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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Myoclonic attacks are not characteristic of a specific syndrome. In infancy and early childhood, they are often observed in the context of syndromes that are associated with other types of seizures and with cognitive impairment but no obvious brain lesion. Characterization of the associated seizures and age of expression allows inclusion of a number of cases in two main subgroups: severe myoclonic epilepsy (SME, or Dravet syndrome) and myoclonic-astatic epilepsy (MAE). Severe myoclonic epilepsy is an epileptic encephalopathy with invariably poor outcome in which myoclonic seizures, though frequently observed, may be absent altogether in some children. Prolonged and repeated febrile and afebrile convulsive seizures starting in infancy are the main feature and are probably causally related to cognitive decline. One third of children harbor mutation of the SCN1A gene, but the genetics of SME is probably more complex than expected with simple monogenic disorders. Treatment is usually disappointing. Myoclonic-astatic epilepsy is perhaps more a conceptual category of idiopathic myoclonic epilepsy than a discrete syndrome. Childhood-onset myoclonic-astatic attacks are the characteristic seizures associated in most with episodes of nonconvulsive status and generalized tonic-clonic seizures. Outcome is unpredictable. Either remission within a few years with normal cognition or long-lasting intractability with cognitive impairment is possible. Likewise, the effectiveness of antiepileptic drugs is variable. A number of cases of myoclonic epilepsies in infancy and early childhood, however, remain unclassified, and intermediate forms between the different syndromes exist. They must be distinguished from other syndromes with frequent brief attacks and repeated falls, especially the Lennox-Gastaut syndrome. This differentiation is often difficult and may require extensive neurophysiologic studies.
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PMID:Epileptic encephalopathies with myoclonic seizures in infants and children (severe myoclonic epilepsy and myoclonic-astatic epilepsy). 1473 34

Mutations, exclusively missense, of voltage-gated sodium channel alpha subunit type 1 (SCN1A) and type 2 (SCN2A) genes were reported in patients with idiopathic epilepsy: generalized epilepsy with febrile seizures plus. Nonsense and frameshift mutations of SCN1A, by contrast, were identified in intractable epilepsy: severe myoclonic epilepsy in infancy (SMEI). Here we describe a first nonsense mutation of SCN2A in a patient with intractable epilepsy and severe mental decline. The phenotype is similar to SMEI but distinct because of partial epilepsy, delayed onset (1 year 7 months), and absence of temperature sensitivity. A mutational analysis revealed that the patient had a heterozygous de novo nonsense mutation R102X of SCN2A. Patch-clamp analysis of Na(v)1.2 wild-type channels and the R102X mutant protein coexpressed in human embryonic kidney 293 cells showed that the truncated mutant protein shifted the voltage dependence of inactivation of wild-type channels in the hyperpolarizing direction. Analysis of the subcellular localization of R102X truncated protein suggested that its dominant negative effect could arise from direct or indirect cytoskeletal interactions of the mutant protein. Haploinsufficiency of Na(v)1.2 protein is one plausible explanation for the pathology of this patient; however, our biophysical findings suggest that the R102X truncated protein exerts a dominant negative effect leading to the patient's intractable epilepsy.
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PMID:A nonsense mutation of the sodium channel gene SCN2A in a patient with intractable epilepsy and mental decline. 1502 61

Mutations in the alpha-subunit of the first neuronal sodium channel gene SCN1A have been described in isolated patients with severe myoclonic epilepsy in infancy or Dravet syndrome and in families with generalized epilepsy with febrile seizures plus. To find phenotype/genotype correlations, we reviewed all published cases of mutations in SCN1A in addition to four new patients reported here. A total of 60 mutations were observed. Approximately 52% (31/60) are truncating mutations correlating with de novo cases of classical Dravet syndrome in 32 of 34 (94%) patients. Missense mutations in the pore-forming part constitute 27% (16/60) and correspond to a classical type in 12 of 16 (75%) patients. Missense mutations in the voltage sensor were present in 12% (7/60) and correlate with a clinical picture ranging from febrile seizures plus to severe myoclonic epilepsy in infancy. Outside these regions missense mutations are rare and account for only 10% (6/60), corresponding mostly with febrile seizures plus. These results illustrate that the clinical spectrum of SCN1A mutations ranges from febrile seizures, febrile seizures plus, over a milder type to the classical form of severe myoclonic epilepsy in infancy, and confirm the clinical experience that severe myoclonic epilepsy in infancy is the most severe form on this spectrum.
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PMID:Clinical correlations of mutations in the SCN1A gene: from febrile seizures to severe myoclonic epilepsy in infancy. 1508

