The genetic landscape of infantile spasms

ALG13-Congenital Disorder of Glycosylation (ALG13-CDG): Updated clinical and molecular review and clinical management guidelines

ALG13-Congenital Disorder of Glycosylation (CDG), is a rare X-linked CDG caused by pathogenic variants in ALG13 (OMIM 300776) that affects the N-linked glycosylation pathway. Affected individuals present with a predominantly neurological manifestation during infancy. Epileptic spasms are a common presenting symptom of ALG13-CDG. Other common phenotypes include developmental delay, seizures, intellectual disability, microcephaly, and hypotonia. Current management of ALG13-CDG is targeted to address patients' symptoms. To date, less than 100 individuals have been reported with ALG13-CDG. In this article, an international group of experts in CDG reviewed all reported individuals affected with ALG13-CDG and suggested diagnostic and management guidelines for ALG13-CDG. The guidelines are based on the best available data and expert opinion. Neurological symptoms dominate the phenotype of ALG13-CDG where epileptic spasm is confirmed to be the most common presenting symptom of ALG13-CDG in association with hypotonia and developmental delay. We propose that ACTH/prednisolone treatment should be trialed first, followed by vigabatrin, however ketogenic diet has been shown to have promising results in ALG13-CDG. In order to optimize medical management, we also suggest early cardiac, gastrointestinal, skeletal, and behavioral assessments in affected patients.

The Utility of Genetic Testing in Infantile Epileptic Spasms Syndrome: A Step-Based Approach in the Next-Generation Sequencing Era

BACKGROUND

To evaluate the utility of genetic testing for etiology-specific diagnosis (ESD) in infantile epileptic spasms syndrome (IESS) with a step-based diagnostic approach in the next-generation sequencing (NGS) era.

METHODS

The study cohort consisted of 314 patients with IESS, followed by the Pediatric Neurology Division of Ege University Hospital between 2005 and 2021. The ESD was evaluated using a step-based approach: step I (clinical phenomenology), step II (neuroimaging), step III (metabolic screening), and step IV (genetic testing). The diagnostic utility of genetic testing was evaluated to compare the early-NGS period (2005 to 2013, n = 183) and the NGS era (2014 to 2021, n = 131).

RESULTS

An ESD was established in 221 of 314 (70.4%) infants with IESS: structural, 40.8%; genetic, 17.2%; metabolic, 8.3%; immune-infectious, 4.1%. The diagnostic yield of genetic testing increased from 8.9% to 41.7% in the cohort during the four follow-up periods. The rate of unknown etiology decreased from 34.9% to 22.1% during the follow-up periods. The genetic ESD was established as 27.4% with genetic testing in the NGS era. The genetic testing in the NGS era increased dramatically in subgroups with unknown and structural etiologies. The diagnostic yields of the epilepsy panels increased from 7.6% to 19.2%. However, the diagnostic yield of whole exome sequencing remained at similar levels during the early-NGS period at 54.5% and in the NGS era at 59%.

CONCLUSIONS

The more genetic ESD (27.4%) was defined for IESS in the NGS era with the implication of precision therapy (37.7%).

Common genes and recurrent causative variants in 957 Asian patients with pediatric epilepsy

OBJECTIVE

We aimed to identify common genes and recurrent causative variants in a large group of Asian patients with different epilepsy syndromes and subgroups.

METHODS

Patients with unexplained pediatric-onset epilepsy were identified from the in-house Severance Neurodevelopmental Disorders and Epilepsy Database. All patients underwent either exome sequencing or multigene panels from January 2017 to December 2019, at Severance Children's Hospital in Korea. Clinical data were extracted from the medical records.

RESULTS

Of the 957 patients studied, 947 (99.0%) were Korean and 570 were male (59.6%). The median age at testing was 4.91 years (interquartile range, 1.53-9.39). The overall diagnostic yield was 32.4% (310/957). Clinical exome sequencing yielded a diagnostic rate of 36.9% (134/363), whereas the epilepsy panel yielded a diagnostic rate of 29.9% (170/569). Diagnostic yield differed across epilepsy syndromes. It was high in Dravet syndrome (87.2%, 41/47) and early infantile developmental epileptic encephalopathy (60.7%, 17/28), but low in West syndrome (21.8%, 34/156) and myoclonic-atonic epilepsy (4.8%, 1/21). The most frequently implicated genes were SCN1A (n = 49), STXBP1 (n = 15), SCN2A (n = 14), KCNQ2 (n = 13), CDKL5 (n = 11), CHD2 (n = 9), SLC2A1 (n = 9), PCDH19 (n = 8), MECP2 (n = 6), SCN8A (n = 6), and PRRT2 (n = 5). The recurrent genetic abnormalities included 15q11.2 deletion/duplication (n = 9), Xq28 duplication (n = 5), PRRT2 deletion (n = 4), MECP2 duplication (n = 3), SCN1A, c.2556+3A>T (n = 3), and 2q24.3 deletion (n = 3).

SIGNIFICANCE

Here we present the results of a large-scale study conducted in East Asia, where we identified several common genes and recurrent variants that varied depending on specific epilepsy syndromes. The overall genetic landscape of the Asian population aligns with findings from other populations of varying ethnicities.

Genetic Advancements in Infantile Epileptic Spasms Syndrome and Opportunities for Precision Medicine

Infantile epileptic spasms syndrome (IESS) is a devastating developmental epileptic encephalopathy (DEE) consisting of epileptic spasms, as well as one or both of developmental regression or stagnation and hypsarrhythmia on EEG. A myriad of aetiologies are associated with the development of IESS; broadly, 60% of cases are thought to be structural, metabolic or infectious in nature, with the remainder genetic or of unknown cause. Epilepsy genetics is a growing field, and over 28 copy number variants and 70 single gene pathogenic variants related to IESS have been discovered to date. While not exhaustive, some of the most commonly reported genetic aetiologies include trisomy 21 and pathogenic variants in genes such as TSC1, TSC2, CDKL5, ARX, KCNQ2, STXBP1 and SCN2A. Understanding the genetic mechanisms of IESS may provide the opportunity to better discern IESS pathophysiology and improve treatments for this condition. This narrative review presents an overview of our current understanding of IESS genetics, with an emphasis on animal models of IESS pathogenesis, the spectrum of genetic aetiologies of IESS (i.e., chromosomal disorders, single-gene disorders, trinucleotide repeat disorders and mitochondrial disorders), as well as available genetic testing methods and their respective diagnostic yields. Future opportunities as they relate to precision medicine and epilepsy genetics in the treatment of IESS are also explored.

Mechanisms of infantile epileptic spasms syndrome: What have we learned from animal models?

The devastating developmental and epileptic encephalopathy of infantile epileptic spasms syndrome (IESS) has numerous causes, including, but not limited to, brain injury, metabolic, and genetic conditions. Given the stereotyped electrophysiologic, age-dependent, and clinical findings, there likely exists one or more final common pathways in the development of IESS. The identity of this final common pathway is unknown, but it may represent a novel therapeutic target for infantile spasms. Previous research on IESS has focused largely on identifying the neuroanatomic substrate using specialized neuroimaging techniques and cerebrospinal fluid analysis in human patients. Over the past three decades, several animal models of IESS were created with an aim to interrogate the underlying pathogenesis of IESS, to identify novel therapeutic targets, and to test various treatments. Each of these models have been successful at recapitulating multiple aspects of the human IESS condition. These animal models have implicated several different molecular pathways in the development of infantile spasms. In this review we outline the progress that has been made thus far using these animal models and discuss future directions to help researchers identify novel treatments for drug-resistant IESS.

Infantile epileptic spasm syndrome as a new NR2F1 gene phenotype

INTRODUCTION

NR2F1 pathogenetic variants are associated with the Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS). Recent studies indicate that BBSOAS patients not only have visual impairments but may also have developmental delays, hypotonia, thin corpus callosum and epileptic seizures. However, reports of BBSOAS occurrence along with infantile epileptic spasm syndrome (IESS) are rare.

METHODS

Here, we report three cases involving children with IESS and BBSOAS caused by de novo NR2F1 pathogenetic variants and summarize the genotype, clinical characteristics, diagnosis and treatment of them.

RESULTS

All three children experienced epileptic spasms and global developmental delays, with brain Magnetic Resonance Imaging (MRI) suggesting abnormalities (thinning of the corpus callosum or widened extracerebral spaces) and two of the children exhibiting abnormal visual evoked potentials.

CONCLUSIONS

Our findings indicate that new missense NR2F1 pathogenetic variants may lead to IESS with abnormal visual evoked potentials. Thus, clinicians should be aware of the Bosch-Boonstra-Schaaf optic atrophy syndrome and regular monitoring of the fundus, and the optic nerve is necessary during follow-up.

Landscape of genetic infantile epileptic spasms syndrome-A multicenter cohort of 124 children from India

OBJECTIVE

Literature on the genotypic spectrum of Infantile Epileptic Spasms Syndrome (IESS) in children is scarce in developing countries. This multicentre collaboration evaluated the genotypic and phenotypic landscape of genetic IESS in Indian children.

METHODS

Between January 2021 and June 2022, this cross-sectional study was conducted at six centers in India. Children with genetically confirmed IESS, without definite structural-genetic and structural-metabolic etiology, were recruited and underwent detailed in-person assessment for phenotypic characterization. The multicentric data on the genotypic and phenotypic characteristics of genetic IESS were collated and analyzed.

