Exome sequencing in 57 patients with self-limited focal epilepsies of childhood with typical or atypical presentations suggests novel candidate genes

Continuous Spike-Waves during Slow Sleep Today: An Update

In the context of childhood epilepsy, the concept of continuous spike-waves during slow sleep (CSWS) includes several childhood-onset heterogeneous conditions that share electroencephalograms (EEGs) characterized by a high frequency of paroxysmal abnormalities during sleep, which have negative effects on the cognitive development and behavior of the child. These negative effects may have the characteristics of a clear regression or of a slowdown in development. Seizures are very often present, but not constantly. The above makes it clear why CSWS have been included in epileptic encephalopathies, in which, by definition, frequent EEG paroxysmal abnormalities have an unfavorable impact on cognitive functions, including socio-communicative skills, causing autistic features, even regardless of the presence of clinically overt seizures. Although several decades have passed since the original descriptions of the electroclinical condition of CSWS, there are still many areas that are little-known and deserve to be further studied, including the EEG diagnostic criteria, the most effective electrophysiological parameter for monitoring the role of the thalamus in CSWS pathogenesis, its long-term evolution, the nosographic location of Landau-Kleffner syndrome, standardized neuropsychological and behavioral assessments, and pharmacological and non-pharmacological therapies.

Functional Evaluation of a Novel GRIN2B Missense Variant Associated with Epilepsy and Intellectual Disability

Epilepsy, a neurological condition, is widely prevalent among individuals with intellectual disability (ID). It is well established that N-methyl-D-aspartate (NMDA) receptors play an important role in both epilepsy and ID. Autosomal dominant mutations in the GRIN2B gene, which encodes the GluN2B subunit of the NMDA receptor, have been reported to be associated with epilepsy and ID. However, the underlying mechanism of this association is not well-understood. In this study, we identified a novel GRIN2B mutation (c.3272A > C, p.K1091T) in a patient with epilepsy and ID. The proband was a one year and ten months old girl. GRIN2B variant was inherited from her mother. We further investigated the functional consequences of this mutation. Our findings revealed that the p.K1091T mutation created a Casein kinase 2 phosphorylation site. Using recombinant NMDA receptors containing the GluN2B-K1091T along with GluN1 in HEK 293T cells, we observed significant defects in its interactions with postsynaptic density 95. It is accompanied by reduced delivery of the receptors to the cell membrane and a decrease in glutamate affinity. Moreover, primary neurons expressing GluN2B-K1091T also exhibited impaired surface expression of NMDA receptors, a reduction in dendritic spine number and excitatory synaptic transmission. In summary, our study reports a novel GRIN2B mutation and provides functional characteristics of this mutation in vitro, thereby contributing to the understanding of GRIN2B variants in epilepsy and ID.

Structural and functional changes in drug-naïve benign childhood epilepsy with centrotemporal spikes and their associated gene expression profiles

Benign epilepsy with centrotemporal spikes (BECTS) is a common pediatric epilepsy syndrome that has been widely reported to show abnormal brain structure and function. However, the genetic mechanisms underlying structural and functional changes remain largely unknown. Based on the structural and resting-state functional magnetic resonance imaging data of 22 drug-naïve children with BECTS and 33 healthy controls, we conducted voxel-based morphology (VBM) and fractional amplitude of low-frequency fluctuation (fALFF) analyses to compare cortical morphology and spontaneous brain activity between the 2 groups. In combination with the Allen Human Brain Atlas, transcriptome-neuroimaging spatial correlation analyses were applied to explore gene expression profiles associated with gray matter volume (GMV) and fALFF changes in BECTS. VBM analysis demonstrated significantly increased GMV in the right brainstem and right middle cingulate gyrus in BECTS. Moreover, children with BECTS exhibited significantly increased fALFF in left temporal pole, while decreased fALFF in right thalamus and left precuneus. These brain structural and functional alterations were closely related to behavioral and cognitive deficits, and the fALFF-linked gene expression profiles were enriched in voltage-gated ion channel and synaptic activity as well as neuron projection. Our findings suggest that brain morphological and functional abnormalities in children with BECTS involve complex polygenic genetic mechanisms.

