide strong evidence for an intrinsic cellular immaturity, underscoring the role of mutant NaV1.1 in the development of FS. Furthermore, our data are strengthening previous findings obtained using transfected cells and recordings on human slices, demonstrating that diseased idNs represent a powerful tool for personalized therapy and ex vivo drug screening for human epileptic disorders.

Phenotypic and Genotypic Characteristics of SCN1A Associated Seizure Diseases

Although SCN1A variants result in a wide range of phenotypes, genotype-phenotype associations are not well established. We aimed to explore the phenotypic characteristics of SCN1A associated seizure diseases and establish genotype-phenotype correlations. We retrospectively analyzed clinical data and results of genetic testing in 41 patients carrying SCN1A variants. Patients were divided into two groups based on their clinical manifestations: the Dravet Syndrome (DS) and non-DS groups. In the DS group, the age of seizure onset was significantly earlier and ranged from 3 to 11 months, with a median age of 6 months, than in the non-DS group, where it ranged from 7 months to 2 years, with a median age of 10 and a half months. In DS group, onset of seizures in 11 patients was febrile, in seven was afebrile, in two was febrile/afebrile and one patient developed fever post seizure. In the non-DS group, onset in all patients was febrile. While in the DS group, three patients had unilateral clonic seizures at onset, and the rest had generalized or secondary generalized seizures at onset, while in the non-DS group, all patients had generalized or secondary generalized seizures without unilateral clonic seizures. The duration of seizure in the DS group was significantly longer and ranged from 2 to 70 min (median, 20 min), than in the non-DS group where it ranged from 1 to 30 min (median, 5 min). Thirty-one patients harbored de novo variants, and nine patients had inherited variants. Localization of missense variants in the voltage sensor region (S4) or pore-forming region (S5–S6) was seen in seven of the 11 patients in the DS group and seven of the 17 patients in the non-DS group. The phenotypes of SCN1A-related seizure disease were diverse and spread over a continuous spectrum from mild to severe. The phenotypes demonstrate commonalities and individualistic differences and are not solely determined by variant location or type, but also due to functional changes, genetic modifiers as well as other known and unknown factors.

Auditory phoneme discrimination, articulation, and language disorders in patients with genetic epilepsy with febrile seizures plus: A case-control study

INTRODUCTION

Genetic epilepsy with febrile seizures plus (GEFS+) is an epilepsy syndrome with clinical heterogeneity that was first described in 1997. Central auditory processing (CAP) is defined as the neurophysiological process in decoding sound waves from the outer ear to the auditory cortex. The present study aimed to analyze CAP and phonological disorders in preschool-age children with GEFS+.

MATERIAL AND METHOD

This is a prospective case-control study. Twenty-seven patients diagnosed with GEFS+ aged between 4 years and 6 years and 6 months and 31 healthy controls in the same age range were included in the study. Phonological sensitivity test (SAT) and auditory discrimination test (İAT) were applied to both groups, and the results of both groups were statistically compared.

RESULTS

The SAT and İAT raw and Z scores of the subjects in the study group were found to be significantly higher than those of the control group (p = 0.001; p < 0.01). Electroencephalography (EEG) status of the patients or the duration of antiseizure medication use did not have a statistically significant effect on the outcome.

CONCLUSION

Patients with GEFS+ have a significantly high impairment in both articulation and auditory discrimination of phonemes compared with the healthy population. Early diagnosis and early treatment of this condition can prevent potential literacy problems and the development of dyslexia in the future.

Role of SCN2A c.56G/A Gene Polymorphism in Egyptian Children with Genetic Epilepsy with Febrile Seizure Plus

BACKGROUND

Febrile Seizures (FS) are the most common seizures in children younger than 5 years. In the last decade, various coding and noncoding sequence variations of voltage-gated sodium channels SCN2A have been identified in patients with seizures, implying their genetic base. We aimed to evaluate the association between SCN2A c. G/A genetic polymorphism among Egyptian children with febrile seizure plus.

METHODS

The present cross-sectional study was carried out on 100 epileptic infants and children, attendants of the Neurology Unit, pediatric department, Menoufia University Hospitals (Group Ι). The patients were sub-classified into two groups, according to response to anti-epileptic treatment; Group Ι a (drug responder) and Group Ι b (drug-resistant). Evenly divided number of apparently healthy, age and gender-matched children were selected as controls (Group II). A complete history, throughout the systemic examination and radiological & metabolic assessment, whenever needed was provided, all participants were genotyped for SCN2A rs17183814 polymorphism by Restriction Fragment Length Polymorphism (PCR-RFLP).

RESULTS

Both of A allele and AA, GA genotypes of SCN2A c. 56 G/A were detected more in patients with febrile seizure plus comparison to the control group with a statistically significant difference at frequencies of 17% and 11% and 12% respectively; OR (CI95%): 10.04 (3.49-28.87) and p <0.001. On classifying epileptic patients into 2 subgroups, carriers of SCN2A rs17183814 AA genotype tended to respond poorly to Anti-epileptic Drugs (AEDs). Moreover, multivariate analysis revealed that rs17183814 A allele and positive family history of epilepsy were considered the highest predicted risk factors for the development of epilepsy; p<0.05.

CONCLUSION

SCN2A rs17183814 (A) allele was specifically associated with developing febrile seizure plus and could modulate the patient's response to anti-epileptic medications.

