Epileptic Encephalopathies-Clinical Syndromes and Pathophysiological Concepts

A Novel De Novo Variant in KCNH5 in a Patient with Refractory Epileptic Encephalopathy

We herein report a novel de novo KCNH5 variant in a patient with refractory epileptic encephalopathy. The patient exhibited seizures at 1 year and 7 months old, which gradually worsened, leading to a bedridden status. Brain magnetic resonance imaging (MRI) showed cerebral atrophy and cerebellar hypoplasia. A trio whole-exome sequence analysis identified a de novo heterozygous c.640A>C, p.Lys214Gln variant in KCNH5 that was predicted to be deleterious. Recent studies have linked KCNH5 to various epileptic encephalopathies, with many patients showing normal MRI findings. The present case expands the clinical spectrum of the disease, as it is characterized by severe neurological prognosis, cerebral atrophy, and cerebellar hypoplasia.

Characteristics of Developmental and Epileptic Encephalopathy Associated with PACS2 p.Glu209Lys Pathogenic Variant-Our Experience and Systematic Review of the Literature

BACKGROUND

Developmental and epileptic encephalopathies (DEE) encompass a group of rare diseases with hereditary and genetic causes as well as acquired causes such as brain injuries or metabolic abnormalities. The phosphofurin acidic cluster sorting protein 2 (PACS2) is a multifunctional protein with nuclear gene expression. The first cases of the recurrent c.625G>A pathogenic variant of PACS2 gene were reported in 2018 by Olson et al. Since then, several case reports and case series have been published.

METHODS

We performed a systematic review of the PUBMED and SCOPUS databases using Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. Our search parameters included DEE66 with a pathogenic PACS2 gene p.Glu209Lys mutation published cases to which we added our own clinical experience regarding this pathology.

RESULTS

A total of 11 articles and 29 patients were included in this review, to which we added our own experience for a total of 30 patients. There was not a significant difference between sexes regarding the incidence of this pathology (M/F: 16/14). The most common neurological and psychiatric symptoms presented by the patients were: early onset epileptic seizures, delayed global development (including motor and speech delays), behavioral disturbances, limited intellectual capacity, nystagmus, hypotonia, and a wide-based gait. Facial dysmorphism and other organs' involvement were also frequently reported. Brain MRIs evidenced anomalies of the posterior cerebellar fossa, foliar distortion of the cerebellum, vermis hypoplasia, white matter reduction, and lateral ventricles enlargement. Genetic testing is more frequent in children. Only 4 cases have been reported in adults to date.

CONCLUSIONS

It is important to maintain a high suspicion of new pathogenic gene variants in adult patients presenting with a characteristic clinical picture correlated with radiologic changes. The neurologist must gradually recognize the distinct evolving phenotype of DEE66 in adult patients, and genetic testing must become a scenario with which the neurologist attending adult patients should be familiar. Accurate diagnosis is required for adequate treatment, genetic counseling, and an improved long-term prognosis.

Epilepsy phenotype and gene ontology analysis of the 129 genes in a large neurodevelopmental disorders cohort

Objective

Although pediatric epilepsy is an independent disease entity, it is often observed in pediatric neurodevelopmental disorders (NDDs) as a major or minor clinical feature, which might provide diagnostic clues. This study aimed to identify the clinical and genetic characteristics of patients with epilepsy in an NDD cohort and demonstrate the importance of genetic testing.

Methods

We retrospectively analyzed the detailed clinical differences of pediatric NDD patients with epilepsy according to their genetic etiology. Among 1,213 patients with NDDs, 477 were genetically diagnosed by exome sequencing, and 168 had epilepsy and causative variants in 129 genes. Causative genes were classified into two groups: (i) the "epilepsy-genes" group resulting in epilepsy as the main phenotype listed in OMIM, Epi25, and ClinGen (67 patients) and (ii) the "NDD-genes" group not included in the "epilepsy-genes" group (101 patients).

Results

Patients in the "epilepsy-genes" group started having seizures, often characterized by epilepsy syndrome, at a younger age. However, overall clinical features, including treatment responses and all neurologic manifestations, showed no significant differences between the two groups. Gene ontology analysis revealed the close interactions of epilepsy genes associated with ion channels and neurotransmitters.

Conclusion

We demonstrated a similar clinical presentation of different gene groups regarding biological/molecular processes in a large NDDs cohort with epilepsy. Phenotype-driven genetic analysis should cover a broad scope, and further studies are required to elucidate integrated pathomechanisms.

