Inclusion Criteria:

• Age between 6 and 60 months.
• Authorized representative (parent/caregiver) must be willing and able to give informed consent for participation in the study.
• Authorized representative (parent/caregiver) must be able to read and understand the consent form which will be in English.
• Subject and their parent/caregiver must be willing and able (in the Investigator’s opinion) to comply with all study requirements (including ability and willingness to comply with virtual visits).
• Subject must be male or female aged between 6 months and 60 months, inclusive, at the time of consent.
• Subject must have a confirmed SCN1A mutation, as demonstrated by genetic testing and enrollment will be decided by an Independent Adjudication Committee (IAC).
• Normal development prior to onset of first seizure as defined by the Centers for Disease Control and Prevention (CDC 2019).
• Onset of seizures, defined as first focal clonic/hemiclonic, generalized/focal tonic, generalized tonic-clonic/clonic, atonic/drop seizure, prolonged seizure, or status epilepticus, between age 3 and 15 months, inclusive, as confirmed by the IAC.
• Parent/caregiver must have completed seizure diary training.

Exclusion Criteria:

• Copy number variant of SCN1A, including SCN1A microdeletion, if affecting other genes as determined by the IAC.
• SCN1A mutation present on both alleles.
• Known pathogenic or clinically suspected mutation in a seizure-associated gene besides SCN1A, as determined by the IAC (including but not limited to SCN9A, CACNB4, etc.).
• Confirmed mutation in a gene besides SCN1A, as determined by the IAC, that is known to increase the severity of the seizure phenotype.
• Subject has a known gain-of-function mutation, as defined by functional studies, including: p.Thr226Met.
• History of notable developmental deficit that was evident prior to seizure onset, by physician report.
• Known central nervous system structural abnormality as found on magnetic resonance imaging or computed tomography scan of brain. Note: Prior scans may be used, and no new scan is required to confirm normal imaging.
• Repeated or prolonged (> 6 consecutive weeks) exposure to anti-epileptic drugs (AEDs) that are contraindicated in SCN1A-positive Dravet Syndrome, including sodium channel blockers, if deemed by the IAC to have affected the subject.