Generalized Epilepsy with Febrile Seizures Plus (GEFS+): Clinical Spectrum in Seven Italian Families Unrelated to SCN1A, SCN1B, and GABRG2 Gene Mutations

ILAE classification and definition of epilepsy syndromes with onset in neonates and infants: Position statement by the ILAE Task Force on Nosology and Definitions

The International League Against Epilepsy (ILAE) Task Force on Nosology and Definitions proposes a classification and definition of epilepsy syndromes in the neonate and infant with seizure onset up to 2 years of age. The incidence of epilepsy is high in this age group and epilepsy is frequently associated with significant comorbidities and mortality. The licensing of syndrome specific antiseizure medications following randomized controlled trials and the development of precision, gene-related therapies are two of the drivers defining the electroclinical phenotypes of syndromes with onset in infancy. The principal aim of this proposal, consistent with the 2017 ILAE Classification of the Epilepsies, is to support epilepsy diagnosis and emphasize the importance of classifying epilepsy in an individual both by syndrome and etiology. For each syndrome, we report epidemiology, clinical course, seizure types, electroencephalography (EEG), neuroimaging, genetics, and differential diagnosis. Syndromes are separated into self-limited syndromes, where there is likely to be spontaneous remission and developmental and epileptic encephalopathies, diseases where there is developmental impairment related to both the underlying etiology independent of epileptiform activity and the epileptic encephalopathy. The emerging class of etiology-specific epilepsy syndromes, where there is a specific etiology for the epilepsy that is associated with a clearly defined, relatively uniform, and distinct clinical phenotype in most affected individuals as well as consistent EEG, neuroimaging, and/or genetic correlates, is presented. The number of etiology-defined syndromes will continue to increase, and these newly described syndromes will in time be incorporated into this classification. The tables summarize mandatory features, cautionary alerts, and exclusionary features for the common syndromes. Guidance is given on the criteria for syndrome diagnosis in resource-limited regions where laboratory confirmation, including EEG, MRI, and genetic testing, might not be available.

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.

SCN1A and Its Related Epileptic Phenotypes

Epilepsy is one of the most common neurological disorders, with a lifetime incidence of 1 in 26. Approximately two-thirds of epilepsy has a substantial genetic component in its etiology. As a result, simultaneous screening for mutations in multiple genes and performing whole exome sequencing (WES) are becoming very frequent in the clinical evaluation of children with epilepsy. In this setting, mutations in voltage-gated sodium channel (SCN) α-subunit genes are the most commonly identified cause of epilepsy, with sodium channel genes (i.e., SCN1A, SCN2A, SCN8A) being the most frequently identified causative genes. SCN1A mutations result in a wide spectrum of epilepsy phenotypes ranging from simple febrile seizures to Dravet syndrome, a severe epileptic encephalopathy. In case of mutation of SCN1A, it is also possible to observe behavioral alterations, such as impulsivity, inattentiveness, and distractibility, which can be framed in an attention deficit hyperactivity disorder (ADHD) like phenotype. Despite more than 1,200 SCN1A mutations being reported, it is not possible to assess a clear phenotype–genotype correlations. Treatment remains a challenge and seizure control is often partial and transitory.

Mutations in the sodium channel genes SCN1A, SCN3A, and SCN9A in children with epilepsy with febrile seizures plus(EFS+)

PURPOSE

To explore disease-causing gene mutations of epilepsy with febrile seizures plus (EFS+) in Southern Chinese Han population.

METHODS

Blood samples and clinical data were collected from 49 Southern Han Chinese patients with EFS+. Gene screening was performed using whole-exome sequencing and panel sequencing for 485 epilepsy-related genes. The pathogenicity of variants was evaluated based on ACMG scoring and assessment of clinical concordance.

RESULTS

We identified 10 putatively causative sodium channel gene variants in 49 patients with EFS+, including 8 variants in SCN1A (R500Q appeared twice), one in SCN3A and one in SCN9A. All these missense mutations were inherited from maternal or paternal and were evaluated to be of uncertain significance according to ACMG. The clinical features of patients were in concordance with the EFS+ phenotype of the mutated SCN1A, SCN3A and SCN9A gene. The clinical phenotypes of 11 probands with these gene variants included febrile seizures plus (FS+, n=7), Dravet Syndrome (n=3), FS+ with focal seizures (n=1). Three probands with SCN1A variants (R500Q located in the non-voltage areas, or G1711D in the pore-forming domain) developed severe Dravet syndrome. The affected individuals with the other 6 SCN1A variants located outside the pore-forming domain showed mild phenotypes. Novel SCN3A variant ((D1688Y) and SCN9A variant (R185H) were identified in two probands respectively and both of the probands had FS+.

CONCLUSION

The SCN1A, SCN3A, and SCN9A gene mutations might be a pathogenic cause of EFS+ in Southern Chinese Han population.