Advances toward precision therapeutics for developmental and epileptic encephalopathies

Developmental and epileptic encephalopathies are childhood syndromes of severe epilepsy associated with cognitive and behavioral disorders. Of note, epileptic seizures represent only a part, although substantial, of the clinical spectrum. Whether the epileptiform activity per se accounts for developmental and intellectual disabilities is still unclear. In a few cases, seizures can be alleviated by antiseizure medication (ASM). However, the major comorbid features associated remain unsolved, including psychiatric disorders such as autism-like and attention deficit hyperactivity disorder-like behavior. Not surprisingly, the number of genes known to be involved is continuously growing, and genetically engineered rodent models are valuable tools for investigating the impact of gene mutations on local and distributed brain circuits. Despite the inconsistencies and problems arising in the generation and validation of the different preclinical models, those are unique and precious tools to identify new molecular targets, and essential to provide prospects for effective therapeutics.

Concise Review: Stem Cell Models of SCN1A-Related Encephalopathies—Current Perspective and Future Therapies

Mutations in the SCN1A gene can cause a variety of phenotypes, ranging from mild forms, such as febrile seizures and generalized epilepsy with febrile seizures plus, to severe, such as Dravet and non-Dravet developmental epileptic encephalopathies. Until now, more than two thousand pathogenic variants of the SCN1A gene have been identified and different pathogenic mechanisms (loss vs. gain of function) described, but the precise molecular mechanisms responsible for the deficits exhibited by patients are not fully elucidated. Additionally, the phenotypic variability proves the involvement of other genetic factors in its final expression. This is the reason why animal models and cell line models used to explore the molecular pathology of SCN1A-related disorders are only of limited use. The results of studies based on such models cannot be directly translated to affected individuals because they do not address each patient’s unique genetic background. The generation of functional neurons and glia for patient-derived iPSCs, together with the generation of isogenic controls using CRISPR/Cas technology, and finally, the 3D brain organoid models, seem to be a good way to solve this problem. Here, we review SCN1A-related encephalopathies, as well as the stem cell models used to explore their molecular basis.

Developmental and epileptic encephalopathies: Is prognosis related to different epileptic network dysfunctions?

Developmental and epileptic encephalopathies are a group of rare, severe epilepsies, which are characterized by refractory seizures starting in infancy or childhood and developmental delay or regression. Developmental changes might be independent of epilepsy. However, interictal epileptic activity and seizures can further deteriorate cognition and behavior. Recently, the concept of developmental and epileptic encephalopathies has moved from the lesions associated with epileptic encephalopathies toward the epileptic network dysfunctions on the functioning of the brain. Early recognition and differentiation of patients with developmental and epileptic encephalopathies is important, as precision therapies need to be holistic to address the often devastating symptoms. In this review, we discuss the evolution of the concept of developmental and epileptic encephalopathies in recent years, as well as the current understanding of the genetic basis of developmental and epileptic encephalopathies. Finally, we will discuss the role of epileptic network dysfunctions on prognosis for these severe conditions.

Genetic-cellular epilepsy: Clues to diagnosing newborns with neonatal seizures

OBJECTIVE

The aim of this study was to analyse clinical characteristics of newborns with genetic-cellular epilepsy (GCE) to compare them to those of newborns with seizures with other aetiologies and elucidate clues to the diagnosis of GCE.

METHODS

This retrospective single-centre study analysed data from an 8-year cohort of newborns with seizures from 2010-2017. Clinical, neurophysiological, laboratory, and imaging data and outcomes of children with GCE were compared to those of newborns with seizures with other aetiologies.

RESULTS

A total of 112 newborns (N = 68; 61% boys) were included. Hypoxic-ischaemic encephalopathy (N = 42; 29%) was the most common seizure aetiology; GCE (with pathogenic variants KCNQ2, KCNQ3, SCN2A, TBC1D24, CHD2, and STXBP) was diagnosed in 9 (6%). The group of newborns with GCE significantly differed from the group with seizures with other aetiologies in terms of family history of epilepsy (p = 0.000), neonatal epileptic status (NES) (p = 0.007), normal imaging studies (p = 0.000), and outcomes (p = 0.034), but did not differ regarding the type and age of seizure onset, number of antiepileptic drugs administered, and EEG results. Positive family history of epilepsy (p = 0.027), presence of NES (p = 0.041), and normal imaging studies (p = 0.002) were most indicative of the diagnosis of GCE. Probability of GCE with this combination was 0.92.