Fever-Associated Seizures or Epilepsy: An Overview of Old and Recent Literature Acquisitions

In addition to central nervous system infections, seizures and fever may occur together in several neurological disorders. Formerly, based on the clinical features and prognostic evolution, the co-association of seizure and fever included classical febrile seizures (FS) divided into simple, complex, and prolonged FS (also called febrile status epilepticus). Later, this group of disorders has been progressively indicated, with a more inclusive term, as "fever-associated seizures or epilepsy" (FASE) that encompasses: (a) FS divided into simple, complex, and prolonged FS; (b) FS plus; (c) severe myoclonic epilepsy in infancy (Dravet syndrome); (d) genetic epilepsy with FS plus; and (e) febrile infection-related epilepsy syndrome (FIRES). Among the FASE disorders, simple FS, the most common and benign condition, is rarely associated with subsequent epileptic seizures. The correlation of FS with epilepsy and other neurological disorders is highly variable. The pathogenesis of FASE is unclear but immunological and genetic factors play a relevant role and the disorders belonging to the FASE group show to have an underlying common clinical, immunological, and genetic pathway. In this study, we have reviewed and analyzed the clinical data of each of the heterogeneous group of disorders belonging to FASE.

The phenotypic spectrum of KCNT1: a new family with variable epilepsy syndromes including mild focal epilepsy

BACKGROUND AND OBJECTIVE

Pathogenic variants in KCNT1 have been associated with severe forms of epilepsy, typically sleep-related hypermotor epilepsy or epilepsy of infancy with migrating focal seizures. To show that pathogenic variants in KCNT1 can be associated with mild extra-frontal epilepsy, we report a KCNT1 family with a wide spectrum of phenotypes ranging from developmental and epileptic encephalopathy to mild focal epilepsy without cognitive regression and not consistent with sleep-related hypermotor epilepsy.

METHODS

A large Canadian family of Caucasian descent including 9 affected family members was recruited. Family members were phenotyped by direct interview and review of existing medical records. Clinical epilepsy gene panel analysis and exome sequencing were performed.

RESULTS

Phenotypic information was available for five family members of which two had developmental and epileptic encephalopathy and three had normal development and focal epilepsy with presumed extra-frontal onset. All three had predominantly nocturnal seizures that did not show hyperkinetic features. All three reported clusters of seizures at night with a feeling of being unable to breathe associated with gasping for air, choking and/or repetitive swallowing possibly suggesting insular or opercular involvement. Genetic analysis identified a heterozygous KCNT1 c.2882G > A, p.Arg961His variant that was predicted to be deleterious.

DISCUSSION

This family demonstrates that the phenotypic spectrum associated with KCNT1 pathogenic variants is broader than previously assumed. Our findings indicate that variants in KCNT1 can be associated with mild focal epilepsy and should not be excluded during variant interpretation in such patients based solely on gene-disease validity.

New avenues in molecular genetics for the diagnosis and application of therapeutics to the epilepsies

Genetic epidemiology studies have shown that most epilepsies involve some genetic cause. In addition, twin studies have helped strengthen the hypothesis that in most patients with epilepsy, a complex inheritance is involved. More recently, with the development of high-density single-nucleotide polymorphism (SNP) microarrays and next-generation sequencing (NGS) technologies, the discovery of genes related to the epilepsies has accelerated tremendously. Especially, the use of whole exome sequencing (WES) has had a considerable impact on the identification of rare genetic variants with large effect sizes, including inherited or de novo mutations in severe forms of childhood epilepsies. The identification of pathogenic variants in patients with these childhood epilepsies provides many benefits for patients and families, such as the confirmation of the genetic nature of the diseases. This process will allow for better genetic counseling, more accurate therapy decisions, and a significant positive emotional impact. However, to study the genetic component of the more common forms of epilepsy, the use of high-density SNP arrays in genome-wide association studies (GWAS) seems to be the strategy of choice. As such, researchers can identify loci containing genetic variants associated with the common forms of epilepsy. The knowledge generated over the past two decades about the effects of the mutations that cause the monogenic epilepsy is tremendous; however, the scientific community is just starting to apply this information in order to generate better target treatments.

Focal epilepsy in SCN1A-mutation carrying patients: is there a role for epilepsy surgery?

Variants in the gene SCN1A are a common genetic cause for a wide range of epilepsy phenotypes ranging from febrile seizures to Dravet syndrome. Focal onset seizures and structural lesions can be present in these patients and the question arises whether epilepsy surgery should be considered. We report eight patients (mean age 13y 11mo [SD 8y 1mo], range 3-26y; four females, four males) with SCN1A variants, who underwent epilepsy surgery. Outcomes were variable and seemed to be directly related to the patient's anatomo-electroclinical epilepsy phenotype. Patients with Dravet syndrome had unfavourable outcomes, whilst patients with focal epilepsy, proven to arise from a single structural lesion, had good results. We conclude that the value of epilepsy surgery in patients with an SCN1A variant rests on two issues: understanding whether the variant is pathogenic and the patient's anatomo-electroclinical phenotype. Careful evaluation of epilepsy phenotype integrated with understanding the significance of genetic variants is essential in determining a patient's suitability for epilepsy surgery. Patients with focal onset epilepsy may benefit from epilepsy surgery, whereas those with Dravet syndrome do not. WHAT THIS PAPER ADDS: Patients should not automatically be excluded from epilepsy surgery evaluation if they carry an SCN1A variant. Patients with focal epilepsy may benefit from epilepsy surgery; those with Dravet syndrome do not.

A Study among the Genotype, Functional Alternations, and Phenotype of 9 SCN1A Mutations in Epilepsy Patients

Mutations in the voltage-gated sodium channel Nav1.1 (SCN1A) are linked to various epileptic phenotypes with different severities, however, the consequences of newly identified SCN1A variants on patient phenotype is uncertain so far. The functional impact of nine SCN1A variants, including five novel variants identified in this study, was studied using whole-cell patch-clamp recordings measurement of mutant Nav1.1 channels expressed in HEK293T mammalian cells. E78X, W384X, E1587K, and R1596C channels failed to produce measurable sodium currents, indicating complete loss of channel function. E788K and M909K variants resulted in partial loss of function by exhibiting reduced current density, depolarizing shifts of the activation and hyperpolarizing shifts of the inactivation curves, and slower recovery from inactivation. Hyperpolarizing shifts of the activation and inactivation curves were observed in D249E channels along with slower recovery from inactivation. Slower recovery from inactivation was observed in E78D and T1934I with reduced current density in T1934I channels. Various functional effects were observed with the lack of sodium current being mainly associated with severe phenotypes and milder symptoms with less damaging channel alteration. In vitro functional analysis is thus fundamental for elucidation of the molecular mechanisms of epilepsy, to guide patients' treatment, and finally indicate misdiagnosis of SCN1A related epilepsies.