RESULTS

Of 124 probands (60% boys, history of consanguinity in 15%) with genetic IESS, 105 had single gene disorders (104 nuclear and one mitochondrial), including one with concurrent triple repeat disorder (fragile X syndrome), and 19 had chromosomal disorders. Of 105 single gene disorders, 51 individual genes (92 variants including 25 novel) were identified. Nearly 85% of children with monogenic nuclear disorders had autosomal inheritance (dominant-55.2%, recessive-14.2%), while the rest had X-linked inheritance. Underlying chromosomal disorders included trisomy 21 (n = 14), Xq28 duplication (n = 2), and others (n = 3). Trisomy 21 (n = 14), ALDH7A1 (n = 10), SCN2A (n = 7), CDKL5 (n = 6), ALG13 (n = 5), KCNQ2 (n = 4), STXBP1 (n = 4), SCN1A (n = 4), NTRK2 (n = 4), and WWOX (n = 4) were the dominant single gene causes of genetic IESS. The median age at the onset of epileptic spasms (ES) and establishment of genetic diagnosis was 5 and 12 months, respectively. Pre-existing developmental delay (94.3%), early age at onset of ES (<6 months; 86.2%), central hypotonia (81.4%), facial dysmorphism (70.1%), microcephaly (77.4%), movement disorders (45.9%) and autistic features (42.7%) were remarkable clinical findings. Seizures other than epileptic spasms were observed in 83 children (66.9%). Pre-existing epilepsy syndrome was identified in 21 (16.9%). Nearly 60% had an initial response to hormonal therapy.

SIGNIFICANCE

Our study highlights a heterogenous genetic landscape and phenotypic pleiotropy in children with genetic IESS.

Retracted: Clinical and genetic evaluations of rare childhood epilepsies in Turkey's national cohort

Aycan Ünalp, Yiğithan Güzin, Bülent Ünay, Ayşe Tosun, Dilek Çavuşoğlu, Hande Gazeteci Tekin, Semra Hız Kurul, Ebru Arhan, Selvinaz Edizer, Gülten Öztürk, Uluç Yiş, Ünsal Yılmaz, Turkish Rare Epilepsies Study Group, Clinical and genetic evaluations of rare childhood epilepsies in Turkey's national cohort, Epileptic Disorders, 2023, (https://doi.org/10.1002/epd2.20150) The above article, published online on 16 August 2023 on Wiley Online Library (www.onlinelibrary.wiley.com), has been retracted by agreement between the authors, the Editor-in-Chief, Sándor Beniczky, and John Wiley & Sons Ltd. The authors asked for a retraction based on an experimental error which would alter the results of the study if corrected.

Drosophila CASK regulates brain size and neuronal morphogenesis, providing a genetic model of postnatal microcephaly suitable for drug discovery

BACKGROUND

CASK-related neurodevelopmental disorders are untreatable. Affected children show variable severity, with microcephaly, intellectual disability (ID), and short stature as common features. X-linked human CASK shows dosage sensitivity with haploinsufficiency in females. CASK protein has multiple domains, binding partners, and proposed functions at synapses and in the nucleus. Human and Drosophila CASK show high amino-acid-sequence similarity in all functional domains. Flies homozygous for a hypomorphic CASK mutation (∆18) have motor and cognitive deficits. A Drosophila genetic model of CASK-related disorders could have great scientific and translational value.

METHODS

We assessed the effects of CASK loss of function on morphological phenotypes in Drosophila using established genetic, histological, and primary neuronal culture approaches. NeuronMetrics software was used to quantify neurite-arbor morphology. Standard nonparametric statistics methods were supplemented by linear mixed effects modeling in some cases. Microfluidic devices of varied dimensions were fabricated and numerous fluid-flow parameters were used to induce oscillatory stress fields on CNS tissue. Dissociation into viable neurons and neurite outgrowth in vitro were assessed.

RESULTS

We demonstrated that ∆18 homozygous flies have small brains, small heads, and short bodies. When neurons from developing CASK-mutant CNS were cultured in vitro, they grew small neurite arbors with a distinctive, quantifiable "bushy" morphology that was significantly rescued by transgenic CASK+. As in humans, the bushy phenotype showed dosage-sensitive severity. To overcome the limitations of manual tissue trituration for neuronal culture, we optimized the design and operation of a microfluidic system for standardized, automated dissociation of CNS tissue into individual viable neurons. Neurons from CASK-mutant CNS dissociated in the microfluidic system recapitulate the bushy morphology. Moreover, for any given genotype, device-dissociated neurons grew larger arbors than did manually dissociated neurons. This automated dissociation method is also effective for rodent CNS.

CONCLUSIONS

These biological and engineering advances set the stage for drug discovery using the Drosophila model of CASK-related disorders. The bushy phenotype provides a cell-based assay for compound screening. Nearly a dozen genes encoding CASK-binding proteins or transcriptional targets also have brain-development mutant phenotypes, including ID. Hence, drugs that improve CASK phenotypes might also benefit children with disorders due to mutant CASK partners.

Interneuron odyssey: molecular mechanisms of tangential migration

Cortical GABAergic interneurons are critical components of neural networks. They provide local and long-range inhibition and help coordinate network activities involved in various brain functions, including signal processing, learning, memory and adaptative responses. Disruption of cortical GABAergic interneuron migration thus induces profound deficits in neural network organization and function, and results in a variety of neurodevelopmental and neuropsychiatric disorders including epilepsy, intellectual disability, autism spectrum disorders and schizophrenia. It is thus of paramount importance to elucidate the specific mechanisms that govern the migration of interneurons to clarify some of the underlying disease mechanisms. GABAergic interneurons destined to populate the cortex arise from multipotent ventral progenitor cells located in the ganglionic eminences and pre-optic area. Post-mitotic interneurons exit their place of origin in the ventral forebrain and migrate dorsally using defined migratory streams to reach the cortical plate, which they enter through radial migration before dispersing to settle in their final laminar allocation. While migrating, cortical interneurons constantly change their morphology through the dynamic remodeling of actomyosin and microtubule cytoskeleton as they detect and integrate extracellular guidance cues generated by neuronal and non-neuronal sources distributed along their migratory routes. These processes ensure proper distribution of GABAergic interneurons across cortical areas and lamina, supporting the development of adequate network connectivity and brain function. This short review summarizes current knowledge on the cellular and molecular mechanisms controlling cortical GABAergic interneuron migration, with a focus on tangential migration, and addresses potential avenues for cell-based interneuron progenitor transplants in the treatment of neurodevelopmental disorders and epilepsy.

Diverse Clinical Phenotypes of CASK-Related Disorders and Multiple Functional Domains of CASK Protein

CASK-related disorders are a form of rare X-linked neurological diseases and most of the patients are females. They are characterized by several symptoms, including microcephaly with pontine and cerebellar hypoplasia (MICPCH), epilepsy, congenital nystagmus, and neurodevelopmental disorders. Whole-genome sequencing has identified various mutations, including nonsense and missense mutations, from patients with CASK-related disorders, revealing correlations between specific mutations and clinical phenotypes. Notably, missense mutations associated with epilepsy and intellectual disability were found throughout the whole region of the CASK protein, while missense mutations related to microcephaly and MICPCH were restricted in certain domains. To investigate the pathophysiology of CASK-related disorders, research groups have employed diverse methods, including the generation of CASK knockout mice and the supplementation of CASK to rescue the phenotypes. These approaches have yielded valuable insights into the identification of functional domains of the CASK protein associated with a specific phenotype. Additionally, recent advancements in the AI-based prediction of protein structure, such as AlphaFold2, and the application of genome-editing techniques to generate CASK mutant mice carrying missense mutations from patients with CASK-related disorders, allow us to understand the pathophysiology of CASK-related disorders in more depth and to develop novel therapeutic methods for the fundamental treatment of CASK-related disorders.

Genotype-phenotype correlations of STXBP1 pathogenic variants and the treatment choices for STXBP1-related disorders in China

BACKGROUND

We aimed to analyze the genotype-phenotype correlations of STXBP1 pathogenic variants, prognostic factors and the treatment choices in a case-series of STXBP1-related disorders from China.

METHODS

The clinical data and genetic results of the children diagnosed with STXBP1-related disorders at Xiangya hospital from 2011 to 2019 were collected retrospectively, and analyzed. We divided our patients into groups for comparison purposes: patients with missense variants and nonsense variants, patients who are seizure-free and not seizure-free, patients with mild to moderate intellectual disability (ID) and severe to profound global developmental delay (GDD).

RESULTS

Nineteen patients were enrolled: 17 (89.5%) unrelated and 2 (10.5%) familial. Twelve (63.2%) were females. Developmental epileptic encephalopathy (DEE) was observed in 18 (94.7%) patients and ID alone in 1 (5.3%) individual. Thirteen patients (68.4%) had profound ID/GDD, 4 (23.53%) severe, 1 (5.9%) moderate and 1 (5.9%) mild. Three patients (15.8%) with profound ID died. A total of 19 variants were detected: pathogenic (n = 15) and likely pathogenic (n = 4). Seven were novel variants: c.664-1G>-, M486R, H245N, H498Pfs*44, L41R, L410del, and D90H. Of the 8 previous reported variants, 2 were recurrent: R406C and R292C. Anti-seizure medications were used in combinations, and 7 patients became seizure-free, and most of them achieved seizure freedom within the first 2 years of life irrespective of the type of the mutation. Effective medications for the seizure-free individuals included adrenocorticotropic (ACTH) and/or levetiracetam and/or phenobarbital and/or sodium valproate and/or topiramate and/or vigabatrin and/or nitrazepam. There was no correlation between the types of pathogenic variants and the phenotypes.

CONCLUSION

Our case-series showed that there is no genotype-phenotype correlation in patients with STXBP1-related disorders. This study adds 7 novel variants which expand the spectrum of STXBP1-related disorders. Combinations of levetiracetam and/or sodium valproate and/or ACTH and/or phenobarbital and/or vigabatrin and/or topiramate and/or nitrazepam were more often associated with seizure freedom in our cohort within 2 years of life.

