SCN8A-related disorders
A spectrum of SCN8A-related epilepsies — from severe early-infantile developmental and epileptic encephalopathy to milder familial epilepsies — with sodium-channel-blocker therapy as a precision-medicine anchor.
SCN8A encodes the voltage-gated sodium channel Naᵥ1.6, which is essential for normal neuronal firing. Pathogenic variants — most commonly gain-of-function — produce a wide phenotypic spectrum: early infantile developmental and epileptic encephalopathy (EIEE13), benign familial infantile epilepsy, intellectual disability without epilepsy, and intermediate phenotypes. Recognising the variant type (gain- vs loss-of-function) is critical, because it determines whether sodium-channel-blocker therapy is the right precision-medicine choice or potentially harmful.
At a glance
- Inheritance
- Autosomal dominant — most severe cases are de novo
- Gene
- SCN8A (12q13.13) — Naᵥ1.6 sodium channel
- Variant effect
- Gain-of-function (most), loss-of-function (some), with very different treatments
- Onset
- Typically 3–6 months for the severe phenotype
- Phenotype
- From severe DEE13 through intellectual disability to mild familial epilepsy
What SCN8A-related disorders are
SCN8A-related disorders sit on a wide spectrum. At the severe end, SCN8A-related developmental and epileptic encephalopathy (formerly EIEE13) presents in the first months of life with focal, tonic and tonic-clonic seizures, profound developmental impairment, dyskinetic movements, autonomic features and a high risk of SUDEP. At the milder end, gain-of-function variants can cause self-limited familial infantile epilepsy with normal development, or intellectual disability without epilepsy. The variant type drives the picture more than SCN8A involvement alone.
Distinguishing gain-of-function from loss-of-function variants is essential, because they require opposite treatment strategies. Gain-of-function variants (the majority) respond to sodium-channel blockers; loss-of-function variants may be made worse by them.
How the diagnosis is made
SCN8A is included in current epilepsy gene panels and is reliably picked up by whole-exome and whole-genome sequencing. Once a variant is identified, careful interpretation of its functional effect — using published functional data, predicted effect from the variant location, and emerging variant-specific functional assays — guides treatment. ClinGen variant curation and SCN8A-specific knowledge bases (e.g. the SCN8A Foundation registry) are useful resources.
EEG in severe cases typically shows multifocal epileptiform discharges; brain MRI is usually normal. Movement-disorder features (chorea, dystonia, dyskinesia) can be a clue to SCN8A even when seizures are not yet the dominant problem.
Treatment today
For gain-of-function variants, sodium-channel blockers — high-dose phenytoin, oxcarbazepine, carbamazepine and lacosamide in particular — are first-line and often produce a dramatic response, especially in the severe early-infantile presentation. This is one of the clearest examples of precision medicine in paediatric epilepsy today: the right drug class chosen on the basis of the gene and variant function.
For loss-of-function variants, sodium-channel blockers should generally be avoided. Treatment becomes individualised, often with valproate, levetiracetam, ketogenic diet and other generic options.
The full plan also includes neurodevelopmental support, swallowing and feeding assessment, movement-disorder management, autonomic-symptom care, and intensive family education on rescue medication and SUDEP risk reduction.
SCN8A is one of the clearest precision-medicine examples in paediatric epilepsy — but the right drug depends on the variant type. Confirm gain- vs loss-of-function with current functional data and your treating team before changing medicines.
Precision-medicine pipeline
Variant-specific antisense oligonucleotide (ASO) approaches to selectively reduce overactive Naᵥ1.6 are in preclinical and early clinical development for gain-of-function SCN8A disorders. Selective Naᵥ1.6 inhibitors are also being explored. The pipeline is being followed closely by patient organisations (the International SCN8A Alliance and others) and academic consortia.
How an educational review can help
SCN8A families face two big questions: what does this particular variant mean (gain- vs loss-of-function), and which precision-medicine options exist now and in the next few years? An educational review can pull together the variant-specific evidence, explain the medication strategy in plain language and prepare focused questions for the treating team.
It is educational — not a diagnosis, treatment or prescription — and does not replace the care of your child's own clinicians.
Selected sources
- Hammer MF et al. SCN8A-related epilepsy with encephalopathy. GeneReviews. Updated 2024.
- Johannesen KM et al. Genotype–phenotype correlations in SCN8A-related disorders. Brain. 2022;145:2991–3009.
- Wagnon JL, Meisler MH. Recurrent and non-recurrent mutations of SCN8A in epileptic encephalopathy. Front Neurol. 2015.
- Boerma RS et al. Remarkable phenytoin sensitivity in 4 children with SCN8A-related epilepsy. Neurotherapeutics. 2016.
- International SCN8A Alliance pipeline updates 2025–2026.
Last reviewed: 2026-05-28
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