Early Epileptic Encephalopathy Research Articles

Developmental and Epileptic Encephalopathies: Need for Bridging the Gaps Between Clinical Syndromes and Underlying Genetic Etiologies.

Advancement in genetic testing has become increasingly important in diagnosing and managing developmental and epileptic encephalopathies (DEEs), a group of rare neurodevelopmental disorders characterized by early-onset seizures, developmental delay, and electroencephalographic (EEG) abnormalities. These early epileptic encephalopathies are often described as various syndromes as per their clearly defined, relatively uniform, and distinct clinical phenotypes with consistent EEG and/or neuroimaging findings. Finding the underlying molecular mechanisms can cause a definitive change in the management strategy. With the evolving overlapping phenotypes, advent of technologies, and discovery of new genes, it is exceedingly becoming challenging to correctly characterise these disorders and plan subsequent evidence-based management. Cytogenetic microarray (CMA) and next generation sequencing (NGS) with improved data analysis pipe-lines and algorithms have revamped the diagnostic yield dramatically. However, as of now, there is a big lacuna in step-wise evaluation guideline or consensus on integration of genetic testing results with management plan. Understanding the genetic etiologies of such syndromes timely has three major implications: (1) Knowing the outcome of such a syndrome, (2) Therapeutic implications including licensing of drugs for certain forms (e.g. genetic syndromes involving ion channels) and (3) Genetic counseling, prenatal testing and choosing reproductive options in future pregnancies in such families. The focus of this review is to provide an understanding of different types of causative variants and their step-wise genetic testing approach; the most pressing clinical need and to develop an optimal diagnostic pathway for this group of patients.

Nurture growth: Ketogenic diet therapy and growth velocity in infants under 12 months with epilepsy − A systematic review and infant data study

Ketogenic diet therapy (KDT) is well established for the treatment of early epileptic encephalopathies and specific aetiologies; however, the impact on growth in infancy remains controversial. Our aim was to examine the influence of early KDT on growth velocity and height percentiles completing two tasks. First, we systematically reviewed the literature on growth in infants younger than 12 months. Second, we analysed data from our prospective database, including infants <12 months (n = 63) treated with KDT. The literature review (n = 7) remains descriptive and includes growth percentiles and z-scores as growth velocity was not described. Studies up to 2010 used fasting, calorie restrictions, and ratios >3:1. In individual cases, significant growth delays were found; other authors did not find any changes in growth parameters. Study endpoints in our own cohort included z-scores of growth velocity, standard deviation (SD) of height, weight, BMI, deviation from individual height percentile, and daily macronutrient intake. The median z-score of growth velocity was 1.03 (first year of life). After three months, median daily intake of protein and energy was 1.68 g/kg and 85 kcal/kg. Until the age of one year, neither growth velocity nor individual growth percentiles decreased. Infants showed distinct growth improvements at three months, likely due to continuous nutritional monitoring and reduction in seizures. In the second year of life, z-scores of growth velocity decreased in patients still receiving KDT (from 1.03 at 12 months to −1.5 at 24 months). Furthermore, younger age at epilepsy onset and at KDT start correlated with slower growth velocities in the first year of life.With appropriate nutritional intake and monitoring, KDT does not reduce growth in the first year of life. Future directions might be to study the impact of KDT on growth velocity and growth hormones throughout childhood.