Mutations in SCN1A, the gene encoding the brain voltage-gated sodium channel alpha(1) subunit (Na(V)1.1), are associated with at least two forms of epilepsy, generalized epilepsy with febrile seizures plus and severe myoclonic epilepsy of infancy (SMEI). We examined the functional properties of five SMEI mutations by using whole-cell patch-clamp analysis of heterologously expressed recombinant human SCN1A. Two mutations (F902C and G1674R) rendered SCN1A channels nonfunctional, and a third allele (G1749E) exhibited minimal functional alterations. However, two mutations within or near the S4 segment of the fourth repeat domain (R1648C and F1661S) conferred significant impairments in fast inactivation, including persistent, noninactivating channel activity resembling the pattern of channel dysfunction observed for alleles associated with generalized epilepsy with febrile seizures plus. Our data provide evidence for a range of SCN1A functional abnormalities in SMEI, including gain-of-function defects that were not anticipated in this disorder. Our results further indicate that a complex relationship exists between phenotype and aberrant sodium channel function in these inherited epilepsies.
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PMID:Noninactivating voltage-gated sodium channels in severe myoclonic epilepsy of infancy. 1526 74

'Severe myoclonic epilepsy in infancy' or Dravet syndrome is a clear example of the impact of severe epilepsy on the developing child. Presenting with febrile seizures in infancy, children later on develop a severe epileptic syndrome with mental retardation. Nearly all children have life-threatening status epilepticus during the first two years of life. The clinical diagnosis can now be confirmed by DNA-analysis in a majority of patients. Most patients have a de novo mutation in the alfa subunit of the neuronal sodium channel SCN1A. In the past few years' treatment of severe myoclonic epilepsy in infancy has changed. Prevention of seizures, avoiding anti-epileptic drugs which only block sodium channels, a simple combination of two major anti-epileptic drugs (sodium valproate and topiramate) and a strict acute seizure treatment significantly improve the quality of life for these patients. Long-term follow up is necessary to evaluate if we can also improve the development possibilities for these children.
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PMID:"Severe myoclonic epilepsy in infancy". Relevance for the clinician of severe epilepsy starting in infancy. 1550 61

A mutation in the sodium channel SCN1A was identified in a small Italian family with dominantly inherited generalized epilepsy with febrile seizures plus (GEFS+). The mutation, D1866Y, alters an evolutionarily conserved aspartate residue in the C-terminal cytoplasmic domain of the sodium channel alpha subunit. The mutation decreased modulation of the alpha subunit by beta1, which normally causes a negative shift in the voltage dependence of inactivation in oocytes. There was less of a shift with the mutant channel, resulting in a 10 mV difference between the wild-type and mutant channels in the presence of beta1. This shift increased the magnitude of the window current, which resulted in more persistent current during a voltage ramp. Computational analysis suggests that neurons expressing the mutant channels will fire an action potential with a shorter onset delay in response to a threshold current injection, and that they will fire multiple action potentials with a shorter interspike interval at a higher input stimulus. These results suggest a causal relationship between a positive shift in the voltage dependence of sodium channel inactivation and spontaneous seizure activity. Direct interaction between the cytoplasmic C-terminal domain of the wild-type alpha subunit with the beta1 or beta3 subunit was first demonstrated by yeast two-hybrid analysis. The SCN1A peptide K1846-R1886 is sufficient for beta subunit interaction. Coimmunoprecipitation from transfected mammalian cells confirmed the interaction between the C-terminal domains of the alpha and beta1 subunits. The D1866Y mutation weakens this interaction, demonstrating a novel molecular mechanism leading to seizure susceptibility.
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PMID:A novel epilepsy mutation in the sodium channel SCN1A identifies a cytoplasmic domain for beta subunit interaction. 1552 88