No association between SCN9A and monogenic human epilepsy disorders

Many studies have demonstrated the clinical utility and importance of epilepsy gene panel testing to confirm the specific aetiology of disease, enable appropriate therapeutic interventions, and inform accurate family counselling. Previously, SCN9A gene variants, in particular a c.1921A>T p.(Asn641Tyr) substitution, have been identified as a likely autosomal dominant cause of febrile seizures/febrile seizures plus and other monogenic seizure phenotypes indistinguishable from those associated with SCN1A, leading to inclusion of SCN9A on epilepsy gene testing panels. Here we present serendipitous findings of genetic studies that identify the SCN9A c.1921A>T p.(Asn641Tyr) variant at high frequency in the Amish community in the absence of such seizure phenotypes. Together with findings in UK Biobank these data refute an association of SCN9A with epilepsy, which has important clinical diagnostic implications.

Copy number variation in genetic epilepsy with febrile seizures plus

AIM

Genetic epilepsy with febrile seizures plus (GEFS+) is a familial epilepsy syndrome in which affected individuals may have a variety of epilepsy phenotypes, the most common being febrile seizures (FS) and febrile seizures plus (FS+). We investigated the possible contribution of copy number variation to GEFS+.

METHOD

We searched our epilepsy research database for patients in GEFS + families who underwent chromosomal microarray analysis. We reviewed the clinical features and results of genetic testing in these families.

RESULTS

Of twelve families with available microarray data, four had at least one copy number variant (CNV) identified. In Family 1, the proband had a maternally-inherited 15q11.2 deletion. In Family 5, four different CNVs were identified, variably present in the affected individuals; this included a 19p13.3 deletion affecting CACNA1A. Finally, in both Families 9 and 10, the proband had Dravet syndrome with pathogenic SCN1A variant, as well as a CNV (10q11.22 duplication in Family 9 and 22q11.2 deletion in Family 10).

INTERPRETATION

The significance of these specific variants is difficult to precisely determine; however, there appeared to be an overrepresentation of CNVs in this small cohort. These findings suggest chromosomal microarray analysis could have clinical utility as part of the workup in GEFS + families.

Advances in genetic testing and optimization of clinical management in children and adults with epilepsy

Introduction: Epileptic disorders are a heterogeneous group of medical conditions with epilepsy as the common denominator. Genetic causes, electro-clinical features, and management significantly vary according to the specific condition.Areas covered: Relevant diagnostic advances have been achieved thanks to the advent of Next Generation Sequencing (NGS)-based molecular techniques. These revolutionary tools allow to sequence all coding (whole exome sequencing, WES) and non-coding (whole genome sequencing, WGS) regions of human genome, with a potentially huge impact on patient care and scientific research.Expert opinion: The application of these tests in children and adults with epilepsy has led to the identification of new causative genes, widening the knowledge on the pathophysiology of epilepsy and resulting in therapeutic implications. This review will explore the most recent advancements in genetic testing and provide up-to-date approaches for the choice of the correct test in patients with epilepsy.

Genetic epilepsy with febrile seizures plus: Refining the spectrum

OBJECTIVE

Following our original description of generalized epilepsy with febrile seizures plus (GEFS+) in 1997, we analyze the phenotypic spectrum in 409 affected individuals in 60 families (31 new families) and expand the GEFS+ spectrum.

METHODS

We performed detailed electroclinical phenotyping on all available affected family members. Genetic analysis of known GEFS+ genes was carried out where possible. We compared our phenotypic and genetic data to those published in the literature over the last 19 years.

RESULTS

We identified new phenotypes within the GEFS+ spectrum: focal seizures without preceding febrile seizures (16/409 [4%]), classic genetic generalized epilepsies (22/409 [5%]), and afebrile generalized tonic-clonic seizures (9/409 [2%]). Febrile seizures remains the most frequent phenotype in GEFS+ (178/409 [44%]), followed by febrile seizures plus (111/409 [27%]). One third (50/163 [31%]) of GEFS+ families tested have a pathogenic variant in a known GEFS+ gene.

CONCLUSION

As 37/409 (9%) affected individuals have focal epilepsies, we suggest that GEFS+ be renamed genetic epilepsy with febrile seizures plus rather than generalized epilepsy with febrile seizures plus. The phenotypic overlap between GEFS+ and the classic generalized epilepsies is considerably greater than first thought. The clinical and molecular data suggest that the 2 major groups of generalized epilepsies share genetic determinants.

A novel inherited SCN1A mutation associated with GEFS+ in benign and encephalopathic epilepsy

Generalized epilepsy with febrile seizures plus (GEFS+) is an autosomal dominant condition often caused by mutations in SCN1A that usually first manifests as childhood simple febrile seizures but may progress to a variety of afebrile generalized seizure types. Here, we describe the case of an 8-year-old boy with a novel SCN1A mutation who developed febrile seizures at 10months of age which eventually advanced to frequent afebrile tonic-clonic seizures. His condition was unresponsive to several antiepileptic drugs and the ketogenic diet, and he experienced gradual cognitive decline. The patient's father carries the same novel mutation, but he only experienced childhood simple febrile seizures. SCN1A mutations display incomplete penetrance and variable expressivity, and the resulting severity may depend on the location and type of mutation, whether the mutation was spontaneous or inherited, and the effect of modifying alleles. The identification of novel pathogenic SCN1A mutations may eventually advance therapeutic development and prognostic capabilities.

