Loss or gain-of-function mutations of SCN1A, encoding for the α subunit of the voltage-gated sodium channel Nav1.1, are both associated with a spectrum of seizure-related disorders in humans, which ranges from a relatively milder form of febrile seizures to a more severe epileptic condition known as Dravet syndrome (DS), previously named severe myoclonic epilepsy of infancy (SMEI). This evidence concerns the gene SCN1A and Dravet syndrome.