Severe myoclonic epilepsy in infancy, or Dravet syndrome, is one of the catastrophic epilepsy syndromes. In the past, treatment was mainly based on valproate and phenobarbital. Recently, some of the new antiepilepsy drugs, such as topiramate and stiripentol, have been shown to be promising in the treatment of this epilepsy syndrome. The treatment regimen of 12 children with Dravet syndrome and proven mutations in the alpha subunit of the sodium channel SCN1A is reported here. Five patients on the "traditional" treatment regimen are compared with seven children on an "optimal" treatment regimen based on a combination of valproate and topiramate. With respect to the literature and our own experience, we propose guidelines for "optimal" treatment of children with severe myoclonic epilepsy in infancy. This includes prevention of hyperthermia, rigorous treatment of fever, avoiding stressful situations, maintenance treatment based on a combination of only two antiepilepsy drugs (ie, valproate and topiramate), and a strict acute seizure treatment based on benzodiazepines. To prevent long-lasting periods of status epilepticus, this acute seizure treatment must be taught to parents and caregivers.
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PMID:Severe myoclonic epilepsy in infancy: toward an optimal treatment. 1552 56

Recent identifications of genes responsible for epilepsies are now contributing to diagnosis and treatment. Mutations of voltage-gated sodium channel genes SCN1A and SCN2A have been reported in epilepsies with a variety of phenotypes including generalized epilepsy with febrile seizures plus (GEFS +), severe myoclonic epilepsy in infancy (SMEI), intractable childhood epilepsy with generalized tonic-clonic seizures (ICEGTC), and benign familial neonatal-infantile seizures (BFNIS). We also identified a sporadic nonsense mutation of SCN2A in a patient with intractable epilepsy with severe mental decline. Lafora's disease (LD) is a fatal autosomal recessive epilepsy characterized by stimuli sensitive myoclonus, grand mal seizures, and progressive intellectual and neurological deterioration. The EPM2A gene has been reported to be responsible for LD. We found multiple disease mutations of EPM2A in LD patients, and also identified a subclass of LD who shows an early onset cognitive defect and correlated with EPM2A exon 1 mutations. We reported that the laforin protein encoded by the EPM2A gene has a dual-specificity phosphatase activity, associates with polyribosome, and interacts with the HIRIP5 protein with NifU-like domain. We recently generated and reported the EPM2A KO mice those develop neurodegeneration and other features similar to those of LD patients.
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PMID:[Molecular genetics of epilepsy]. 1565 14

Generalized epilepsy with febrile seizures plus (GEFS+) is an inherited epileptic syndrome with a marked clinical and genetic heterogeneity. Here we report the molecular characterization of a large pedigree with a severe clinical form of GEFS+. Genetic linkage analysis implied the involvement of the FEB3 in the disease phenotype of this family (parametric two-point lod-score of 2.2). Sequencing of the SCN1A gene revealed a novel aspartic acid for glycine substitution at position 1742 of this sodium channel subunit. The amino-acid replacement lies in the pore-forming region of domain IV of SCN1A. Our observations are consistent with the genotype-phenotype correlation studies suggesting that mutations in the pore-forming loop of SCN1A can lead to a clinically more severe epileptic syndrome.
Seizure 2005 Mar
PMID:A novel SCN1A mutation associated with severe GEFS+ in a large South American pedigree. 1569 66

Generalised epilepsy with febrile seizures plus (GEFS+) is a clinically and genetically heterogeneous epilepsy syndrome. Using positional cloning strategies, mutations in SCN1B, SCN1A, and GABRG2 have been identified as genetic causes of GEFS+. In the present study, we describe a large four generation family with GEFS+ in which we performed a 10 cM density genome-wide scan. We obtained conclusive evidence for a novel GEFS+ locus on chromosome 2p24 with a maximum two point logarithm of the odds (LOD) score of 4.22 for marker D2S305 at zero recombination. Fine mapping and haplotype segregation analysis in this family delineated a candidate region of 3.24 cM, corresponding to a physical distance of 4.2 Mb. Linkage to 2p24 was confirmed (p = 0.007) in a collection of 50 nuclear and multiplex families with febrile seizures and epilepsy. Transmission disequilibrium testing and association studies provided further evidence (p < 0.05) that 2p24 is a susceptibility locus for febrile seizures and epilepsy. Furthermore, we could reduce the candidate region to a 2.14 cM interval, localised between D2S1360 and D2S2342, based upon an ancestral haplotype. Identification of the disease gene at this locus will contribute to a better understanding of the complex genetic aetiology of febrile seizures and epilepsy.
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PMID:A novel susceptibility locus at 2p24 for generalised epilepsy with febrile seizures plus. 1582 91


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