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PCDH19 is a nonclustered protocadherin molecule involved in axon bundling, synapse function, and transcriptional coregulation. Pathogenic variants in PCDH19 cause infantile-onset epilepsy known as PCDH19-clustering epilepsy or PCDH19-CE. Recent advances in DNA-sequencing technologies have led to a significant increase in the number of reported PCDH19-CE variants, many of uncertain significance. We aimed to determine the best approaches for assessing the disease relevance of missense variants in PCDH19. The application of the American College of Medical Genetics and Association for Molecular Pathology (ACMG-AMP) guidelines was only 50% accurate. Using a training set of 322 known benign or pathogenic missense variants, we identified MutPred2, MutationAssessor, and GPP as the best performing in silico tools. We generated a protein structural model of the extracellular domain and assessed 24 missense variants. We also assessed 24 variants using an in vitro reporter assay. A combination of these tools was 93% accurate in assessing known pathogenic and benign PCDH19 variants. We increased the accuracy of the ACMG-AMP classification of 45 PCDH19 variants from 50% to 94%, using these tools. In summary, we have developed a robust toolbox for the assessment of PCDH19 variant pathogenicity to improve the accuracy of PCDH19-CE variant classification. Refereed/Peer-reviewed

ObjectiveTo identify the causative gene in a large unsolved family with genetic epilepsy with febrile seizures plus (GEFS+), we sequenced the genomes of family members, and then determined the contribution of the identified gene to the pathogenicity of epilepsies by examining sequencing data from 2,772 additional patients.MethodsWe performed whole genome sequencing of 3 members of a GEFS+ family. Subsequently, whole exome sequencing data from 1,165 patients with epilepsy from the Epi4K dataset and 1,329 Australian patients with epilepsy from the Epi25 dataset were interrogated. Targeted resequencing was performed on 278 patients with febrile seizures or GEFS+ phenotypes. Variants were validated and familial segregation examined by Sanger sequencing.ResultsEight previously unreported missense variants were identified in SLC32A1, coding for the vesicular inhibitory amino acid cotransporter VGAT. Two variants cosegregated with the phenotype in 2 large GEFS+ families containing 8 and 10 affected individuals, respectively. Six further variants were identified in smaller families with GEFS+ or idiopathic generalized epilepsy (IGE).ConclusionMissense variants in SLC32A1 cause GEFS+ and IGE. These variants are predicted to alter γ-aminobutyric acid (GABA) transport into synaptic vesicles, leading to altered neuronal inhibition. Examination of further epilepsy cohorts will determine the full genotype–phenotype spectrum associated with SLC32A1 variants.

The major and most well-studied genetic cause of Fragile-X syndrome (FXS) is expansion of a CGG repeat in the 5'-UTR of the FMR1 gene. Routine testing for this expansion is performed globally. Overall, there is a paucity of intragenic variants explaining FXS, a fact which is being addressed by a more systematic application of whole exome (WES) and whole genome (WGS) sequencing, even in the diagnostic setting. Here we report two families comprising probands with a clinical suspicion of FXS and no CGG repeat expansions. Using WES/WGS we identified deleterious variants within the coding region of FMR1 in both families. In a family from Finland we identified a complex indel c.1021-1028delinsTATTGG in exon 11 of FMR1 which gives rise to a frameshift and a premature termination codon (PTC), p.Asn341Tyrfs*7. Follow-up mRNA and protein studies on a cell line from the proband revealed that although the mRNA levels of FMR1 were not altered, Fragile X Mental Retardation 1 Protein (FMRP) was undetectable. Additionally, we identified a variant, c.881-1G > T, affecting the canonical acceptor splice site of exon 10 of FMR1 in an Australian family. Our findings reinforce the importance of intragenic FMR1 variant testing, particularly in cases with clinical features of FXS and no CGG repeat expansions identified.

Objective Benign familial infantile seizures (BFIS), paroxysmal kinesigenic dyskinesia (PKD), and their combination—known as infantile convulsions and paroxysmal choreoathetosis (ICCA)—are related autosomal dominant diseases. PRRT2 (proline-rich transmembrane protein 2 gene) has been identified as the major gene in all 3 conditions, found to be mutated in 80 to 90% of familial and 30 to 35% of sporadic cases. Methods We searched for the genetic defect in PRRT2-negative, unrelated families with BFIS or ICCA using whole exome or targeted gene panel sequencing, and performed a detailed cliniconeurophysiological workup. Results In 3 families with a total of 16 affected members, we identified the same, cosegregating heterozygous missense mutation (c.4447G>A; p.E1483K) in SCN8A, encoding a voltage-gated sodium channel. A founder effect was excluded by linkage analysis. All individuals except 1 had normal cognitive and motor milestones, neuroimaging, and interictal neurological status. Fifteen affected members presented with afebrile focal or generalized tonic–clonic seizures during the first to second year of life; 5 of them experienced single unprovoked seizures later on. One patient had seizures only at school age. All patients stayed otherwise seizure-free, most without medication. Interictal electroencephalogram (EEG) was normal in all cases but 2. Five of 16 patients developed additional brief paroxysmal episodes in puberty, either dystonic/dyskinetic or “shivering” attacks, triggered by stretching, motor initiation, or emotional stimuli. In 1 case, we recorded typical PKD spells by video-EEG-polygraphy, documenting a cortical involvement. Interpretation Our study establishes SCN8A as a novel gene in which a recurrent mutation causes BFIS/ICCA, expanding the clinical–genetic spectrum of combined epileptic and dyskinetic syndromes. ANN NEUROL 2016;79:428–436

Objective Focal epilepsies are the most common form observed and have not generally been considered to be genetic in origin. Recently, we identified mutations in DEPDC5 as a cause of familial focal epilepsy. In this study, we investigated whether mutations in the mammalian target of rapamycin (mTOR) regulators, NPRL2 and NPRL3, also contribute to cases of focal epilepsy. Methods We used targeted capture and next-generation sequencing to analyze 404 unrelated probands with focal epilepsy. We performed exome sequencing on two families with multiple members affected with focal epilepsy and linkage analysis on one of these. Results In our cohort of 404 unrelated focal epilepsy patients, we identified five mutations in NPRL2 and five in NPRL3. Exome sequencing analysis of two families with focal epilepsy identified NPRL2 and NPRL3 as the top candidate-causative genes. Some patients had focal epilepsy associated with brain malformations. We also identified 18 new mutations in DEPDC5. Interpretation We have identified NPRL2 and NPRL3 as two new focal epilepsy genes that also play a role in the mTOR-signaling pathway. Our findings show that mutations in GATOR1 complex genes are the most significant cause of familial focal epilepsy identified to date, including cases with brain malformations. It is possible that deregulation of cellular growth control plays a more important role in epilepsy than is currently recognized.

