The ENVISION study has generated a robust data set that shows consistency in the seizure and non-seizure manifestations of SCN1A+ Dravet syndrome.

This is a multicenter, prospective, 2-year observational study in infants and children with developmental and epileptic encephalopathies (DEEs). The DEE currently being investigated is SCN1A-positive Dravet Syndrome.

This prospective, longitudinal, natural history master protocol has been designed to define the seizure, neurodevelopmental, and behavioral characteristics of SCN1A-positive Dravet Syndrome in infants and children between 6 and 60 months. It will also explore the impact of the disease on the participant's parent/caregiver quality of life (QoL) and healthcare resource utilization (HCRU).

Inclusion Criteria:

• Aged between 6 months and 60 months.
• Confirmed SCN1A mutation.
• Normal development prior to onset of first seizure as defined by the Centers for Disease -Control and Prevention (CDC 2019).
• Onset of seizures between age 3 and 15 months, inclusive.

Exclusion Criteria:

• Copy number variant of SCN1A, including SCN1A microdeletion, if affecting other genes.
• SCN1A mutation present on both alleles.
• Known pathogenic or clinically suspected mutation in a seizure-associated gene besides SCN1A.
• Confirmed mutation in a gene besides SCN1A that is known to increase the severity of the seizure phenotype.
• Known gain-of-function genetic mutation, as defined by functional studies, including p.Thr226Met.
• History of notable developmental deficit that was evident prior to seizure onset.
• Known central nervous system structural abnormality as found on magnetic resonance imaging or computed tomography scan of brain.
• Currently taking or has taken for 6 or more consecutive weeks anti-seizure medications (ASMs) at a therapeutic dose that are contraindicated in SCN1A-positive Dravet Syndrome, including sodium channel blockers.
• Known concomitant genetic mutation or clinical comorbidity that potentially confounds typical Dravet phenotype.

Infants and children aged between 6 and 60 months with SCN1A-positive Dravet Syndrome.

Plan is undecided