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.

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.

Improving molecular diagnosis in epilepsy by a dedicated high-throughput sequencing platform

We analyzed by next-generation sequencing (NGS) 67 epilepsy genes in 19 patients with different types of either isolated or syndromic epileptic disorders and in 15 controls to investigate whether a quick and cheap molecular diagnosis could be provided. The average number of nonsynonymous and splice site mutations per subject was similar in the two cohorts indicating that, even with relatively small targeted platforms, finding the disease gene is not an univocal process. Our diagnostic yield was 47% with nine cases in which we identified a very likely causative mutation. In most of them no interpretation would have been possible in absence of detailed phenotype and familial information. Seven out of 19 patients had a phenotype suggesting the involvement of a specific gene. Disease-causing mutations were found in six of these cases. Among the remaining patients, we could find a probably causative mutation only in three. None of the genes affected in the latter cases had been suspected a priori. Our protocol requires 8-10 weeks including the investigation of the parents with a cost per patient comparable to sequencing of 1-2 medium-to-large-sized genes by conventional techniques. The platform we used, although providing much less information than whole-exome or whole-genome sequencing, has the advantage that can also be run on 'benchtop' sequencers combining rapid turnaround times with higher manageability.

Can we predict the response in the treatment of epilepsy with vagus nerve stimulation?

Despite the introduction of new antiepileptic drugs and advances in the surgical treatment of epilepsy, an important group of patients still remains uncontrolled by any of these methods. The relatively recent introduction of vagus nerve stimulation is yet another possible treatment for refractory epilepsy. This safe, simple, and adjustable technique reduces the number of seizures and multiple publications support its increasing efficacy and effectiveness, with few adverse effects. The goal of our study is to determine the efficacy of this procedure and the factors predicting a response, particularly in the presence of a temporal lobe discharge on the video electroencephalogram (video-EEG) and magnetic resonance imaging (MRI) lesions. We undertook a retrospective study of all the patients with refractory epilepsy who underwent implantation of a vagus nerve stimulator between 2003 and 2009, and with a minimum follow-up of 6 months. The statistical analysis was done with SPSS for Windows. The stimulator was implanted in 40 patients, of whom 38 had a minimum follow-up of 6 months. In one patient, the device had to be removed due to infection, so the series comprised 37 patients. These were divided into different groups, according to the epidemiologic, clinical, radiologic, and electroencephalographic data. In addition, an analysis of the response was performed. The efficacy of the procedure was established according to the reduction in the mean seizure frequency. The baseline value of these seizures was 80.97 ± 143.59, falling to 37 ± 82.51 at the last revision. The response rate (reduction in seizures ≥ 50 %) at 6 months was 51.4 %, with 62.2 % of the patients showing this reduction at the last evaluation. Significant differences in the response were seen for the variables: baseline frequency of seizures, temporal lobe discharge on VideoEEG and MRI lesions. The mean time to response was 10 months in patients with lower rate of seizures versus 25 months of those with the higher rate (p = 0.024), and the response at 6 months was higher (p = 0.05). Patients with temporal lobe discharge alone or in combination with discharges over other regions had a mean time to response of 11 months versus 26 months in those without temporal discharge (p = 0.037). In the analysis of the MRI, we had seen that at the last revision, 82.4 % of the patients with lesion had achieved response versus 45 % without lesion (p = 0.02). Vagus nerve stimulation reduces the frequency of seizures. A temporal lobe discharge on the video-EEG is an indicator of an early response and the presence of an MRI lesion indicates a late response. Patients with fewer rates of seizures have a better prognosis.

Idiopathic generalized epilepsies

Idiopathic generalized epilepsies (IGEs) may start in infancy, childhood, or adolescence, but some have an onset in adulthood. They are genetically determined and affect otherwise healthy people of both sexes and all races, and are generally lifelong. Some, however, are age related. IGEs account for nearly a third of all epilepsies. According to the International League Against Epilepsy (ILAE) proposed classification, the following IGEs are recognized in accordance with the age at onset (Engel, 2001): benign myoclonic epilepsy in infancy (BMEI), generalized epilepsies with febrile seizures plus (GEFS+), epilepsy with myoclonic-astatic seizures (EMAS), epilepsy with myoclonic absences (EMA), childhood absence epilepsy (CAE), and IGEs with variable phenotypes (IGEVP) that include juvenile absence epilepsy (JAE), juvenile myoclonic epilepsy (JME), and epilepsy with generalized tonic-clonic seizures only (EGTCSO). These IGEs raise a conceptual issue since some conditions are epilepsy syndromes (a combination of a given age of onset, seizure type(s), and interictal and clinical and EEG features) (i.e., BMEI, EMAS, EMA, CAE, JAE, JME) whereas others join several types of epilepsy in a given family (i.e., GEFS+and eventually IGEVP and EGTCSO). This chapter describes the electroclinical features, evolution, and therapeutic aspects of IGEs.

