早期ミオクロニー脳症

Early infantile developmental and epileptic encephalopathy (EIDEE) is among the most severe epilepsy syndromes, with onset before three months of age and an estimated incidence of approximately 10 per 100,000 live births. The 2022 International League Against Epilepsy classification unified the historically distinct Ohtahara syndrome and early myoclonic encephalopathy under a single diagnostic framework defined by frequent drug-resistant tonic and/or myoclonic seizures, an abnormal neurological examination, and an abnormal interictal electroencephalogram-most characteristically a burst-suppression pattern. This narrative review synthesizes the clinical, electrophysiological, neuroimaging, genetic, and therapeutic literature within the EIDEE framework. The clinical phenotype is characterized by central hypotonia, postnatal microcephaly, cortical visual impairment, and age-dependent syndromic evolution toward infantile epileptic spasms syndrome or Lennox-Gastaut syndrome in the majority of patients. Electroencephalography remains essential for syndromic classification, while systematic metabolic screening and early trio whole-exome or whole-genome sequencing are central to the etiologic workup, achieving diagnostic yields of 60-65%. The most commonly identified genetic causes include STXBP1, KCNQ2, and SCN2A variants. Outcomes are poor overall and strongly etiology-dependent: vitamin-responsive disorders carry a substantially more favorable prognosis, whereas mortality reaches 25% in genetic cohorts. Genotype-guided pharmacotherapy is now applicable to a clinically meaningful subset of patients, with sodium channel blockers, potassium channel openers, and emerging antisense oligonucleotide therapies representing important therapeutic advances. Gene therapy trials are underway but have encountered early safety signals, underscoring the vulnerability of this population. Critical unmet needs include earlier molecular diagnosis, precision therapies targeting developmental outcomes beyond seizure control, and prospective international registries to characterize the long-term natural history of EIDEE.

According to the World Health Organization, more than 50 million people worldwide have epilepsy, and about 5 million new cases are reported annually. According to other data, the number of patients exceeds 70.000.000, highlighting the relevance of this condition. Studies of developmental epileptic encephalopathies leading to early disability are particularly relevant. About 900 gene mutations associated with different types of epilepsy have been identified so far. One of the prominent «channelopathy genes» representatives is KCNT1, coding the largest subunit of the sodium-activated potassium channel, KNa1.1. Its mutations are associated with many neurological disorders, such as leukodystrophy, leukoencephalopathy, West syndrome, Ohtahara syndrome, early myoclonic encephalopathy, focal epilepsy, and multifocal epilepsy. A clinical case of a typical course of KCNT1-associated epilepsy with early onset (in the first half of life), focal and asynchronous paroxysms, psychomotor retardation, and drug resistance is presented. The effectiveness of the anticonvulsants used and the nature of pharmacological resistance were analyzed. The applicability of four «Drug Resistance Hypotheses» to this case is shown: genetic, since the pathogenesis of this particular case is based on a change in the properties of potassium channels; a change in the sensitivity of the anticonvulsant targets explains the intermittent (according to Schmidt and Löscher) nature of resistance. The «Neural Networks Hypothesis» is illustrated by the change of encephalographic indicators from multifocal epileptiform activity with an intact background to pronounced dysrhythmia with periods of the «burst-suppression» pattern after several months. All these features, combined, refer to the «Intrinsic Severity» hypothesis by Rogawski and Johnson, since the child's disease was initially severe due to the intensity and frequency of epileptic seizures. As a result, a conclusion was made about the complexity of the refractoriness formation mechanisms, even in cases with a simple and understandable pathogenesis of channelopathy.