SCN8A Mutation in Infantile Epileptic Encephalopathy: Report of Two Cases

Early infantile epileptic encephalopathy type 13 is a severe form of epilepsy caused by mutations in the sodium channel 8 alpha (SCN8A) gene. This gene encodes the neuronal voltage-gated sodium channel which plays vital role in neuronal excitability. Here we present two cases with SCN8A encephalopathy. Both cases had mutation in p.Arg1872Gin the SCN8A gene, which was detected by targeted next generation sequencing. Case 1 was a 14-month old boy, who had a normal birth history with normal development up to 6 months and then developed repeated generalized seizure, which was nonresponsive to multiple antiepileptic drugs. He also had neuroregression and dystonia. His electroencephalogram (EEG) showed progressive background abnormality with burst suppression pattern. His metabolic panel was normal and had partial response to carbamazepine. The second case was for an 11-month old boy with the onset of seizure at the age of 7 months. Seizure was generalized, resistant to multiple antiepileptic drugs. He had developmental delay from beginning, no movement disorder. EEG showed focal discharge from left temporal and occipital region. He showed partial response to oxcarbazepine. Our cases had similarities with the previously reported cases. The detailed discussion of our cases would contribute to early detection and targeted treatment of SCN8A encephalopathy. This also gives special emphasis on a genetic test in infants with intractable epilepsy, movement disorder and developmental delay.

Modifier genes in SCN1A-related epilepsy syndromes

Background

SCN1A is one of the most important epilepsy‐related genes, with pathogenic variants leading to a range of phenotypes with varying disease severity. Different modifying factors have been hypothesized to influence SCN1A‐related phenotypes. We investigate the presence of rare and more common variants in epilepsy‐related genes as potential modifiers of SCN1A‐related disease severity.

Methods

87 patients with SCN1A‐related epilepsy were investigated. Whole‐exome sequencing was performed by the Beijing Genomics Institute (BGI). Functional variants in 422 genes associated with epilepsy and/or neuronal excitability were investigated. Differences in proportions of variants between the epilepsy genes and four control gene sets were calculated, and compared to the proportions of variants in the same genes in the ExAC database.

Results

Statistically significant excesses of variants in epilepsy genes were observed in the complete cohort and in the combined group of mildly and severely affected patients, particularly for variants with minor allele frequencies of <0.05. Patients with extreme phenotypes showed much greater excesses of epilepsy gene variants than patients with intermediate phenotypes.

Conclusion

Our results indicate that relatively common variants in epilepsy genes, which would not necessarily be classified as pathogenic, may play a large role in modulating SCN1A phenotypes. They may modify the phenotypes of both severely and mildly affected patients. Our results may be a first step toward meaningful testing of modifier gene variants in regular diagnostics for individual patients, to provide a better estimation of disease severity for newly diagnosed patients.

Optimization of in silico tools for predicting genetic variants: individualizing for genes with molecular sub-regional stratification

Genes are unique in functional role and differ in their sensitivities to genetic defects, but with difficulties in pathogenicity prediction. This study attempted to improve the performance of existing in silico algorithms and find a common solution based on individualization strategy. We initiated the individualization with the epilepsy-related SCN1A variants by sub-regional stratification. SCN1A missense variants related to epilepsy were retrieved from mutation databases, and benign missense variants were collected from ExAC database. Predictions were performed by using 10 traditional tools with stepwise optimizations. Model predictive ability was evaluated using the five-fold cross-validations on variants of SCN1A, SCN2A, and KCNQ2. Additional validation was performed in SCN1A variants of damage-confirmed/familial epilepsy. The performance of commonly used predictors was less satisfactory for SCN1A with accuracy less than 80% and varied dramatically by functional domains of Nav1.1. Multistep individualized optimizations, including cutoff resetting, domain-based stratification, and combination of predicting algorithms, significantly increased predictive performance. Similar improvements were obtained for variants in SCN2A and KCNQ2. The predictive performance of the recently developed ensemble tools, such as Mendelian clinically applicable pathogenicity, combined annotation-dependent depletion and Eigen, was also improved dramatically by application of the strategy with molecular sub-regional stratification. The prediction scores of SCN1A variants showed linear correlations with the degree of functional defects and the severity of clinical phenotypes. This study highlights the need of individualized optimization with molecular sub-regional stratification for each gene in practice.

Social cognition and psychopathology in childhood and adolescence

There is a substantial body of research on social cognition in adults with epilepsy, and in broad categories such as focal and generalized epilepsies, but much less has been written about social cognition in children with epilepsy (CWE), and in childhood-onset epilepsy syndromes specifically. In several of these syndromes, autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD), two disorders with social cognitive impairments, are reported. There is strong evidence for social cognitive deficits in juvenile myoclonic epilepsy (JME). There is also a considerable amount of evidence for such deficits in a number of syndromes that may be associated with ASD or ADHD, including West syndrome (WS), Dravet syndrome (DS), and the Landau-Kleffner syndrome (LKS). However, the evidence is of variable quality and incomplete across the range of childhood epilepsy syndromes. In some syndromes, childhood epilepsy substantially increases the risk of severe social cognitive impairment, which may persist after the seizures remit. This paper presents an overview of current research on social cognition in childhood epilepsy, with a particular focus on syndromes with a high prevalence of autistic and behavioral comorbidities. Social cognitive impairments represent a considerable additional challenge for patients and caregivers. Early diagnosis and intervention might significantly improve long-term social cognitive outcomes, highlighting the need for greater awareness among clinicians of this important topic. This article is part of the Special Issue "Epilepsy and social cognition across the lifespan".

