SCN1A-related epilepsy is a spectrum of seizure disorders caused by pathogenic variants in SCN1A, the gene encoding the Nav1.1 voltage-gated sodium-channel alpha subunit. The spectrum ranges from relatively mild febrile-seizure disorders to severe developmental and epileptic encephalopathies such as Dravet syndrome.
This page covers the wider SCN1A spectrum. Dravet syndrome has its own dedicated page because its diagnostic and treatment implications are substantial.
One gene, many phenotypes
A pathogenic SCN1A variant does not automatically mean Dravet syndrome.
Recognised phenotypes include simple febrile seizures, febrile seizures plus, GEFS+, Dravet syndrome and other childhood epilepsies. Severity can vary even within the same family.
What SCN1A does
SCN1A encodes Nav1.1, a voltage-gated sodium channel highly expressed in inhibitory interneurons.
Many severe SCN1A epilepsies result from reduced Nav1.1 function, which disproportionately impairs inhibitory neuronal networks and increases network excitability.
Loss-of-function and gain-of-function
Classic Dravet syndrome is most commonly associated with loss-of-function mechanisms.
Rare SCN1A gain-of-function variants can produce different neurological phenotypes, sometimes with very early seizures, movement abnormalities or developmental impairment. Functional mechanism matters because medication response can differ.
Febrile seizures
At the milder end of the spectrum, some people have febrile seizures without persistent epilepsy.
Others develop febrile seizures plus, in which fever-associated seizures continue beyond the usual age or afebrile seizures occur.
GEFS+
SCN1A is one important cause of GEFS+, a familial spectrum in which different relatives can show different febrile and afebrile seizure phenotypes.
However, most GEFS+ should not be described as an SCN1A-only disorder because several other genes are involved.
Dravet syndrome
Dravet syndrome is the best-known severe SCN1A phenotype. It typically begins in infancy with prolonged febrile or afebrile hemiclonic or tonic-clonic seizures, followed later by additional seizure types and developmental slowing.
Not every child with an SCN1A variant meets Dravet syndrome criteria.
Other SCN1A phenotypes
SCN1A variants have also been reported in epilepsy with focal seizures, myoclonic-atonic epilepsy, infantile spasms and other developmental epilepsy phenotypes.
Clinical classification should therefore be based on the person’s actual syndrome, not the gene result alone.
Genetic testing
An SCN1A diagnosis is established by identifying a pathogenic or likely pathogenic variant that fits the phenotype.
Variants of uncertain significance should not be treated as proof of causation without additional genetic and clinical evidence.
De novo and inherited variants
Many severe Dravet-causing variants occur de novo, meaning they are new in the affected child.
Milder GEFS+ or febrile-seizure phenotypes are more often inherited, though exceptions occur.
Parental mosaicism
A parent can carry an SCN1A pathogenic variant in only a proportion of cells and have few or no symptoms.
This mosaicism can affect recurrence risk and is one reason genetic counselling remains important even when routine parental testing appears negative.
Medication implications
In classic SCN1A loss-of-function Dravet syndrome, chronic sodium-channel-blocking medicines such as carbamazepine and oxcarbazepine can worsen seizures.
That principle should not be automatically applied to every SCN1A phenotype. Rare gain-of-function disorders may respond differently, so treatment increasingly depends on both syndrome and molecular mechanism.
Precision medicine
SCN1A is a major target for emerging precision therapies, including approaches designed to increase functional Nav1.1 expression or modify gene regulation.
These therapies remain an active research area and are not yet a universal replacement for established antiseizure treatments.
Development and cognition
Cognitive outcome varies enormously across the spectrum.
People with mild febrile-seizure phenotypes may have normal development, while severe developmental encephalopathy can produce substantial intellectual, language, motor and behavioural impairment.
Why genotype alone is not prognosis
Variant type and location provide useful information, but they do not perfectly predict outcome.
Clinical phenotype, seizure burden, developmental trajectory and functional data all contribute to interpretation.
Worldwide access
SCN1A testing is increasingly available through epilepsy panels and genomic sequencing, but access remains unequal.
Where testing is unavailable, syndrome recognition—especially Dravet and GEFS+—still guides treatment and counselling.
The central point
SCN1A is a spectrum gene, not a synonym for Dravet syndrome. The same gene can be associated with mild febrile-seizure phenotypes, familial GEFS+ or severe developmental epilepsy, and treatment must match the actual phenotype and mechanism.
Related reading
Dravet Syndrome →
GEFS+ →
Genetics & Epilepsy →
Genetic Testing in Epilepsy →
Sources
Medical note: medication decisions should not be based on the gene name alone. Variant mechanism and clinical syndrome matter.
Evidence checked: September 2026.