INTRODUCTION: Developmental and epileptic encephalopathy (DEE) is epilepsy related to developmental impairment that may be caused by both the underlying etiology (developmental encephalopathy) and superimposed epileptic activity (epileptic encephalopathy). The origin of DEE and the causes of its variations remain unknown. Owing the lack of clarity regarding the role of genetic variables in DEE, we conducted a scoping review to qualitatively identify the genes most important in the development of DEE to provide an up-to-date review. MATERIAL AND METHODS: We searched all published studies related to the genetic factors of DEE. The identified publications were screened and selected by the authors on basis of on inclusion and exclusion criteria and assessed for methodological quality. Eighteen articles were included. The extracted data included age of onset, sex, gene mutations and inheritance (e.g. nucleotide change, protein change, and family testing), clinical manifestation, electroencephalogram, imaging, medication, and outcomes. RESULT: A total of 18 studies were included in this scoping review. The most frequently reported gene variants were STXBP1 in Ohtahara Syndrome, SLC1A2 in Early Myoclonic Encephalopathy (EME), CDKL5 in West Syndrome, SCN1A in Dravet Syndrome, and KCNT1 in Epilepsy of Infancy with Migrating Focal Seizures (EIMFS). Each gene was associated with distinct electroclinical features, including differences in age of onset, seizure type, EEG patterns, and developmental outcomes. While genotype and phenotype associations were heterogeneous, certain variants showed consistent patterns indicative of more severe disease courses. CONCLUSIONS: This review identified key gene variants commonly associated with early-onset DEE in infants, particularly STXBP1, SLC1A2, CDKL5, SCN1A, and KCNT1, each linked to unique clinical presentations and outcomes. These findings support the clinical utility of next-generation sequencing (NGS) for early diagnosis and tailored treatment planning in DEE. Understanding genotype-phenotype correlations may enhance prognostication and highlight potential avenues for targeted therapy in future research.

PURPOSE: Drug-resistant epilepsy is seen in patients with inborn errors of metabolism and metabolic dysfunction in neurons is crucial to brain disorders associated with psychomotor impairment. Diagnostic rates of metabolic causes of developmental and epileptic encephalopathy (DEE) using next generation sequencing have been rarely studied in literature. METHODS: A prospective hospital study was carried out in 384 children with DEE, who underwent genetic testing. Metabolic disorders were evaluated with biochemical blood/urine assays and when required CSF estimations performed. RESULTS: A total of 154 pathogenic/likely pathogenic variants in 384 children were identified. Out of 384 children, 89 were clinically suspected to have probable or possible metabolic disorders. Pathogenic/likely pathogenic variants in metabolic genes were identified in 39 out of 89 (43.8 %) and promising VUS in 28 (31.4 %). These included variants for progressive myoclonus epilepsies (21; 53.8 %), DEE with focal/multifocal seizures (8; 20.5 %), generalized epilepsy (5;12.8 %), early myoclonic encephalopathy (2; 5.1 %), LGS (1; 2.6 %) and West syndrome (2; 5.1 %). CONCLUSION: Our cohort demonstrates for the first time from the Indian subcontinent that identification of metabolic variants can guide investigations and has therapeutic implications in patients with variable DEE phenotypes. A high utility is noted with regard to diagnosis and prognostication, given the low yield of available biochemical tests, indicating cost-effectiveness of this approach.

Phillip L. Pearl Seminars in Pediatric Neurology Volume 23, Issue 2, May 2016, Pages 158-166 Vitamin-dependent epilepsies and multiple metabolic epilepsies are amenable to treatment that markedly improves the disease course. Knowledge of these amenably treatable severe pediatric epilepsies allows for early identification, testing, and treatment. These disorders present with various phenotypes, including early onset epileptic encephalopathy (refractory neonatal seizures, early myoclonic encephalopathy, and early infantile epileptic encephalop athy), infantile spasms, or mixed generalized seizure types in infancy, childhood, or even adolescence and adulthood. The disorders are presented as vitamin responsive epilepsies such as pyridoxine, pyridoxal-5-phosphate, folinic acid, and biotin; transportopathies like GLUT-1, cerebral folate deficiency, and biotin thiamine responsive disorder; amino and organic acidopathies including serine synthesis defects, creatine synthesis disorders, molybdenum cofactor deficiency, and cobalamin deficiencies; mitochondrial disorders; urea cycle disorders; neurotransmitter defects; and disorders of glucose homeostasis. In each case, targeted intervention directed toward the underlying metabolic pathophysiology affords for the opportunity to significantly effect the outcome and prognosis of an otherwise severe pediatric epilepsy.