Transcriptomes of Dravet syndrome iPSC derived GABAergic cells reveal dysregulated pathways for chromatin remodeling and neurodevelopment

Dravet syndrome (DS) is an early onset refractory epilepsy typically caused by de novo heterozygous variants in SCN1A encoding the α-subunit of the neuronal sodium channel Na_v1.1. The syndrome is characterized by age-related progression of seizures, cognitive decline and movement disorders. We hypothesized that the distinct neurodevelopmental features in DS are caused by the disruption of molecular pathways in Na_v1.1 haploinsufficient cells resulting in perturbed neural differentiation and maturation. Here, we established DS-patient and control induced pluripotent stem cell derived neural progenitor cells (iPSC NPC) and GABAergic inter-neuronal (iPSC GABA) cells. The DS-patient iPSC GABA cells showed a shift in sodium current activation and a perturbed response to induced oxidative stress. Transcriptome analysis revealed specific dysregulations of genes for chromatin structure, mitotic progression, neural plasticity and excitability in DS-patient iPSC NPCs and DS-patient iPSC GABA cells versus controls. The transcription factors FOXM1 and E2F1, positive regulators of the disrupted pathways for histone modification and cell cycle regulation, were markedly up-regulated in DS-iPSC GABA lines. Our study highlights transcriptional changes and disrupted pathways of chromatin remodeling in Na_v1.1 haploinsufficient GABAergic cells, providing a molecular framework that overlaps with that of neurodevelopmental disorders and other epilepsies.

Gene expression profiling in a mouse model of Dravet syndrome

Dravet syndrome is a severe, early-onset epileptic encephalopathy frequently resulting from de novo mutations of SCN1A. Mice with heterozygous deletion of Scn1a (Scn1a^+/-) model many features of Dravet syndrome, including spontaneous seizures and premature lethality. Scn1a^+/- mice exhibit variable phenotype penetrance and expressivity dependent upon the strain background. On the 129S6/SvEvTac (129) strain, Scn1a^+/- mice do not display an overt phenotype. However Scn1a^+/- mice on the [129S6xB6]F1 strain (F1.Scn1a^+/-) exhibit juvenile-onset spontaneous seizures and premature lethality. QTL mapping identified several modifier loci responsible for strain-dependent differences in survival of Scn1a^+/- mice, but these loci do not account for all the observed phenotypic variance. Global RNA-seq analysis was performed to identify additional genes and pathways that may contribute to variable phenotypes. Hippocampal gene expression was analyzed in wild-type (WT) and Scn1a^+/- mice on both F1 and 129 strains, at two time points during disease development. There were few gene expression differences between 129.WT and 129.Scn1a^+/- mice and approximately 100 genes with small expression differences (6-36%) between F1.WT and F1.Scn1a^+/- mice. Strain-specific gene expression differences were more pronounced, with dozens of genes with >1.5-fold expression differences between 129 and F1 strains. Age-specific and seizure-related gene expression differences were most prominent, with hundreds of genes with >2-fold differences in expression identified between groups with and without seizures, suggesting potential differences in developmental trajectory and/or homeostatic plasticity during disease onset. Global expression differences in the context of Scn1a deletion may account for strain-dependent variation in seizure susceptibility and survival observed in Scn1a^+/- mice.

Functional Modulation of Voltage-Gated Sodium Channels by a FGF14-Based Peptidomimetic

Protein-protein interactions (PPI) offer unexploited opportunities for CNS drug discovery and neurochemical probe development. Here, we present ZL181, a novel peptidomimetic targeting the PPI interface of the voltage-gated Na⁺ channel Nav1.6 and its regulatory protein fibroblast growth factor 14 (FGF14). ZL181 binds to FGF14 and inhibits its interaction with the Nav1.6 channel C-tail. In HEK-Nav1.6 expressing cells, ZL181 acts synergistically with FGF14 to suppress Nav1.6 current density and to slow kinetics of fast inactivation, but antagonizes FGF14 modulation of steady-state inactivation that is regulated by the N-terminal tail of the protein. In medium spiny neurons in the nucleus accumbens, ZL181 suppresses excitability by a mechanism that is dependent upon expression of FGF14 and is consistent with a state-dependent inhibition of FGF14. Overall, ZL181 and derivatives could lay the ground for developing allosteric modulators of Nav channels that are of interest for a broad range of CNS disorders.

Benign and severe early-life seizures: a round in the first year of life

BACKGROUND

At the onset, differentiation between abnormal non-epileptic movements, and epileptic seizures presenting in early life is difficult as is clinical diagnosis and prognostic evaluation of the various seizure disorders presenting at this age. Seizures starting in the first year of life including the neonatal period might have a favorable course, such as in infants presenting with benign familial neonatal epilepsy, febrile seizures simplex or acute symptomatic seizures. However, in some cases, the onset of seizures at birth or in the first months of life have a dramatic evolution with severe cerebral impairment. Seizure disorders starting in early life include the "epileptic encephalopathies", a group of conditions characterized by drug resistant seizures, delayed developmental skills, and intellective disability. This group of disorders includes early infantile epileptic encephalopathy also known as Ohtahara syndrome, early myoclonic encephalopathy, epilepsy of infancy with migrating focal seizures, infantile spasms syndrome (also known as West syndrome), severe myoclonic epilepsy in infancy (also known as Dravet syndrome) and, myoclonic encephalopathies in non-progressive disorder. Here we report on seizures manifesting in the first year of life including the neonatal period. Conditions with a benign course, and those with severe evolution are presented. At this early age, clinical identification of seizures, distinction of each of these disorders, type of treatment and prognosis is particularly challenging. The aim of this report is to present the clinical manifestations of each of these disorders and provide an updated review of the conditions associated with seizures in the first year of life.