Autosomal dominant mutations in the sodium-gated potassium channel subunit gene KCNT1 have been associated with two distinct seizure syndromes, nocturnal frontal lobe epilepsy (NFLE) and malignant migrating focal seizures of infancy (MMFSI). To further explore the phenotypic spectrum associated with KCNT1, we examined individuals affected with focal epilepsy or an epileptic encephalopathy for mutations in the gene. We identified KCNT1 mutations in 12 previously unreported patients with focal epilepsy, multifocal epilepsy, cardiac arrhythmia, and in a family with sudden unexpected death in epilepsy (SUDEP), in addition to patients with NFLE and MMFSI. In contrast to the 100% penetrance so far reported for KCNT1 mutations, we observed incomplete penetrance. It is notable that we report that the one KCNT1 mutation, p.Arg398Gln, can lead to either of the two distinct phenotypes, ADNFLE or MMFSI, even within the same family. This indicates that genotype–phenotype relationships for KCNT1 mutations are not straightforward. We demonstrate that KCNT1 mutations are highly pleiotropic and are associated with phenotypes other than ADNFLE and MMFSI. KCNT1 mutations are now associated with Ohtahara syndrome, MMFSI, and nocturnal focal epilepsy. They may also be associated with multifocal epilepsy and cardiac disturbances Refereed/Peer-reviewed

We recently identified DEPDC5 as the gene for familial focal epilepsy with variable foci and found mutations in >10% of small families with nonlesional focal epilepsy. Here we show that DEPDC5 mutations are associated with both lesional and nonlesional epilepsies, even within the same family. DEPDC5-associated malformations include bottom-of-the-sulcus dysplasia (3 members from 2 families), and focal band heterotopia (1 individual). DEPDC5 negatively regulates the mammalian target of rapamycin (mTOR) pathway, which plays a key role in cell growth. The clinicoradiological phenotypes associated with DEPDC5 mutations share features with the archetypal mTORopathy, tuberous sclerosis, raising the possibility of therapies targeted to this pathway.

Objective Mutations in KCNT1 have been implicated in autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) and epilepsy of infancy with migrating focal seizures (EIMFS). More recently, a whole exome sequencing study of epileptic encephalopathies identified an additional de novo mutation in 1 proband with EIMFS. We aim to investigate the electrophysiological and pharmacological characteristics of hKCNT1 mutations and examine developmental expression levels. Methods Here we use a Xenopus laevis oocyte-based automated 2-electrode voltage clamp assay. The effects of quinidine (100 and 300 μM) are also tested. Using quantitative reverse transcriptase polymerase chain reaction, the relative levels of mouse brain mKcnt1 mRNA expression are determined. Results We demonstrate that KCNT1 mutations implicated in epilepsy cause a marked increase in function. Importantly, there is a significant group difference in gain of function between mutations associated with ADNFLE and EIMFS. Finally, exposure to quinidine significantly reduces this gain of function for all mutations studied. Interpretation These results establish direction for a targeted therapy and potentially exemplify a translational paradigm for in vitro studies informing novel therapies in a neuropsychiatric disease.

Genetic variation in SLC12A5 which encodes KCC2, the neuronspecific cation-chloride cotransporter that is essential for hyperpolarizing GABAergic signaling and formation of cortical dendritic spines, has not been reported in human disease. Screening of SLC12A5 revealed a co-segregating variant (KCC2-R952H) in an Australian family with febrile seizures. We show that KCC2-R952H reduces neuronal Cl extrusion and has a compromised ability to induce dendritic spines in vivo and in vitro. Biochemical analyses indicate a reduced surface expression of KCC2-R952H which likely contributes to the functional deficits. Our data suggest that KCC2- R952H is a bona fide susceptibility variant for febrile seizures. Refereed/Peer-reviewed

The Emerging Science abstracts were presented at the 2013 AAN Annual Meeting. Abstracts qualify for Emerging Science presentations by having key aspects of research conducted after the October 15th abstract submission deadline and must be new and of sufficient scientific importance to warrant expedited presentation and publication. The Science Committee is committed to presenting the best neuroscientific research at the Annual Meeting; 12 abstracts were accepted for dual presentation and 9 were accepted as poster presentations. William Hu, MD, PhD; Kelly Watts, MS; Murray Grossman, MD, FAAN; Jonathan Glass; James Lah, MD; John Trojanowski, MD, PhD; Allan Levey, MD, PhD OBJECTIVE: To validate five previously identified CSF biomarkers for FTLD-TDP, and to report a novel, robust, stand-alone CSF biomarker for FTLD-TDP. BACKGROUND: There is currently no reliable way to predict the underlying FTLD pathology while the patients are still living, and an ante-mortem biomarker for one of the main FTLD subtypes (FTLD-TDP or FTLD-Tau) can significantly enhance the pathology-based FTLD diagnosis and clinical trials for FTLD-TDP and FTLD-Tau. DESIGN/METHODS: Two independent cohorts of patients with frontotemporal dementia (FTD) were recruited independently from Emory University (Atlanta, GA) and University of Pennsylvania (Penn; Philadelphia, PA) to undergo CSF analysis. These include patients with high likelihood FTLD-TDP (FTD patients with amyotrophic lateral sclerosis or FTD patients with mutations in PGRN or C9ORF72) and patients with high likelihood FTLD-Tau (FTD patients with progressive supranuclear palsy or FTD patients with mutations in MAPT). Levels of five CSF previously identified proteins were measured, along with levels of total Tau (t-Tau) and Tau phosphorylated at threonine 181 (p-Tau181). RESULTS : 29 Emory patients and 40 Penn patients participated in the study, including 43 patients with high likelihood FTLD-TDP and 26 patients with high likelihood FTLD-Tau. Using the Emory cohort, we validated the group level differences in …