Utility of next generation sequencing in paediatric neurological disorders: experience from South Africa

Next generation sequencing (NGS)-based tests have become routine first-line investigative modalities in paediatric neurology clinics in many high-income countries (HICs). Studies from these countries show that these tests are both cost-effective and reliable in diagnosing many complex childhood neurological diseases. However, NGS-based testing in low-and middle-income countries (LMICs) is limited due to affordability constraints. The primary objective of this study was to evaluate the diagnostic yield and impact of targeted gene panel sequencing in a selected paediatric cohort attending a tertiary paediatric neurology clinic in the Western Cape Province of South Africa. This retrospective study included 124 consecutive paediatric patients with neurological disease, aged 6 weeks to 17 years, referred for NGS-based multi-gene panel testing over a 41-month period. Twenty-four different disease group-specific panels were utilized. A caregiver experience questionnaire was administered when a pathogenic variant was identified. The overall study diagnostic yield (DY) was 45% (56/124 patients). The diagnostic yield in this study is similar to previously reported paediatric cohorts in HICs. The high yields for neuromuscular disorders (52%) and early epileptic encephalopathies (41%) suggest that NGS-based panels may be more cost-effective as first-line testing in well-defined phenotypes. The latter finding argues for early inclusion of all children with developmental epileptic encephalopathies (DEE), as early diagnosis leads to better treatment and avoidance of unnecessary investigations.

SCN8A epileptic encephalopathy: literature review and own observation

A genetic disease caused by pathogenetic nucleotide variants in the SCN8A gene (Sodium channel protein type 8 subunit alpha, also known as Nav1.6), encoding the α-subunit of the Na channel type 8, is included in the group of early epileptic encephalopathies. In most cases, this pathology is characterized by the development of polymorphic pharmacoresistant epileptic seizures over the first year of a child’s life, a lag in psychomotor development or regression, loss of skills. In some patients, seizures may appear during the first days of life, while in others they appear later (at the age of 2 to 7 months), against the background of a pronounced or slight developmental delay. Types of seizures may include generalized, tonic-clonic seizures, infantile spasms, absences and focal seizures. Other signs and symptoms of encephalopathy caused by mutations of the SCN8A gene may include low muscle tone (hypotension), high pain threshold, motor disorders (such as dystonia and ataxia), mild to severe mental retardation, sleep problems and autistic traits. In some people with SCN8A encephalopathy, various other pathological changes in the body have been reported, including hearing or vision impairment, scoliosis, and thermoregulation difficulties. The disease is inherited by an autosomal dominant type.&#x0D; To date, the disease in the OMIM system is referred to as «Developmental encephalopathy and epileptic encephalopathy type 13». Previously, the disease was called «Early infantile (infantile) epileptic encephalopathy, type 13». The serial number «13» indicates this form of early epileptic encephalopathy to be caused by a heterozygous mutation in the gene on the long arm of chromosome 12 in chromosome region 12q13.13.&#x0D; This report also presents a clinical description of a patient suffering from early infantile epileptic encephalopathy, type 13.

Early infantile epileptic encephalopathy related to NECAP1: Clinical delineation of the disease and review.

Epileptic encephalopathy (EE) refers to a heterogeneous group of epilepsy syndromes characterized by seizures as well as encephalopathies, leading to cognitive and behavioral disturbances. These conditions vary in their age at onset, their severity, and their electroencephalographic patterns. Whereas genetic factors are involved in approximately 40% of all epilepsy cases, they contribute to 80% of early infantile EEs (EIEEs), with approximately 125 genes previously linked to this disease. Whole exome sequencing (WES) was performed in a 9-month-old Lebanese girl presenting with EIEE. WES enabled the detection of a homozygous missense mutation in the NECAP1 gene (NM_015509.3: p.Glu8Lys) in the proband. Here, we report the first homozygous missense mutation in the NECAP1 gene in a 9-month-old girl presenting with EIEE. Our findings allow a better characterization of the NECAP1-linked disease and enable broadening its clinical spectrum by including, in addition to EIEE, severe generalized hypotonia, poor feeding, developmental delay, severe microcephaly, delayed myelination, abnormalities of the corpus callosum, and eye abnormalities.