CONCLUSION

In a heterogenous group of newborns with seizures, a positive family history of epilepsy, presence of NES, and normal imaging studies were most indicative of the diagnosis of GCE.

Screening Platforms for Genetic Epilepsies-Zebrafish, iPSC-Derived Neurons, and Organoids

Recent advances in molecular and cellular engineering, such as human cell reprogramming, genome editing, and patient-specific organoids, have provided unprecedented opportunities for investigating human disorders in both animals and human-based models at an improved pace and precision. This progress will inevitably lead to the development of innovative drug-screening platforms and new patient-specific therapeutics. In this review, we discuss recent advances that have been made using zebrafish and human-induced pluripotent stem cell (iPSC)-derived neurons and organoids for modeling genetic epilepsies. We also provide our prospective on how these models can potentially be combined to build new screening platforms for antiseizure and antiepileptogenic drug discovery that harness the robustness and tractability of zebrafish models as well as the patient-specific genetics and biology of iPSC-derived neurons and organoids.

WDR45, one gene associated with multiple neurodevelopmental disorders

The WDR45 gene is localized on the X-chromosome and variants in this gene are linked to six different neurodegenerative disorders, i.e., ß-propeller protein associated neurodegeneration, Rett-like syndrome, intellectual disability, and epileptic encephalopathies including developmental and epileptic encephalopathy, early-onset epileptic encephalopathy and West syndrome and potentially also specific malignancies. WDR45/WIPI4 is a WD-repeat β-propeller protein that belongs to the WIPI (WD repeat domain, phosphoinositide interacting) family. The precise cellular function of WDR45 is still largely unknown, but deletions or conventional variants in WDR45 can lead to macroautophagy/autophagy defects, malfunctioning mitochondria, endoplasmic reticulum stress and unbalanced iron homeostasis, suggesting that this protein functions in one or more pathways regulating directly or indirectly those processes. As a result, the underlying cause of the WDR45-associated disorders remains unknown. In this review, we summarize the current knowledge about the cellular and physiological functions of WDR45 and highlight how genetic variants in its encoding gene may contribute to the pathophysiology of the associated diseases. In particular, we connect clinical manifestations of the disorders with their potential cellular origin of malfunctioning and critically discuss whether it is possible that one of the most prominent shared features, i.e., brain iron accumulation, is the primary cause for those disorders.

Abbreviations: ATG/Atg: autophagy related; BPAN: ß-propeller protein associated neurodegeneration; CNS: central nervous system; DEE: developmental and epileptic encephalopathy; EEG: electroencephalograph; ENO2/neuron-specific enolase, enolase 2; EOEE: early-onset epileptic encephalopathy; ER: endoplasmic reticulum; ID: intellectual disability; IDR: intrinsically disordered region; MRI: magnetic resonance imaging; NBIA: neurodegeneration with brain iron accumulation; NCOA4: nuclear receptor coactivator 4; PtdIns3P: phosphatidylinositol-3-phosphate; RLS: Rett-like syndrome; WDR45: WD repeat domain 45; WIPI: WD repeat domain, phosphoinositide interacting

Developmental outcome after corpus callosotomy for infants and young children with drug-resistant epilepsy

AIM

To examine the developmental and seizure outcomes after corpus callosotomy (CC) in early childhood.

METHODS

We retrospectively identified 106 patients who underwent CC for drug-resistant epilepsy before the age of 6 years, at the Nagasaki Medical Center, between July 2002 and July 2016. Patients' developmental outcomes were evaluated one year after CC using the Kinder Infant Development Scale.

RESULTS

The mean preoperative developmental quotient (DQ) was 25.0 (standard deviation [SD], 20.8), and the mean difference between preoperative DQ and one-year postoperative DQ was -1.6 points (SD, 11.6). However, 42.5% of patients had a mean DQ increase of 6.5 points (SD, 6.4), one year after CC from that before surgery. Factors related to the improvement in postoperative DQ were 'low preoperative DQ', 'developmental gain 1 month postoperatively', and 'postoperative seizure-free state'. Approximately 21.7% of patients were seizure-free 1 year after CC.

INTERPRETATION

Performing CC, in infancy and early childhood for patients with drug-resistant epilepsy and severe developmental impairment, was associated with improved development in 42.5% of patients. Remission of seizures, even if only for a short period, contributed to developmental improvement. From a developmental perspective, CC for drug-resistant epilepsy in early childhood is an effective treatment.