OBJECTIVE: Focal epilepsies are the most common form observed and have not generally been considered to be genetic in origin. Recently, we identified mutations in DEPDC5 as a cause of familial focal epilepsy. In this study, we investigated whether mutations in the mammalian target of rapamycin (mTOR) regulators, NPRL2 and NPRL3, also contribute to cases of focal epilepsy. METHODS: We used targeted capture and next-generation sequencing to analyze 404 unrelated probands with focal epilepsy. We performed exome sequencing on two families with multiple members affected with focal epilepsy and linkage analysis on one of these. RESULTS: In our cohort of 404 unrelated focal epilepsy patients, we identified five mutations in NPRL2 and five in NPRL3. Exome sequencing analysis of two families with focal epilepsy identified NPRL2 and NPRL3 as the top candidate-causative genes. Some patients had focal epilepsy associated with brain malformations. We also identified 18 new mutations in DEPDC5. INTERPRETATION: We have identified NPRL2 and NPRL3 as two new focal epilepsy genes that also play a role in the mTOR-signaling pathway. Our findings show that mutations in GATOR1 complex genes are the most significant cause of familial focal epilepsy identified to date, including cases with brain malformations. It is possible that deregulation of cellular growth control plays a more important role in epilepsy than is currently recognized.

Objective: To analyze the clinical syndromes and inheritance patterns of multiplex families with epilepsy toward the ultimate aim of uncovering the underlying molecular genetic basis. Methods: Following the referral of families with 2 or more relatives with epilepsy, individuals were classified into epilepsy syndromes. Families were classified into syndromes where at least 2 family members had a specific diagnosis. Pedigrees were analyzed and molecular genetic studies were performed as appropriate. Results: A total of 211 families were ascertained over an 11-year period in Israel. A total of 169 were classified into broad familial epilepsy syndrome groups: 61 generalized, 22 focal, 24 febrile seizure syndromes, 33 special syndromes, and 29 mixed. A total of 42 families remained unclassified. Pathogenic variants were identified in 49/211 families (23%). The majority were found in established epilepsy genes (e.g., SCN1A , KCNQ2 , CSTB ), but in 11 families, this cohort contributed to the initial discovery (e.g., KCNT1 , PCDH19 , TBC1D24 ). We expand the phenotypic spectrum of established epilepsy genes by reporting a familial LAMC3 homozygous variant, where the predominant phenotype was epilepsy with myoclonic-atonic seizures, and a pathogenic SCN1A variant in a family where in 5 siblings the phenotype was broadly consistent with Dravet syndrome, a disorder that usually occurs sporadically. Conclusion: A total of 80% of families were successfully classified, with pathogenic variants identified in 23%. The successful characterization of familial electroclinical and inheritance patterns has highlighted the value of studying multiplex families and their contribution towards uncovering the genetic basis of the epilepsies.

We aimed to refine the phenotypic spectrum and map the causative gene in two families with familial focal epilepsy with variable foci (FFEVF). A new five-generation Australian FFEVF family (A) underwent electroclinical phenotyping, and the original four-generation Australian FFEVF family (B) (Ann Neurol, 44, 1998, 890) was re-analyzed, including new affected individuals. Mapping studies examined segregation at the chromosome 22q12 FFEVF region. In family B, the original whole genome microsatellite data was reviewed. Five subjects in family A and 10 in family B had FFEVF with predominantly awake attacks and active EEG studies with a different phenotypic picture from other families. In family B, reanalysis excluded the tentative 2q locus reported. Both families mapped to chromosome 22q12. Our results confirm chromosome 22q12 as the solitary locus for FFEVF. Both families show a subtly different phenotype to other published families extending the clinical spectrum of FFEVF.

Benign neonatal sleep myoclonus is an uncommon, nonepileptic disorder characterized by myoclonic jerks appearing in the neonatal period that occur predominantly during sleep. Although self-limiting, the disorder is frequently confused with epileptic neonatal seizures. A few familial cases have been reported; however the genetics has not been studied. We ascertained 3 families with 2 or more affected individuals and analyzed the pedigrees. We used microsatellite markers to determine if the disorder was possibly linked to KCNQ2 or KCNQ3, the 2 genes that cause most cases of benign familial neonatal seizures, a disorder that it could be easily confused with. The 3 pedigrees, including one with 4 affected individuals, were suggestive of autosomal dominant inheritance. The loci for KCNQ2 and KCNQ3 were excluded in the 2 larger families. We conclude that benign neonatal sleep myoclonus can show autosomal dominant inheritance and is not allelic with benign familial neonatal seizures. Refereed/Peer-reviewed

A family with dominantly inherited neonatal seizures and intellectual disability was atypical for neonatal and infantile seizure syndromes associated with potassium (KCNQ2 and KCNQ3) and sodium (SCN2A) channel mutations. Microsatellite markers linked to KCNQ2, KCNQ3, and SCN2A were examined to exclude candidate locations, but instead revealed a duplication detected by observation of three alleles for two markers flanking SCN2A. Characterization revealed a 1.57 Mb duplication at 2q24.3 containing eight genes including SCN2A, SCN3A, and the 3¢ end of SCN1A. The duplication was partially inverted and inserted within or near SCN1A, probably affecting the expression levels of associated genes, including sodium channels. Rare or unique microchromosomal copy number mutations might underlie familial epilepsies that do not fit within the clinical criteria for the established syndromes.

BACKGROUND: Benign familial neonatal seizures are most often caused by mutations in the voltage-gated potassium channel subunit gene KCNQ2. More than 60 mutations have been described in BFNS families, approximately half of which lead to protein truncation. The hypothesis of this study was that deletion or duplication of >or=1 exons of KCNQ2 could cause BFNS in cases without coding or splicing mutations. METHODS: Multiplex ligation-dependent probe amplification (MLPA) was used to test a group of 21 unrelated patients with clinical features consistent with either BFNS, benign familial neonatal-infantile seizures or sporadic neonatal seizures, for exonic deletions and duplications. RESULTS: Three deletions and one duplication mutation were identified in four familial cases and cascade testing of their available family members showed that the mutations segregated with the phenotype in each family. The junction fragment for one of the deletions was amplified by PCR and sequenced to characterise the breakpoint and verify that a deletion had occurred. CONCLUSIONS: Submicroscopic deletions or duplications of KCNQ2 are seen in a significant proportion of BFNS families: four of nine (44%) cases previously testing negative for coding or splice site mutation by sequencing KCNQ2 and KCNQ3. MLPA is an efficient second-tier testing strategy for KCNQ2 to identify pathogenic intragenic mutations not detectable by conventional DNA sequencing methods.

