Efficacy of anti-seizure medications and alternative therapies (ketogenic diet, CBD, and quinidine) in KCNT1-related epilepsy: A systematic review.

OBJECTIVE: KCNT1-related epilepsies encompass three main phenotypes: (i) epilepsy of infancy with migrating focal seizures (EIMFS), (ii) autosomal dominant or sporadic sleep-related hypermotor epilepsy [(AD)SHE], and (iii) different types of developmental and epileptic encephalopathies (DEE). Many patients present with drug-resistant seizures and global developmental delays. In addition to conventional anti-seizure medications (ASM), multiple alternative therapies have been tested including the ketogenic diet (KD), cannabidiol (CBD-including Epidyolex © and other CBD derivatives) and quinidine (QUIN). We aimed to clarify the current state of the art concerning the benefits of those therapies administered to the three groups of patients. METHODS: We performed a literature review on PubMed and EMBase with the keyword "KCNT1" and selected articles reporting qualitative and/or quantitative information on responses to these treatments. A treatment was considered beneficial if it improved seizure frequency and/or intensity and/or quality of life. Patients were grouped by phenotype. RESULTS: A total of 43 studies including 197 patients were reviewed. For EIMFS patients (32 studies, 135 patients), KD resulted in benefit in 62.5% (25/40), all types of CBD resulted in benefit in 50% (6/12), and QUIN resulted in benefit in 44.6% (25/56). For (AD)SHE patients (10 studies, 32 patients), we found only one report of treatment with KD, with no benefit noted. QUIN was trialed in 8 patients with no reported benefit. For DEE patients (10 studies, 30 patients), KD resulted in benefit for 4/7, CBD for 1/2, and QUIN for 6/9. In all groups, conventional ASM are rarely reported as beneficial (in 5%-25% of patients). SIGNIFICANCE: Ketogenic diet, CBD, and QUIN treatments appear to be beneficial in a subset of patient with drug-resistant epilepsy. The KD and CBD are reasonable to trial in patients with KCNT1-related epilepsy. Further studies are needed to identify optimal treatment strategies and to establish predictive response factors. PLAIN LANGUAGE SUMMARY: We performed an extensive review of scientific articles providing information about the therapeutic management of epilepsy in patients with epilepsy linked to a mutation in the KCNT1 gene. Conventional anti-seizure treatments were rarely reported to be beneficial. The ketogenic diet (a medical diet with very high fat, adequate protein and very low carbohydrate intake) and cannabidiol appeared to be useful, but larger studies are needed to reach a conclusion.

[Developmental and epileptic encephalopathy produced by the ATP1A2 mutation]. / Entsefalopatiya s narusheniem razvitiya i epilepsiei, vyzvannaya mutatsiei gena ATP1A2.

A case of DEE98, a rare developmental and epileptic encephalopathy related to previously reported the de novo missense mutation p.Arg908Gln in the ATP1A2 gene, is described. A girl examined first time in 11 months had microcephaly, severe mental and motor delay, strabismus, spastic paraparesis and pachypolymicrogyria on brain MRI that is atypical for DEE98. Epilepsy with polymorphic seizures started at the age of 15 months. There was a remission lasting 9 months, after which seizures renewed. DEE98 was diagnosed at the age of 2 years 9 months by exome sequencing verified by trio Sanger sequencing. Another finding from high-throughput exome sequencing were two previously undescribed heterozygous variants of uncertain pathogenicity in the SPART gene, which causes autosomal recessive spastic paraplegia type 20 (SPG20); Sanger sequencing confirmed the trans position of the variants. The common clinical sign with typical SPG20 was early spastic paraparesis with contractures; other symptoms did not coincide. Considering the phenotypic diversity of SPG20 and the possibility of a combination of two independent diseases, we performed an additional study of the pathogenicity of SPART variants at the mRNA level: pathogenicity was not confirmed, and there were no grounds to diagnose SPG20.

Efficacy of enteral feeding by gastrostomy tube placement in patients with Lennox-Gastaut syndrome on body weight and days of hospitalization: A retrospective case series.

