In fact, SCN1A-associated epilepsies range from simple febrile seizures, to Generalized Epilepsy with Febrile Seizures (GEFS+; OMIM 604233; Escayg et al., 2000), an autosomal dominant epilepsy disorder associated to missense mutations, to Severe Myoclonic Epilepsy of Infancy (SMEI or Dravet syndrome, OMIM 607208; Dravet et al., 1992; Engel and International League Against Epilepsy [ILAE], 2001), a much more severe form of epilepsy often caused by mutations causing truncation or deletions of Nav1.1 channels. This evidence concerns the gene SCN1A and encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.