Seizure susceptibility is high in human infants compared to adults, presumably because of developmentally regulated changes in neural excitability. Benign familial neonatal-infantile seizures (BFNIS), characterized by both early onset and remission, are caused by mutations in the gene encoding a human sodium channel (NaV1.2). We analyzed neonatal and adult splice forms of NaV1.2 with a BFNIS mutation (L1563V) in human embryonic kidney cells. Computer modeling revealed that neonatal channels are less excitable than adult channels. Introduction of the mutation increased excitability in the neonatal channels to a level similar to adult channels. By contrast, the mutation did not affect the adult channel variant. This "adult-like" increased excitability is likely to be the mechanism underlying BFNIS in infants with this mutation. More generally, developmentally regulated NaV1.2 splicing may be one mechanism that counters the normally high excitability of neonatal neurons and helps to reduce seizure susceptibility in normal human infants.

Mutations in the sodium-gated potassium channel subunit gene KCNT1 have recently emerged as a cause of several different epileptic disorders. This review describes the mutational and phenotypic spectrum associated with the gene and discusses the comorbidities found in patients, which include intellectual disability and psychiatric features. The gene may also be linked with cardiac disorders. KCNT1 missense mutations have been found in 39% of patients with the epileptic encephalopathy malignant migrating focal seizures of infancy (MMFSI), making it the most significant MMFSI disease-causing gene identified to date. Mutations in KCNT1 have also been described in eight unrelated cases of sporadic and familial autosomal-dominant nocturnal frontal lobe epilepsy (ADNFLE). These patients have a high frequency of associated intellectual disability and psychiatric features. Two mutations in KCNT1 have been associated with both ADNFLE and MMFSI, suggesting that the genotype-phenotype relationship for KCNT1 mutations is not straightforward. Mutations have also been described in several patients with infantile epileptic encephalopathies other than MMFSI. Notably, all mutations in KCNT1 described to date are missense mutations, and electrophysiological studies have shown that they result in increased potassium current. Together, these genetic and electrophysiological studies raise the possibility of delivering precision medicine by treating patients with KCNT1 mutations using drugs that alter the action of potassium channels to specifically target the biological effects of their disease-causing mutation. Such trials are now in progress. Better understanding of the mechanisms underlying KCNT1-related disease will produce further improvements in treatment of the associated severe seizure disorders. Refereed/Peer-reviewed

Nucleotide alterations in the gene encoding proline-rich transmembrane protein 2 (PRRT2) have been identified in most patients with benign partial epilepsies in infancy (BPEI)/benign familial infantile epilepsy (BFIE). However, not all patients harbor these PRRT2 mutations, indicating the involvement of genes other than PRRT2. In this study, we performed whole exome sequencing analysis for a large family affected with PRRT2-unrelated BPEI. We identified a non-synonymous single nucleotide variation (SNV) in the voltage-sensitive chloride channel 6 gene (CLCN6). A cohort study of 48 BPEI patients without PRRT2 mutations revealed a different CLCN6 SNV in a patient, his sibling and his father who had a history of febrile seizures (FS) but not BPEI. Another study of 48 patients with FS identified an additional SNV in CLCN6. Chloride channels (CLCs) are involved in a multitude of physiologic processes and some members of the CLC family have been linked to inherited diseases. However, a phenotypic correlation has not been confirmed for CLCN6. Although we could not detect significant biological effects linked to the identified CLCN6 SNVs, further studies should investigate potential CLCN6 variants that may underlie the genetic susceptibility to convulsive disorders. Refereed/Peer-reviewed

Progressive myoclonus epilepsies (PMEs) are a group of rare, inherited disorders manifesting with action myoclonus, tonic-clonic seizures and ataxia. We sequenced the exomes of 84 unrelated individuals with PME of unknown cause and molecularly solved 26 cases (31 %). Remarkably, a recurrent de novo mutation, c. 959G>A (p.Arg320His), in KCNC1 was identified as a new major cause for PME. Eleven unrelated exome-sequenced (13%) and two affected individuals in a secondary cohort (7%) had this mutation. KCNC1 encodes KV3.1, a subunit of the KV3 voltage-gated potassium ion channels, which are major determinants of high-frequency neuronal firing. Functional analysis of the Arg320His mutant channel showed a dominant-negative loss-of-function effect. Ten cases had pathogenic mutations in known PME-associated genes (NEU1, NHLRC1, AFG3L2, EPM2A, CLN6 and SERPINI1). Identification of mutations in PRNP, SACS and TBC1D24 expand their phenotypic spectra to PME. These findings provide insights into the molecular genetic basis of PME and show the role of de novo mutations in this disease entity. Refereed/Peer-reviewed

Summary: Purpose: We describe seven Italian families with generalized epilepsy with febrile seizures plus (GEFS+), in which mutations of SCN1A, SCN1B, and GABRG2 genes were excluded and compare their clinical spectrum with that of previously reported GEFS+ with known mutations. Methods: We performed a clinical study of seven families (167 individuals). The molecular study included analysis of polymerase chain reaction (PCR) fragments of SCN1A and SCN1B exons by denaturing high-performance liquid chromatography (DHPLC) and direct sequencing of GABRG2 in all families. We excluded SCN1A, SCN1B, and GABRG2 genes with linkage analysis in a large pedigree and directly sequenced SCN2A in a family with neonatal–infantile seizures onset. We compared the epilepsy phenotypes observed in our families with those of GEFS+ families harboring mutations of SCN1A, SCN1B, and GABRG2 and estimated the percentage of mutations of these genes among GEFS+ cases by reviewing all published studies. Results: Inheritance was autosomal dominant with 69% penetrance. Forty-one individuals had epilepsy: 29 had a phenotype consistent with GEFS+; seven had idiopathic generalized epilepsy (IGE); in three, the epilepsy type could not be classified; and two were considered phenocopies. Clinical phenotypes included FS+ (29.2%), FS (29.2%), IGE (18.2%), FS+ with focal seizures (13%) or absence seizures (2.6%), and FS with absence seizures (2.6%). Molecular study of SCN1A, SCN2A, SCN1B, and GABRG2 did not reveal any mutation. Results of our study and literature review indicate that mutations of SCN1A, SCN2A, SCN1B, and GABRG2 in patients with GEFS+ are rare. Conclusions: The most frequently observed phenotypes matched those reported in families with mutations of the SCN1A, SCN1B, and GABRG2 genes. IGE and GEFS+ may overlap in some families, suggesting a shared genetic mechanism. The observation that 13% of affected individuals had focal epilepsy confirms previously reported rates and should prompt a reformulation of the “GEFS+” concept to include focal epileptogenesis.