BACKGROUND: Lennox-Gastaut syndrome (LGS) is a severe form of drug-resistant epilepsy that begins during childhood and frequently leads to significant neurological impairments. Patients with LGS are likely to receive improper oral nutrition because of issues such as dysphagia and aspiration risk, potentially resulting in long-term tube feeding and eventual gastrostomy tube placement. Therefore, we investigated the effects of gastrostomy tube placement on nutrition outcomes and frequency of hospitalization in LGS. METHODS: We retrospectively examined 67 patients diagnosed with LGS who had undergone gastrostomy tube placement between January 2005 and August 2022. Comprehensive clinical data and complications arising from the procedure were collected. Patients' nutrition condition and frequency of hospitalizations were analyzed before and after gastrostomy tube placement. RESULTS: Gastrostomy tube placement was performed for the following reasons: high risk of aspiration (50 out of 67, 74.6%), dysphagia (13 out of 67, 25.4%), persistent nasogastric tube feeding (2 out of 67, 3.0%), and severe malnutrition (2 out of 67, 3.0%). After the procedure, z scores for weight-for-age improved significantly, shifting from -3.35 ± 3.57 to -2.54 ± 2.70 over a 2-year interval (P < 0.001). Additionally, the total days of hospitalization and days of hospitalization due to respiratory symptoms reduced significantly from 41.94 ± 51.76 to 15.27 ± 26.68 (P < 0.001) and from 23.75 ± 36.92 to 10.52 ± 22.98 (P = 0.009), respectively. Among the patients, 50 (74.6%) experienced complications resulting from gastrostomy, with a relatively small proportion of major complications (11 out of 67, 16.4%) and no mortality. CONCLUSION: Gastrostomy tube placement is a relatively safe procedure with favorable effects on nutrition status and hospitalization rates in patients with LGS.

Gnao1 is a molecular switch that regulates the Rho signaling pathway in differentiating neurons.

GNAO1 encodes G protein subunit alpha O1 (Gαo). Pathogenic variations in GNAO1 cause developmental delay, intractable seizures, and progressive involuntary movements from early infancy. Because the functional role of GNAO1 in the developing brain remains unclear, therapeutic strategies are still unestablished for patients presenting with GNAO1-associated encephalopathy. We herein report that siRNA-mediated depletion of Gnao1 perturbs the expression of transcripts associated with Rho GTPase signaling in Neuro2a cells. Consistently, siRNA treatment hampered neurite outgrowth and extension. Growth cone formation was markedly disrupted in monolayer neurons differentiated from iPSCs from a patient with a pathogenic variant of Gαo (p.G203R). This variant disabled neuro-spherical assembly, acquisition of the organized structure, and polarized signals of phospho-MLC2 in cortical organoids from the patient's iPSCs. We confirmed that the Rho kinase inhibitor Y27632 restored these morphological phenotypes. Thus, Gαo determines the self-organizing process of the developing brain by regulating the Rho-associated pathway. These data suggest that Rho GTPase pathway might be an alternative target of therapy for patients with GNAO1-associated encephalopathy.

Innovative drug discovery strategies in epilepsy: integrating next-generation syndrome-specific mouse models to address pharmacoresistance and epileptogenesis.

INTRODUCTION: Although there are numerous treatment options already available for epilepsy, over 30% of patients remain resistant to these antiseizure medications (ASMs). Historically, ASM discovery has relied on the demonstration of efficacy through the use of 'traditional' acute in vivo seizure models (e.g. maximal electroshock, subcutaneous pentylenetetrazol, and kindling). However, advances in genetic sequencing technologies and remaining medical needs for people with treatment-resistant epilepsy or special patient populations have encouraged recent efforts to identify novel compounds in syndrome-specific models of epilepsy. Syndrome-specific models, including Scn1a variant models of Dravet syndrome and APP/PS1 mice associated with familial early-onset Alzheimer's disease, have already led to the discovery of two mechanistically novel treatments for developmental and epileptic encephalopathies (DEEs), namely cannabidiol and soticlestat, respectively. AREAS COVERED: In this review, the authors discuss how it is likely that next-generation drug discovery efforts for epilepsy will more comprehensively integrate syndrome-specific epilepsy models into early drug discovery providing the reader with their expert perspectives. EXPERT OPINION: The percentage of patients with pharmacoresistant epilepsy has remained unchanged despite over 30 marketed ASMs. Consequently, there is a high unmet need to reinvent and revise discovery strategies to more effectively address the remaining needs of patients with specific epilepsy syndromes, including drug-resistant epilepsy and DEEs.

Clinical features and genetic analysis of developmental and epileptic encephalopathy caused by biallelic variants of CACNA1B.