Differential effects on sodium current impairments by distinct SCN1A mutations in GABAergic neurons derived from Dravet syndrome patients

BACKGROUND

We investigated how two distinct mutations in SCN1A differentially affect electrophysiological properties of the patient-derived GABAergic neurons and clinical severities in two Dravet syndrome (DS) patients.

MATERIALS AND METHODS

We established induced pluripotent stem cells from two DS patients with different mutations in SCN1A and subsequently differentiated them into forebrain GABAergic neurons. Functionality of differentiated GABAergic neurons was examined by electrophysiological recordings.

RESULTS

DS-1 patient had a missense mutation, c.4261G > T [GenBank: NM_006920.4] and DS-2 patient had a nonsense frameshift mutation, c.3576_3580 del TCAAA [GenBank: NM_006920.4]. Clinically, contrary to our expectations, DS-1 patient had more severe symptoms including frequency of seizure episodes and the extent of intellectual ability penetration than DS-2 patient. Electrophysiologic recordings showed significantly lower sodium current density and reduced action potential frequency at strong current injection (>60 pA) in GABAergic neurons derived from both. Intriguingly, unique genetic alterations of SCN1A differentially impacted electrophysiological impairment of the neurons, and the impairment's extent corresponded with the symptomatic severity of the donor from which the iPSCs were derived.

CONCLUSION

Our results suggest the possibility that patient-derived iPSCs may provide a reliable in vitro system that reflects clinical severities in individuals with DS.

Cognitive Function and Neuropsychological Comorbidities in Children with Newly Diagnosed Idiopathic Epilepsy

BACKGROUND

In this study, we aimed to identify cognitive function and neuropsychological comorbidities in children with newly diagnosed idiopathic epilepsy.

METHODS

We retrospectively reviewed the records of 97 antiepileptic drug-naïve children (9.7 ± 2.9 years; 54 males and 43 females) with newly diagnosed idiopathic epilepsy, all of whom underwent a neuropsychological battery. The battery consisted of the Korean Wechsler Intelligence Scale, Attention Deficit Hyperactivity Disorder (ADHD) Rating Scale, ADHD Diagnostic System, Children's Depression Inventory, and State-Trait Anxiety Inventory for Children. We investigated association between scores of the neuropsychological battery and epilepsy classification, lateralization of interictal epileptiform discharges (IEDs) on electroencephalography (EEG), and variables related to seizures.

RESULTS

Thirteen patients (14.3%) had ADHD symptoms. Three patients (4.1%) had depressive symptoms, and 9 (12.3%) had anxiety symptoms. Patients with idiopathic generalized epilepsy (IGE) had significantly lower full-scale intelligence and performance intelligence quotient scores than patients with idiopathic localization-related epilepsy (ILRE) (89.0 ± 17.6 vs. 96.3 ± 14.8; P = 0.030 and 88.9 ± 16.3 vs. 97.0 ± 16.4; P = 0.016, respectively). Patients with ILRE having unilateral IEDs had significantly higher full-scale intelligence quotient scores than patients with ILRE having bilateral IEDs and patients with IGE (99.9 ± 12.2 vs. 93.7 ± 16.1 vs. 89.0 ± 17.6; P = 0.039, respectively).

CONCLUSION

Our results suggest that idiopathic epilepsy may be accompanied by various neuropsychological comorbidities even at initial diagnosis. Patients with IGE and ILRE having bilateral IEDs on EEG appear more likely to be at high risk of decreased cognitive function.

Ion Channels in Genetic Epilepsy: From Genes and Mechanisms to Disease-Targeted Therapies

Epilepsy is a common and serious neurologic disease with a strong genetic component. Genetic studies have identified an increasing collection of disease-causing genes. The impact of these genetic discoveries is wide reaching-from precise diagnosis and classification of syndromes to the discovery and validation of new drug targets and the development of disease-targeted therapeutic strategies. About 25% of genes identified in epilepsy encode ion channels. Much of our understanding of disease mechanisms comes from work focused on this class of protein. In this study, we review the genetic, molecular, and physiologic evidence supporting the pathogenic role of a number of different voltage- and ligand-activated ion channels in genetic epilepsy. We also review proposed disease mechanisms for each ion channel and highlight targeted therapeutic strategies.

Clinical and molecular characterization of KCNT1-related severe early-onset epilepsy

OBJECTIVE

To characterize the phenotypic spectrum, molecular genetic findings, and functional consequences of pathogenic variants in early-onset KCNT1 epilepsy.

METHODS

We identified a cohort of 31 patients with epilepsy of infancy with migrating focal seizures (EIMFS) and screened for variants in KCNT1 using direct Sanger sequencing, a multiple-gene next-generation sequencing panel, and whole-exome sequencing. Additional patients with non-EIMFS early-onset epilepsy in whom we identified KCNT1 variants on local diagnostic multiple gene panel testing were also included. When possible, we performed homology modeling to predict the putative effects of variants on protein structure and function. We undertook electrophysiologic assessment of mutant KCNT1 channels in a xenopus oocyte model system.

RESULTS

We identified pathogenic variants in KCNT1 in 12 patients, 4 of which are novel. Most variants occurred de novo. Ten patients had a clinical diagnosis of EIMFS, and the other 2 presented with early-onset severe nocturnal frontal lobe seizures. Three patients had a trial of quinidine with good clinical response in 1 patient. Computational modeling analysis implicates abnormal pore function (F346L) and impaired tetramer formation (F502V) as putative disease mechanisms. All evaluated KCNT1 variants resulted in marked gain of function with significantly increased channel amplitude and variable blockade by quinidine.

