De novo loss-of-function mutations in the VGSC SCN1A (encoding Nav1.1 channels) are the main cause of Dravet syndrome (DS), a catastrophic early-life encephalopathy associated with prolonged and recurrent early-life febrile seizures (FSs), refractory afebrile epilepsy, cognitive and behavioral deficits, and a 15–20% mortality rate (Claes et al., 2001, 2009; Wallace et al., 2003; Lossin, 2009; Escayg and Goldin, 2010). This evidence concerns the gene SCN1A and Freeman-Sheldon syndrome.