Clinical whole exome sequencing revealed de novo heterozygous stop-gain and missense variants in the STXBP1 gene associated with epilepsy in Saudi families

Intellectual disability and developmental encephalopathies are mostly linked with infant epilepsy. Epileptic encephalopathy is a term that is used to define association between developmental delay and epilepsy. Mutations in the STXBP1 (Syntaxin-binding protein 1) gene have been previously reported in association with multiple severe early epileptic encephalopathies along with many neurodevelopmental disorders. Among the disorders produced due to any mutations in the STXBP1 gene is developmental and epileptic encephalopathy 4 (OMIM: 612164), is an autosomal dominant neurologic disorder categorized by the onset of tonic seizures in early infancy (usually in the first months of life). In this article, we report two Saudi families one with de novo heterozygous stop-gain mutation c.364C > T and a novel missense c. 305C > A p.Ala102Glu in exon 5 of the STXBP1 gene (OMIM: 602926) lead to development of epileptic encephalopathy 4. The variants identified in the current study broadened the genetic spectrum of STXBP1 gene related with diseases, which will help to add in the literature and benefit to the studies addressing this disease in the future.

Monoamine neurotransmitters in early epileptic encephalopathies: New insights into pathophysiology and therapy

AimTo study neurotransmitter status in children with early epileptic and developmental and epileptic encephalopathy (DEE) and to explore the clinical response to dopaminergic and serotoninergic therapies in a group of patients.MethodTwo hundred and five patients (111 males [54.1.%] and 94 females [45.9%], mean age 10 months at the onset of epilepsy [SD 1 year 1 month], range 0–3 year) with epileptic encephalopathy/DEE were recruited, including those with West syndrome, Ohtahara syndrome, early myoclonic encephalopathy, epilepsy of infancy with migrating focal seizures, myoclonic encephalopathy in non‐progressive disorders, infantile spasms, Doose syndrome, Lennox–Gastaut syndrome, Landau–Kleffner syndrome, and those unclassified. Cerebrospinal fluid (CSF) neurotransmitter studies and patients' medical records were reviewed. Additionally, we present clinical data of 10 patients with low CSF neurotransmitter levels who received dopaminergic/serotoninergic treatments.ResultsAbnormal neurotransmitter values were identified in 68 (33%) patients. 5‐Hydroxyindoleacetic acid (5‐HIAA) deficit was the most prevalent alteration (91%). Low CSF 5‐HIAA levels were significantly higher in 1‐ to 3‐year‐old children. A negative significant correlation was found between 5‐HIAA levels and epilepsy duration before CSF study (Spearman's ρ=−0.191, p=0.007). Abnormalities in deep grey matter were associated with low levels of CSF homovanillic acid and 5‐HIAA. Ten patients with low CSF neurotransmitter levels received dopamine and/or serotonin therapies. Six of them showed initial decrease of seizure frequency and severity and maintained improvement in some neurodevelopmental skills.InterpretationA considerable number of patients showed neurotransmitter abnormalities. Age at seizure onset and duration of epilepsy before CSF study were the principal factors related to neurotransmitter depletion. Early monoamine supplementation would seem advisable as a neuroprotective strategy.What this paper adds 5‐Hydroxyindoleacetic acid homeostasis is especially vulnerable in patients with epileptic encephalopathy/developmental and epileptic encephalopathy. Age of seizure onset and duration of epilepsy are determinants of neurotransmitter depletion.

Experience with the use of a ketogenic diet with type 1 glucose transporter deficiency (De Vivo disease)

De Vivo disease is characterized by early epileptic encephalopathy, delayed psychomotor development, spasticity, the formation of microcephaly, ataxia, dysarthria, alternating hemiplegia, and a decrease in glucose and lactate levels in the cerebrospinal fluid. Epilepsy is pharmacoresistant and the therapy for this syndrome is the ketogenic diet (until the time when will development of genetic targeted therapy). In GLUT1 deficiency syndrome, mutations are found in the SLC2A1 gene that lead to a decrease in glucose transport across the cell membrane. The “classic” ketogenic diet is a special high-fat, low-carbohydrate diet that helps to control seizures in some people with epilepsy. It is prescribed by a physician and carefully monitored by a dietitian. It is usually used in children with seizures that do not respond to medications. It is stricter than the modified Atkins diet, requiring careful measurements of calories, fluids, and proteins. Foods are weighed and measured. Normal dietary fats, which are used predominantly in the classical ketogenic diet, consist of a mixture of mainly long chain triglyceride (LCT) fats with a small amount of short and medium chain triglyceride (MCT) fats. The MCT ketogenic diet uses a fat supplement that consists only of MCT fats (MCT oil).