CONCLUSIONS

Gain-of-function KCNT1 pathogenic variants cause a spectrum of severe focal epilepsies with onset in early infancy. Currently, genotype-phenotype correlations are unclear, although clinical outcome is poor for the majority of cases. Further elucidation of disease mechanisms may facilitate the development of targeted treatments, much needed for this pharmacoresistant genetic epilepsy.

SCN8A mutations in Chinese patients with early onset epileptic encephalopathy and benign infantile seizures

Background

SCN8A mutations have recently been associated with epilepsy and neurodevelopmental disorders. This study aimed to broaden the phenotypic-spectrum of disease related with SCN8A mutations.

Methods

To identify the pathogenic gene of a Chinese family, in which six members suffered from epilepsy, whole-exome sequencing was performed. In addition, target next-generation sequencing (NGS) was performed on 178 sporadic patients, who had epilepsy of unknown etiology within 6 months after birth. A detailed clinical history was obtained.

Results

A heterozygous missense mutation of SCN8A was identified in the Chinese family. Six de novo mutations of SCN8A were detected in 6 sporadic patients with epilepsy. In the family, six members developed seizures within a few years after birth. Five of them had milder clinical performance, that they had normal cognition and developmental milestones, and seizure-free was achieved by mono-therapy. The other one affected member presented with refractory epilepsy and developmental regression. She died from sudden unexpected death in epilepsy (SUDEP) at 17-year-old. Clinical features of six sporadic patients with SCN8A mutations were diverse, ranging from severe epileptic encephalopathy to benign epilepsy with normal cognition. Seizures started at the mean age of 3.9 months (from 2 months to 6 months). Seizure-free was achieved in four of them by mono- or multi-antiepileptic drugs. Five of them demonstrated mild or severe psychomotor retardation, whereas the other one was normal in development and intelligence.

Conclusions

Our findings extend the spectrum of SCN8A mutations and the clinical features of patients with SCN8A mutations. The majority of SCN8A mutations were de novo, inherited mutations from the heterozygous parents can also occur. The phenotypic spectrum of SCN8A mutation varied largely. Most affected patients manifested as refractory epilepsy and severe intellectual disability, only a small number of patients presented with milder clinical patterns. Additionally, our study confirmed that the same mutation can lead to different phenotypes.

Electronic supplementary material

The online version of this article (10.1186/s12881-017-0460-1) contains supplementary material, which is available to authorized users.

The role of genetic testing in epilepsy diagnosis and management

INTRODUCTION

Epilepsy is a common neurological disorder characterized by recurrent unprovoked seizures. More than 500 epilepsy-associated genes have been described in the literature. Most of these genes play an important role in neuronal excitability, cortical development or synaptic transmission. A growing number of genetic variations have implications on diagnosis and prognostic or therapeutic advice in terms of a personalized medicine. Area covered: The review presents the different forms of genetic epilepsies with respect to their underlying genetic and functional pathophysiology and aims to give advice for recommended genetic testing. Moreover, it discusses ethical and legal guidelines, costs and technical limitations which should be considered. Expert commentary: Genetic testing is an important component in the diagnosis and treatment of many forms of epilepsy.

Large-scale structural alteration of brain in epileptic children with SCN1A mutation

Objective

Mutations in SCN1A gene encoding the alpha 1 subunit of the voltage gated sodium channel are associated with several epilepsy syndromes including genetic epilepsy with febrile seizures plus (GEFS +) and severe myoclonic epilepsy of infancy (SMEI). However, in most patients with SCN1A mutation, brain imaging has reported normal or non-specific findings including cerebral or cerebellar atrophy. The aim of this study was to investigate differences in brain morphometry in epileptic children with SCN1A mutation compared to healthy control subjects.

Methods

We obtained cortical morphology (thickness, and surface area) and brain volume (global, subcortical, and regional) measurements using FreeSurfer (version 5.3.0, https://surfer.nmr.mgh.harvard.edu) and compared measurements of children with epilepsy and SCN1A gene mutation (n = 21) with those of age and gender matched healthy controls (n = 42).

Results

Compared to the healthy control group, children with epilepsy and SCN1A gene mutation exhibited smaller total brain, total gray matter and white matter, cerebellar white matter, and subcortical volumes, as well as mean surface area and mean cortical thickness. A regional analysis revealed significantly reduced gray matter volume in the patient group in the bilateral inferior parietal, left lateral orbitofrontal, left precentral, right postcentral, right isthmus cingulate, right middle temporal area with smaller surface area and white matter volume in some of these areas. However, the regional cortical thickness was not significantly different in two groups.

Significance

This study showed large-scale developmental brain changes in patients with epilepsy and SCN1A gene mutation, which may be associated with the core symptoms of the patients. Further longitudinal MRI studies with larger cohorts are required to confirm the effect of SCN1A gene mutation on structural brain development.

•

Surface-based morphometry was performed in epileptic children with SCN1A mutation.

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Cortical GM and WM volumes, cerebellar WM volume and surface area are smaller.

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Patients group showed similar age effect on total brain volume and GM volume.

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No significant difference were obtained in regional cortical thickness.

Familial aggregation of focal seizure semiology in the Epilepsy Phenome/Genome Project

OBJECTIVE

To improve phenotype definition in genetic studies of epilepsy, we assessed the familial aggregation of focal seizure types and of specific seizure symptoms within the focal epilepsies in families from the Epilepsy Phenome/Genome Project.

METHODS

We studied 302 individuals with nonacquired focal epilepsy from 149 families. Familial aggregation was assessed by logistic regression analysis of relatives' traits (dependent variable) by probands' traits (independent variable), estimating the odds ratio for each symptom in a relative given presence vs absence of the symptom in the proband.