Objective: To analyze the clinical features and genetic etiology of a patient with developmental and epileptic encephalopathy. Methods: The clinical information and peripheral blood of the patient and their family members were collected before the whole exome sequencing analysis was performed and Sanger sequencing was employed to verify the potential variant. Results: The patient presented with epilepsy and cerebral palsy with his parents, brother, and sister being all healthy. Whole exome sequencing analysis revealed that the child carried the paternal c.823del (p. R275Gfs*31) heterozygous variant and the maternal c.2456del (p.V819Gfs*190) heterozygous variant of the CACNA1B gene. Pedigree verification found that the elder brother and amniotic fluid of fetus in womb carried the paternal c.823del heterozygous variant, and the elder sister carried the maternal c.2456del heterozygous variant, which conformed to the law of autosomal recessive inheritance. Neither of these two variants has been reported in the literature and has not been included in the Genomic Mutation Frequency Database (gnomAD); according to the American Academy of Medical Genetics and Genomics Variation Grading Guidelines (ACMG), both variants are classified as pathogenic variants (PVS1+PM2-Supporting + PM3). Conclusion: This study reported the first case of a child with neurodevelopmental disorder and epilepsy caused by a new compound heterozygous variant of the CACNA1B gene in China, clarified its genetic etiology, enriched the mutation spectrum and disease spectrum of CACNA1B gene, and provided a basis for prenatal diagnosis of the family.

A retrospective study of the yield of next-generation sequencing in the diagnosis of developmental and epileptic encephalopathies and epileptic encephalopathies in 0-12 years aged children at a single tertiary care hospital in South India.

OBJECTIVE: Studies on the genetic yield of developmental and epileptic encephalopathy and Epileptic encephalopathies using next-generation sequencing techniques are sparse from the Indian subcontinent. Hence, the study was conducted to assess the yield of genetic testing and the proportion of children where a positive genetic yield influenced treatment decisions. METHODS: In this retrospective observational study, electronic medical records of children (0-12 years) with suspected genetic epilepsy who underwent genetic testing using whole exome sequencing, focused exome sequencing and epilepsy gene panels were retrieved. Genetic yield was ascertained based on the detection of pathogenic and likely pathogenic variants. RESULTS: A total of 100 patients with epilepsy underwent genetic testing. A yield of 53.8% (42/78) was obtained. Pathogenic variants were identified in 18 (42.8%) cases and likely pathogenic variants in 24 (57.1%) cases. Yield was 66.6% each through whole exome sequencing, focused exome sequencing and 40% through Epilepsy gene panels (p = .07). Yield was not statistically significant across different age groups (p = .2). It was however found to significantly vary across different epilepsy syndromes with maximum yield in Epilepsy in infancy with migrating focal seizures in 2 (100%), followed by developmental and epileptic encephalopathy unspecified in 14 (77.7%), Dravet syndrome in 14 (60.8%), early infantile developmental and epileptic encephalopathy in 3 (60%), infantile epileptic spasm syndrome in 5 (35.7%), and other epileptic encephalopathies in 4 (30.7%) cases (p = .04). After genetic diagnosis and drug optimization, drug-refractory proportion reduced from 73.8% to 45.3%. About half of the cases achieved seizure control. SIGNIFICANCE: A reasonably high yield of 53.8% was obtained irrespective of the choice of panel or exome or age group using next-generation sequencing-based techniques. Yield was however higher in certain epilepsy syndromes and low in Infantile epileptic spasms syndrome. A specific genetic diagnosis facilitated tailored treatment leading to seizure freedom in 28.6% and marked seizure reduction in 54.7% cases.

Nav1.2 channel mutations preventing fast inactivation lead to SCN2A encephalopathy.