We recently reported mutations in the sodium channel gene SCN2A in two families with benign familial neonatal-infantile seizures (BFNISs). Here, we aimed to refine the molecular-clinical correlation of SCN2A mutations in early childhood epilepsies. SCN2A was analyzed in 2 families with probable BFNIS, 9 with possible BFNIS, 10 with benign familial infantile seizures, and in 93 additional families with various early childhood epilepsies. Mutations effecting changes in conserved amino acids were found in two of two probable BFNIS families, in four of nine possible BFNIS families, and in none of the others. Our eight families had six different SCN2A mutations; one mutation (R1319Q) occurred in three families. BFNIS is an autosomal dominant disorder presenting between day 2 and 7 months (mean, 11.2 +/- 9.2 weeks) with afebrile secondarily generalized partial seizures; neonatal seizures were not seen in all families. The frequency of seizures varied; some individuals had only a few attacks without treatment and others had clusters of many per day. Febrile seizures were rare. All cases remitted by 12 months. Ictal recordings in four subjects showed onset in the posterior quadrants. SCN2A mutations appear specific for BFNIS; the disorder can now be strongly suspected clinically and the families can be given an excellent prognosis.

Objective: Analysis of twins with epilepsy to explore the genetic architecture of specific epilepsies, to evaluate the applicability of the 2010 International League Against Epilepsy (ILAE) organization of epilepsy syndromes, and to integrate molecular genetics with phenotypic analyses. Methods: A total of 558 twin pairs suspected to have epilepsy were ascertained from twin registries (69%) or referral (31%). Casewise concordance estimates were calculated for epilepsy syndromes. Epilepsies were then grouped according to the 2010 ILAE organizational scheme. Molecular genetic information was utilized where applicable. Results: Of 558 twin pairs, 418 had confirmed seizures. A total of 534 twin individuals were affected. There were higher twin concordance estimates for monozygotic (MZ) than for dizygotic (DZ) twins for idiopathic generalized epilepsies (MZ = 0.77; DZ = 0.35), genetic epilepsy with febrile seizures plus (MZ = 0.85; DZ = 0.25), and focal epilepsies (MZ = 0.40; DZ = 0.03). Utilizing the 2010 ILAE scheme, the twin data clearly demonstrated genetic influences in the syndromes designated as genetic. Of the 384 tested twin individuals, 10.9% had mutations of large effect in known epilepsy genes or carried validated susceptibility alleles. Conclusions: Twin studies confirm clear genetic influences for specific epilepsies. Analysis of the twin sample using the 2010 ILAE scheme strongly supported the validity of grouping the “genetic” syndromes together and shows this organizational scheme to be a more flexible and biologically meaningful system than previous classifications. Successful selected molecular testing applied to this cohort is the prelude to future large-scale next-generation sequencing of epilepsy research cohorts. Insights into genetic architecture provided by twin studies provide essential data for optimizing such approaches.

Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) is an uncommon, idiopathic partial epilepsy characterized by clusters of motor seizures occurring in sleep. We describe a mutation of the beta2 subunit of the nicotinic acetylcholine receptor, effecting a V287M substitution within the M2 domain. The mutation, in an evolutionary conserved region of CHRNB2, is associated with ADNFLE in a Scottish family. Functional receptors with the V287M mutation are highly expressed in Xenopus oocytes and characterized by an approximately 10-fold increase in acetylcholine sensitivity. CHRNB2 is a new gene for idiopathic epilepsy, the second acetylcholine receptor subunit implicated in ADNFLE.

We recently identified DEPDC5 as the gene for familial focal epilepsy with variable foci and found mutations in10% of small families with nonlesional focal epilepsy. Here we show that DEPDC5 mutations are associated with both lesional and nonlesional epilepsies, even within the same family. DEPDC5-associated malformations include bottom-of-the-sulcus dysplasia (3 members from 2 families), and focal band heterotopia (1 individual). DEPDC5 negatively regulates the mammalian target of rapamycin (mTOR) pathway, which plays a key role in cell growth. The clinicoradiological phenotypes associated with DEPDC5 mutations share features with the archetypal mTORopathy, tuberous sclerosis, raising the possibility of therapies targeted to this pathway.

The majority of epilepsies are focal in origin, with seizures emanating from one brain region. Although focal epilepsies often arise from structural brain lesions, many affected individuals have normal brain imaging. The etiology is unknown in the majority of individuals, although genetic factors are increasingly recognized. Autosomal dominant familial focal epilepsy with variable foci (FFEVF) is notable because family members have seizures originating from different cortical regions. Using exome sequencing, we detected DEPDC5 mutations in two affected families. We subsequently identified mutations in five of six additional published large families with FFEVF. Study of families with focal epilepsy that were too small for conventional clinical diagnosis with FFEVF identified DEPDC5 mutations in approximately 12% of families (10/82). This high frequency establishes DEPDC5 mutations as a common cause of familial focal epilepsies. Shared homology with G protein signaling molecules and localization in human neurons suggest a role of DEPDC5 in neuronal signal transduction. Refereed/Peer-reviewed

Mutations in the gene PRRT2 encoding proline-rich transmembrane protein 2 have recently been identified as the cause of three clinical entities: benign familial infantile epilepsy (BFIE), infantile convulsions with choreoathetosis (ICCA) syndrome, and paroxysmal kinesigenic dyskinesia (PKD). Patients with ICCA have both BFIE and PKD and families with ICCA may contain individuals who exhibit all three phenotypes. These three phenotypes were all mapped by linkage analyses to the pericentromeric region of chromosome 16, and were hypothesised to have the same genetic basis due to the co-occurrence of the disorders in some families. Despite considerable effort, the gene or genes for BFIE, ICCA, and PKD were not identified for many years after the linkage region was identified. Mutations in the gene PRRT2 were identified in several Chinese families with PKD, suggesting that the gene may also be responsible for ICCA and BFIE in families linked to the chromosome 16 locus. This was demonstrated to be the case, with the majority of families with ICCA and BFIE found to have PRRT2 mutations. The vast majority of these mutations are truncating and are predicted to lead to haploinsufficiency. PRRT2 is a largely uncharacterised protein. It is expressed in the brain and has been demonstrated to interact with SNAP-25, a component of the molecular machinery involved in the release of neurotransmitters at the presynaptic membrane. Therefore, the PRRT2 protein may play a role in this process. However, the molecular mechanisms underlying the remarkable pleiotropy associated with PRRT2 mutations have still to be determined. Refereed/Peer-reviewed