Cortical Parvalbumin-Positive Interneuron Development and Function Are Altered in the APC Conditional Knockout Mouse Model of Infantile and Epileptic Spasms Syndrome

Infantile and epileptic spasms syndrome (IESS) is a childhood epilepsy syndrome characterized by infantile or late-onset spasms, abnormal neonatal EEG, and epilepsy. Few treatments exist for IESS, clinical outcomes are poor, and the molecular and circuit-level etiologies of IESS are not well understood. Multiple human IESS risk genes are linked to Wnt/β-catenin signaling, a pathway that controls developmental transcriptional programs and promotes glutamatergic excitation via β-catenin's role as a synaptic scaffold. We previously showed that deleting adenomatous polyposis coli (APC), a component of the β-catenin destruction complex, in excitatory neurons (APC cKO mice, APCfl/fl x CaMKIIαCre) increased β-catenin levels in developing glutamatergic neurons and led to infantile behavioral spasms, abnormal neonatal EEG, and adult epilepsy. Here, we tested the hypothesis that the development of GABAergic interneurons (INs) is disrupted in APC cKO male and female mice. IN dysfunction is implicated in human IESS, is a feature of other rodent models of IESS, and may contribute to the manifestation of spasms and seizures. We found that parvalbumin-positive INs (PV+ INs), an important source of cortical inhibition, were decreased in number, underwent disproportionate developmental apoptosis, and had altered dendrite morphology at P9, the peak of behavioral spasms. PV+ INs received excessive excitatory input, and their intrinsic ability to fire action potentials was reduced at all time points examined (P9, P14, P60). Subsequently, GABAergic transmission onto pyramidal neurons was uniquely altered in the somatosensory cortex of APC cKO mice at all ages, with both decreased IPSC input at P14 and enhanced IPSC input at P9 and P60. These results indicate that inhibitory circuit dysfunction occurs in APC cKOs and, along with known changes in excitation, may contribute to IESS-related phenotypes.SIGNIFICANCE STATEMENT Infantile and epileptic spasms syndrome (IESS) is a devastating epilepsy with limited treatment options and poor clinical outcomes. The molecular, cellular, and circuit disruptions that cause infantile spasms and seizures are largely unknown, but inhibitory GABAergic interneuron dysfunction has been implicated in rodent models of IESS and may contribute to human IESS. Here, we use a rodent model of IESS, the APC cKO mouse, in which β-catenin signaling is increased in excitatory neurons. This results in altered parvalbumin-positive GABAergic interneuron development and GABAergic synaptic dysfunction throughout life, showing that pathology arising in excitatory neurons can initiate long-term interneuron dysfunction. Our findings further implicate GABAergic dysfunction in IESS, even when pathology is initiated in other neuronal types.

Biochemical mechanisms in pathogenesis of infantile epileptic spasm syndrome

The molecular mechanisms leading to infantile epileptic spasm syndrome (IESS) remain obscure. The only common factor seems to be that the spasms are restricted to a limited period of infancy, during a certain maturational state. Here the current literature regarding the biochemical mechanisms of brain maturation in IESS is reviewed, and various hypotheses of the pathophysiology are put together. They include: (1) imbalance of inhibitory (NGF, IGF-1, ACTH, GABA) and excitatory factors (glutamate, nitrites) which distinguishes the different etiological subgroups, (2) abnormality of the hypothalamic pituitary adrenal (HPA) axis linking insults and early life stress, (3) inflammation (4) yet poorly known genetic and epigenetic factors, and (5) glucocorticoid and vigabatrin action on brain development, pinpointing at molecular targets of the pathophysiology from another angle. An altered maturational process may explain why so many, seemingly independent etiological factors lead to the same clinical syndrome and frequently to developmental delay. Understanding these factors can provide ideas for novel therapies.

Exome sequencing as first-tier genetic testing in infantile-onset pharmacoresistant epilepsy: diagnostic yield and treatment impact

Pharmacoresistant epilepsy presenting during infancy poses both diagnostic and therapeutic challenges. We aim to identify diagnostic yield and treatment implications of exome sequencing (ES) as first-tier genetic testing for infantile-onset pharmacoresistant epilepsy. From June 2016 to December 2020, we enrolled patients with infantile-onset (age ≤ 12 months) pharmacoresistant epilepsy. 103 unrelated patients underwent ES. Clinical characteristics and changes in management due to the molecular diagnosis were studied. 42% (43/103) had epilepsy onset within the first month of life. After ES as first-tier genetic testing, 62% (64/103) of the cases were solved. Two partially solved cases (2%; 2/103) with heterozygous variants identified in ALDH7A1 known to cause autosomal recessive pyridoxine dependent epilepsy underwent genome sequencing (GS). Two novel large deletions in ALDH7A1 were detected in both cases. ES identified 66 pathogenic and likely pathogenic single nucleotide variants (SNVs) in 27 genes. 19 variants have not been previously reported. GS identified two additional copy number variations (CNVs). The most common disease-causing genes are SCN1A (13%; 13/103) and KCNQ2 (8%; 8/103). Eight percent (8/103) of the patients had treatable disorders and specific treatments were provided resulting in seizure freedom. Pyridoxine dependent epilepsy was the most common treatable epilepsy (6%; 6/103). Furthermore, 35% (36/103) had genetic defects which guided gene-specific treatments. Altogether, the diagnostic yield is 64%. Molecular diagnoses change management in 43% of the cases. This study substantiates the use of next generation sequencing (NGS) as the first-tier genetic investigation in infantile-onset pharmacoresistant epilepsy.

Epileptic spasms related to neuronal differentiation factor 2 (NEUROD2) mutation respond to combined vigabatrin and high dose prednisolone therapy

BACKGROUND

Epileptic spasms are a devastating form of early infantile epileptic encephalopathy (EIEE) with various etiologies. Early diagnosis and a shorter lead time to treatment are crucial to stop the seizures and optimize the neurodevelopmental outcome. Genetic testing has become an integral part of epilepsy care that directly guides management and family planning and discovers new targeted treatments. Neuronal differentiation Factor 2 (NEUROD2) variants have recently been a cause of neurodevelopmental disorders (NDDs) and EIEEs with distinctive features. However, there is limited information about the clinical and electroencephalographic response of epileptic spasm treatment in NEUROD2-related NDD syndrome.

CASE PRESENTATION

We report a female patient of Southeast Asian ethnicity with global developmental delay and epileptic spasms commencing in the first few months of life. A novel de novo heterozygous pathogenic NEUROD2 variant, p. E130Q, was subsequently identified by whole-exome sequencing. Electroencephalogram before treatment showed multifocal independent spikes predominantly in both posterior head regions and demonstrated marked improvement following combined vigabatrin and high-dose prednisolone treatment. However, multiple courses of relapse occurred after weaning off the antiseizure medication.

CONCLUSIONS

We propose that epileptic spasms related to de novo NEUROD2 pathogenic variant respond well to combined vigabatrin and high-dose prednisolone therapy. These findings may imply the benefit of using combination therapy to treat epileptic spasms in NEUROD2-related NDD syndrome.

Rates of rare copy number variants in different circumstances among patients with genetic developmental and epileptic encephalopathy

BACKGROUND

Most patients with developmental and epileptic encephalopathy (DEE) have genetic etiology, which has been uncovered with different methods. Although chromosomal microarray analysis (CMA) has been broadly used in patients with DEE, data is still limited.

METHODS

Among 560 children (<18 years) who underwent CMA in our hospital between January 2013 and June 2021, 146 patients with developmental delay and recurrent seizures were screened. Patients with major brain abnormalities, metabolic abnormalities, and specific syndromes were excluded. The rate of rare copy number variants (CNVs) was estimated in total and according to seizure-onset age, relation to first seizure with the diagnosis of developmental delay, epilepsy syndromes, and organ anomalies.

RESULTS

Among the 110 patients enrolled, the rate of rare CNVs was 16.4%, varying by seizure-onset age: 33.3% in three neonates, 21.2% in 33 infants, 13.3% in 45 early childhood patients, 5.3% in 19 late childhood patients, and 30.0% in 10 adolescents. In relation to the first seizure with the diagnosis of developmental delay, the rates were 3.7%, 22.2%, and 12.5% in "before", "after", and "concurrent" subclasses, respectively. The rates of rare CNVs were 16.7% in "other predominantly focal or multifocal epilepsy", 28.6% in "other predominantly generalized epilepsy (PGE)", and 15.4% in West syndrome. The rates were 27.8% in minor brain anomalies, 37.5% in facial dysmorphism, and 22.2%, 20.0%, and 57.1% in endocrine, genitourinary and cardiovascular anomalies, respectively.

CONCLUSION

The rate of rare CNVs in patients with genetic DEE was 16.4% in total, which was higher in seizures occurring below the infantile period or after the diagnosis of developmental delay, in PGE, and in the presence of facial dysmorphism or cardiovascular anomalies.

Decreased cerebrospinal fluid kynurenic acid in epileptic spasms: A biomarker of response to corticosteroids

Background

Epileptic (previously infantile) spasms is the most common epileptic encephalopathy occurring during infancy and is frequently associated with abnormal neurodevelopmental outcomes. Epileptic spasms have a diverse range of known (genetic, structural) and unknown aetiologies. High dose corticosteroid treatment for 4 weeks often induces remission of spasms, although the mechanism of action of corticosteroid is unclear. Animal models of epileptic spasms have shown decreased brain kynurenic acid, which is increased after treatment with the ketogenic diet. We quantified kynurenine pathway metabolites in the cerebrospinal fluid (CSF) of infants with epileptic spasms and explored clinical correlations.