SCN2A gene-related early-infantile developmental and epileptic encephalopathy (EI-DEE) is a rare and severe disorder that manifests in early infancy. SCN2A mutations affecting the fast inactivation gating mechanism can result in altered voltage dependence and incomplete inactivation of the encoded neuronal Nav1.2 channel and lead to abnormal neuronal excitability. In this study, we evaluated clinical data of seven missense Nav1.2 variants associated with DEE and performed molecular dynamics simulations, patch-clamp electrophysiology, and dynamic clamp real-time neuronal modelling to elucidate the molecular and neuron-scale phenotypic consequences of the mutations. The N1662D mutation almost completely prevented fast inactivation without affecting activation. The comparison of wild-type and N1662D channel structures suggested that the ambifunctional hydrogen bond formation between residues N1662 and Q1494 is essential for fast inactivation. Fast inactivation could also be prevented with engineered Q1494A or Q1494L Nav1.2 channel variants, whereas Q1494E or Q1494 K variants resulted in incomplete inactivation and persistent current. Molecular dynamics simulations revealed a reduced affinity of the hydrophobic IFM-motif to its receptor site with N1662D and Q1494L variants relative to wild-type. These results demonstrate that the interactions between N1662 and Q1494 underpin the stability and the orientation of the inactivation gate and are essential for the development of fast inactivation. Six DEE-associated Nav1.2 variants, with mutations mapped to channel segments known to be implicated in fast inactivation were also evaluated. Remarkably, the L1657P variant also prevented fast inactivation and produced biophysical characteristics that were similar to those of N1662D, whereas the M1501 V, M1501T, F1651C, P1658S, and A1659 V variants resulted in biophysical properties that were consistent with gain-of-function and enhanced action potential firing of hybrid neurons in dynamic action potential clamp experiments. Paradoxically, low densities of N1662D or L1657P currents potentiated action potential firing, whereas increased densities resulted in sustained depolarization. Our results provide novel structural insights into the molecular mechanism of Nav1.2 channel fast inactivation and inform treatment strategies for SCN2A-related EI-DEE. The contribution of non-inactivating Nav1.2 channels to neuronal excitability may constitute a distinct cellular mechanism in the pathogenesis of SCN2A-related DEE.

Knockdown of NeuroD2 leads to seizure-like behavior, brain neuronal hyperactivity and a leaky blood-brain barrier in a Xenopus laevis tadpole model of DEE75.

Developmental and Epileptic Encephalopathies (DEE) are a genetically diverse group of severe, early onset seizure disorders. DEE are normally identified clinically in the first six months of life by the presence of frequent, difficult to control seizures and accompanying stalling or regression of development. DEE75 results from de novo mutations of the NEUROD2 gene that result in loss of activity of the encoded transcription factor, and the seizure phenotype was shown to be recapitulated in Xenopus tropicalis tadpoles. We used CRISPR/Cas9 to make a DEE75 model in Xenopus laevis, to further investigate the developmental etiology. NeuroD2.S CRISPR/Cas9 edited tadpoles were more active, swam faster on average, and had more seizures (C-shaped contractions resembling unprovoked C-start escape responses) than their sibling controls. Live imaging of Ca2+ signaling revealed prolongued, strong signals sweeping through the brain, indicative of neuronal hyperactivity. While the resulting tadpole brain appeared grossly normal, the blood-brain barrier (BBB) was found to be leakier than that of controls. Additionally, the TGFß antagonist Losartan was shown to have a short-term protective effect, reducing neuronal hyperactivity and reducing permeability of the BBB. Treatment of NeuroD2 CRISPant tadpoles with 5 mM Losartan decreased seizure events by more than 4-fold compared to the baseline. Our results support a model of DEE75 resulting from reduced NeuroD2 activity during vertebrate brain development, and indicate that a leaky BBB contributes to epileptogenesis.

Missense variants in ANO4 cause sporadic encephalopathic or familial epilepsy with evidence for a dominant-negative effect.

Anoctamins are a family of Ca2+-activated proteins that may act as ion channels and/or phospholipid scramblases with limited understanding of function and disease association. Here, we identified five de novo and two inherited missense variants in ANO4 (alias TMEM16D) as a cause of fever-sensitive developmental and epileptic or epileptic encephalopathy (DEE/EE) and generalized epilepsy with febrile seizures plus (GEFS+) or temporal lobe epilepsy. In silico modeling of the ANO4 structure predicted that all identified variants lead to destabilization of the ANO4 structure. Four variants are localized close to the Ca2+ binding sites of ANO4, suggesting impaired protein function. Variant mapping to the protein topology suggests a preliminary genotype-phenotype correlation. Moreover, the observation of a heterozygous ANO4 deletion in a healthy individual suggests a dysfunctional protein as disease mechanism rather than haploinsufficiency. To test this hypothesis, we examined mutant ANO4 functional properties in a heterologous expression system by patch-clamp recordings, immunocytochemistry, and surface expression of annexin A5 as a measure of phosphatidylserine scramblase activity. All ANO4 variants showed severe loss of ion channel function and DEE/EE associated variants presented mild loss of surface expression due to impaired plasma membrane trafficking. Increased levels of Ca2+-independent annexin A5 at the cell surface suggested an increased apoptosis rate in DEE-mutant expressing cells, but no changes in Ca2+-dependent scramblase activity were observed. Co-transfection with ANO4 wild-type suggested a dominant-negative effect. In summary, we expand the genetic base for both encephalopathic sporadic and inherited fever-sensitive epilepsies and link germline variants in ANO4 to a hereditary disease.

