Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Severe myoclonic epilepsy of infancy (SMEI or Dravet syndrome) is a rare disorder occurring in young children often without a family history of a similar disorder. The earliest disease manifestations are usually fever-associated seizures. Later in life, patients display different types of afebrile seizures including myoclonic seizures. Arrest of psychomotor development occurs in the second year of life and most patients become ataxic. Patients are resistant to antiepileptic drug therapy. Recently, we described de novo mutations of the neuronal sodium channel alpha-subunit gene SCN1A in seven isolated SMEI patients. To investigate the contribution of SCN1A mutations to the etiology of SMEI, we examined nine additional SMEI patients. We observed eight coding and one noncoding mutation. In contrast to our previous study, most mutations are missense mutations clustering in the S4-S6 region of SCN1A. These findings demonstrate that de novo mutations in SCN1A are a major cause of isolated SMEI.
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PMID:De novo SCN1A mutations are a major cause of severe myoclonic epilepsy of infancy. 1275 8

Severe myoclonic epilepsy in infancy (SMEI) is characterized by intractable febrile and afebrile seizures, severe mental decline, and onset during the first year of life. Nonsense, frameshift, and missense mutations of SCN1A gene encoding the voltage-gated Na(+) channel alpha-subunit type I (Na(v)1.1) have been identified in patients with SMEI. Here, we performed whole-cell patch-clamp analyses on HEK293 cells expressing human Na(v)1.1 channels bearing SMEI nonsense and missense mutations. The mutant channels showed remarkably attenuated or barely detectable inward sodium currents. Our findings indicate that SMEI mutations lead to loss-of-function and may contribute to the development of SMEI phenotypes.
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PMID:Nav1.1 channels with mutations of severe myoclonic epilepsy in infancy display attenuated currents. 1283 71

We report on the electroclinical findings and the results of a molecular genetic study of a patient with typical severe myoclonic epilepsy in infancy (TSME) and three with borderline SME (BSME) who showed paroxysmal movement disorders, such as choreoathetosis, dystonia and ballismus, during their clinical course. BSME was defined as a clinical entity that shares common characteristics with TSME but lacks myoclonic seizures associated with ictal EEG changes. When the paroxysmal movement disorders were first observed, all the patients in this study were being treated with polytherapy including phenytoin (PHT), and these abnormal movements disappeared when PHT was discontinued or reduced. However, on other occasions, two of our cases also showed the same abnormal movements even when not being treated with PHT. One patient with TSME and two of the three patients with BSME had SCN1A gene mutations that lead to truncation of the associated protein. We conclude that paroxysmal movement disorders seen in SME patients were closely related to their AED therapy, especially the use of PHT. It is thought that patients with both TSME and BSME have some predisposition toward paroxysmal movement disorders, and that this predisposition is partly related to sodium channel dysfunction, although some other factors might influence the occurrence of this phenomenon.
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PMID:Paroxysmal movement disorders in severe myoclonic epilepsy in infancy. 1290 73

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

'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

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

SCN1A is part of the SCN1A-SCN2A-SCN3A gene cluster on chromosome 2q24 that encodes for alpha pore forming subunits of sodium channels. The 26 exons of SCN1A are spread over 100 kb of genomic DNA. Genetic defects in the coding sequence lead to generalized epilepsy with febrile seizures plus (GEFS+) and a range of childhood epileptic encephalopathies of varied severity (e.g., SMEI). All published mutations are collated. More than 100 novel mutations are spread throughout the gene with the more debilitating usually de novo. Some clustering of mutations is observed in the C-terminus and the loops between segments 5 and 6 of the first three domains of the protein. Functional studies so far show no consistent relationship between changes to channel properties and clinical phenotype. Of all the known epilepsy genes SCN1A is currently the most clinically relevant, with the largest number of epilepsy related mutations so far characterized.
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PMID:SCN1A mutations and epilepsy. 1588 Mar 51