Genetic Diagnosis in Children with Epilepsy and Developmental Disorders by Targeted Gene Panel Analysis in a Developing Country.

Background and PurposeIn childhood epilepsy, genetic etiology is increasingly recognized in recent years with the advent of next generation sequencing. This has broadened the scope of precision medicine in intractable epilepsy, particularly epileptic encephalopathy (EE). Developmental disorder (DD) is an integral part of childhood uncontrolled epilepsy. This study was performed to investigate the genetic etiology of childhood epilepsy and DD.MethodsIn this study, 40 children with epilepsy and DD with positive genetic mutation were included retrospectively. It was done in a tertiary care referral hospital of Bangladesh from January 2019 to December 2020. Genetic study was done by next generation sequencing. In all cases electroencephalography, neuroimaging was done and reviewed.ResultsIn total, 40 children were enrolled and the average age was 41.4±35.850 months with a male predominance (67.5%). Generalized seizure was the predominant type of seizure. Regarding the association, intellectual disability and attention deficit hyperactivity disorder was common. Seventeen cases had genetically identified early infantile EE and common mutations observed were SCN1A (3), SCN8A (2), SLC1A2 (2), KCNT1 (2), and etc. Five patients of progressive myoclonic epilepsy were diagnosed and the mutations identified were in KCTD7, MFSD8, and CLN6 genes. Three cases had mitochondrial gene mutation (MT-ND5, MT-CYB). Some rare syndromes like Gibbs syndrome, Kohlschütter-Tönz syndrome, Cockayne syndrome, Pitt-Hopkins syndrome and cerebral creatine deficiency were diagnosed.ConclusionsThis is the first study from Bangladesh on genetics of epilepsy and DD. This will help to improve the understanding of genetics epilepsy of this region as well as contribute in administering precision medicine in these patients.

A description of novel variants and review of phenotypic spectrum in UBA5-related early epileptic encephalopathy.

Early infantile epileptic encephalopathy-44 (EIEE44, MIM: 617132) is a previously described condition resulting from biallelic variants in UBA5, a gene involved in a ubiquitin-like post-translational modification system called UFMylation. Here we report five children from four families with biallelic pathogenic variants in UBA5. All five children presented with global developmental delay, epilepsy, axial hypotonia, appendicular hypertonia, and a movement disorder, including dystonia in four. Affected individuals in all four families have compound heterozygous pathogenic variants in UBA5. All have the recurrent mild c.1111G > A (p.Ala371Thr) variant in trans with a second UBA5 variant. One patient has the previously described c.562C > T (p. Arg188*) variant, two other unrelated patients have a novel missense variant, c.907T > C (p.Cys303Arg), and the two siblings have a novel missense variant, c.761T > C (p.Leu254Pro). Functional analyses demonstrate that both the p.Cys303Arg variant and the p.Leu254Pro variants result in a significant decrease in protein function. We also review the phenotypes and genotypes of all 15 previously reported families with biallelic UBA5 variants, of which two families have presented with distinct phenotypes, and we describe evidence for some limited genotype–phenotype correlation. The overlap of motor and developmental phenotypes noted in our cohort and literature review adds to the increasing understanding of genetic syndromes with movement disorders-epilepsy.