Global modified-Delphi consensus on comorbidities and prognosis of SCN8A-related epilepsy and/or neurodevelopmental disorders.

OBJECTIVES: We aimed to develop consensus on comorbidities (frequency, severity, and prognosis) and overall outcomes in epilepsy, development, and cognition for the five phenotypes of SCN8A-related disorders. METHODS: A core panel consisting of 13 clinicians, 1 researcher, and 6 caregivers was formed and split into three workgroups. One group focused on comorbidities and prognosis. All groups performed a literature review and developed questions for use in a modified-Delphi process. Twenty-eight clinicians, one researcher, and 13 caregivers from 16 countries participated in three rounds of the modified-Delphi process. Consensus was defined as follows: strong consensus ≥80% fully agree; moderate consensus ≥80% fully or partially agree, <10% disagree; and modest consensus 67%-79% fully or partially agree, <10% disagree. RESULTS: Consensus was reached on the presence of 14 comorbidities in patients with Severe Developmental and Epileptic Encephalopathy (Severe DEE) spanning non-seizure neurological disorders and other organ systems; impacts were mostly severe and unlikely to improve or resolve. Across Mild/Moderate Developmental and Epileptic Encephalopathy (Mild/Moderate DEE), Neurodevelopmental Delay with Generalized Epilepsy (NDDwGE), and NDD without Epilepsy (NDDwoE) phenotypes, cognitive and sleep-related comorbidities as well as fine and gross motor delays may be present but are less severe and more likely to improve compared to Severe DEE. There was no consensus on comorbidities in the SeL(F)IE phenotype but strong conesensus that seizures would largely resolve. Seizure freedom is rare in patients with Severe DEE but may occur in some with Mild/Moderate DEE and NDDwGE. SIGNIFICANCE: Significant comorbidities are present in most phenotypes of SCN8A-related disorders but are most severe and pervasive in the Severe DEE phenotype. We hope that this work will improve recognition, early intervention, and long-term management for patients with these comorbidities and provide the basis for future evidence-based studies on optimal treatments of SCN8A-related disorders. Identifying the prognosis of patients with SCN8A-related disorders will also improve care and quality-of-life for patients and their caregivers.

Global modified Delphi consensus on diagnosis, phenotypes, and treatment of SCN8A-related epilepsy and/or neurodevelopmental disorders.

OBJECTIVE: We aimed to develop consensus for diagnosis/management of SCN8A-related disorders. Utilizing a modified Delphi process, a global cohort of experienced clinicians and caregivers provided input on diagnosis, phenotypes, treatment, and management of SCN8A-related disorders. METHODS: A Core Panel (13 clinicians, one researcher, six caregivers), divided into three subgroups (diagnosis/phenotypes, treatment, comorbidities/prognosis), performed a literature review and developed questions for the modified Delphi process. Twenty-eight expert clinicians, one researcher, and 13 caregivers from 16 countries participated in the subsequent three survey rounds. We defined consensus as follows: strong consensus, ≥80% fully agree; moderate consensus, ≥80% fully/partially agree, <10% disagree; and modest consensus, 67%-79% fully/partially agree, <10% disagree. RESULTS: Early diagnosis is important for long-term clinical outcomes in SCN8A-related disorders. There are five phenotypes: three with early seizure onset (severe developmental and epileptic encephalopathy [DEE], mild/moderate DEE, self-limited (familial) infantile epilepsy [SeL(F)IE]) and two with later/no seizure onset (neurodevelopmental delay with generalized epilepsy [NDDwGE], NDD without epilepsy [NDDwoE]). Caregivers represented six patients with severe DEE, five mild/moderate DEE, one NDDwGE, and one NDDwoE. Phenotypes vary by age at seizures/developmental delay onset, seizure type, electroencephalographic/magnetic resonance imaging findings, and first-line treatment. Gain of function (GOF) versus loss of function (LOF) is valuable for informing treatment. Sodium channel blockers are optimal first-line treatment for GOF, severe DEE, mild/moderate DEE, and SeL(F)IE; levetiracetam is relatively contraindicated in GOF patients. First-line treatment for NDDwGE is valproate, ethosuximide, or lamotrigine; sodium channel blockers are relatively contraindicated in LOF patients. SIGNIFICANCE: This is the first-ever global consensus for the diagnosis and treatment of SCN8A-related disorders. This consensus will reduce knowledge gaps in disease recognition and inform preferred treatment across this heterogeneous disorder. Consensus of this type allows more clinicians to provide evidence-based care and empowers SCN8A families to advocate for their children.