Methods

A panel of nine metabolites in the kynurenine pathway (tryptophan, kynurenine, kynurenic acid, 3-hydroxykynurenine, xanthurenic acid, anthranilic acid, 3-hydroxyanthranilic acid, quinolinic acid, and picolinic acid) were measured using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). CSF collected from paediatric patients less than 3 years of age with epileptic spasms (n=34, 19 males, mean age 0.85, median 0.6, range 0.3–3 yrs) were compared with other epilepsy syndromes (n=26, 9 males, mean age 1.44, median 1.45, range 0.3–3 yrs), other non-inflammatory neurological diseases (OND) (n=29, 18 males, mean age 1.47, median 1.6, range 0.1–2.9 yrs) and inflammatory neurological controls (n=12, 4 males, mean age 1.80, median 1.80, range 0.8–2.5 yrs).

Findings

There was a statistically significant decrease of CSF kynurenic acid in patients with epileptic spasms compared to OND (p<0.0001). In addition, the kynurenic acid/kynurenine (KYNA/KYN) ratio was lower in the epileptic spasms subgroup compared to OND (p<0.0001). Epileptic spasms patients who were steroid responders or partial steroid responders had lower KYNA/KYN ratio compared to patients who were refractory to steroids (p<0.005, p<0.05 respectively).

Interpretation

This study demonstrates decreased CSF kynurenic acid and KYNA/KYN in epileptic spasms, which may also represent a biomarker for steroid responsiveness. Given the anti-inflammatory and neuroprotective properties of kynurenic acid, further therapeutics able to increase kynurenic acid should be explored.

Funding

Financial support for the study was granted by Dale NHMRC Investigator grant APP1193648, Petre Foundation, Cerebral Palsy Alliance and Department of Biochemistry at the Children's Hospital at Westmead. Prof Guillemin is funded by NHMRC Investigator grant APP1176660 and Macquarie University.

Mutation in the STXBP1 Gene Associated with Early Onset West Syndrome: A Case Report and Literature Review

Syntaxin-binding protein1 (STXBP1) is a member of the Sec1/Munc18-1 protein family, which comprises important regulators of the secretory and synaptic vesicle fusion machinery underlying hormonal and neuronal transmission, respectively. STXBP1 pathogenic variants are associated with multiple neurological disorders. Herein, we present the case of a Japanese girl with a mutation in the STXBP1 gene, who was born at 40 weeks without neonatal asphyxia. At 15 days old, she developed epilepsy and generalized seizures. Around 88 days old, she presented with a series of nodding spasms, with the seizure frequency gradually increasing. Interictal EEG indicated hypsarrhythmia and she presented with developmental regression. At 1.5 years old, genetic testing was performed and mutational analysis revealed an STXBP1 gene mutation (c.875G > A: p.Arg292His). Accordingly, she was diagnosed with developmental and epileptic encephalopathy, presenting West syndrome’s clinical characteristics caused by the STXBP1 gene mutation. Although drug treatment has reduced the frequency of epileptic seizures, her development has remained regressive. The relationship between the location and type of genetic abnormality and the phenotype remains unclear. Future studies should investigate the genotype−phenotype correlation and the underlying pathophysiology to elucidate the causal relationships among the multiple phenotype-determining factors.

Whole genomic approach in mutation discovery of infantile spasms patients

Infantile spasms (IS) are a clinically and genetically heterogeneous group of epilepsy disorders in early infancy. The genetic backgrounds of IS have been gradually unraveled along with the increased application of next-generation sequencing (NGS). However, to date, only selected genomic regions have been sequenced using a targeted approach in most cases of IS, and the genetic etiologies of the majority of patients remain unknown. We conducted a proof-of-concept study using whole-genome sequencing (WGS) for the genetic diagnosis of IS. We included 16 patients with IS for this study, and WGS was applied as a first-tier test for genetic diagnosis. In total, we sequenced the whole genomes of 28 participants, including the genomes of six patients, which were sequenced with those of their parents. Among variants identified, we focused on those located in epilepsy or seizure-associated genes. We used two different methods to call relevant large deletions from WGS results. We found pathogenic or likely pathogenic variants in four patients (25.0%); a de novo variant in HDAC4, compound heterozygous variants in GRM7, and heterozygous variants in CACNA1E and KMT2E. We also selected two more candidate variants in SOX5 and SHROOM4 intronic regions. Although there are currently several difficulties in applying WGS for genetic diagnosis, especially in clinical interpretation of non-coding variants, we believe that developing sequencing technologies would overcome these hurdles in the near future. Considering the vast genetic heterogeneity and the substantial portion of patients with unknown etiologies, further studies using whole genomic approaches are necessary for patients with IS.

Case Report: Identification of Two Variants of ALG13 in Families With or Without Seizure and Binocular Strabismus: Phenotypic Spectrum Analysis

Background: Genetic causes in most affected children with intellectual disability and/or development delay remain unknown. Methods: To identify potential variants responsible for these disorders, we recruited 161 affected families and performed whole-exome sequencing and associated bioinformatics analysis. Results: In the present study, we report the identification of variants in the ALG13 gene in two of the families. In family 1, a known pathogenic missense variant (c.23T > C; p.V8A) of ALG13 was identified in a boy and his mother. In family 2, a novel missense variant (c.862C > G; p.L288V) of the same gene was identified in the affected boy and his phenotypically normal mother. Genotype-phenotype correlation analysis by comparing reported 28 different variants (HGMD) showed that three major phenotypes, including various seizures/epilepsy, intellectual disability, and development delay (such as growth, speech, motor, etc.), are present in most affected individuals. However, other phenotypes, such as strabismus and absence of seizure in our second patient, are not reported if any, which may represent a unique case of X-linked recessive nonsyndromic disorder caused by a mutation in ALG13. Conclusion: We identified two missense variants in ALG13 in a cohort of 161 families with affected individuals diagnosed as intellectual disability and/or development delay. A novel c.862C > G mutation may represent a case of X-linked recessive.

Delineating the epilepsy phenotype of NRROS-related microgliopathy: A case report and literature review

BACKGROUND

Negative regulator of reactive oxygen species (NRROS) related microgliopathy, a rare and recently recognized neurodegenerative condition, is caused by pathogenic variants in the NRROS gene, which plays a major role in the regulation of transforming growth factor-beta 1.

METHODS

We report a child presenting with infantile spasms syndrome (ISS) with subsequent progressive neurodegeneration who was identified to harbour a novel likely pathogenic NRROS variant (c.1359del; p.Ser454Alafs*11). The previously published reports of patients with this disorder were also reviewed systematically.

RESULTS

Including our index patient, 11 children (6 girls) were identified in total. Early development was normal in seven of these eleven children. All had a history of drug-resistant epilepsy, with 3 having epileptic spasms. The median age at seizure onset and developmental regression was 12 months, and the median age at death was 36 months. Intracranial calcifications were described in eight of eleven children. Neuroimaging revealed progressive cerebral atrophy and white matter loss in all children. The most common reported genetic variation was c.1981delC; (p.Leu661Serfs*97) observed in two families (likely due to a founder effect).

CONCLUSIONS

Pathogenic variants in NRROS should be suspected in children with neuro-regression and drug-resistant epilepsy including ISS with onset in the first two years of life. Punctate or serpiginous calcifications at the grey-white matter junction and acquired microcephaly are further clues towards the diagnosis.

A de novo variant in CASK gene causing intellectual disability and brain hypoplasia: a case report and literature review

Background

The pathogenic variation of CASK gene can cause CASK related mental disorders. The main clinical manifestations are microcephaly with pontine and cerebellar hypoplasia, X-linked mental disorders with or without nystagmus and FG syndrome. The main pathogenic mechanism is the loss of function of related protein caused by variant. We reported a Chinese male newborn with a de novo variant in CASK gene.

Case presentation

We present an 18-day-old baby with growth retardation and brain hypoplasia. Whole-exome sequencing was performed, which detected a hemizygous missense variant c.764G > A of CASK gene. The variant changed the 255th amino acid from Arg to His. Software based bioinformatics analyses were conducted to infer its functional effect.

Conclusions

In this paper, a de novo variant of CASK gene was reported. Moreover, a detailed description of all the cases described in the literature is reported. CASK variants cause a variety of clinical phenotypes. Its diagnosis is difficult due to the lack of typical clinical symptoms. Genetic testing should be performed as early as possible if this disease is suspected. This case provides an important reference for the diagnosis and treatment of future cases.

Whole-exome sequencing and adrenocorticotropic hormone therapy in individuals with infantile spasms

AIM

To identify additional genes associated with infantile spasms using a cohort with defined infantile spasms.

METHOD

Whole-exome sequencing (WES) was performed on 21 consented individuals with infantile spasms and their unaffected parents (a trio-based study). Clinical history and imaging were reviewed. Potentially deleterious exonic variants were identified and segregated. To refine potential candidates, variants were further prioritized on the basis of evidence for relevance to disease phenotype or known associations with infantile spasms, epilepsy, or neurological disease.

RESULTS

Likely pathogenic de novo variants were identified in NR2F1, GNB1, NEUROD2, GABRA2, and NDUFAF5. Suggestive dominant and recessive candidate variants were identified in PEMT, DYNC1I1, ASXL1, RALGAPB, and STRADA; further confirmation is required to support their relevance to disease etiology.

INTERPRETATION

This study supports the utility of WES in uncovering the genetic etiology in undiagnosed individuals with infantile spasms with an overall yield of five out of 21. High-priority candidates were identified in an additional five individuals. WES provides additional support for previously described disease-associated genes and expands their already broad mutational and phenotypic spectrum.

Genetic and Phenotype Analysis of a Chinese Cohort of Infants and Children With Epilepsy

Background: Epilepsy in childhood is a common and diverse neurological disorder. We conducted a genetic and phenotype analysis of a Chinese cohort of infants and children with epilepsy.

Methods: We conducted a pedigree analysis of 260 Chinese patients with epilepsy onset during infancy or childhood by whole exome sequencing (WES).