RESULTS

In families containing multiple individuals with nonacquired focal epilepsy, we found significant evidence for familial aggregation of ictal motor, autonomic, psychic, and aphasic symptoms. Within these categories, ictal whole body posturing, diaphoresis, dyspnea, fear/anxiety, and déjà vu/jamais vu showed significant familial aggregation. Focal seizure type aggregated as well, including complex partial, simple partial, and secondarily generalized tonic-clonic seizures.

CONCLUSION

Our results provide insight into genotype-phenotype correlation in the nonacquired focal epilepsies and a framework for identifying subgroups of patients likely to share susceptibility genes.

In vivo assessment of neurological channelopathies: Application of peripheral nerve excitability studies

With the rapid evolution of understanding of neurological channelopathies comes a need for sensitive tools to evaluate patients in clinical practice. Neurological channelopathies with a single-gene basis can manifest as seizures, headache, ataxia, vertigo, confusion, weakness and neuropathic pain and it is likely that other genetic factors contribute to the phenotype of many of these disorders. Ion channel dysfunction can result in abnormal cell membrane excitability but utilisation of advanced neurophysiology techniques has lagged behind developments in clinical, genetic and imaging evaluation of channelopathies. However, momentum in the application of in vivo axonal excitability testing sees these tests emerging as valuable tools, with the capacity to provide sensitive and specific insights into the mechanism of disease. While single-channel function cannot be directly measured in vivo, evaluation of subjects with single-gene channelopathies has provided insights into the effects of mutation-related alterations of membrane excitability, as well as compensatory adaptive changes. By showing how ion channel dysfunction can affect axonal excitability in vivo, studies of the excitability of peripheral nerve axons complement in vitro analysis of single channel activity. The interpretation of results is enhanced by mathematical modelling of axonal function and insights provided by in vitro work. This article is part of the Special Issue entitled 'Channelopathies.'

SCN3A deficiency associated with increased seizure susceptibility

Mutations in voltage-gated sodium channels expressed highly in the brain (SCN1A, SCN2A, SCN3A, and SCN8A) are responsible for an increasing number of epilepsy syndromes. In particular, mutations in the SCN3A gene, encoding the pore-forming Na_v1.3 α subunit, have been identified in patients with focal epilepsy. Biophysical characterization of epilepsy-associated SCN3A variants suggests that both gain- and loss-of-function SCN3A mutations may lead to increased seizure susceptibility. In this report, we identified a novel SCN3A variant (L247P) by whole exome sequencing of a child with focal epilepsy, developmental delay, and autonomic nervous system dysfunction. Voltage clamp analysis showed no detectable sodium current in a heterologous expression system expressing the SCN3A-L247P variant. Furthermore, cell surface biotinylation demonstrated a reduction in the amount of SCN3A-L247P at the cell surface, suggesting the SCN3A-L247P variant is a trafficking-deficient mutant. To further explore the possible clinical consequences of reduced SCN3A activity, we investigated the effect of a hypomorphic Scn3a allele (Scn3a^Hyp) on seizure susceptibility and behavior using a gene trap mouse line. Heterozygous Scn3a mutant mice (Scn3a^+/Hyp) did not exhibit spontaneous seizures nor were they susceptible to hyperthermia-induced seizures. However, they displayed increased susceptibility to electroconvulsive (6Hz) and chemiconvulsive (flurothyl and kainic acid) induced seizures. Scn3a^+/Hyp mice also exhibited deficits in locomotor activity and motor learning. Taken together, these results provide evidence that loss-of-function of SCN3A caused by reduced protein expression or deficient trafficking to the plasma membrane may contribute to increased seizure susceptibility.

SCN1A clinical spectrum includes the self-limited focal epilepsies of childhood

INTRODUCTION

Amongst autosomal dominant genetic epilepsy with febrile seizures plus (GEFS+) families, SCN1A variants are the most common genetic cause. Initially regarded as a generalized form of epilepsy, the GEFS+ spectrum is now known to include some focal epilepsies, but it is generally not conceptualized as extending to the self-limited focal epilepsies of childhood, such as Panayiotopoulos syndrome. There are, however, three reports of SCN1A variants in Panayiotopoulos syndrome. We describe the variable clinical phenotypes that include the self-limited focal epilepsies of childhood, present in a large GEFS+ family, segregating a heterozygous SCN1A missense variant.

MATERIAL AND METHODS

Electro-clinical details on all putatively affected family members were sought and blood samples were taken for genetic analysis. Two individuals were chosen for SCN1A testing. All 26 exons and exon-intron junctions were amplified, sequenced and analyzed. This was followed by pedigree segregation analysis of the variant identified.

RESULTS

A pathogenic heterozygous SCN1A (c.2624C>A; p.Thr875Lys) variant was identified. Sixteen of the 18 variant positive family members were affected (88% penetrance): 8 with febrile seizures, 2 febrile seizures plus, 1 unclassified seizures and 5 with self-limited focal epilepsy of childhood. Of these, one was diagnosed with atypical childhood epilepsy with centrotemporal spikes and four with Panayiotopoulos syndrome.

DISCUSSION

By characterizing the heterogeneous clinical phenotypes in a large, SCN1A mutation positive GEFS+ family, we conclude that the GEFS+ spectrum can extend to the self-limited focal epilepsies of childhood, including Panayiotopoulos syndrome, and in turn highlight the complex genotype-phenotype correlations associated with SCN1A-related epilepsies.

Vagus nerve stimulation for genetic epilepsy with febrile seizures plus (GEFS+) accompanying seizures with impaired consciousness

Genetic epilepsy with febrile seizures plus (GEFS⁺) is characterized by childhood-onset epilepsy syndrome. It involves febrile seizures and a variety of afebrile epileptic seizure types within the same pedigree with autosomal-dominant inheritance. Approximately 10% of individuals with GEFS⁺ harbor SCN1A, a gene mutation in one of the voltage-gated sodium channel subunits. Considerably less common are focal epilepsies including complex partial seizures. We report vagus nerve stimulation (VNS) in a 6-year-old girl with GEFS⁺ who exhibited refractory generalized tonic-clonic seizures and complex partial seizures.