Population-based study of rare epilepsy incidence in a US urban population.

OBJECTIVE: This study was undertaken to estimate incidence of rare epilepsies and compare with literature. METHODS: We used electronic health record text search to identify children with 28 rare epilepsies in New York City (2010-2014). We estimated cumulative incidence and compared with literature. RESULTS: Eight of 28 rare epilepsies had five or more prior estimates, and our measurements were within the published range for all. The most common were infantile epileptic spasms syndrome (1 in 2920 live births), Lennox-Gastaut syndrome (1 in 9690), and seizures associated with tuberous sclerosis complex (1 in 14 300). Fifteen of 28 had fewer than five prior estimates, and of these, we provided additional estimates for early infantile developmental and epileptic encephalopathy (1 in 32 700), epilepsy with myoclonic-atonic seizures (1 in 34 100), Sturge-Weber syndrome plus seizures/epilepsy (1 in 40 900), epilepsy in infancy with migrating focal seizures (1 in 54 500), Aicardi syndrome plus seizures/epilepsy (1 in 71 600), hypothalamic hamartoma with seizures (1 in 225 000), and Rasmussen syndrome (1 in 450 000). Five of 28 rare epilepsies had no prior estimates, and of these, we provided a new estimate for developmental/epileptic encephalopathy with spike-and-wave activation in sleep and/or continuous spikes and waves during sleep (1 in 34 100). Data were limited for the remaining 12 rare epilepsies, which were all genetic epilepsies, including PCDH19, CDKL5, Alpers disease, SCN8A, KCNQ2, SCN2A, GLUT1 deficiency, Phelan-McDermid syndrome, myoclonic epilepsy with ragged-red fibers, dup15q syndrome, ring chromosome 14, and ring chromosome 20. SIGNIFICANCE: We estimated the incidence of rare epilepsies using population-based electronic health record data and literature review. More research is needed to better estimate the incidence of genetic epilepsies with nonspecific clinical features. Electronic health records may be a valuable data source for studying rare epilepsies and other rare diseases, particularly as genetic testing becomes more widely adopted.

Clinical phenotypes of developmental and epileptic encephalopathy-related recurrent KCNH5 missense variant p.R327H in Chinese children.

KCNH5 gene encodes for the voltage-gated potassium channel protein Kv10.2. Here, we investigated the clinical features of developmental and epileptic encephalopathy (DEE) in five Chinese pediatric patients with a missense mutation (p.R327H) in KCNH5 gene. These patients had undergone video EEG to evaluate background features and epileptiform activity, as well as 3.0 T MRI scans for structural analysis and intelligence assessments using the Gesell Developmental Observation or Wechsler Intelligence Scale for Children. Seizure onset occurs between 4 and 10 months of age, with focal and generalized tonic-clonic seizures being common. Initial EEG findings showed multiple multifocal sharp waves, sharp slow waves or spike slow waves, and spike waves. Brain MRI revealed widened extracerebral space in only one patient. Mechanistically, the KCNH5 mutation disrupts the two hydrogen bonds between Arg327 and Asp304 residues, potentially altering the protein's structural stability and function. Almost 80 % of patients receiving add-on valproic acid (VPA) therapy experienced a reduction in epileptic seizure frequency. Altogether, this study presents the first Chinese cohort of pediatric DEE patients with the KCNH5 p.R327H mutation, highlighting focal seizures as the predominant seizure type and incomplete mutation penetrance. Add-on VPA therapy was likely effective in the early stages of DEE pathogenesis.

Clinical and genetic analysis of 18 patients with KCNQ2 mutations from South China.