Genetics of idiopathic epilepsies

One of the most exciting areas in epilepsy has been the explosion in our understanding of the genetics of the epilepsies over the last decade. Built on a long history of careful clinical genetic studies of the epilepsies, the relatively recent discovery of epilepsy genes has enabled insights into pathways causing seizure disorders. A variety of mutational mechanisms can cause epilepsy resulting from different, and sometimes surprising, molecular processes such as copy number variation within the genome. The majority of known epilepsy genes encode ion channel subunits leading many of the genetic epilepsies to be regarded as channelopathies. Understanding how dysfunction of a mutant protein leads to hyperexcitability is key to understanding the pathophysiology of this group of serious and common childhood disorders. The architecture of the common genetic epilepsies following complex inheritance, where multiple genes are involved, is also beginning to be unraveled. The clinical approach to understanding the genetics of the epilepsies has matured and requires a detailed family history of seizures together with delineation of the child's epilepsy syndrome. Recognition of specific genetic epilepsy syndromes enables optimal treatment and prognostic and genetic counseling.

De-novo mutations and genetic variation in the SCN1A gene in Malaysian patients with generalized epilepsy with febrile seizures plus (GEFS+)

Generalized epilepsy with febrile seizures plus (GEFS+) comprises a group of clinically and genetically heterogeneous epilepsy syndrome. Here, we provide the first report of clinical presentation and mutational analysis of SCN1A gene in 36 Malaysian GEFS+ patients. Mutational analysis of SCN1A gene revealed twenty seven sequence variants (missense mutation and silent polymorphism also intronic polymorphism), as well as 2 novel de-novo mutations were found in our patients at coding regions, c.5197A>G (N1733D) and c.4748A>G (H1583R). Our findings provide potential genetic insights into the pathogenesis of GEFS+ in Malaysian populations concerning the SCN1A gene mutations.

Na+ channelopathies and epilepsy: recent advances and new perspectives

Mutations of ion channel genes have a major role in the pathogenesis of several epilepsies, confirming that some epilepsies are disorders due to the impairment of ion channel function (channelopathies). Voltage-gated Na(+) channels (VGSCs) play an essential role in neuronal excitability; it is, therefore, not surprising that most mutations associated with epilepsy have been identified in genes coding for VGSCs subunits. Epilepsies linked to VGSCs mutations range in severity from mild disorders, such as benign neonatal-infantile familial seizures and febrile seizures, to severe and drug-resistant epileptic encephalopathies. SCN1A is the most clinically relevant of all of the known epilepsy genes, several hundred mutations have been identified in this gene. This review will summarize recent advances and new perspectives on Na(+) channels and epilepsy. A better understanding of the genetic basis and of how gene defects cause seizures is mandatory to direct future research for newer selective and more efficacious treatments.

Polymorphisms of the SCN1A gene in children and adolescents with primary headache and idiopathic or cryptogenic epilepsy: is there a linkage?

The purpose of this study was to evaluate the distribution of the polymorphisms of the SCN1A gene in a series of children and adolescents with primary headache and idiopathic or cryptogenic epilepsy compared to controls. Five non-synonymous exonic polymorphisms (1748A > T, 2656T > C, 3199A > G, 5771G > A, 5864T > C) of the SCN1A gene were selected and their genotyping was performed, by high resolution melting (HRM), in 49 cases and 100 controls. We found that among the five polymorphisms, only 3199A > G was a true polymorphism. We did not find a statistically significant difference between distribution of 3199A > G genotypes between cases and controls. We excluded the role of the SCN1A gene in the pathogenesis of comorbidity between headache (especially migraine) and epilepsy. The SCN1A gene is a major gene in different epilepsies and epilepsy syndromes; the HRM could be the new methodology, more rapid and efficacious, for molecular analysis of the SCN1A gene.

Mutation screening of three Chinese families with genetic epilepsy with febrile seizures plus

Genetic epilepsy with febrile seizures plus (GEFS+) is a familial autosomal dominant condition characterized by genetic heterogeneity. Five genes for GEFS+ identified in large families account for only a small proportion of families. Mutation in the majority of families with GEFS+ has not identified yet. The aim of our study is to search for the gene responsible for GEFS+ in three Chinese families by linkage analyses and a sequencing approach and to investigate the importance of coding and noncoding regions variations of four known GEFS+ genes (SCN1A, SCN1B, GABRG2 and SCN2A) in Chinese families. Results showed that a 6-cM candidate interval at 5q33-34 with a maximum LOD scores of 2.043 was identified in families B. Sequencing candidate gene GABRG2 and GABRA1 in this region did not identify a causative mutation. Moreover, no mutation was found in coding and noncoding regions of the four genes in three Chinese families. Besides excluding coding regions of four known GEFS+ genes, we also excluded the possibility of a mutation in the promoter, exon-intron boundaries, 5' untranslated regions (5' UTRs), and 3' UTRs of four known GEFS+ genes in three Chinese families. In conclusion, the present study demonstrates the heterogeneity of the etiologies of GEFS+. There are as yet undiscovered mechanisms underlying GEFS+.