Results: Of the 260 probands analyzed, a genetic diagnosis was established in 135 patients. One-hundred eighty-eight phenotypes were detected in those 135 positive/likely positive patients, 106 patients had more than two phenotypes, and 67 patients had more than three phenotypes. A total of 142 variants of 81 genes were detected among the positive/likely positive patients. Among these 142 variants, of which 87 of 66 genes were novel.

Conclusion: Our findings extend the variant spectrum of genes related to epilepsy. Our results will be useful for genetic testing and counseling for patients with epilepsy.

Pathophysiological Heterogeneity of the BBSOA Neurodevelopmental Syndrome

The formation and maturation of the human brain is regulated by highly coordinated developmental events, such as neural cell proliferation, migration and differentiation. Any impairment of these interconnected multi-factorial processes can affect brain structure and function and lead to distinctive neurodevelopmental disorders. Here, we review the pathophysiology of the Bosch–Boonstra–Schaaf Optic Atrophy Syndrome (BBSOAS; OMIM 615722; ORPHA 401777), a recently described monogenic neurodevelopmental syndrome caused by the haploinsufficiency of NR2F1 gene, a key transcriptional regulator of brain development. Although intellectual disability, developmental delay and visual impairment are arguably the most common symptoms affecting BBSOAS patients, multiple additional features are often reported, including epilepsy, autistic traits and hypotonia. The presence of specific symptoms and their variable level of severity might depend on still poorly characterized genotype–phenotype correlations. We begin with an overview of the several mutations of NR2F1 identified to date, then further focuses on the main pathological features of BBSOAS patients, providing evidence—whenever possible—for the existing genotype–phenotype correlations. On the clinical side, we lay out an up-to-date list of clinical examinations and therapeutic interventions recommended for children with BBSOAS. On the experimental side, we describe state-of-the-art in vivo and in vitro studies aiming at deciphering the role of mouse Nr2f1, in physiological conditions and in pathological contexts, underlying the BBSOAS features. Furthermore, by modeling distinct NR2F1 genetic alterations in terms of dimer formation and nuclear receptor binding efficiencies, we attempt to estimate the total amounts of functional NR2F1 acting in developing brain cells in normal and pathological conditions. Finally, using the NR2F1 gene and BBSOAS as a paradigm of monogenic rare neurodevelopmental disorder, we aim to set the path for future explorations of causative links between impaired brain development and the appearance of symptoms in human neurological syndromes.

Drosophila carrying epilepsy-associated variants in the vitamin B6 metabolism gene PNPO display allele- and diet-dependent phenotypes

Both genetic and environmental factors contribute to epilepsy. Understanding their contributions and interactions helps disease management. However, it is often challenging to study gene–environment interaction in humans due to their heterogeneous genetic background and less controllable environmental factors. The fruit fly, Drosophila melanogaster, has been proven to be a powerful model to study human diseases, including epilepsy. We generated knock-in flies carrying different epilepsy-associated pyridox(am)ine 5^′-phosphate oxidase (PNPO) alleles and studied the developmental, behavioral, electrophysiological, and fitness effects of each mutant allele under different dietary conditions. We showed that phenotypes in knock-in flies are allele and diet dependent, providing clues for timely and specific diet interventions. Our results offer biological insights into mechanisms underlying phenotypic variations and specific therapeutic strategies.

Pyridox(am)ine 5^′-phosphate oxidase (PNPO) catalyzes the rate-limiting step in the synthesis of pyridoxal 5^′-phosphate (PLP), the active form of vitamin B6 required for the synthesis of neurotransmitters gamma-aminobutyric acid (GABA) and the monoamines. Pathogenic variants in PNPO have been increasingly identified in patients with neonatal epileptic encephalopathy and early-onset epilepsy. These patients often exhibit different types of seizures and variable comorbidities. Recently, the PNPO gene has also been implicated in epilepsy in adults. It is unclear how these phenotypic variations are linked to specific PNPO alleles and to what degree diet can modify their expression. Using CRISPR-Cas9, we generated four knock-in Drosophila alleles, h^WT, h^R116Q, h^D33V , and h^R95H, in which the endogenous Drosophila PNPO was replaced by wild-type human PNPO complementary DNA (cDNA) and three epilepsy-associated variants. We found that these knock-in flies exhibited a wide range of phenotypes, including developmental impairments, abnormal locomotor activities, spontaneous seizures, and shortened life span. These phenotypes are allele dependent, varying with the known biochemical severity of these mutations and our characterized molecular defects. We also showed that diet treatments further diversified the phenotypes among alleles, and PLP supplementation at larval and adult stages prevented developmental impairments and seizures in adult flies, respectively. Furthermore, we found that h^R95H had a significant dominant-negative effect, rendering heterozygous flies susceptible to seizures and premature death. Together, these results provide biological bases for the various phenotypes resulting from multifunction of PNPO, specific molecular and/or genetic properties of each PNPO variant, and differential allele–diet interactions.

Etiologic Classification of 541 Infantile Spasms Cases: A Cohort Study

OBJECTIVE

To explore the etiology of infantile spasms (IS) in a large Chinese cohort based on the United States National Infantile Spasms Consortium (NISC) classification.

METHODS

In the present study, we recruited IS patients diagnosed at a single center (Xiangya Hospital, Central South University) between Jan 2010 and Aug 2019. Thereafter, we collected their clinical and genetic information retrospectively. Their underlying etiologies were classified according to the NISC classification and then compared in different scenarios to understand their distribution.

RESULTS

A total of 541 patients with IS from 18 provinces were included in this study. The underlying etiology was identified in 53.2% of the cases: structural-acquired, 25.3%; genetic, 12.9%; genetic-structural, 7.2%; structural-congenital, 5.0%; metabolic, 2.4%; infections, 0.4% and immune, 0%. Whole-exome sequencing (WES) provided the highest diagnostic yield (26.9%). In structural-acquired IS, the proportion of hypoglycemic brain injuries was significant, second only to hypoxic-ischemic encephalopathy. There was no patient discovered to have Down syndrome. STXBP1, CDKL5, TSC2, KCNQ2, IRF2BPL, and TSC1 were the most frequently implicated genes. Genetic causes were found to be the most common cause of IS in the early onset group, while structural-acquired etiologies were common in males and preterm babies. Patients with pre-spasm seizures were associated with a higher proportion of identified causes than those without. Non-acquired structural etiologies were more common in patients without hypsarrhythmia than in those with hypsarrhythmia.

SIGNIFICANCE

The most prevalent cause of IS was structural acquired followed by genetic causes. When brain MRI fails to detect the etiology, we propose WES as the next step. Structural-acquired IS and cases with genetic disorders are characteristic of the Chinese cohort, however, the etiology differs with the patient's age of onset, gestation age at birth, sex, and the presence/absence of both pre-spasm seizures, and hypsarrhythmia.

Genetic testing for the epilepsies: A systematic review

OBJECTIVE

Numerous genetic testing options for individuals with epilepsy have emerged over the past decade without clear guidelines regarding optimal testing strategies. We performed a systematic evidence review (SER) and conducted meta-analyses of the diagnostic yield of genetic tests commonly utilized for patients with epilepsy. We also assessed nonyield outcomes (NYOs) such as changes in treatment and/or management, prognostic information, recurrence risk determination, and genetic counseling.

METHODS

We performed an SER, in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses), using PubMed, Embase, CINAHL, and Cochrane Central through December of 2020. We included studies that utilized genome sequencing (GS), exome sequencing (ES), multigene panel (MGP), and/or genome-wide comparative genomic hybridization/chromosomal microarray (CGH/CMA) in cohorts (n ≥ 10) ascertained for epilepsy. Quality assessment was undertaken using ROBINS-I (Risk of Bias in Non-Randomized Studies of Interventions). We estimated diagnostic yields and 95% confidence intervals with random effects meta-analyses and narratively synthesized NYOs.

RESULTS

From 5985 nonduplicated articles published through 2020, 154 met inclusion criteria and were included in meta-analyses of diagnostic yield; 43 of those were included in the NYO synthesis. The overall diagnostic yield across all test modalities was 17%, with the highest yield for GS (48%), followed by ES (24%), MGP (19%), and CGH/CMA (9%). The only phenotypic factors that were significantly associated with increased yield were (1) the presence of developmental and epileptic encephalopathy and/or (2) the presence of neurodevelopmental comorbidities. Studies reporting NYOs addressed clinical and personal utility of testing.

SIGNIFICANCE

This comprehensive SER, focused specifically on the literature regarding patients with epilepsy, provides a comparative assessment of the yield of clinically available tests, which will help shape clinician decision-making and policy regarding insurance coverage for genetic testing. We highlight the need for prospective assessment of the clinical and personal utility of genetic testing for patients with epilepsy and for standardization in reporting patient characteristics.

A genome-wide association study for shoulder impingement and rotator cuff disease

BACKGROUND

The purpose of the study was to identify genetic variants associated with rotator cuff disease by performing a genome-wide association study (GWAS) for shoulder impingement using the UK Biobank (UKB) cohort and then combining the GWAS data with a prior GWAS for rotator cuff tears. The loci identified by the GWAS and meta-analysis were examined for changes in expression following rotator cuff tearing using RNA sequencing.

METHODS

A GWAS was performed using data from UKB with 3864 cases of shoulder impingement. The summary statistics from shoulder impingement and a prior study on rotator cuff tears were combined in a meta-analysis. Also, the previous association of 2 single-nucleotide polymorphisms (SNPs) with shoulder impingement from a published GWAS using the UKB was tested. Rotator cuff tendon biopsies were obtained from 24 patients with full-thickness rotator cuff tears who underwent arthroscopic rotator cuff repair (cases) and 9 patients who underwent open reduction internal fixation for a proximal humeral fracture (controls). Total RNA was extracted and differential gene expression was measured by RNA sequencing for genes with variants associated with rotator cuff tearing.