BACKGROUND: We aimed to delineate the genotype and phenotype of patients with KCNQ2 mutations from South China. METHODS: Clinical manifestations and characteristics of KCNQ2 mutations of patients from South China were analyzed. Previous patients with mutations detected in this study were reviewed. RESULTS: Eighteen epilepsy patients with KCNQ2 mutations, including seven self-limited neonatal epilepsy (SeLNE), two self-limited infantile epilepsy (SeLIE) and nine developmental and epileptic encephalopathy (DEE) were enrolled. The age of onset (p=0.006), mutation types (p=0.029), hypertonia (p=0.000), and seizure offset (p=0.029) were different in self-limited epilepsy (SeLE) and DEE. De novo mutations were mainly detected in DEE patients (p=0.026). The mutation position, EEG or the age of onset were not predictive for the seizure or ID/DD outcome in DEE, while the development of patients free of seizures was better than that of patients with seizures (p=0.008). Sodium channel blockers were the most effective anti-seizure medication, while the age of starting sodium channel blockers did not affect the seizure or development offset. We first discovered the seizure recurrence ratio in SeLNE/SeLIE was 23.1% in South China. Four novel mutations (c.790T>C, c.355_363delGAGAAGAG, c.296+2T>G, 20q13.33del) were discovered. Each of eight mutations (c.1918delC, c.1678C>T, c.683A>G, c.833T>C, c.868G>A, c.638G>A, c.997C>T, c.830C>T) only resulted in SeLE or DEE, while heterogeneity was also found. Six patients in this study have enriched the known phenotype caused by the mutations (c.365C>T, c.1A>G, c.683A>G, c.833T>C, c.830C>T, c.1678C>T). CONCLUSION: This research has expanded known phenotype and genotype of KCNQ2-related epilepsy, and the different clinical features of SeLE and DEE from South China.

Expanded clinical phenotype spectrum correlates with variant function in SCN2A-related disorders.

SCN2A-related disorders secondary to altered function in the voltage-gated sodium channel Nav1.2 are rare, with clinically heterogeneous expressions that include epilepsy, autism and multiple severe to profound impairments and other conditions. To advance understanding of the clinical phenotypes and their relationship to channel function, 81 patients (36 female, 44%, median age 5.4 years) with 69 unique SCN2A variants were systematically phenotyped and their Nav1.2 channel function systematically assessed. Participants were recruited through the FamileSCN2A Foundation. Primary phenotype (epilepsy of neonatal onset, n = 27; infant onset, n = 18; and later onset n = 24; and autism without seizures, n = 12) was strongly correlated with a non-seizure severity index (P = 0.002), which was based on presence of severe impairments in gross motor, fine motor, communication abilities, gastrostomy tube dependence and diagnosis of cortical visual impairment and scoliosis. Non-seizure severity was greatest in the neonatal-onset group and least in the autism group (P = 0.002). Children with the lowest severity indices were still severely impaired, as reflected by an average Vineland Adaptive Behavior composite score of 49.5 (>3 standard deviations below the norm-referenced mean of the test). Epileptic spasms were significantly more common in infant-onset (67%) than in neonatal (22%) or later-onset (29%) epilepsy (P = 0.007). Primary phenotype was also strongly correlated with variant function (P < 0.0001); gain-of-function and mixed function variants predominated in neonatal-onset epilepsy, shifting to moderate loss of function in infant-onset epilepsy and to severe and complete loss of function in later-onset epilepsy and autism groups. Exploratory cluster analysis identified five groups, representing: (i) primarily later-onset epilepsy with moderate loss-of-function variants and low severity indices; (ii) mostly infant-onset epilepsy with moderate loss-of-function variants but higher severity indices; and (iii) late-onset and autism only, with the lowest severity indices (mostly zero) and severe/complete loss-of-function variants. Two exclusively neonatal clusters were distinguished from each other largely on non-seizure severity scores and secondarily on variant function. The relationship between primary phenotype and variant function emphasizes the role of developmental factors in the differential clinical expression of SCN2A variants based on their effects on Nav1.2 channel function. The non-seizure severity of SCN2A disorders depends on a combination of the age at seizure onset (primary phenotype) and variant function. As precision therapies for SCN2A-related disorders advance towards clinical trials, knowledge of the relationship between variant function and clinical disease expression will be valuable for identifying appropriate patients for these trials and in selecting efficient clinical outcomes.

Identification of a Novel Homozygous GLS Gene Variant Associated with Developmental and Epileptic Encephalopathy (DEE) Type 71.