Coexistence of idiopathic generalized epilepsy among surgically treated patients with drug-resistant temporal lobe epilepsy

INTRODUCTION

Failure to identify the association antiepileptic drug (AED)-resistant temporal lobe epilepsy (TLE) with idiopathic generalized epilepsy (IGE) can interfere with decision for anterior temporal lobectomy (ATL) and prediction of post-ATL seizure outcome.

METHODS

Out of the 664 consecutive patients who underwent ATL between March 1995 and December 2007, 12 (1.8%) had coexisting IGE. The decision for ATL was made after a thorough discussion in the multidisciplinary patient management conference based upon the concordance between the clinical, electroencephalographic and magnetic resonance imaging data. All of them underwent epilepsy surgery for AED-resistant TLE.

RESULTS

In seven of the 12 patients, IGE was not identified until post-ATL. During a median follow-up period of 8.5 years, 8 of our 12 patients were seizure-free; the remaining 4 patients only had infrequent myoclonus. In two them, AEDs were discontinued; others were on montherapy for IGE.

CONCLUSIONS

Our study highlights the rare association of IGE with TLE, the most common AED-resistant focal epilepsy syndrome. As the seizure outcome following ATL is similar in AED-resistant TLE patients with and without IGE, their co-existence is not a contraindication for ATL. Future studies should explore the molecular genetic basis of the rare association between these two epilepsy syndromes.

Genetic evaluation and counseling for epilepsy

The contribution of genetics to both rare and common epilepsies is rapidly being elucidated, and neurologists are routinely considering genetic testing in the work-up of several epilepsy syndromes of both known and unknown cause. Simultaneously, advances in molecular technology foreshadow additional discoveries in epilepsy etiology, implying a greater role than ever before for genetics in the epilepsy clinic. Genetic testing can be valuable not only for diagnosis but also for guiding treatment and for informing reproductive choices. In this Review, we outline the principles of genetic evaluation and counseling, and describe how to interpret genetic test results for epilepsy in the following five common clinical scenarios: Dravet syndrome, infantile spasms, epilepsy with cortical malformation, epilepsy with mental retardation, and idiopathic epilepsy syndromes. We differentiate clinical situations in which genetic testing is of high and low utility, and predict future areas for the application of genetics in epilepsy practice.

Vaccines, encephalopathies, and mutations

De-Novo Mutations of the Sodium Channel Gene SCN1A in Alleged Vaccine Encephalopathy: A Retrospective Study. Berkovic SF, Harkin L, McMahon JM, Pelekanos JT, Zuberi SM, Wirrell EC, Gill DS, Iona X, Mulley JC, Scheffer IE. Lancet Neurol 2006;5:488–492.

Background

Vaccination, particularly for pertussis, has been implicated as a direct cause of an encephalopathy with refractory seizures and intellectual impairment. We postulated that cases of so-called vaccine encephalopathy could have mutations in the neuronal sodium channel α1 subunit gene ( SCN1A) because of a clinical resemblance to severe myoclonic epilepsy of infancy (SMEI) for which such mutations have been identified.

Methods

We retrospectively studied 14 patients with alleged vaccine encephalopathy in whom the first seizure occurred within 72 h of vaccination. We reviewed the relation to vaccination from source records and assessed the specific epilepsy phenotype. Mutations in SCN1A were identified by PCR amplification and denaturing high performance liquid chromatography analysis, with subsequent sequencing. Parental DNA was examined to ascertain the origin of the mutation.

Results

SCN1A mutations were identified in 11 of 14 patients with alleged vaccine encephalopathy; a diagnosis of a specific epilepsy syndrome was made in all 14 cases. Five mutations predicted truncation of the protein and six were missense in conserved regions of the molecule. In all nine cases where parental DNA was available the mutations arose de novo. Clinical-molecular correlation showed mutations in eight of eight cases with phenotypes of SMEI, in three of four cases with borderline SMEI, but not in two cases with Lennox–Gastaut syndrome.

Conclusion

Cases of alleged vaccine encephalopathy could in fact be a genetically determined epileptic encephalopathy that arose de novo. These findings have important clinical implications for diagnosis and management of encephalopathy and, if confirmed in other cohorts, major societal implications for the general acceptance of vaccination.

Variable neurologic phenotype in a GEFS+ family with a novel mutation in SCN1A

PURPOSE

To describe the spectrum of clinical disease in a mutliplex family with an autosomal dominant form of generalized epilepsy with febrile seizures plus (GEFS+) and determine its genetic etiology.