RESULTS

The shoulder impingement GWAS identified 4 new loci: LOC100506457, LSP1P3, LOC100506207, and MIS18BP1/LINC00871. Combining data with a prior GWAS for rotator cuff tears in a meta-analysis resulted in the identification of an additional 7 loci: SLC39A8/UBE2D3, C5orf63, ASTN2, STK24, FRMPD4, ACOT9/SAT1, and LINC00890/ALG13. Many of the identified loci have known biologic functions or prior associations with diseases, suggesting possible biologic pathways leading to rotator cuff disease. RNA sequencing experiments show that expression of STK24 increases whereas expression of SAT1 and UBE2D3 decreases following rotator cuff tearing. Two SNPs previously reported to show an association with shoulder impingement from a prior UKB GWAS were not validated in our study.

CONCLUSION

This is the first GWAS for shoulder impingement in which new data from UKB enabled the identification of 4 loci showing a genetic association. A meta-analysis with a prior GWAS for rotator cuff tearing identified an additional 7 loci. The known biologic roles of many of the 11 loci suggest plausible biologic mechanisms underlying the etiology of rotator cuff disease. The risk alleles from each of the genetic loci can be used to assess the risk for rotator cuff disease in individual patients, enabling preventative or restorative actions via personalized medicine.

Molecular tools for the characterization of seizure susceptibility in genetic rodent models of epilepsy

Epilepsy is a chronic neurological disorder characterized by abnormal neuronal activity that arises from imbalances between excitatory and inhibitory synapses, which are highly correlated to functional and structural changes in specific brain regions. The difference between the normal and the epileptic brain may harbor genetic alterations, gene expression changes, and/or protein alterations in the epileptogenic nucleus. It is becoming increasingly clear that such differences contribute to the development of distinct epilepsy phenotypes. The current major challenges in epilepsy research include understanding the disease progression and clarifying epilepsy classifications by searching for novel molecular biomarkers. Thus, the application of molecular techniques to carry out comprehensive studies at deoxyribonucleic acid, messenger ribonucleic acid, and protein levels is of utmost importance to elucidate molecular dysregulations in the epileptic brain. The present review focused on the great diversity of technical approaches available and new research methodology, which are already being used to study molecular alterations underlying epilepsy. We have grouped the different techniques according to each step in the flow of information from DNA to RNA to proteins, and illustrated with specific examples in animal models of epilepsy, some of which are our own. Separately and collectively, the genomic and proteomic techniques, each with its own strengths and limitations, provide valuable information on molecular mechanisms underlying seizure susceptibility and regulation of neuronal excitability. Determining the molecular differences between genetic rodent models of epilepsy and their wild-type counterparts might be a key in determining mechanisms of seizure susceptibility and epileptogenesis as well as the discovery and development of novel antiepileptic agents. This article is part of the Special Issue "NEWroscience 2018".

Epilepsy Syndromes in the First Year of Life and Usefulness of Genetic Testing for Precision Therapy

The high pace of gene discovery has resulted in thrilling advances in the field of epilepsy genetics. Clinical testing with comprehensive gene panels, exomes, or genomes are now increasingly available and have led to a significant higher diagnostic yield in early-onset epilepsies and enabled precision medicine approaches. These have been instrumental in providing insights into the pathophysiology of both early-onset benign and self-limited syndromes and devastating developmental and epileptic encephalopathies (DEEs). Genetic heterogeneity is seen in many epilepsy syndromes such as West syndrome and epilepsy of infancy with migrating focal seizures (EIMFS), indicating that two or more genetic loci produce the same or similar phenotypes. At the same time, some genes such as SCN2A can be associated with a wide range of epilepsy syndromes ranging from self-limited familial neonatal epilepsy at the mild end to Ohtahara syndrome, EIFMS, West syndrome, Lennox–Gastaut syndrome, or unclassifiable DEEs at the severe end of the spectrum. The aim of this study was to review the clinical and genetic heterogeneity associated with epilepsy syndromes starting in the first year of life including: Self-limited familial neonatal, neonatal-infantile or infantile epilepsies, genetic epilepsy with febrile seizures plus spectrum, myoclonic epilepsy in infancy, Ohtahara syndrome, early myoclonic encephalopathy, West syndrome, Dravet syndrome, EIMFS, and unclassifiable DEEs. We also elaborate on the advantages and pitfalls of genetic testing in such conditions. Finally, we describe how a genetic diagnosis can potentially enable precision therapy in monogenic epilepsies and emphasize that early genetic testing is a cornerstone for such therapeutic strategies.

ALG13 X-linked intellectual disability: New variants, glycosylation analysis, and expanded phenotypes

Pathogenic variants in ALG13 (ALG13 UDP-N-acetylglucosaminyltransferase subunit) cause an X-linked congenital disorder of glycosylation (ALG13-CDG) where individuals have variable clinical phenotypes that include developmental delay, intellectual disability, infantile spasms, and epileptic encephalopathy. Girls with a recurrent de novo c.3013C>T; p.(Asn107Ser) variant have normal transferrin glycosylation. Using a highly sensitive, semi-quantitative flow injection-electrospray ionization-quadrupole time-of-flight mass spectrometry (ESI-QTOF/MS) N-glycan assay, we report subtle abnormalities in N-glycans that normally account for <0.3% of the total plasma glycans that may increase up to 0.5% in females with the p.(Asn107Ser) variant. Among our 11 unrelated ALG13-CDG individuals, one male had abnormal serum transferrin glycosylation. We describe seven previously unreported subjects including three novel variants in ALG13 and report a milder neurodevelopmental course. We also summarize the molecular, biochemical, and clinical data for the 53 previously reported ALG13-CDG individuals. We provide evidence that ALG13 pathogenic variants may mildly alter N-linked protein glycosylation in both female and male subjects, but the underlying mechanism remains unclear.

Confirming the contribution and genetic spectrum of de novo mutation in infantile spasms: Evidence from a Chinese cohort

Objective

We determined the yield, genetic spectrum, and actual origin of de novo mutations (DNMs) for infantile spasms (ISs) in a Chinese cohort. The efficacy of levetiracetam (LEV) for STXBP1‐related ISs was explored also.

Methods

Targeted sequencing of 153 epilepsy‐related candidate genes was applied to 289 Chinese patients with undiagnosed ISs. Trio‐based amplicon deep sequencing was used for all DNMs to distinguish somatic/mosaic mutations from germline ones.

Results

Total of 26 DNMs were identified from 289 recruited Chinese patients with undiagnosed ISs. Among them, 24 DNMs were interpreted as pathogenic mutations based on American College of Medical Genetics and Genomics guidelines, contributing to 8.3% (24/289) of diagnosis yield in the Chinese IS cohort. CDKL5 and STXBP1 are the top genes with recurrent DNMs, accounting for 3.1% (9/289) of yield. Further deep resequencing for the trio members showed that 22.7% (5/22) of DNMs are actually somatic in the proband or a parent. These somatic carriers presented milder seizure attacks than those with true germline DNMs. After treatment with LEV for half a year, three patients with DNM in STXBP1 showed improved clinical symptoms, including seizure‐free and normal electroencephalogram, except for a patient with a second DNM in DIAPH3.

Significance

Our study confirmed the contribution and genetic spectrum of DNMs in Chinese IS patients. Somatic mutation account for a quarter of DNMs in IS cases. Treatment with LEV improved the prognosis of STXBP1‐related ISs.

Syntaxin Binding Protein 1 Related Epilepsies

Syntaxin binding protein 1 (STXBP1), commonly known as MUNC18–1, is a member of SEC1 family membrane trafficking proteins; their function consists in controlling the soluble N-ethylmaleimide-sensitive factor attachment protein receptors complex assembly, making them essentials regulators of vesicle fusion. The precise function and molecular mechanism through which Munc18–1 contributes to neurotransmitter releasing is not entirely understood, but several evidences suggest its probable role in exocytosis. In 2008, heterozygous de novo mutations in neuronal protein Munc18–1 were first referred as a cause of Ohtahara syndrome development. Currently, a wide examination of the published data proved that 3.1% of patients with severe epilepsy carry a pathogenic de novo mutation including STXBP1 and approximately 10.2% of early onset epileptic encephalopathy is due to an aberrant STXBP1 form codified by the mutated gene. STXBP1 mutations can be associated to a wide clinical heterogeneity. All affected individuals show developmental delay and approximately the 95% of cases have seizures and early onset epileptic encephalopathy, characterized by infantile spasms as the main consistent feature. Burst suppression pattern and hypsarrhythmia are the most frequent EEG anomalies. Other neuronal disorders include Rett syndrome and behavioral and movement disorders. Mild dysmorphic features have been detected in a small number of cases. No genotype–phenotype correlation has been reported. Management of STXBP1 encephalopathy requires a multidisciplinary approach, including epilepsy control and neurological rehabilitation. About 25% of patients are refractory to standard therapy. A single or combined antiepileptic drugs may be required. Several studies described vigabatrin, valproic acid, levetiracetam, topiramate, clobazam, and oxcarbazepine as effective in seizure control. Lamotrigine, zonisamide, and phenobarbital are also commonly used. To date, it remains unclear which therapy is the most effective. Severe morbidity and high mortality are inevitable consequences in some of these patients.

Aristaless-Related Homeobox (ARX): Epilepsy Phenotypes beyond Lissencephaly and Brain Malformations

The Aristaless-related homeobox (ARX) transcription factor is involved in the development of GABAergic and cholinergic neurons in the forebrain. ARX mutations have been associated with a wide spectrum of neurodevelopmental disorders in humans and are responsible for both malformation (in particular lissencephaly) and nonmalformation complex phenotypes. The epilepsy phenotypes related to ARX mutations are West syndrome and X-linked infantile spasms, X-linked myoclonic epilepsy with spasticity and intellectual development and Ohtahara and early infantile epileptic encephalopathy syndrome, which are related in most of the cases to intellectual disability and are often drug resistant. In this article, we shortly reviewed current knowledge of the function of ARX with a particular attention on its consequences in the development of epilepsy during early childhood.

