International SCN8A Alliance Logo

Understanding phenotypes is key for several reasons, most critically because it directly influences care strategies and family support plans. Below are essential insights that will guide you through the latest research on SCN8A phenotypes. Here, you can find links to detailed information about each of the 5 phenotypes.

SCN8A Phenotypes

An SCN8A phenotype refers to the unique set of symptoms and characteristics seen in individuals. These are caused by variations in the SCN8A gene, primarily affecting a child’s neurological development and function.

The spectrum of SCN8A-related disorders ranges from intense neurological challenges to milder, even temporary conditions, affecting each individual uniquely.

SCN8A phenotypes are categorized by two important characteristics gene variant and function type.

SCN8A phenotypes are categorized by two important characteristics gene variant and function type.

Variants are errors or changes within the SCN8A gene. These changes can disrupt how parts of brain cells called sodium channels are built and function, potentially leading to a wide range of health and developmental problems.

When talking about the SCN8A gene and how it works, the word “function” means – too much – or – too little – voltage, which causes the sodium channel gate to either stay open or closed. This issue with the sodium channel gate disrupts the sodium levels within the brain cells. Knowing the SCN8A function is critical in determining treatment, especially the use of medications.

Gain-of-Function (GOF) Variants

These variants typically cause the sodium channels gates to stay open. This can lead to seizures and other neurological problems.

Loss-of-Function (LOF) Variants

These variants typically prevent the sodium channels from opening properly. This can also lead to neurological problems and may present more mildly than GOF variants.

Important: While not common, some with SCN8A present with both GOF and LOF functions. This underscores the need to understand each SCN8A gene variant.


Severe DEE

Severe Developmental
& Epileptic Encephalopathy

Gain-of-Function

Mild/moderate Developmental &  Epileptic Encephalopathy

Gain-of-Function


SeL(F)IE

Self-Limited (Familial) Infantile Epilepsy


Gain-of-Function


NDD w/ GE

Neurodevelopmental Delay with Generalized Epilepsy

Loss-of-Function


NDD w/o Epilepsy

Neurodevelopmental Delay without Epilepsy


Loss-of-Function

Additional Information

  • Refinement of Phenotypes: Ongoing research needed to further define and differentiate phenotypes based on large cohorts and genotype-phenotype correlations.
  • Treatment Efficacy and Options: Expanding understanding of first-line and subsequent treatment options for complex cases, including those resistant to current first-line therapies.
  • Personalized Treatment Approaches: Importance of considering individual variant functions and potential mixed gain and loss-of-function scenarios.
  • Age of Onset: Varies significantly across phenotypes, from early months to years.
  • Seizure Types and EEG/MRI Findings: Differ across phenotypes; initial EEGs may be normal, becoming abnormal with the course of the condition. MRIs may show atrophy in severe cases.
  • Treatment Approaches: Tailored based on phenotype, with a strong emphasis on the distinction between gain-of-function and loss-of-function variants.

There are 5 distinct phenotypes of SCN8A-related disorders, varying in severity, age of onset, seizure types, and other clinical features.

  • Gain-of-Function Phenotypes (Early Seizure Onset):
    • Severe DEE
    • Mild/Moderate DEE
    • Self-Limited (Familial) Infantile Epilepsy (SeL(F)IE)
  • Loss-of-Function Phenotypes (Later or No Seizure Onset):
    • Neurodevelopmental Delay with Generalized Epilepsy (NDDwGE)
    • Neurodevelopmental Delay without Epilepsy (NDDwoE)
SCN8A Research

For Clinicians & Researchers

We are excited about collaboration. If you are interested in collaborating around SCN8A patient care and /or research for SCN8A-releated disorders, PLEASE let us know. We want to hear from you. Currently we work with over a dozen labs and leading SCN8A clinicians to advance the science of SCN8A.

Learn about the work of the Invitation only SCN8A Research Consortium meeting quarterly to share updates on ongoing work, share assets, and develop new collaborative projects [not sure if we’d open up an application process??]

Learn about the International SCN8A Registry, highlights of what’s been learned and how to collaborate/get access to registry data for planned research projects

Follow the public Facebook group where updates on our programs, research, and new findings from the SCN8A Registry are shared

Learn more about the Alliance’s Global Research Strategy and efforts to accelerate progress toward better treatments and outcomes – and how I might get involved

Be added to the periodic SCN8A Newsletter


SCN8A Diagnosis

SCN8A Phenotypes

SCN8A Treatment

Clinical Features

SCN8A Prognosis

Consensus Process

Important Information

IMPORTANT: While this consensus data provides new and valuable insights about best practices in the diagnosis and treatment of SCN8A, this is not medical advice. It can inform clinicians and caregivers alike in developing optimal treatment plans for each individual.

IMPORTANT: While this consensus data provides new and valuable insights about best practices in the diagnosis and treatment of SCN8A, this is not treatment advice. We encourage you and your doctor to visit our website for more details.