METHODS

Medical and family history was obtained on 11 clinically affected individuals and their relatives across three generations through medical chart review and home visits. A candidate gene approach including haplotype analysis and direct sequencing was used.

RESULTS

An epilepsy-associated haplotype was identified on 2q24. Direct sequencing of the entire SCN1A gene identified seven sequence variants. However, only one of these, c.1162 T>C, was not found in population controls. This transition in exon 8 of SCN1A predicts a substitution (Y388H) of a highly conserved tyrosine residue in the loop between transmembrane segments S5 and S6 of the sodium channel protein (Na(v)1.1). Clinical features in mutation carriers of this novel missense mutation were highly variable, ranging from febrile seizures to severe refractory epilepsy.

CONCLUSION

A novel missense mutation in the pore-forming region of the sodium channel gene SCN1A causes GEFS+ with a variable phenotype that includes mood and anxiety disorders, as well as ataxia, expanding the GEFS+ spectrum to include neuropsychiatric disease.

A novel inherited mutation in the voltage sensor region of SCN1A is associated with Panayiotopoulos syndrome in siblings and generalized epilepsy with febrile seizures plus

We report 2 families harboring a novel SCN1A mutation, one of whom had Panayiotopoulos syndrome and the other a phenotype consistent with generalized epilepsy with febrile seizures plus. Two siblings had recurrent episodes of autonomic status epilepticus with focal features consistent with the diagnosis of Panayiotopoulos syndrome. Both have the SCN1A mutation p.Phe218Leu. The mutation was present in their father who has never had a seizure. The same mutation was identified in a child diagnosed with intractable childhood epilepsy with generalized tonic clonic seizures. From the age of 5, he developed complex focal seizures associated with left hippocampal sclerosis. The mutation was present in his mother, aged 25, who had febrile seizures and developed generalized tonic clonic seizures and his sister who had 1 febrile seizure. Our findings suggest that SCN1A mutations may cause susceptibility to an idiopathic focal epilepsy phenotype, the final phenotype depending on other (genetic or nongenetic) factors.

SCN1A, SCN1B, and GABRG2 gene mutation analysis in Chinese families with generalized epilepsy with febrile seizures plus

Generalized epilepsy with febrile seizures plus (GEFS+; MIM#604233) is a familial epilepsy syndrome characterized by phenotypic and genetic heterogeneity. It was associated with mutations in the neuronal voltage-gated sodium channel subunit gene (SCN1A, SCN2A, SCN1B) and ligand-gated gamma aminobutyric acid receptors genes (GABRG2, GABRD). We investigated the roles of SCN1A, SCN1B, and GABRG2 mutations in the etiology of Chinese GEFS+ families. Genomic deoxyribonucleic acid (DNA) was extracted from peripheral blood lymphocytes of 23 probands and their family members. The sequences of SCN1A, SCN1B, and GABRG2 genes were analyzed by polymerase chain reaction (PCR) and direct sequencing. The major phenotypes of affected members in the 23 GEFS+ families exhibited FS and FS+, whereas rare phenotypes afebrile generalized tonic-clonic seizures (AGTCS), myoclonic-astatic epilepsy (MAE), and partial seizures were also observed. A novel SCN1A mutation, p.N935H, was identified in one family and another novel mutation in GABRG2, p.W390X, in another family. However, no SCN1B mutation was identified. The combined frequency of SCN1A, SCN1B, and GABRG2 mutations was 8.7% (2/23), extending the distribution of SCN1A and GABRG2 mutations to Chinese GEFS+ families. There were still unidentified genes contributing to the pathogenesis of GEFS+.

Patients with a sodium channel alpha 1 gene mutation show wide phenotypic variation

We investigated the roles of mutations in voltage-gated sodium channel alpha 1 subunit gene (SCN1A) in epilepsies and psychiatric disorders. The SCN1A gene was screened for mutations in three unrelated Japanese families with generalized epilepsy with febrile seizure plus (GEFS+), febrile seizure with myoclonic seizures, or intractable childhood epilepsy with generalized tonic-clonic seizures (ICEGTC). In the family with GEFS+, one individual was affected with panic disorder and seizures, and another individual was diagnosed with Asperger syndrome and seizures. The novel mutation V1366I was found in all probands and patients with psychiatric disorders of the three families. These results suggest that SCN1A mutations may confer susceptibility to psychiatric disorders in addition to variable epileptic seizures. Unidentified modifiers may play critical roles in determining the ultimate phenotype of patients with sodium channel mutations.

Association between D18S474 locus on chromosome 18q12 and idiopathic generalized epilepsy

Idiopathic generalized epilepsy is one of the most common forms of epilepsy. The aetiology of IGE is genetically determined, but the pattern of inheritance is still undefined. Recent studies in common IGE showed evidence for linkage on chromosome 18q12 at the D18S474 locus. The aim of our study was to compare the distribution of allelic variants of D18S474 locus in children affected by generalized tonic-clonic seizures and in healthy controls. We studied 295 children: 121 cases and 174 controls. We found that the D18S474(8) allele was significantly more frequent and D18S474(9) significantly less frequent in cases compared with controls (p<.001). In conclusions, our findings show the association between the D18S474 marker and IGE in which early onset GTCS represent the most prevalent seizure type.