Seizures and Epilepsy in Autism Spectrum Disorder

Epilepsy and autism frequently co-occur. Epilepsy confers an increased risk of autism and autism confers an increased risk of epilepsy. Specific epilepsy syndromes, intellectual disability, and female gender present a particular risk of autism in individuals with epilepsy. Epilepsy and autism are likely to share common etiologies, which predispose individuals to either or both conditions. Genetic factors, metabolic disorders, mitochondrial disorders, and immune dysfunction all can be implicated.

CASK related disorder: Epilepsy and developmental outcome

OBJECTIVE

CASK pathogenic variants are associated with variable features, as intellectual disability, optic atrophy, brainstem/cerebellar hypoplasia, and epileptic encephalopathy. Few studies describe the electroclinical features of epilepsy in patients with CASK pathogenic variants and their relationship with developmental delay.

METHODS

this national multicentre cohort included genetically confirmed patients with different CASK pathogenic variants. Our findings were compared with cohorts reported in the literature.

RESULTS

we collected 34 patients (29 females) showing from moderate (4 patients) to severe (22) and profound (8) developmental delay; all showed pontine and cerebellar hypoplasia, all except three with microcephaly. Seventeen out of 34 patients (50%) suffered from epileptic seizures, including spasms (11 patients, 32.3%), generalized (5) or focal seizures (1). In 8/17 individuals (47.1%), epilepsy started at or beyond the age of 24 months. Seven (3 males) out of the 11 children with spasms showed EEG features and a course supporting the diagnosis of a developmental and epileptic encephalopathy (DEE). Drug resistance was frequent in our cohort (52.9% of patients with epilepsy). EEG abnormalities included poorly organized background activity with diffuse or multifocal epileptiform abnormalities and sleep-activation, with possible appearance over the follow-up period. Developmental delay degree was not statistically different among patients with or without seizures but feeding difficulties were more frequent in patients with epilepsy.

CONCLUSIONS

epilepsy is a frequent comorbidity with a high incidence of spasms and drug resistance. Overall developmental disability does not seem to be more severe in the group of patients with epilepsy nor to be linked to specific epilepsy/EEG characteristics. A childhood onset of epilepsy is frequent, with possible worsening over time, so that serial and systematic monitoring is mandatory.

Congenital Disorders of Glycosylation from a Neurological Perspective

Most plasma proteins, cell membrane proteins and other proteins are glycoproteins with sugar chains attached to the polypeptide-glycans. Glycosylation is the main element of the post-translational transformation of most human proteins. Since glycosylation processes are necessary for many different biological processes, patients present a diverse spectrum of phenotypes and severity of symptoms. The most frequently observed neurological symptoms in congenital disorders of glycosylation (CDG) are: epilepsy, intellectual disability, myopathies, neuropathies and stroke-like episodes. Epilepsy is seen in many CDG subtypes and particularly present in the case of mutations in the following genes: ALG13, DOLK, DPAGT1, SLC35A2, ST3GAL3, PIGA, PIGW, ST3GAL5. On brain neuroimaging, atrophic changes of the cerebellum and cerebrum are frequently seen. Brain malformations particularly in the group of dystroglycanopathies are reported. Despite the growing number of CDG patients in the world and often neurological symptoms dominating in the clinical picture, the number of performed screening tests eg transferrin isoforms is systematically decreasing as broadened genetic testing is recently more favored. The aim of the review is the summary of selected neurological symptoms in CDG described in the literature in one paper. It is especially important for pediatric neurologists not experienced in the field of metabolic medicine. It may help to facilitate the diagnosis of this expanding group of disorders. Biochemically, this paper focuses on protein glycosylation abnormalities.

The phenotypic spectrum of X-linked, infantile onset ALG13-related developmental and epileptic encephalopathy

Objective

Asparagine‐linked glycosylation 13 (ALG13) deficiencies have been repeatedly described in the literature with the clinical phenotype of a developmental and epileptic encephalopathy (DEE). Most cases were females carrying the recurrent ALG13 de novo variant, p.(Asn107Ser), with normal transferrin electrophoresis.

Methods

We delineate the phenotypic spectrum of 38 individuals, 37 girls and one boy, 16 of them novel and 22 published, with the most common pathogenic ALG13 variant p.(Asn107Ser) and additionally report the phenotype of three individuals carrying other likely pathogenic ALG13 variants.

Results

The phenotypic spectrum often comprised pharmacoresistant epilepsy with epileptic spasms, mostly with onset within the first 6 months of life and with spasm persistence in one‐half of the cases. Tonic seizures were the most prevalent additional seizure type. Electroencephalography showed hypsarrhythmia and at a later stage of the disease in one‐third of all cases paroxysms of fast activity with electrodecrement. ALG13‐related DEE was usually associated with severe to profound developmental delay; ambulation was acquired by one‐third of the cases, whereas purposeful hand use was sparse or completely absent. Hand stereotypies and dyskinetic movements including dystonia or choreoathetosis were relatively frequent. Verbal communication skills were absent or poor, and eye contact and pursuit were often impaired.

Significance

X‐linked ALG13‐related DEE usually manifests as West syndrome with severe to profound developmental delay. It is predominantly caused by the recurrent de novo missense variant p.(Asn107Ser). Comprehensive functional studies will be able to prove or disprove an association with congenital disorder of glycosylation.

West Syndrome Is an Exceptional Presentation of Pyridoxine- and Pyridoxal Phosphate-Dependent Epilepsy: Data From a French Cohort and Review of the Literature

Objective: To characterize the electro-clinical presentation of patients with pyridoxine-dependent epilepsy (PDE) and pyridoxal phosphate (PLP)-dependent epilepsy in order to determine whether some of them could be diagnosed as de novo West syndrome, i. e., West syndrome that starts after the age of 2 months without other types of seizures (focal seizures for instance) before the onset of epileptic spasms. Methods: We analyzed data from an unpublished cohort of 28 genetically confirmed cases of PDE with antiquitine (ATQ) deficiency and performed a review of the literature looking for description of West syndrome in patients with either PDE with ATQ deficiency or PLP-dependent epilepsy with Pyridox(am)ine phosphate oxidase (PNPO) deficiency. Results: Of the 28 cases from the ATQ deficiency French cohort, 5 had spasms. In four cases, spasms were associated with other types of seizures (myoclonus, focal seizures). In the last case, seizures started on the day of birth. None of these cases corresponded to de novo West syndrome. The review of the literature found only one case of PNPO deficiency presenting as de novo West syndrome and no case of ATQ deficiency. Significance: The presentation of PDE- and PLP-dependent epilepsy as de novo West syndrome is so exceptional that it probably does not justify a systematic trial of pyridoxine or PLP. We propose considering a therapeutic trial with these vitamins in West syndrome if spasms are associated with other seizure types or start before the age of 2 months.

Clinical sequencing yield in epilepsy, autism spectrum disorder, and intellectual disability: A systematic review and meta-analysis

Objective

Clinical genetic sequencing is frequently utilized to diagnose individuals with neurodevelopmental disorders (NDDs). Here we perform a meta‐analysis and systematic review of the success rate (diagnostic yield) of clinical sequencing through next‐generation sequencing (NGS) across NDDs. We compare the genetic testing yield across NDD subtypes and sequencing technology.

Methods

We performed a systematic review of the PubMed literature until May 2020. We included clinical sequencing studies that utilized NGS in individuals with epilepsy, autism spectrum disorder (ASD), or intellectual disability (ID). Data were extracted, reviewed, and categorized according to the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines. Two investigators performed clinical evaluation and grouping following the International League Against Epilepsy (ILAE) guidelines. Pooled rates of the diagnostic yield and 95% confidence intervals were estimated with a random‐effects model.

Results

We identified 103 studies (epilepsy, N = 72; ASD, N = 14; ID, N = 21) across 32,331 individuals. Targeted gene panel sequencing was used in 73, and exome sequencing in 36 cohorts. Given highly selected patient cohorts, the diagnostic yield was 17.1% for ASD, 24% for epilepsy, and 28.2% for ID (23.7% overall). The highest diagnostic yield for epilepsy subtypes was observed in individuals with ID (27.9%) and early onset seizures (36.8%). The diagnostic yield for exome sequencing was higher than for panel sequencing, even though not statistically significant (27.2% vs 22.6%, P = .071). We observed that clinical sequencing studies are performed predominantly in countries with a high Inequality‐adjusted Human Development Index (IHDI) (countries with sequencing studies: IHDI median = 0.84, interquartile range [IQR] = 0.09 vs countries without sequencing studies: IHDI median = 0.56, IQR = 0.3). No studies from Africa, India, or Latin America were identified, indicating potential barriers to genetic testing.

Significance

This meta‐analysis and systematic review provides a comprehensive overview of clinical sequencing studies of NDDs and will help guide policymaking and steer decision‐making in patient management.

Predominant and novel de novo variants in 29 individuals with ALG13 deficiency: Clinical description, biomarker status, biochemical analysis, and treatment suggestions

Asparagine-linked glycosylation 13 homolog (ALG13) encodes a nonredundant, highly conserved, X-linked uridine diphosphate (UDP)-N-acetylglucosaminyltransferase required for the synthesis of lipid linked oligosaccharide precursor and proper N-linked glycosylation. De novo variants in ALG13 underlie a form of early infantile epileptic encephalopathy known as EIEE36, but given its essential role in glycosylation, it is also considered a congenital disorder of glycosylation (CDG), ALG13-CDG. Twenty-four previously reported ALG13-CDG cases had de novo variants, but surprisingly, unlike most forms of CDG, ALG13-CDG did not show the anticipated glycosylation defects, typically detected by altered transferrin glycosylation. Structural homology modeling of two recurrent de novo variants, p.A81T and p.N107S, suggests both are likely to impact the function of ALG13. Using a corresponding ALG13-deficient yeast strain, we show that expressing yeast ALG13 with either of the highly conserved hotspot variants rescues the observed growth defect, but not its glycosylation abnormality. We present molecular and clinical data on 29 previously unreported individuals with de novo variants in ALG13. This more than doubles the number of known cases. A key finding is that a vast majority of the individuals presents with West syndrome, a feature shared with other CDG types. Among these, the initial epileptic spasms best responded to adrenocorticotropic hormone or prednisolone, while clobazam and felbamate showed promise for continued epilepsy treatment. A ketogenic diet seems to play an important role in the treatment of these individuals.