Heterozygous mutations in PRRT2 have recently been identified as the major cause of autosomal dominant benign familial infantile epilepsy (BFIE), infantile convulsions with choreoathetosis syndrome (ICCA), and paroxysmal kinesigenic dyskinesia (PKD). Homozygous mutations in PRRT2 have also been reported in two families with intellectual disability (ID) and seizures. Heterozygous mutations in the genes KCNQ2 and SCN2A cause the two other autosomal dominant seizure disorders of infancy: benign familial neonatal epilepsy and benign familial neonatal-infantile epilepsy. Mutations in KCNQ2 and SCN2A also contribute to severe infantile epileptic encephalopathies (IEEs) in which seizures and intellectual disability co-occur. We therefore hypothesized that PRRT2 mutations may also underlie cases of IEE. We examined PRRT2 for heterozygous, compound heterozygous or homozygous mutations to determine their frequency in causing epileptic encephalopathies (EEs). Two hundred twenty patients with EEs with onset by 2 years were phenotyped. An assay for the common PRRT2 c.649-650insC mutation and high resolution-melt analysis for mutations in the remaining exons of PRRT2 were performed. Neither the common mutation nor any other pathogenic variants in PRRT2 were detected in the 220 patients. Our findings suggest that mutations in PRRT2 are not a common cause of IEEs. Refereed/Peer-reviewed

Objective: To establish the occurrence of an autosomal dominant form of vasovagal syncope (VVS) by detailed phenotyping of multiplex families and identification of the causative locus. Methods: Patients with VVS and a family history of syncope were recruited. A standardized questionnaire was administered to all available family members and medical records were reviewed. Of 44 families recruited, 6 were suggestive of autosomal dominant inheritance. Genome-wide linkage was performed in family A using single nucleotide polymorphism genotyping microarrays. Targeted analysis of chromosome 15q26 with microsatellite markers was implemented in 4 families; 1 family was too small for analysis. Results: Family A contained 30 affected individuals over 3 generations with a median onset of 8 to 9 years. The other families comprised 4 to 14 affected individuals. Affected individuals reported typical triggers of VVS (sight of blood, injury, medical procedures, prolonged standing, pain, frightening thoughts). The triggers varied considerably within the families. Significant linkage to chromosome 15q26 (logarithm of odds score 3.28) was found in family A. Linkage to this region was excluded in 2 medium-sized families but not in 2 smaller families. Sequence analysis of the candidate genes SLCO3A1, ST8SIA2, and NR2F2 within the linkage interval did not reveal any mutations. Conclusions: Familial VVS, inherited in an autosomal dominant manner, may not be rare and has similar features to sporadic VVS. The chromosome 15q26 locus in family A increases the susceptibility to VVS but does not predispose to a particular vasovagal trigger. Linkage analysis in the remaining families established likely genetic heterogeneity. Refereed/Peer-reviewed

Alteration of ATP-binding cassette subfamily B member 1 transporter (ABCB1) can plausibly cause drug-resistant epilepsy as it influences brain penetration of drugs. The CC genotype at the ABCB1 C3435T polymorphism was reported to be associated with multidrug resistance. A replication study in 401 drug-resistant and 208 drug-responsive subjects with epilepsy showed no significant association between the CC genotype and drug-resistant epilepsy. The authors suggest the initial association may have arisen by chance.

We aimed to refine the phenotypic spectrum and map the causative gene in two families with familial focal epilepsy with variable foci (FFEVF). A new five-generation Australian FFEVF family (A) underwent electroclinical phenotyping, and the original four-generation Australian FFEVF family (B) (Ann Neurol, 44, 1998, 890) was re-analyzed, including new affected individuals. Mapping studies examined segregation at the chromosome 22q12 FFEVF region. In family B, the original whole genome microsatellite data was reviewed. Five subjects in family A and 10 in family B had FFEVF with predominantly awake attacks and active EEG studies with a different phenotypic picture from other families. In family B, reanalysis excluded the tentative 2q locus reported. Both families mapped to chromosome 22q12. Our results confirm chromosome 22q12 as the solitary locus for FFEVF. Both families show a subtly different phenotype to other published families extending the clinical spectrum of FFEVF.

We performed genomic mapping of a family with autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) and intellectual and psychiatric problems, identifying a disease-associated region on chromosome 9q34.3. Whole-exome sequencing identified a mutation in KCNT1, encoding a sodium-gated potassium channel subunit. KCNT1 mutations were identified in two additional families and a sporadic case with severe ADNFLE and psychiatric features. These findings implicate the sodium-gated potassium channel complex in ADNFLE and, more broadly, in the pathogenesis of focal epilepsies. Refereed/Peer-reviewed

Benign familial infantile epilepsy (BFIE) is a self-limited seizure disorder that occurs in infancy and has autosomal-dominant inheritance. We have identified heterozygous mutations in PRRT2, which encodes proline-rich transmembrane protein 2, in 14 of 17 families (82%) affected by BFIE, indicating that PRRT2 mutations are the most frequent cause of this disorder. We also report PRRT2 mutations in five of six (83%) families affected by infantile convulsions and choreoathetosis (ICCA) syndrome, a familial syndrome in which infantile seizures and an adolescent-onset movement disorder, paroxysmal kinesigenic choreoathetosis (PKC), co-occur. These findings show that mutations in PRRT2 cause both epilepsy and a movement disorder. Furthermore, PRRT2 mutations elicit pleiotropy in terms of both age of expression (infancy versus later childhood) and anatomical substrate (cortex versus basal ganglia). Refereed/Peer-reviewed