N-Type Ca Channel in Epileptic Syndromes and Epilepsy: A Systematic Review of Its Genetic Variants

N-type voltage-gated calcium channel controls the release of neurotransmitters from neurons. The association of other voltage-gated calcium channels with epilepsy is well-known. The association of N-type voltage-gated calcium channels and pain has also been established. However, the relationship between this type of calcium channel and epilepsy has not been specifically reviewed. Therefore, the present review systematically summarizes existing publications regarding the genetic associations between N-type voltage-dependent calcium channel and epilepsy.

Epilepsy syndromes in cerebral palsy: varied, evolving and mostly self-limited

Seizures occur in approximately one-third of children with cerebral palsy. This study aimed to determine epilepsy syndromes in children with seizures and cerebral palsy due to vascular injury, anticipating that this would inform treatment and prognosis. We studied a population-based cohort of children with cerebral palsy due to prenatal or perinatal vascular injuries, born 1999-2006. Each child's MRI was reviewed to characterize patterns of grey and white matter injury. Children with syndromic or likely genetic causes of cerebral palsy were excluded, given their inherent association with epilepsy and our aim to study a homogeneous cohort of classical cerebral palsy. Chart review, parent interview and EEGs were used to determine epilepsy syndromes and seizure outcomes. Of 256 children, 93 (36%) had one or more febrile or afebrile seizures beyond the neonatal period and 87 (34%) had epilepsy. Children with seizures were more likely to have had neonatal seizures, have spastic quadriplegic cerebral palsy and function within Gross Motor Function Classification System level IV or V. Fifty-six (60%) children with seizures had electroclinical features of a self-limited focal epilepsy of childhood; we diagnosed these children with a self-limited focal epilepsy-variant given the current International League Against Epilepsy classification precludes a diagnosis of self-limited focal epilepsy in children with a brain lesion. Other epilepsy syndromes were focal epilepsy-not otherwise specified in 28, infantile spasms syndrome in 11, Lennox-Gastaut syndrome in three, genetic generalized epilepsies in two and febrile seizures in nine. No epilepsy syndrome could be assigned in seven children with no EEG. Twenty-one changed syndrome classification during childhood. Self-limited focal epilepsy-variant usually manifested with a mix of autonomic and brachio-facial motor features, and occipital and/or centro-temporal spikes on EEG. Of those with self-limited focal epilepsy-variant, 42/56 (75%) had not had a seizure for >2 years. Favourable seizure outcomes were also seen in some children with infantile spasms syndrome and focal epilepsy-not otherwise specified. Of the 93 children with seizures, at last follow-up (mean age 15 years), 61/91 (67%) had not had a seizure in >2 years. Children with cerebral palsy and seizures can be assigned specific epilepsy syndrome diagnoses typically reserved for normally developing children, those syndromes commonly being age-dependent and self-limited. Compared to typically developing children with epilepsy, self-limited focal epilepsy-variant occurs much more commonly in children with cerebral palsy and epilepsy. These findings have important implications for treatment and prognosis of epilepsy in cerebral palsy, and research into pathogenesis of self-limited focal epilepsy.

Compound heterozygous loss-of-function variants in BRAT1 cause lethal neonatal rigidity and multifocal seizure syndrome

BACKGROUND

Lethal neonatal rigidity and multifocal seizure syndrome (RMFSL, OMIM 614498) is a rare autosomal recessive disease characterized by the onset of rigidity and intractable seizures at or soon after birth. The BRAT1 has been identified to be the disease-causing gene for RMFSL. This study aimed to determine the underlying pathogenic mutations of a Chinese family with RMFSL and to confirm the effect of the splice-site mutation by reverse transcription analysis.

METHODS

Detailed family history and clinical data were recorded, and peripheral blood samples were collected from all available family members. Whole exome sequencing (WES), Sanger sequencing, and bioinformatics analysis were performed to investigate the causative variants. The impact of the intronic variant on splicing was subsequently analyzed by RT-PCR analysis.

