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SCN8A-related epilepsy with encephalopathy
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

SCN8A-Related Epilepsy with Encephalopathy

SCN8A-related epilepsy with encephalopathy is a severe infantile-onset condition marked by recurrent, often treatment-resistant seizures, cognitive decline, and developmental challenges.

Overview

SCN8A-related epilepsy with encephalopathy is a condition characterized by recurrent seizures (epilepsy), abnormal brain function (encephalopathy), and intellectual disability. The signs and symptoms of this condition typically begin in infancy.

Symptoms

The clinical features of this condition involve a combination of neurological and developmental challenges:

Seizure Types

Most individuals with this condition experience more than one type of seizure. The frequency of seizures can range from hundreds per day to fewer than one per month. In many individuals, the seizures are described as refractory because they do not respond to therapy with anti-epileptic medications. Seizure types include:

  • Infantile spasms: Involuntary muscle contractions that occur before age 1
  • Absence seizures: Partial or complete loss of consciousness
  • Myoclonic seizures: Involuntary muscle twitches
  • Tonic-clonic seizures: Loss of consciousness accompanied by muscle rigidity and convulsions

Developmental and Behavioral Features

  • Intellectual disability ranging from mild to severe
  • Developmental regression and cognitive decline: Some infants experience normal early development but begin to lose previously acquired skills and thinking abilities once epilepsy develops
  • Movement problems: These are common, and about half of affected infants are unable to perform intentional movements
  • Behavior disorders
  • Sudden unexpected death in epilepsy (SUDEP): In rare cases, individuals with this condition may die unexpectedly for no known reason

Frequency

There are at least 140 individuals identified with this condition. It is estimated to account for approximately 1 percent of all cases of epilepsy with encephalopathy.

Causes

This condition is caused by mutations in the SCN8A gene. This gene provides instructions for making the alpha subunit of a sodium channel called Nav1.6. This channel allows positively charged sodium ions to pass into nerve cells (neurons) and plays a key role in the ability of neurons to generate and transmit electrical signals for communication.

The mutations in the SCN8A gene result in altered Nav1.6 channels that remain open longer than usual, increasing the flow of sodium ions into neurons. This persistent opening abnormally increases electrical signals, leading to excess activation (excitation) of neurons in the brain, which causes seizures.

It is currently unknown how these mutations lead to intellectual disability, movement problems, and other non-seizure features of the condition. While some children experience developmental regression after the onset of seizures, suggesting that seizures may impair brain function, this relationship remains unclear.

Associated Genes

  • SCN8A

Inheritance

This condition is inherited in an autosomal dominant pattern, meaning one copy of the altered gene in each cell is sufficient to cause the disorder.

Most cases of this condition result from new (de novo) mutations in the gene that occur during the formation of reproductive cells (eggs or sperm) or during early embryonic development. These cases occur in individuals with no history of the disorder in their family.

Other Names for This Condition

  • Early infantile epileptic encephalopathy 13
  • EIEE13
  • SCN8A encephalopathy

Frequently Asked Questions

First‑line options include high‑dose valproate, levetiracetam, or topiramate, but many patients remain refractory. Alternative approaches such as the ketogenic diet, responsive neurostimulation, or vagus‑nerve stimulation have shown benefit in some cases. Emerging research on sodium‑channel blockers (e.g., phenytoin, carbamazepine) and targeted gene‑silencing therapies is ongoing, but these remain experimental.
Early intervention programs that incorporate speech, occupational, and physical therapy can help maintain communication and motor skills. Structured routines, visual schedules, and sensory‑friendly environments support learning. Behavioral strategies, including positive reinforcement and consistent discipline, can mitigate aggression or anxiety. Regular neuropsychological assessments guide individualized educational plans and monitor progress.
DNA test from a blood sample identifies pathogenic variants in the SCN8A gene. The mutation is typically de‑novo, meaning it arises spontaneously, so the recurrence risk for future pregnancies is low (about 1–2%). However, if a parent carries a germline mosaic mutation, the risk could be higher. Genetic counseling is advised for families considering additional children.
Infantile spasms present as sudden, brief contractions of the neck, trunk, or limbs, often occurring in clusters. Absence seizures involve brief lapses in awareness, usually with a staring spell. Myoclonic seizures are rapid, involuntary twitches, while tonic‑clonic seizures involve loss of consciousness with muscle rigidity and convulsions. Video‑EEG monitoring is the gold standard for distinguishing these types and confirming the diagnosis.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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