Dyshomeostatic modulation of Ca2+-activated K+ channels in a human neuronal model of KCNQ2 encephalopathy

Mutations in KCNQ2, which encodes a pore-forming K⁺ channel subunit responsible for neuronal M-current, cause neonatal epileptic encephalopathy, a complex disorder presenting with severe early-onset seizures and impaired neurodevelopment. The condition is exceptionally difficult to treat, partially because the effects of KCNQ2 mutations on the development and function of human neurons are unknown. Here, we used induced pluripotent stem cells (iPSCs) and gene editing to establish a disease model and measured the functional properties of differentiated excitatory neurons. We find that patient iPSC-derived neurons exhibit faster action potential repolarization, larger post-burst afterhyperpolarization and a functional enhancement of Ca²⁺-activated K⁺ channels. These properties, which can be recapitulated by chronic inhibition of M-current in control neurons, facilitate a burst-suppression firing pattern that is reminiscent of the interictal electroencephalography pattern in patients. Our findings suggest that dyshomeostatic mechanisms compound KCNQ2 loss-of-function leading to alterations in the neurodevelopmental trajectory of patient iPSC-derived neurons.

Recent advances in epilepsy genomics and genetic testing

Developmental and epileptic encephalopathies (DEEs) are a group of severe, early onset epilepsies characterized by refractory seizures, developmental delay or regression associated with ongoing epileptic activity, and generally poor prognosis. DEE is genetically and phenotypically heterogeneous, and there is a plethora of genetic testing options to investigate the rapidly growing list of epilepsy genes. However, more than 50% of patients with DEE remain without a genetic diagnosis despite state-of-the-art genetic testing. In this review, we discuss the major advances in epilepsy genomics that have surfaced in recent years. The goal of this review is to reach a larger audience and build a better understanding of pathogenesis and genetic testing options in DEE.

Identification of a Loss-of-Function Mutation in the Context of Glutaminase Deficiency and Neonatal Epileptic Encephalopathy

Importance

The identification and understanding of the monogenic causes of neurodevelopmental disorders are of high importance for personalized treatment and genetic counseling.

Objective

To identify and characterize novel genes for a specific neurodevelopmental disorder characterized by refractory seizures, respiratory failure, brain abnormalities, and death in the neonatal period; describe the outcome of glutaminase deficiency in humans; and understand the underlying pathological mechanisms.

Design, Setting, and Participants

We performed exome sequencing of cases of neurodevelopmental disorders without a clear genetic diagnosis, followed by genetic and bioinformatic evaluation of candidate variants and genes. Establishing pathogenicity of the variants was achieved by measuring metabolites in dried blood spots by a hydrophilic interaction liquid chromatography method coupled with tandem mass spectrometry. The participants are 2 families with a total of 4 children who each had lethal, therapy-refractory early neonatal seizures with status epilepticus and suppression bursts, respiratory insufficiency, simplified gyral structures, diffuse volume loss of the brain, and cerebral edema. Data analysis occurred from October 2017 to June 2018.

Main Outcomes and Measures

Early neonatal epileptic encephalopathy with glutaminase deficiency and lethal outcome.

Results

A total of 4 infants from 2 unrelated families, each of whom died less than 40 days after birth, were included. We identified a homozygous frameshift variant p.(Asp232Glufs*2) in GLS in the first family, as well as compound heterozygous variants p.(Gln81*) and p.(Arg272Lys) in GLS in the second family. The GLS gene encodes glutaminase (Enzyme Commission 3.5.1.2), which plays a major role in the conversion of glutamine into glutamate, the main excitatory neurotransmitter of the central nervous system. All 3 variants probably lead to a loss of function and thus glutaminase deficiency. Indeed, glutamine was increased in affected children (available z scores, 3.2 and 11.7). We theorize that the potential reduction of glutamate and the excess of glutamine were a probable cause of the described physiological and structural abnormalities of the central nervous system.

Conclusions and Relevance

We identified a novel autosomal recessive neurometabolic disorder of loss of function of glutaminase that leads to lethal early neonatal encephalopathy. This inborn error of metabolism underlines the importance of GLS for appropriate glutamine homeostasis and respiratory regulation, signal transduction, and survival.