RESULTS

We identified two compound heterozygous variants in the BRAT1, c.431-2A>G in intron 3 and c.1359_1361del(p.Leu454del) in exon 9 in the proband, one inherited from each parent. Furthermore, the 3'-splice site acceptor (c.431-2A>G) variant was found to activate a cryptic acceptor splice site, which resulted in the loss of 29 nucleotides and generation of a premature stop codon at code 180, producing a truncated BRAT1 (c.432_460del; p.Ala145Argfs*36).

CONCLUSIONS

This research identified two mutations in the BRAT1 of one Chinese family with RMFSL. These data can aid in developing clinical diagnoses as well as providing genetic counseling and prenatal interventions to the family. These findings also expand our knowledge of the spectrum of BRAT1 pathogenic variants in RMFSL syndrome.

Gastrointestinal and Autonomic Symptoms—How to Improve the Diagnostic Process in Panayiotopoulos Syndrome?

One of the most common epileptic disorders in the pediatric population is Panayiotopoulos syndrome. Clinical manifestations of this idiopathic illness include predominantly autonomic symptoms and dysfunction of the cardiorespiratory system. Another feature constitutes prolonged seizures that usually occur at sleep. It is crucial to differentiate the aforementioned disease from other forms of epilepsy, especially occipital and structural epilepsy and non-epileptic disorders. The diagnostic process is based on medical history, clinical examination, neuroimaging and electroencephalography—though results of the latter may be unspecific. Patients with Panayiotopoulos syndrome (PS) do not usually require treatment, as the course of the disease is, in most cases, mild, and the prognosis is good. The purpose of this review is to underline the role of central autonomic network dysfunction in the development of Panayiotopoulos syndrome, as well as the possibility of using functional imaging techniques, especially functional magnetic resonance imaging (fMRI), in the diagnostic process. These methods could be crucial for understanding the pathogenesis of PS. More data arerequired to create algorithms that will be able to predict the exposure to various complications of PS. It also concerns the importance of electroencephalography (EEG) as a tool to distinguish Panayiotopoulos syndrome from other childhood epileptic syndromes and non-epileptic disorders.

Gain of function due to increased opening probability by two KCNQ5 pore variants causing developmental and epileptic encephalopathy

Variants in genes encoding neuronally expressed potassium channel subunits are frequent causes of developmental and epileptic encephalopathies (DEEs). Characterization of their functional consequences is critical to confirm diagnosis, assess prognosis, and implement personalized treatments. In the present work, we describe two patients carrying variants in KCNQ5, a gene very recently and rarely found involved in DEEs, and reveal that they both cause remarkable gain-of-function consequences on channel activity. A PIP₂-independent increase in open probability, without effects on membrane abundance or single-channel conductance, was responsible for the observed mutation-induced functional changes, thus revealing a pathomolecular disease mechanism for DEEs.

Developmental and epileptic encephalopathies (DEEs) are neurodevelopmental diseases characterized by refractory epilepsy, distinct electroencephalographic and neuroradiological features, and various degrees of developmental delay. Mutations in KCNQ2, KCNQ3, and, more rarely, KCNQ5 genes encoding voltage-gated potassium channel subunits variably contributing to excitability control of specific neuronal populations at distinct developmental stages have been associated to DEEs. In the present work, the clinical features of two DEE patients carrying de novo KCNQ5 variants affecting the same residue in the pore region of the Kv7.5 subunit (G347S/A) are described. The in vitro functional properties of channels incorporating these variants were investigated with electrophysiological and biochemical techniques to highlight pathophysiological disease mechanisms. Currents carried by Kv7.5 G347 S/A channels displayed: 1) large (>10 times) increases in maximal current density, 2) the occurrence of a voltage-independent component, 3) slower deactivation kinetics, and 4) hyperpolarization shift in activation. All these functional features are consistent with a gain-of-function (GoF) pathogenetic mechanism. Similar functional changes were also observed when the same variants were introduced at the corresponding position in Kv7.2 subunits. Nonstationary noise analysis revealed that GoF effects observed for both Kv7.2 and Kv7.5 variants were mainly attributable to an increase in single-channel open probability, without changes in membrane abundance or single-channel conductance. The mutation-induced increase in channel opening probability was insensitive to manipulation of membrane levels of the critical Kv7 channel regulator PIP₂. These results reveal a pathophysiological mechanism for KCNQ5-related DEEs, which might be exploited to implement personalized treatments.