Helping Families Cope with the Severe Stress of Dravet Syndrome

A child with Dravet syndrome shakes family life to the core. Dravet syndrome usually has three phases: (1) up to 1-1½ years: with episodes of febrile status epilepticus but normal development; (2) age 1½ to ~6-10 years: with frequent seizures of varying types, developmental stagnation, behavioural and sleep problems; (3) after ~10 years: improvement in seizures, deteriorating gait, intellectual disability but some developmental gains. Complete seizure control is rare—simply prescribing medication is inadequate to help families. Based on structured interviews with 24 families and confirmed by more informal discussions with other families, we suggest strategies for coping with this catastrophe. A child with Dravet syndrome usually means that one parent cannot work—financial pressures should be anticipated. In Stage 1, the approach to status should include a written protocol. An indwelling catheter for rapid venous access may be helpful. In Stage 2, assistance finding qualified babysitters is required, and the extended family needs encouragement to help. Appropriate equipment, rescue medication and protocols should travel with the child. Siblings may benefit from a system of one parent “on call.” An internet support group provides an invaluable lifeline. In Stage 3, family isolation may be extreme—respite care and personal time for parents are important. Death from status, accidents and SUDEP (sudden unexplained death in epilepsy) occurs in 15%. Fear of SUDEP needs to be addressed. Moving from paediatric to adult care is frightening; an epilepsy transition clinic is useful. Attention to these realities may improve the quality of life for both child and family.

Cognitive impairment in childhood onset epilepsy: up-to-date information about its causes

Cognitive impairment associated with childhood-onset epilepsy is an important consequence in the developing brain owing to its negative effects on neurodevelopmental and social outcomes. While the cause of cognitive impairment in epilepsy appears to be multifactorial, epilepsy-related factors such as type of epilepsy and underlying etiology, age at onset, frequency of seizures, duration of epilepsy, and its treatment are considered important. In recent studies, antecedent cognitive impairment before the first recognized seizure and microstructural and functional alteration of the brain at onset of epilepsy suggest the presence of a common neurobiological mechanism between epilepsy and cognitive comorbidity. However, the overall impact of cognitive comorbidity in children with epilepsy and the independent contribution of each of these factors to cognitive impairment have not been clearly delineated. This review article focuses on the significant contributors to cognitive impairment in children with epilepsy.

The genetics of the epilepsies

While genetic causes of epilepsy have been hypothesized from the time of Hippocrates, the advent of new genetic technologies has played a tremendous role in elucidating a growing number of specific genetic causes for the epilepsies. This progress has contributed vastly to our recognition of the epilepsies as a diverse group of disorders, the genetic mechanisms of which are heterogeneous. Genotype-phenotype correlation, however, is not always clear. Nonetheless, the developments in genetic diagnosis raise the promise of a future of personalized medicine. Multiple genetic tests are now available, but there is no one test for all possible genetic mutations, and the balance between cost and benefit must be weighed. A genetic diagnosis, however, can provide valuable information regarding comorbidities, prognosis, and even treatment, as well as allow for genetic counseling. In this review, we will discuss the genetic mechanisms of the epilepsies as well as the specifics of particular genetic epilepsy syndromes. We will include an overview of the available genetic testing methods, the application of clinical knowledge into the selection of genetic testing, genotype-phenotype correlations of epileptic disorders, and therapeutic advances as well as a discussion of the importance of genetic counseling.

Diagnostic Approach to Genetic Causes of Early-Onset Epileptic Encephalopathy

Epileptic encephalopathies are characterized by recurrent clinical seizures and prominent interictal epileptiform discharges seen during the early infantile period. Although epileptic encephalopathies are mostly associated with structural brain defects and inherited metabolic disorders, pathogenic gene mutations may also be involved in the development of epileptic encephalopathies even when no clear genetic inheritance patterns or consanguinity exist. The most common epileptic encephalopathies are Ohtahara syndrome, early myoclonic encephalopathy, epilepsy of infancy with migrating focal seizures, West syndrome and Dravet syndrome, which are usually unresponsive to traditional antiepileptic medication. Many of the diagnoses describe the phenotype of these electroclinical syndromes, but not the underlying causes. To date, approximately 265 genes have been defined in epilepsy and several genes including STXBP1, ARX, SLC25A22, KCNQ2, CDKL5, SCN1A, and PCDH19 have been found to be associated with early-onset epileptic encephalopathies. In this review, we aimed to present a diagnostic approach to primary genetic causes of early-onset epileptic encephalopathies.

Novel GABRG2 mutations cause familial febrile seizures

Objective:

To identify the genetic cause in a large family with febrile seizures (FS) and temporal lobe epilepsy (TLE) and subsequently search for additional mutations in a cohort of 107 families with FS, with or without epilepsy.

Methods:

The cohort consisted of 1 large family with FS and TLE, 64 smaller French families recruited through a national French campaign, and 43 Italian families. Molecular analyses consisted of whole-exome sequencing and mutational screening.

Results:

Exome sequencing revealed a p.Glu402fs*3 mutation in the γ2 subunit of the GABA_A receptor gene (GABRG2) in the large family with FS and TLE. Three additional nonsense and frameshift GABRG2 mutations (p.Arg136*, p.Val462fs*33, and p.Pro59fs*12), 1 missense mutation (p.Met199Val), and 1 exonic deletion were subsequently identified in 5 families of the follow-up cohort.

Conclusions:

We report GABRG2 mutations in 5.6% (6/108) of families with FS, with or without associated epilepsy. This study provides evidence that GABRG2 mutations are linked to the FS phenotype, rather than epilepsy, and that loss-of-function of GABA_A receptor γ2 subunit is the probable underlying pathogenic mechanism.