Objective: KCNQ2 and KCNQ3 mutations are known to be responsible for benign familial neonatal seizures (BFNS). A few reports on patients with a KCNQ2 mutation with a more severe outcome exist, but a definite relationship has not been established. In this study we investigated whether KCNQ2/3 mutations are a frequent cause of epileptic encephalopathies with an early onset and whether a recognizable phenotype exists. Methods: We analyzed 80 patients with unexplained neonatal or early-infantile seizures and associated psychomotor retardation for KCNQ2 and KCNQ3 mutations. Clinical and imaging data were reviewed in detail. Results: We found 7 different heterozygous KCNQ2 mutations in 8 patients (8/ 80; 10%); 6 mutations arose de novo. One parent with a milder phenotype was mosaic for the mutation. No KCNQ3 mutations were found. The 8 patients had onset of intractable seizures in the first week of life with a prominent tonic component. Seizures generally resolved by age 3 years but the children had profound, or less frequently severe, intellectual disability with motor impairment. Electroencephalography (EEG) at onset showed a burst-suppression pattern or multifocal epileptiform activity. Early magnetic resonance imaging (MRI) of the brain showed characteristic hyperintensities in the basal ganglia and thalamus that later resolved. Interpretation: KCNQ2 mutations are found in a substantial proportion of patients with a neonatal epileptic encephalopathy with a potentially recognizable electroclinical and radiological phenotype. This suggests that KCNQ2 screening should be included in the diagnostic workup of refractory neonatal seizures of unknown origin. ANN NEUROL 2012; 71: 15-25

Three benign epilepsy syndromes with autosomal dominant inheritance are recognised in infancy. These are Benign Familial Neonatal Epilepsy (BFNE), Benign Familial NeonatalInfantile Epilepsy (BFNIE) and Benign Familial Infantile Epilepsy (BFIE). These disorders were previously known as Benign Familial Neonatal Seizures, Benign Familial NeonatalInfantile Seizures and Benign Familial Infantile Seizures, respectively (Berg et al., 2010). They were recently renamed by the International League Against Epilepsy Classification Committee. The three disorders differ in their average ages of onset but age of onset distributions overlap between the syndromes. Ages of onset vary within syndromes and within families affected with any of the syndromes. BFNE patients have lateralised motor seizures with a mean age of onset of around 3 days of age and a mean age of seizure offset of 3 months of age. Subsequent neurological development usually proceeds normally. However, about 15% of patients have later seizures or epilepsy and occasional cases deteriorate into severe epileptic encephalopathies with intellectual disability (Dedek et al., 2003; Borgatti et al., 2004; Steinlein et al., 2007). The benign form of the disorder was originally described in an Austrian family by Rett and Teubel (1964). Since then numerous BFNE families have been described, many with potassium channel subunit mutations, to provide a well established range of presentations. BFIE was originally described by Watanabe and colleagues in 1987, and is sometimes referred to as Watanabe syndrome. Watanabe observed that a subgroup of infants with generalised motor seizures had subsequent normal development and became seizure-free by 3 years of age. Similar families were subsequently described by Vigevano and colleagues (1992). Onset of seizures in BFIE occurs between 4 and 6 months of age with seizure offset generally occurring by 12 months of age. Seizures are generally not seen in later life. However, some cases develop paroxysmal dyskinesia or paroxysmal kinesigenic choreoathetosis in adolescence. This is known as infantile convulsions and choreoathetosis (ICCA) syndrome. BFNIE patients have similar seizures to those seen in BFNE and BFIE, with the average age of onset intermediate between the other two. Although BFNIE differs from these disorders in the average age of seizure onset, the age of onset distribution which can range within a single family from 3 days up to 13 months of age (Herlenius et al., 2007), significantly

Epilepsy is increasingly recognized as a disease that reaches well beyond seizures. Cognitive and psychiatric impairment afflict half of all epilepsy patients, and to date there are no specific treatments for these symptoms. It is unclear which of these comorbidities are directly due to seizures and which are due to separable, parallel mechanisms to those underlying ictal activity. Cellular and molecular mechanisms underlying synaptic modulation are central to both the ictal and non-ictal changes in epilepsy. Current diagnostic methods are rapidly advancing to better delineate the nature and extent of ictal activity, and could soon be critical in identifying patterns unique to the cognitive and psychiatric comorbidities.

Sixty cases of febrile seizures from a Chinese cohort had previously been reported with a strong association between variants in the seizure-related (SEZ) 6 gene and febrile seizures. They found a striking lack of genetic variation in their controls. We found genetic variation inSEZ6at similar levels at the same DNA sequence positions in our 94 febrile seizure cases as in our 96 unaffected controls. Two of our febrile seizure cases carried rare variants predicted to have damaging consequences. Combined with some of the variants from the Chinese cohort, these data are compatible with a role forSEZ6as a susceptibility gene for febrile seizures. However, the polygenic determinants underlying most cases of febrile seizures with complex inheritance remain to be determined.

Objective: Two unrelated families were ascertained in which sisters had infantile onset of epilepsy and developmental delay. Mutations in the protocadherin 19 ( PCDH19 ) gene cause epilepsy and mental retardation limited to females (EFMR). Despite both sister pairs having a PCDH19 mutation, neither parent in each family was a heterozygous carrier of the mutation. The possibility of parental mosaicism of PCDH19 mutations was investigated. Methods: Genomic DNA from peripheral blood was obtained and sequenced for PCDH19 mutations. Parentage was confirmed by markers. Results: Both sister pairs have a mutation in PCDH19 . Sister pair 1 has a missense mutation, c.74T>C, L25P, while sequence analysis indicates both of their parents are negative for the mutation. Diagnostic restriction enzyme analysis detected low-level mosaicism of the mutation in their mother. Sister pair 2 are half-sisters who share a mother and each has the missense PCDH19 mutation c.1019 A>G, N340S. The sequence chromatograph of their mother shows reduced signal for the same mutation. These data indicate maternal somatic and gonadal mosaicism of the PCDH19 mutation in both sister pairs. Phenotyping is suggestive of, and PCDH19 mutation detection is diagnostic for, the disorder EFMR in the affected girls. Conclusions: We show that gonadal mosaicism of a PCDH19 mutation in a parent is an important molecular mechanism associated with the inheritance of EFMR. This should be considered when providing genetic counseling for couples who have one affected daughter as they may risk recurrence of affected daughters and having sons at risk of transmitting EFMR.