Infantile spasms: Etiology, lead time and treatment response in a resource limited setting

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Neonatal hypoglycemic brain injury was the commonest cause of Infantile Spasms (IS).

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Comprehensive genetic evaluation was performed in presumed genetic IS patients.

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Molecular diagnosis was achieved in 44% of presumed genetic patients.

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Longer lead time to treatment was significantly associated with resistant spasms.

This study explores the etiology and lead time to treatment for infantile spasm (IS) patients and their effect on treatment responsiveness, in a limited resource setting. Patients with IS onset age ≤12 months’, seen over 3 years were recruited retrospectively. Clinical information, neuroimaging and genetic results retrieved. Patients categorized into three primary etiological groups: Structural (including Structural Genetic), Genetic, and Unknown. The effect of etiology and lead time from IS onset to initiating appropriate treatment on spasm resolution, evaluated. Total 113 patients were eligible. Mean IS onset age was 6.86(±4.25) months (M: F 3.3:1). Patients were grouped into: Structural 85, Genetic 11 and Unknown 17. Etiology was ascertained in 94/113 (83.1%) with neonatal hypoglycemic brain injury (NHBI) being the most common (40/113, 36%). A genetic etiology identified in 17 (including 6 Structural Genetic, of which five had Tuberous Sclerosis). Structural group was less likely to be treatment resistant (p = 0.013, OR 0.30 [0.12–0.76]). Median treatment lead time – 60 days. Longer lead time to treatment was significantly associated with resistant spasms (χ² for trend = 10.0, p = 0.0015). NHBI was the commonest underlying cause of IS. There was significant time lag to initiating appropriate treatment, affecting treatment responsiveness.

Whole-Exome Sequencing in NF1-Related West Syndrome Leads to the Identification of KCNC2 as a Novel Candidate Gene for Epilepsy

Patients with neurofibromatosis type 1 (NF1) have an increased risk for West syndrome (WS), but the underlying mechanisms linking NF1 and WS are unknown. In contrast to other neurocutaneous syndromes, intracerebral abnormalities explaining the course of infantile spasms (IS) are often absent and the seizure outcome is usually favorable. Several studies have investigated a potential genotype-phenotype correlation between NF1 and seizure susceptibility, but an association was not identified. Therefore, we identified three patients with NF1-related WS (NF1-WS) in a cohort of 51 NF1 patients and performed whole-exome sequencing (WES) to identify genetic modifiers. In two NF1 patients with WS and good seizure outcome, we did not identify variants in epilepsy-related genes. However, in a single patient with NF1-WS and transition to drug-resistant epilepsy, we identified a de novo variant in KCNC2 (c.G499T, p.D167Y) coding for Kv3.2 as a previously undescribed potassium channel to be correlated to epilepsy. Electrophysiological studies of the identified KCNC2 variant demonstrated both a strong loss-of-function effect for the current amplitude and a gain-of-function effect for the channel activation recommending a complex network effect. These results suggest that systematic genetic analysis for potentially secondary genetic etiologies in NF1 patients and severe epilepsy presentations should be done.

Use of the International League Against Epilepsy (ILAE) 1989, 2010, and 2017 Classification of Epilepsy in children in a low-resource setting: A hospital-based cross-sectional study

OBJECTIVES

This cross-sectional study was designed to test the applicability of the 1989, 2010, and 2017 International League Against Epilepsy (ILAE) classification of epilepsy in children from a resource-limited setting in India.

METHODS

Classification of seizure types and syndromes was done through parental interviews and review of medical records in children with epilepsy aged one month to 18 years. Available investigations including EEG, MRI, and metabolic/genetic tests were used in classifying patients as per the 1989, 2010, and 2017 ILAE (level II-epilepsy type) classification. We compared the proportion of children remaining unclassified by each scheme.

RESULTS

Seven hundred and twenty-six children (436 males, mean age 6.4 ± 4.6 years) were enrolled. Using the 1989 ILAE classification, we were able to classify 95.7%, and 82.6% children by the 2010 scheme. The 2017 ILAE classification could classify all 726 children at level I (seizure type), 664 (91.0%) children at level II (epilepsy type), and an electroclinical syndrome could be identified in 409 (56.1%) of the children. An etiology could be identified in 75%, perinatal brain injury being the most frequent. West syndrome was the most common electroclinical syndrome, identified in 22.7% patients. The 1989 ILAE classification system was superior to the 2010 system (P = .01) in epilepsy classification. There was no difference between the 1989 and 2017 schemes (P = .31) or the 2010 and 2017 schemes (P = .10).

SIGNIFICANCE

The 2017 ILAE classification, being multidimensional, allowed classification of children who could not undergo extensive evaluation due to economic constraints and also provided room for overlapping etiologies.

Survival of a male patient harboring CASK Arg27Ter mutation to adolescence

Background

CASK is an X‐linked gene in mammals and its deletion in males is incompatible with life. CASK heterozygous mutations in female patients associate with intellectual disability, microcephaly, pontocerebellar hypoplasia, and optic nerve hypoplasia, whereas CASK hemizygous mutations in males manifest as early infantile epileptic encephalopathy with a grim prognosis. Here, we report a rare case of survival of a male patient harboring a CASK null mutation to adolescent age.

Methods

Trio whole exome sequencing analysis was performed from blood genomic DNA. Magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), and electroencephalogram (EEG) analyses were performed to determine anomalies in brain development, metabolite concentrations, and electrical activity, respectively.

Results

Trio‐WES analysis identified a de novo c.79C>T (p.Arginine27Ter) mutation in CASK causing a premature translation termination at the very N‐terminus of the protein. The 17‐years, and 11‐month‐old male patient displayed profound intellectual disability, microcephaly, dysmorphism, ponto‐cerebellar hypoplasia, and intractable epilepsy. His systemic symptoms included overall reduced somatic growth, dysautonomia, ventilator and G tube dependence, and severe osteopenia. Brain MRI revealed a severe cerebellar and brain stem hypoplasia with progressive cerebral atrophy. EEG spectral analysis revealed a global functional defect with generalized background slowing and delta waves dominating even in the awake state.

Conclusion

This case study is the first to report survival of a male patient carrying a CASK loss‐of‐function mutation to adolescence and highlights that improved palliative care could extend survival. Moreover, the genomic position encoding Arg27 in CASK may possess an increased susceptibility to mutations.

Seizures and Epilepsy in Autism Spectrum Disorder

Epilepsy and autism frequently co-occur. Epilepsy confers an increased risk of autism and autism confers an increased risk of epilepsy. Specific epilepsy syndromes, intellectual disability, and female gender present a particular risk of autism in individuals with epilepsy. Epilepsy and autism are likely to share common etiologies, which predispose individuals to either or both conditions. Genetic factors, metabolic disorders, mitochondrial disorders, and immune dysfunction all can be implicated.

Genotype-phenotype correlates of infantile-onset developmental & epileptic encephalopathy syndromes in South India: A single centre experience

INTRODUCTION

A paucity of literature exists on genotype- phenotype correlates of 'unknown-etiology' infantile-onset developmental-epileptic encephalopathies (DEE) from India. The primary objective was to explore the yield of genetic testing in identifying potential disease causing variants in electro-clinical phenotypes of DEE METHODS: An observational hospital-based study was undertaken on children with unexplained refractory seizure-onset ≤12 months age and developmental delay, whose families consented and underwent genetic testing during a three year time period (2016-2018) by next-generation sequencing (NGS) or multiplex ligand protein amplification. Yield was considered based on demonstration of pathogenic/likely pathogenic variants only and variants of unknown significance (VUS) were documented.

RESULTS

Pathogenic/likely pathogenic variants were identified in 26 (31.7 %) out of 82 children with DEE. These included those variants responsible for primarily DEE- 21(76.7 %); neuro-metabolic disorders- 3(18.6 %) and chromosomal deletions- 2(4.7 %). Of these patients, early-infantile epilepsy onset ≤ 6 months age was noted in 22(84.6 %). The DEE studied included Ohtahara syndrome associated with STXBP1 and SCN8A variants with yield of 50 % (2/4 tested); early myoclonic encephalopathy (no yield in 2); West syndrome with CDKL5, yield of 13.3 % (2/15 tested); epilepsy of infancy with migrating partial seizures due to CACNA1A and KCNT1 variants, yield of 67 % (2/3 tested); DEE-unclassified with KCNQ2, AP3B2, ZEB2, metabolic variants (SUOX, ALDH7A1, GLDC) and chromosome deletions (chr 1p36, chr2q24.3); yield of 32 % (8/25 tested). Patients with Dravet syndrome/Dravet-like phenotypes (N = 33) had variants in SCN1A (N = 10), SCN1B, CHD2; yield of 36.4 % (12/33 tested; 57.1 % from NGS). Eighteen patients with potential variants (SCN1A, SCN2A, SCN8A, KCNQ2, ALDH7A1 which also included VUS) could be offered targeted therapy.

CONCLUSIONS

Our study confirms a good yield of genetic testing in neonatal and infantile-onset DEE provided robust phenotyping of infants is attempted with prognostic and therapeutic implications, particularly relevant to centres with resource constraints.