Early Myoclonic Epileptic Encephalopathy in a Newborn: Successfully Control Seizures and Suppression-Burst EEG with Levetiracetam

Early Myoclonic Epileptic Encephalopathy in a Newborn: Successfully Control Seizures and Suppression-Burst EEG with Levetiracetam

Clinical Genetic Characteristics of Epilepsy Due to Mutations in the PCDH19 Gene (OMIM: 300088)

Objectives: to analyze the clinical genetic characteristics of PCDH19-associated epilepsy in a cohort of patients from the population of the Russian Federation. Materials and methods. The cohort of patients with early epileptic encephalopathy consisted of 16 patients aged from 10 months to 30 years. All patients underwent neurological examination by standard methods, exome sequencing, and electroencephalogram monitoring. Results. Most of the mutations detected were frameshift mutations or mutations forming a stop codon. Six were duplications and four were deletions of a single nucleotide, while three were nonsense mutations. Polymorphism in the clinical manifestations of convulsions were found, which were independent of the type of mutation and its location, which is consistent with results reported by other authors. Conclusions. This study of the clinical genetic features of our patients leads to the conclusion that the PCDH19 gene has so-called hot spots, which are mutated more frequently than other parts of the gene, and that the clinical picture of epileptic encephalopathy type 9, induced by mutations in the PCDH19 gene, is variable.

STXBP1 encephalopathies: Clinical spectrum, disease mechanisms, and therapeutic strategies.

Mutations in Munc18-1/STXBP1 (syntaxin-binding protein 1) are linked to various severe early epileptic encephalopathies and neurodevelopmental disorders. Heterozygous mutations in the STXBP1 gene include missense, nonsense, frameshift, and splice site mutations, as well as intragenic deletions and duplications and whole-gene deletions. No genotype-phenotype correlation has been identified so far, and patients are treated by anti-epileptic drugs because of the lack of a specific disease-modifying therapy. The molecular disease mechanisms underlying STXBP1-linked disorders are yet to be fully understood, but both haploinsufficiency and dominant-negative mechanisms have been proposed. This review focuses on the current understanding of the phenotypic spectrum of STXBP1-linked disorders, as well as discusses disease mechanisms in the context of the numerous pathways in which STXBP1 functions in the brain. We additionally evaluate the available animal models to study these disorders and highlight potential therapeutic approaches for treating these devastating diseases.

Clinical and genetic characteristics of the early 66th type epileptic encephalopathy (literature review and own observation)

Early epileptic encephalopathy-66 was first diagnosed in a male patient from Russia using whole-exome sequencing. Early epileptic encephalopathy- 66 is a unique disorder in the group of early epileptic encephalopathies. The same recurrent heterozygous variant of the nucleotide sequence was found in all known patients, but the severity of seizures and dysmorphic signs significantly vary between patients. The current study of a recurrent pathogenic variant in PACS2 gene expands the phenotype spectrum of early epileptic encephalopathy-66 and will improve the management of patients with that disorder in Russia in the future.

Malignant migratory partial seizures of infancy: description of clinical observations

Epileptic encephalopathies of infancy are difficult-to-treat destructive cases of epilepsy in infants and young children, which include the two clinical observations of Coppola Dulac syndrome (malignant migrating partial attacks of infancy) given in this article. Epileptic encephalopathies are a genetically heterogeneous group of disorders that are characterized by the presence of a convulsive syndrome and are accompanied by cognitive and behavioral disorders. As a result of intensive development of methods of molecular genetic research, ideas about the causes of epilepsy in children began to change, this fact led to the fact that the international League against epilepsy replaced the term idiopathic epilepsy with genetic epilepsy. To date, about 60 phenotypic variants of early epileptic encephalopathies have been registered in children, including those associated with mutations of genes that regulate the functions of voltage-dependent calcium and sodium channels. In our work, we consider clinical observations of genetic epileptic encephalopathies caused by mutations in the CACNA1A and SCN8A genes, respectively, which are channelopathy. Malignant migrating partial attacks of infancy (infant epilepsy with migrating focal attacks, Coppola Dulac syndrome) are manifested at an early age, from the first days to 6 months of life, and are characterized by typical multifocal attacks with a tendency to change hemispheres and involve opposite limbs. G. Coppola based on the analysis of their own observations, described in 1995 a new age dependent epileptic syndrome, introducing a definition for it migrating partial attacks of infancy. Currently, it is recommended to use the term infant epilepsy with migrating focal seizures. We present our own clinical and neurophysiological observations of this rare syndrome.