Increased sensitivity of the neuronal nicotinic receptor alpha 2 subunit causes familial epilepsy with nocturnal wandering and ictal fear

Sleep has traditionally been recognized as a precipitating factor for some forms of epilepsy, although differential diagnosis between some seizure types and parasomnias may be difficult. Autosomal dominant frontal lobe epilepsy is characterized by nocturnal seizures with hyperkinetic automatisms and poorly organized stereotyped movements and has been associated with mutations of the alpha 4 and beta 2 subunits of the neuronal nicotinic acetylcholine receptor. We performed a clinical and molecular genetic study of a large pedigree segregating sleep-related epilepsy in which seizures are associated with fear sensation, tongue movements, and nocturnal wandering, closely resembling nightmares and sleep walking. We identified a new genetic locus for familial sleep-related focal epilepsy on chromosome 8p12.3-8q12.3. By sequencing the positional candidate neuronal cholinergic receptor alpha 2 subunit gene (CHRNA2), we detected a heterozygous missense mutation, I279N, in the first transmembrane domain that is crucial for receptor function. Whole-cell recordings of transiently transfected HEK293 cells expressing either the mutant or the wild-type receptor showed that the new CHRNA2 mutation markedly increases the receptor sensitivity to acetylcholine, therefore indicating that the nicotinic alpha 2 subunit alteration is the underlying cause. CHRNA2 is the third neuronal cholinergic receptor gene to be associated with familial sleep-related epilepsies. Compared with the CHRNA4 and CHRNB2 mutations reported elsewhere, CHRNA2 mutations cause a more complex and finalized ictal behavior.

Adult epilepsy

The epilepsies are one of the most common serious brain disorders, can occur at all ages, and have many possible presentations and causes. Although incidence in childhood has fallen over the past three decades in developed countries, this reduction is matched by an increase in elderly people. Monogenic Mendelian epilepsies are rare. A clinical syndrome often has multiple possible genetic causes, and conversely, different mutations in one gene can lead to various epileptic syndromes. Most common epilepsies, however, are probably complex traits with environmental effects acting on inherited susceptibility, mediated by common variation in particular genes. Diagnosis of epilepsy remains clinical, and neurophysiological investigations assist with diagnosis of the syndrome. Brain imaging is making great progress in identifying the structural and functional causes and consequences of the epilepsies. Current antiepileptic drugs suppress seizures without influencing the underlying tendency to generate seizures, and are effective in 60-70% of individuals. Pharmacogenetic studies hold the promise of being able to better individualise treatment for each patient, with maximum possibility of benefit and minimum risk of adverse effects. For people with refractory focal epilepsy, neurosurgical resection offers the possibility of a life-changing cure. Potential new treatments include precise prediction of seizures and focal therapy with drug delivery, neural stimulation, and biological grafts.

Epilepsy in children

10.5 million children worldwide are estimated to have active epilepsy. Over the past 15 years, syndrome-oriented clinical and EEG diagnosis, and better aetiological diagnosis, especially supported by neuroimaging, has helped to clarify the diversity of epilepsy in children, and has improved management. Perinatal and postinfective encephalopathy, cortical dysplasia, and hippocampal sclerosis account for the most severe symptomatic epilepsies. Ion channel defects can underlie both benign age-related disorders and severe epileptic encephalopathies with a progressive disturbance in cerebral function. However, the reasons for age-related expression in children are not understood. Neither are the mechanisms whereby an epileptic encephalopathy originates. Several new drugs have been recently introduced but have provided limited therapeutic benefits. However, treatment and quality of life have improved because the syndrome-specific efficacy profile of drugs is better known, and there is heightened awareness that compounds with severe cognitive side-effects and heavy polytherapies should be avoided. Epilepsy surgery is an important option for a few well-selected individuals, but should be considered with great caution when there is no apparent underlying brain lesion.

Genome-wide linkage of febrile seizures and epilepsy to the FEB4 locus at 5q14.3-q23.1 and no MASS1 mutation

Febrile seizures (FS) represent the most common seizure disorder in childhood and contribution of a genetic predisposition has been clearly proven. In some families FS is associated with a wide variety of afebrile seizures. Generalized epilepsy with febrile seizures plus (GEFS+) is a familial epilepsy syndrome with a spectrum of phenotypes including FS, atypical febrile seizures (FS+) and afebrile generalized and partial seizures. Mutations in the genes SCN1B, SCN1A and GABRG2 were identified in GEFS+ families. GEFS+ is genetically heterogeneous and mutations in these three genes were detected in only a minority of the families. We performed a 10 cM density genome-wide scan in a multigenerational family with febrile seizures and epilepsy and obtained a maximal multipoint LOD score of 3.12 with markers on chromosome 5q14.3-q23.1. Fine mapping and segregation analysis defined a genetic interval of approximately 33 cM between D5S2103 and D5S1975. This candidate region overlapped with a previously reported locus for febrile seizures (FEB4) in the Japanese population, in which MASS1 was proposed as disease gene. Mutation analysis of the exons and exon-intron boundaries of MASS1 in our family did not reveal a disease causing mutation. Our linkage data confirm for the first time that a locus on chromosome 5q14-q23 plays a role in idiopathic epilepsies. However, our mutation data is negative and do not support a role for MASS1 suggesting that another gene within or near the FEB4 locus might exist.