Genetic Epilepsy Syndromes

PURPOSE OF REVIEW

This article reviews the clinical features, typical EEG findings, treatment, prognosis, and underlying molecular etiologies of the more common genetic epilepsy syndromes. Genetic generalized epilepsy, self-limited focal epilepsy of childhood, self-limited neonatal and infantile epilepsy, select developmental and epileptic encephalopathies, progressive myoclonus epilepsies, sleep-related hypermotor epilepsy, photosensitive occipital lobe epilepsy, and focal epilepsy with auditory features are discussed. Also reviewed are two familial epilepsy syndromes: genetic epilepsy with febrile seizures plus and familial focal epilepsy with variable foci.

RECENT FINDINGS

Recent years have seen considerable advances in our understanding of the genetic factors underlying genetic epilepsy syndromes. New therapies are emerging for some of these conditions; in some cases, these precision medicine approaches may dramatically improve the prognosis.

SUMMARY

Many recognizable genetic epilepsy syndromes exist, the identification of which is a crucial skill for neurologists, particularly those who work with children. Proper diagnosis of the electroclinical syndrome allows for appropriate treatment choices and counseling regarding prognosis and possible comorbidities.

A peculiar family with recurrent self-limited epileptic syndrome and associated developmental disorders in six girls

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Self-Limited Epilepsies may evolve to Developmental and/or Epileptic Encephalopathy.

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Family cases may present with recurrent phenotype and complex genetic background.

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Genetic testing could not provide useful elements for early aetiological diagnosis.

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This electroclinical phenotype had remarkable impact on development.

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It’s important an early identification of genetic risk factors of family cases.

We describe a complex family with two couples (two sisters who married two brothers) with consistent social and neuropsychiatric problems, originally from Sardinia. Each couple had three daughters, which shared electroclinical epileptic syndrome and developmental disorders. All patients suffered from mild to moderate intellectual disability, speech difficulties and behavioural disorders. Four out of six patients had epilepsy onset between 3 and 4 years of age. The epileptic history almost reflected the typical clinical course of a self-Limited Focal Epilepsy of Childhood. However, our patients don’t have the complete features characteristic of one of the four specific self-Limited Focal Epilepsies of Childhood; a progressive evolution into a Developmental and/or Epileptic Encephalopathy with spike-wave activation in sleep was observed in the two older sister of the first family, which developed more severe developmental disorder too. In the other epileptic patients, improvement of EEG pattern was not coincident with an improvement of the developmental disorders. Brain MRI, performed in three patients, showed normal findings. Genetic analysis carried out so far (SNP-array, study of Runs of homozygosity, FMR1 triplet-repeat primer-PCR assay, Next Generation Sequencing based gene panel for epilepsy and neurodevelopmental disorders and Exome Sequencing), did not provide useful elements for an aetiological diagnosis.

Pädiatrische epileptische Enzephalopathien mit Manifestation oberhalb des Neugeborenenalters: ein Up-date

Entwicklungs-und epileptische Enzephalopathien manifestieren sich überwiegend bereits im Säuglings-und frühen Kleinkindesalter. Mit der neuen ILAE-Klassifikation der Epilepsien konnten epileptische Enzephalopathien sowohl hinsichtlich des elektroklinischen Phänotyps als auch des ätiologischen Spektrums und assoziierter Komorbiditäten genauer definiert werden. Einige elektroklinischer Entitäten wie das West-Syndrom oder das Dravet-Syndrom können auf der Basis ihres Genotyps inzwischen als spezifische Enzephalopathien klassifiziert werden. Das EEG stellt eine wichtige Zusatzdiagnostik in der Abklärung einer epileptischen Enzephalopathie dar. Es hat einen besonderen Stellenwert für die Diagnose von Komplikationen wie z. B. subklinischer Anfälle oder eines Status epilepticus sowie für ein adäquates Therapiemonitoring. Der Betrag fasst anhand ausgewählter pädiatrischer Epilepsiesyndrome aktuelle Aspekte zur Komplexität der pädiatrischen epileptischen Enzephalopathien und den Stellenwert der EEG-Diagnostik zusammen.