Gene replacement ameliorates deficits in mouse and human models of cyclin-dependent kinase-like 5 disorder.

Cyclin-dependent kinase-like 5 disorder is a severe neurodevelopmental disorder caused by mutations in the X-linked cyclin-dependent kinase-like 5 (CDKL5) gene. It predominantly affects females who typically present with severe early epileptic encephalopathy, global developmental delay, motor dysfunction, autistic features and sleep disturbances. To develop a gene replacement therapy, we initially characterized the human CDKL5 transcript isoforms expressed in the brain, neuroblastoma cell lines, primary astrocytes and embryonic stem cell-derived cortical interneurons. We found that the isoform 1 and to a lesser extent the isoform 2 were expressed in human brain, and both neuronal and glial cell types. These isoforms were subsequently cloned into recombinant adeno-associated viral (AAV) vector genome and high-titre viral vectors were produced. Intrajugular delivery of green fluorescence protein via AAV vector serotype PHP.B in adult wild-type male mice transduced neurons and astrocytes throughout the brain more efficiently than serotype 9. Cdkl5 knockout male mice treated with isoform 1 via intrajugular injection at age 28-30 days exhibited significant behavioural improvements compared to green fluorescence protein-treated controls (1012 vg per animal, n = 10 per group) with PHP.B vectors. Brain expression of the isoform 1 transgene was more abundant in hindbrain than forebrain and midbrain. Transgene brain expression was sporadic at the cellular level and most prominent in hippocampal neurons and cerebellar Purkinje cells. Correction of postsynaptic density protein 95 cerebellar misexpression, a major fine cerebellar structural abnormality in Cdkl5 knockout mice, was found in regions of high transgene expression within the cerebellum. AAV vector serotype DJ efficiently transduced CDKL5-mutant human induced pluripotent stem cell-derived neural progenitors, which were subsequently differentiated into mature neurons. When treating CDKL5-mutant neurons, isoform 1 expression led to an increased density of synaptic puncta, while isoform 2 ameliorated the calcium signalling defect compared to green fluorescence protein control, implying distinct functions of these isoforms in neurons. This study provides the first evidence that gene therapy mediated by AAV vectors can be used for treating CDKL5 disorder.

Characteristics of people with the STXBP1 syndrome in Spain: Implications for diagnosis

IntroductionSTXBP1 syndrome is a genetic disorder that affects one of the regulatory mechanisms of neurotransmitter release by the synaptic vesicles and has serious implications for neurodevelopment. Symptoms usually appear in the first days or months of life, and very often include epilepsy, psychomotor delay, and intellectual disability. Although it was initially regarded as an early epileptic encephalopathy, the increase in the number of cases diagnosed, as well as the advances in research have been expanding the phenotype and characterising this disease as a disorder of neurodevelopment. Furthermore, on being linked to epileptic problems, this genetic mutation could be associated with many cases of intellectual disability and movement disorders of unknown cause. ObjectivesTo describe the characteristics of the patients identified in Spain with STXBP1 syndrome, and the implications for the diagnosis of these characteristics. Patients and methodsThe details are presented on 17 individuals, aged between 2 years and 17 years, diagnosed in Spain with STXBP1 syndrome. ConclusionsThere is a clear under-diagnosis of STXBP1 syndrome in Spain. Besides the inherent diversity of the disorder, with the increase in the number diagnoses the variability of the phenotype is even wider. The description of the alarm signs is necessary in order to identify those individuals with less prototypical manifestations of the disorder