Sodium channel mutations in epilepsy and other neurological disorders

Since the first mutations of the neuronal sodium channel SCN1A were identified 5 years ago, more than 150 mutations have been described in patients with epilepsy. Many are sporadic mutations and cause loss of function, which demonstrates haploinsufficiency of SCN1A. Mutations resulting in persistent sodium current are also common. Coding variants of SCN2A, SCN8A, and SCN9A have also been identified in patients with seizures, ataxia, and sensitivity to pain, respectively. The rapid pace of discoveries suggests that sodium channel mutations are significant factors in the etiology of neurological disease and may contribute to psychiatric disorders as well.

Generalized epilepsy with febrile seizures plus: Clinical and genetic analysis of three Serbian families

The results of clinical and genetic analysis of three Serbian families (pedigrees) with autosomal dominant inheritance, incomplete penetrance and phenotypic features of GEFS+ are presented in this study. Mutation analysis of the SCN1A, SCN1B and GABRG2 genes was performed in all affected and some unaffected members of these three families. Twentysix exons of SCN1A, five exons of SCN1B and nine exons of GABRG2 were individually amplified using primers based on intronic sequence. PCR products were sequenced in both forward and reverse directions. Subsequently, the samples were run and analyzed using 377 DNA automated sequencer. No consanguinity was noticed. The MM and OM family members live in Republic of Srpska while KS family originates from the central Serbia. No mutations of the exons of SCN1A, SCN1B and GABRG2 genes were found in tested subjects. Obligate carriers in MM family (III-1, III-2, and III-4) exhibit variable expressivity or incomplete penetrance rather than proof of polygenetic inheritance. OM pedigree follows autosomal dominant pattern despite reduced penetrance. Bilinear transmission may assume the possibility of multigenetic mode of inheritance in KS family. The fact that all affected members in three Serbian families were negative for mutations in SCN1A, SCN1B and GABRG2 genes strongly supports the hypothesis of significant genetic heterogeneity of GEFS+. Recognizing GEFS+ on clinical grounds contributes to more precise integration of this syndrome into already existing classification of epileptic syndromes.

Clinical and genetic aspects of idiopathic epilepsies in childhood

The identification of the first genes associated with idiopathic epilepsy has been an important breakthrough in the field of epilepsy research. In almost all cases these genes were found to encode components of voltage- or ligand-gated ion channels or functionally related structures. For many other idiopathic syndromes, there is linkage evidence to one or more chromosomes, but the genes have not yet been identified. Identification of the responsible genes and their gene products will further increase the knowledge of the pathogenic mechanisms involved in epilepsy, and will hopefully facilitate the development of drug targets for the effective treatment of epilepsy. This review gives an overview of the clinical characteristics and an update of genetic research of those idiopathic childhood epilepsies for which genes have been identified and the monogenic idiopathic childhood epilepsies for which mapping data are available.

Fever, genes, and epilepsy

About 13% of patients with epilepsy have a history of febrile seizures (FS). Studies of familial forms suggest a genetic component to the epidemiological link. Indeed, in certain monogenic forms of FS, for which several loci have been reported, some patients develop epilepsy with a higher risk than in the general population. Patients with generalised epilepsy with febrile seizures plus (GEFS+) can have typical and isolated FS, FS lasting more beyond age 6 years, and subsequent afebrile (typically generalised) seizures. Mutations associated with GEFS+ were identified in genes for subunits of the voltage-gated sodium channel and the gamma2 subunit of the ligand-gated GABAA receptor. Screening for these genes in patients with severe myoclonic epilepsy in infancy showed de novo mutations of the alpha1 subunit of the voltage-gated sodium channel. Antecedent FS are commonly observed in temporal-lobe epilepsy (TLE). In sporadic mesial TLE-characterised by the sequence of complex FS in childhood, hippocampal sclerosis, and refractory temporal-lobe seizures-association studies suggested the role of several susceptibility genes. Work on some large pedigrees also suggests that FS and temporal-lobe seizures may have a common genetic basis, whether hippocampus sclerosis is present or not. The molecular defects identified in the genetic associations of FS and epileptic seizures are very attractive models to aid our understanding of epileptogenesis and susceptibility to seizure-provoking factors, especially fever.