Severe myoclonic epilepsy in infancy (SMEI), severe idiopathic generalized epilepsy of infancy (SIGEI) with generalized tonic clonic seizures (GTCS), and myoclonic astatic epilepsy (MAE) may show semiological overlaps. In GEFS+ families, all three phenotypes were found associated with mutations in the SCN1A gene. We analyzed the SCN1A gene in 20 patients with non-familial myoclonic astatic epilepsy -- including 12 probands of the original cohort used by Doose et al. in 1970 to delineate MAE. In addition, 18 patients with sporadic SIGEI -- mostly without myoclonic-astatic seizures -- were analyzed. Novel SCN1A mutations were found in 3 individuals. A frame shift resulting in an early premature stop codon in a now 35-year-old woman with a borderline phenotype of MAE and SIGEI (L433fsX449) was identified. A splice site variant (IVS18 + 5 G --> C) and a missense mutation in the conserved pore region (40736 C --> A; R946 S) were detected each in a child with SIGEI. We conclude that, independent of precise syndromic delineation, myoclonic-astatic seizures are not predictive of SCN1A mutations in sporadic myoclonic epilepsies of infancy and early childhood.
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PMID:SCN1A mutation analysis in myoclonic astatic epilepsy and severe idiopathic generalized epilepsy of infancy with generalized tonic-clonic seizures. 1594 8

Severe myoclonic epilepsy in infancy (SMEI) is an age-dependent epileptic encephalopathy occurring in the first year of life and is one of the intractable epilepsies. Heterozygous mutations in the voltage-gated sodium channel alpha subunit type1 gene (SCN1A) are frequently identified in patients with SMEI; two-thirds of these mutations are truncation mutations (non-sense and frameshift), and one-third are missense mutations. Although most reported SMEI cases arise as sporadic mutations, close relatives of SMEI patients have also been shown to manifest other types of epilepsies at a higher rate than that in the general population. Here, we report a familial case of SMEI, in which two brothers were affected with SMEI while their father had previously experienced simple febrile seizures. A gene-based analysis identified a novel missense mutation in the SCN1A gene (c.5138G>A, S1713N) in both brothers and in their father. Clinically, both siblings showed failure in locomotion, an impairment of the sleep-wake cycle after late infancy, and the subsequent appearance of frontal foci. The similarity in clinical manifestations in both brothers suggests that the impairment of elements of the brainstem, particularly aminergic neurons, develops after late infancy in SMEI. However, the siblings differed in age at onset of SMEI and of myoclonic seizures, as well as in the severity of speech delay. Our molecular and clinical findings suggest that different genetic backgrounds and/or environmental factors may critically affect the clinical features of patients with SCN1A mutations, consistent with the heterogeneity prevalent in this disorder.
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PMID:A missense mutation in SCN1A in brothers with severe myoclonic epilepsy in infancy (SMEI) inherited from a father with febrile seizures. 1612 30

A mutation in the voltage-gated sodium-channel Scn2a results in moderate epilepsy in transgenic Scn2a(Q54) mice maintained on a C57BL/6J strain background. The onset of progressive epilepsy begins in adults with short-duration partial seizures that originate in the hippocampus. The underlying abnormality is an increase in persistent sodium current in hippocampal neurons. The voltage-gated potassium channel Kcnq2 is responsible for generating M current (I(KM)) that is thought to control excitability and limit repetitive firing of hippocampal neurons. To determine whether impaired M current would exacerbate the seizure phenotype of Scn2a(Q54) mice, we carried out genetic crosses with two mutant alleles of Kcnq2. Szt1 mice carry a spontaneous deletion that removes the C-terminal domain of Kcnq2. A novel Kcnq2 missense mutation V182M was identified by screening the offspring of ENU-treated males for reduced threshold to electrically evoked minimal clonic seizures. Double mutant mice carrying the Scn2a(Q54) transgene together with either of the Kcnq2 mutations exhibited severe epilepsy with early onset, generalized tonic-clonic seizures and juvenile lethality by 3 weeks of age. This dramatic exacerbation of the sodium-channel mutant phenotype indicates that M current plays a critical role in preventing seizure initiation and spreading in this animal model. The genetic interaction between Scn2a and Kcnq2 demonstrates that combinations of mild alleles of monogenic epilepsy genes can result in severe disease and provides a model for complex inheritance of human epilepsy. The data suggest that interaction between these genes might contribute to the variable expressivity observed in human families with sodium-channel mutations. In a screen of 23 SMEI patients with missense mutations of SCN1A, no second-site mutations in KCNQ2 were identified.
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PMID:Severe epilepsy resulting from genetic interaction between Scn2a and Kcnq2. 1646 83


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