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Phenotypic features of epilepsy due to sodium channelopathies - A single center experience from India
Lakshminarayanapuram Gopal Viswanathan1, Sandhya Alapati1, Madhu Nagappa1
1Department of Neurology, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India.
Insights
Genetic mutations in sodium channels cause a spectrum of pediatric epilepsies, often with diverse seizure types and additional neurological features. Early diagnosis of these sodium channelopathies is crucial for effective treatment and management.
Area of Science:
- Genetics
- Neurology
- Pediatrics
Background:
- Nearly 40% of pediatric epilepsies have a genetic origin, with significant heterogeneity in genetic and phenotypic presentations.
- Sodium channelopathies, particularly those involving SCN1A, are a key genetic cause of epilepsy syndromes with varying severity.
- Other sodium channel genes are increasingly implicated in epilepsy and neurodevelopmental disorders.
Purpose of the Study:
- To characterize the clinical and genetic phenotypes of sodium channelopathies in children with epilepsy.
- To describe the spectrum of epilepsy syndromes and associated features in affected pediatric patients.
- To evaluate the utility of genetic testing in managing pediatric epilepsy cases.
Main Methods:
- A retrospective, descriptive, single-center study of 112 children with epilepsy who underwent genetic testing from 2017 to 2021.
- Identification of 23 probands with clinically significant sodium channel mutations.
- Recording of clinical presentation, electroencephalography, imaging, and the impact of genetic test results on patient management.
Main Results:
- The age at seizure onset ranged from the neonatal period to 3.5 years.
- Identified epilepsy syndromes included Dravet syndrome, early infantile epileptic encephalopathy, and drug-resistant epilepsy.
- Focal impaired awareness seizures were most common (78.2%), with other features including movement disorders, microcephaly, and cerebellar ataxia.
Conclusions:
- Sodium channelopathies present a diverse range of seizure phenotypes and can be associated with non-epileptic clinical features like movement disorders.
- Early clinical diagnosis is essential for optimizing patient treatment strategies.
- Genetic analysis plays a vital role in understanding and managing pediatric epilepsy.
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.
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