A family with dominantly inherited neonatal seizures and intellectual disability was atypical for neonatal and infantile seizure syndromes associated with potassium (KCNQ2 and KCNQ3) and sodium (SCN2A) channel mutations. Microsatellite markers linked to KCNQ2, KCNQ3, and SCN2A were examined to exclude candidate locations, but instead revealed a duplication detected by observation of three alleles for two markers flanking SCN2A. Characterization revealed a 1.57 Mb duplication at 2q24.3 containing eight genes including SCN2A, SCN3A, and the 3¢ end of SCN1A. The duplication was partially inverted and inserted within or near SCN1A, probably affecting the expression levels of associated genes, including sodium channels. Rare or unique microchromosomal copy number mutations might underlie familial epilepsies that do not fit within the clinical criteria for the established syndromes.

Background Dravet syndrome is a severe infantile epileptic encephalopathy caused in approximately 80% of cases by mutations in the voltage gated sodium channel subunit gene SCN1A . The majority of these mutations are de novo. The parental origin of de novo mutations varies widely among genetic disorders and the aim of this study was to determine this for Dravet syndrome. Methods 91 patients with de novo SCN1A mutations and their parents were genotyped for single nucleotide polymorphisms (SNPs) in the region surrounding their mutation. Allele specific polymerase chain reaction (PCR) based on informative SNPs was used to separately amplify and sequence the paternal and maternal alleles to determine in which parental chromosome the mutation arose. Results The parental origin of SCN1A mutations was established in 44 patients for whom both parents were available and SNPs were informative. The mutations were of paternal origin in 33 cases and of maternal origin in the remaining 11 cases. De novo mutation of SCN1A most commonly, but not exclusively, originates from the paternal chromosome. The average age of parents originating mutations did not differ from that of the general population. Conclusions The greater frequency of paternally derived mutations in SCN1A is likely to be due to the greater chance of mutational events during the increased number of mitoses which occur during spermatogenesis compared to oogenesis, and the greater susceptibility to mutagenesis of the methylated DNA characteristic of sperm cells.

Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) is a relatively benign epilepsy syndrome with few comorbidities. Here we describe two families with unusually severe ADNFLE, with associated psychiatric, behavioral, and cognitive features. Detailed clinical data on 17 affected individuals were obtained, and genotyping of microsatellite markers, linkage analysis, and sequencing of candidate genes was performed. The severe ADNFLE phenotype in these families was often refractory to treatment, with status epilepticus occurring in 24% of subjects. Psychiatric or behavioral disorders occurred in 53%, with intellectual disability in 24%, and developmental regression in two individuals. No mutations were identified in alpha4, alpha2, or beta2 nAChR subunits. In one family there was evidence of linkage to a region of 15q24 without nAChR subunit genes. In conclusion, severe ADNFLE has significant medical, psychiatric, and intellectual morbidity. The molecular basis of severe ADNFLE is unknown but may involve non-nAChR-related mechanisms.

Approximately 40% of epilepsy has a complex genetic basis with an unknown number of susceptibility genes. The effect of each susceptibility gene acting alone is insufficient to account for seizure phenotypes, but certain numbers or combinations of variations in susceptibility genes are predicted to raise the level of neuronal hyperexcitability above a seizure threshold for a given individual in a given environment. Identities of susceptibility genes are beginning to be determined, initially by translation of knowledge gained from gene discovery in the monogenic epilepsies. This entree into idiopathic epilepsies with complex genetics has led to the experimental validation of susceptibility variants in the first few susceptibility genes. The genetic architecture so far emerging from these results is consistent with what we have designated as a polygenic heterogeneity model for the epilepsies with complex genetics.

Two novel mutations (R85C and R85H) on the extracellular immunoglobulin-like domain of the sodium channel beta1 subunit have been identified in individuals from two families with generalized epilepsy with febrile seizures plus (GEFS+). The functional consequences of these two mutations were determined by co-expression of the human brain NaV1.2 alpha subunit with wild type or mutant beta1 subunits in human embryonic kidney (HEK)-293T cells. Patch clamp studies confirmed the regulatory role of beta1 in that relative to NaV1.2 alone the NaV1.2+beta1 currents had right-shifted voltage dependence of activation, fast and slow inactivation and reduced use dependence. In addition, the NaV1.2+beta1 current entered fast inactivation slightly faster than NaV1.2 channels alone. The beta1(R85C) subunit appears to be a complete loss of function in that none of the modulating effects of the wild type beta1 were observed when it was co-expressed with NaV1.2. Interestingly, the beta1(R85H) subunit also failed to modulate fast kinetics, however, it shifted the voltage dependence of steady state slow inactivation in the same way as the wild type beta1 subunit. Immunohistochemical studies revealed cell surface expression of the wild type beta1 subunit and undetectable levels of cell surface expression for both mutants. The functional studies suggest association of the beta1(R85H) subunit with the alpha subunit where its influence is limited to modulating steady state slow inactivation. In summary, the mutant beta1 subunits essentially fail to modulate alpha subunits which could increase neuronal excitability and underlie GEFS+ pathogenesis.

a Department of Genetic Medicine, Women’s and Children’s Hospital, 72 King William Road, North Adelaide, SA 5006, Australia b University of Melbourne and Austin Health, Banksia Street, West Heidelberg, Vic. 3081, Australia c Department of Paediatrics, University of Melbourne, Royal Children’s Hospital, Flemington Road, Parkville, Vic. 3052, Australia d School of Molecular Biosciences, University of Adelaide, Adelaide, SA 5005, Australia

Approximately 70% of all patients with epilepsy lack an obvious extraneous cause and are presumed to have a predominantly genetic basis. Both familial and de novo mutations in neuronal voltage-gated and ligand-gated ion channel subunit genes have been identificd in autosomal dominant epilepsies. However, patients with dominant familial mutations are rare and the majority of idiopathic epilepsy is likely to be the result of polygenic susceptibility alleles (complex epilepsy). Data on the identity of the genes involved in complex epilepsy is currently sparse but again points to neuronal ion channels. The number of genes and gene families associated with epilepsy is rapidly increasing and this increase is likely to escalate over the coming years with advances in mutation detection technologics. The genetic heterogeneity underlying idiopathic epilepsy presents challenges for the rational selection of therapics targeting particular ion channels. Too little is currently known about the genetic architecture of the epilepsies, and genetic testing for the known epilepsy genes remains costly. Pharmacogenetic studies have yet to explain why 30% of patients do not respond to the usual anticpileptic drugs. Despite this, the recognition that the idiopathic epilepsies are a group of channelopathies has, to a limited extent, explained the therapeutic action of the common anticpileptic drugs and has assisted clinical diagnosis of some epilepsy syndromes.