Cannabidiol for epilepsy: a new indication for an old drug

Medicinal cannabis, and cannabidiol in particular, has garnered much attention in the media and medical community as a possible therapeutic for multiple conditions including epilepsy. Although the use of cannabis has been reported for centuries, evidence in its usefulness in the treatment of epilepsy has been mainly anecdotal. This review discusses emerging research on cannabidiol in the treatment of severe pediatric epilepsies, including Dravet syndrome and Lennox Gastaut syndrome. We discuss the data from both open-label and Phase III trials and report a consistently significant reduction in seizures but also concomitant drug interactions and adverse effects. Future directions of research are considered to determine the full therapeutic potential of this old, but new, class of compounds.

Modeling Pediatric Epilepsy Through iPSC-Based Technologies

In the current review, we discuss the process of modeling pediatric epileptic encephalopathies with a focus on in vitro iPSC-based technologies. We highlight the potential benefits as well as the challenges of these approaches and propose appropriate standards for the field.

A Recurrent De Novo PACS2 Heterozygous Missense Variant Causes Neonatal-Onset Developmental Epileptic Encephalopathy, Facial Dysmorphism, and Cerebellar Dysgenesis

Developmental and epileptic encephalopathies (DEEs) represent a large clinical and genetic heterogeneous group of neurodevelopmental diseases. The identification of pathogenic genetic variants in DEEs remains crucial for deciphering this complex group and for accurately caring for affected individuals (clinical diagnosis, genetic counseling, impacting medical, precision therapy, clinical trials, etc.). Whole-exome sequencing and intensive data sharing identified a recurrent de novo PACS2 heterozygous missense variant in 14 unrelated individuals. Their phenotype was characterized by epilepsy, global developmental delay with or without autism, common cerebellar dysgenesis, and facial dysmorphism. Mixed focal and generalized epilepsy occurred in the neonatal period, controlled with difficulty in the first year, but many improved in early childhood. PACS2 is an important PACS1 paralog and encodes a multifunctional sorting protein involved in nuclear gene expression and pathway traffic regulation. Both proteins harbor cargo(furin)-binding regions (FBRs) that bind cargo proteins, sorting adaptors, and cellular kinase. Compared to the defined PACS1 recurrent variant series, individuals with PACS2 variant have more consistently neonatal/early-infantile-onset epilepsy that can be challenging to control. Cerebellar abnormalities may be similar but PACS2 individuals exhibit a pattern of clear dysgenesis ranging from mild to severe. Functional studies demonstrated that the PACS2 recurrent variant reduces the ability of the predicted autoregulatory domain to modulate the interaction between the PACS2 FBR and client proteins, which may disturb cellular function. These findings support the causality of this recurrent de novo PACS2 heterozygous missense in DEEs with facial dysmorphim and cerebellar dysgenesis.

[Trends and expectations the research on the molecular background of epileptic encephalopathies - state of the art in 2017]

Epilepsy is common neurological condition affecting 0.8-1% of the human population. Since 80% of patients are under 20 years of age, it is mainly a disease of the developmental period. The causes of epilepsy are heterogeneous, but the disease has always been considered a genetic disorder, which no longer doubted. Epilepsy genetics has undergone a revolution since the discovery of the first gene responsible for epilepsy. This is mainly because of introduction of the next generation sequencing as research and diagnostic tool, and transition from studies of pedigrees with epilepsy to the analysis of cases of epileptic encephalopathies. In a short time more than 50 early infantile epileptic encephalopathies were recognized due to the causative genes. Whole exome or targeted panel sequencing has been used as a diagnostic tool with a diagnostic yield of about 30-40%. The "genetic diagnosis" that is obtained makes it possible to introduce targeted treatment in an increasing number of cases. Since epileptic encephalopaties are often regarded as the model disease for epilepsy, these therapeutic strategies can provide treatment for patients with common epilepsies.

Life impact of caregiving for severe childhood epilepsy: Results of expert panels and caregiver focus groups

Severe epilepsy in children and young adults can significantly affect the lives of their caregivers. However, the lack of a reliable and valid measure of caregiver impact has limited our understanding of the scope and correlates of this impact, as well as our ability to measure the effects of treatments that could lessen it. The purpose of this study was to facilitate focus groups and interviews with an international group of clinician experts and caregivers to identify the most important domains that should be assessed in a measure of caregiver impact. Ten specific subdomains emerged from the panel discussions, which could be classified into the four overarching categories of physical health, mental health, social function, and financial resources. The caregivers highlighted the impact on the subdomains of sleep and fatigue as most critical. A review of existing caregiver impact measures confirmed that there is no measure currently available that assesses all of these relevant domains, indicating the need for the development of such a measure. The current findings highlight the significant life effects of caring for a child with severe epilepsy and can be used to inform the development of such a tool.