Developmental and epileptic encephalopathy (DEEs) (OMIM#618,328) is characterized by seizures, hypotonia, and brain abnormalities, often arising from mutations in genes crucial for brain function. Among these genes, GLS stands out due to its vital role in the central nervous system (CNS), with homozygous variants potentially causing DEE type 71. Using Whole Exome Sequencing (WES) on a patient exhibiting symptoms of epileptic encephalopathy, we identified a novel homozygous variant, NM_014905.5:c.1849G > T; p.(Asp617Tyr), in the GLS gene. The 5-year-old patient, born to consanguineous parents, presented with developmental delay, encephalopathy, frequent seizures, and hypotonia. Sanger sequencing further validated the GLS gene variant in both the patient and his family. Furthermore, our bioinformatics analysis indicated that this missense variant could lead to alteration of splicing, resulting in the activation of a cryptic donor site and potentially causing loss of protein function. Our finding highlights the pathogenic significance of the GLS gene, particularly in the context of brain disorders, specifically DEE71.

Genotype-phenotype correlation in CLCN4-related developmental and epileptic encephalopathy.

CLCN4-related disorder is a rare X-linked neurodevelopmental condition with a pathogenic mechanism yet to be elucidated. CLCN4 encodes the vesicular 2Cl-/H+ exchanger ClC-4, and CLCN4 pathogenic variants frequently result in altered ClC-4 transport activity. The precise cellular and molecular function of ClC-4 remains unknown; however, together with ClC-3, ClC-4 is thought to have a role in the ion homeostasis of endosomes and intracellular trafficking. We reviewed our research database for patients with CLCN4 variants and epilepsy, and performed thorough phenotyping. We examined the functional properties of the variants in mammalian cells using patch-clamp electrophysiology, protein biochemistry, and confocal fluorescence microscopy. Three male patients with developmental and epileptic encephalopathy were identified, with differing phenotypes. Patients #1 and #2 had normal growth parameters and normal-appearing brains on MRI, while patient #3 had microcephaly, microsomia, complete agenesis of the corpus callosum and cerebellar and brainstem hypoplasia. The p.(Gly342Arg) variant of patient #1 significantly impaired ClC-4's heterodimerization capability with ClC-3 and suppressed anion currents. The p.(Ile549Leu) variant of patient #2 and p.(Asp89Asn) variant of patient #3 both shift the voltage dependency of transport activation by 20 mV to more hyperpolarizing potentials, relative to the wild-type, with p.(Asp89Asn) favouring higher transport activity. We concluded that p.(Gly342Arg) carried by patient #1 and the p.(Ile549Leu) expressed by patient #2 impair ClC-4 transport function, while the p.(Asp89Asn) variant results in a gain-of-transport function; all three variants result in epilepsy and global developmental impairment, but with differences in epilepsy presentation, growth parameters, and presence or absence of brain malformations.

Adolescent-onset epilepsy and deterioration associated with CAD deficiency: A case report.

INTRODUCTION: CAD (MIM*114010) encodes a large multifunctional protein with the enzymatic activity of the first three enzymes initiating and controlling the de novo pyrimidine biosynthesis pathway. Biallelic pathogenic variants in CAD cause the autosomal recessive developmental and epileptic encephalopathy 50 (MIM #616457) or CAD deficiency presenting with epilepsy, status epilepticus (SE), neurological deterioration and anemia with anisopoikilocytosis. Mortality is around 9% of patients, mainly related to the no use of its specific treatment with uridine. Majority of reported cases have an early onset during infancy, with some few starting later in childhood. CASE REPORT: Here we report a deceased female patient with CAD deficiency whose epilepsy started at 14 years. She showed a rapid neurologic deterioration including cognitive decline, electroencephalographic background slowing which later evolved to a fatal refractory SE and supra and infratentorial atrophy on neuroimaging. Anemia developed after SE onset. METHODS AND RESULTS: her post-mortem whole exome sequencing identified biallelic missense variants in CAD (NM_004341.5): c.[2944G > A];[5366G > A] p.[(Asp982Asn)];[(Arg1789Gln)]. Our review of twenty-eight reported cases (2015-2023) revealed an epilepsy age onset from neonatal period to 7 years and the SE prevalence of 46 %. DISCUSSION: With our case, we highlight the relevance of suspecting this treatable condition in older patients and in SE with no evident etiology.