Case series of early SCN1A-related developmental and epileptic encephalopathies

The clinical and genetic landscape of developmental and epileptic encephalopathies in Egyptian children

Developmental and epileptic encephalopathies (DEEs) are a heterogeneous group of epilepsies characterized by early-onset, refractory seizures associated with developmental regression or impairment, with a heterogeneous genetic landscape including genes implicated in various pathways and mechanisms. We retrospectively studied the clinical and genetic data of patients with genetic DEE who presented at two tertiary centers in Egypt over a 10-year period. Exome sequencing was used for genetic testing. We report 74 patients from 63 unrelated Egyptian families, with a high rate of consanguinity (58%). The most common seizure type was generalized tonic-clonic (58%) and multiple seizure types were common (55%). The most common epilepsy syndrome was early infantile DEE (50%). All patients showed variable degrees of developmental impairment. Microcephaly, hypotonia, ophthalmological involvement and neuroimaging abnormalities were common. Eighteen novel variants were identified and the phenotypes of five DEE genes were expanded with novel phenotype-genotype associations. Obtaining a genetic diagnosis had implications on epilepsy management in 17 patients with variants in 12 genes. In this study, we expand the phenotype and genotype spectrum of DEE in a large single ethnic cohort of patients. Reaching a genetic diagnosis guided precision management of epilepsy in a significant proportion of patients.

A Novel Case of SCN1A Mutation Presenting as Hyperkinetic Movement Disorder

SCN1A mutation is most often associated with Dravet syndrome, which is characterized by severe encephalopathy. One of the other presentations of SCN1A mutation is developmental and epileptic encephalopathy-6B (DEE6B). It is a severe neurodevelopmental disorder characterized by early-infantile seizure onset, profoundly impaired intellectual development, and a hyperkinetic movement disorder. Here we report a rare case of novel SCN1A mutation presenting as hyperkinetic movement disorder in the form of multifocal dystonia and parakinesia in a 12-year-old boy, which aggravated with the use of sodium channel blockers.

Impact of variant subtype on electro-clinical phenotype of Dravet syndrome- a South Indian cohort study

OBJECTIVE

We aimed to compare the electroclinical correlates of truncating and missense variants of SCN1A variants in children with Dravet syndrome (DS) and to determine phenotypic features in relation to variants identified and seizure outcomes.

METHODS

A single center prospective study was carried out on a South Indian cohort. Patients below 18 years of age who met the clinical criteria for DS who had undergone genetic testing and completed a minimum of one year follow up were included. We compared the differences in clinical profile, seizure outcome, developmental characteristics and anti-seizure medication (ASM) responsiveness profiles between patients with missense and truncating variants.

RESULTS

Out of a total of 3967 children with drug-resistant epilepsy during the period 2015-2021, 49 patients who fulfilled the inclusion criteria were studied. Thirty-seven had positive genetic tests, out of which 29 were SCN1A variants and 9 were other novel variants. The proportion of missense (14; 48.3%) and truncating SCN1A variants (15; 51.7%) was similar. A significant trend for developing multiple seizure types was noted among children with truncating variants (p = 0.035) and seizure freedom was more likely among children with missense variants (p = 0.042). All patients with truncating variants had ASM resistant epilepsy (p = 0.020). Developmental outcomes did not differ between the variant subtypes.

CONCLUSION

Our results show that children harbouring missense variants demonstrated a significantly lower propensity for multiple seizure subtypes and a higher proportion with seizure freedom. However developmental implications appear to be independent of variant subtype.

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.

Phenotypic features of epilepsy due to sodium channelopathies - A single center experience from India

Objectives

Nearly 40% of pediatric epilepsies have a genetic basis. There is significant phenotypic and genotypic heterogeneity, especially in epilepsy syndromes caused by sodium channelopathies. Sodium channel subunit 1A (SCN1A)-related epilepsy represents the archetypical channel-associated gene that has been linked to a wide spectrum of epilepsies of varying severity. Subsequently, other sodium channels have also been implicated in epilepsy and other neurodevelopmental disorders. This study aims to describe the phenotypes in children with sodium channelopathies from a center in Southern India.

Materials and Methods

This is a retrospective, descriptive, and single-center study. Out of 112 children presenting with epilepsy who underwent genetic testing between 2017 and 2021, 23 probands (M: F = 12:11) were identified to have clinically significant sodium channel mutations. Clinical presentation, electroencephalography, and imaging features of these patients were recorded. The utility of genetic test results (e.g., in planning another child, withdrawal of medications, or change in treatment) was also recorded.

Results

Age at onset of seizures ranged from day 4 of life to 3.5 years. Clinical epilepsy syndromes included generalized epilepsy with febrile seizures plus (n = 3), Dravet syndrome (n = 5), early infantile epileptic encephalopathy (n = 7), drug-resistant epilepsy (n = 5), and epilepsy with associated movement disorders (n = 3). The most common type of seizure was focal with impaired awareness (n = 18, 78.2%), followed by myoclonic jerks (n = 8, 34.78%), epileptic spasms (n = 7, 30.4%), bilateral tonic-clonic seizures/generalized tonic-clonic seizures (n = 3, 13%), and atonic seizures (n = 5, 23.8%). In addition to epilepsy, other phenotypic features that were discerned were microcephaly (n = 1), cerebellar ataxia (n = 2), and chorea and dystonia (n = 1).

Conclusion

Sodium channelopathies may present with seizure phenotypes that vary in severity. In addition to epilepsy, patients may also have other clinical features such as movement disorders. Early clinical diagnosis may aid in tailoring treatment for the given patient.