Clinical and genetic characteristics of epilepsy caused by mutations in the PCDH19 gene (OMIM: 300088)

To analyze clinical and genetic characteristics of PCDH19-associated epilepsy in a sample of patients from the Russian population. The sample of patients with early epileptic encephalopathies included 16 people aged 10 month to 30 years. All patients underwent neurological examination according to standard methods, exome sequencing and EEG monitoring. Most of the identified mutations led to a shift in the reading frame or the formation of a termination codon. Six of them were duplications, four were deletions of one nucleotide, and three were nonsense mutations. Consistent with earlier studies, the authors identified the polymorphism of clinical manifestations of seizures that did not depend on the type of mutation and its localization. Based on the study of the clinical and genetic characteristics of the patients, the authors conclude that the so-called 'hot spots' are present in the PCDH19 gene, which are more common in the group of patients with mutations in this gene, and that the clinical picture of early infantile epileptic encephalopathy type 9 is variable.

Fetal brain MRI findings and neonatal outcome of common diagnosis at a tertiary care center.

Identify common brain malformations on fetal MRI and evaluate perinatal course. Fetal consultations from 10/2016 to 12/2017 reviewed. Hundred consultations were requested; 94 were completed. Findings included: posterior fossa malformations (19%), agenesis/dysgenesis of corpus callosum (15%), congenital aqueductal stenosis (CAS) (14%), ventriculomegaly (11%), isolated cortical malformations (8.5%), and holoprosencephaly (6%). Posterior fossa malformations were more likely to be associated with genetic conditions and cardiac malformations. Patients with CAS all required intensive care unit admission. Overall, few patients with congenital brain malformations required feeding or respiratory support at discharge. None had seizures as neonates except two with early epileptic encephalopathy syndromes. Even though long term neurological prognosis is poor for many conditions including high lifetime risk of epilepsy, most are discharged with no feeding or respiratory support. Seizures are rarely seen in the neonatal period.

Gene mutations in paediatric epilepsies cause NMDA-pathy, and phasic and tonic GABA-pathy.

The aim of this study was to disentangle mechanisms of epileptogenesis in monogenic epilepsies in children. We reviewed paediatric monogenic epilepsies excluding brain malformation or an inborn error of metabolism, but including the gene function whether there is loss-of-function or gain-of-function, age at gene expression when available, and associated epilepsy syndrome. Genes for which at least five patients with similar epilepsy phenotype had been reported were selected. Three mechanisms are shared by most monogenic epilepsies: (1) excess of N-methyl-d-aspartate (NMDA) transmission activation (NMDA-pathies); (2)abnormal gamma-aminobutyric acid (GABA) transmission with reduced inhibition (phasic GABA-pathies); and (3) tonic activation of extrasynaptic GABAA receptors by extracellular GABA (tonic GABA-pathies). NMDA-pathies comprise early epileptic encephalopathy with suppression-burst, neonatal/infantile benign seizures, West and Lennox-Gastaut syndromes, and encephalopathy with continuous spike waves in slow sleep, thus brief seizures with major interictal spiking. Phasic GABA-pathies comprise mostly generalized epilepsy with febrile seizures plus and Dravet syndrome, thus long-lasting seizures with mild interictal spiking. Tonic GABA-pathies cause epilepsy with myoclonic-atonic seizures and Angelman syndrome, thus major high-amplitude slow-wave activity. This pathophysiological approach to monogenic epilepsies provides diagnostic clues and helps to guide treatment strategy. WHAT THIS PAPER ADDS: In paediatric monogenic epilepsies, electroclinical patterns point to three main mechanisms: NMDA-pathies, and phasic and tonic GABA-pathies. Antiepileptic treatment choice could be guided by each of these mechanisms.