Heterozygous loss-of-function mutations in the Nav1.1 gene (SCN1A) are responsible for the development of the vast majority of Dravet syndrome cases, a severe early onset pediatric epilepsy coincident with cognitive impairment, deterioration of motor skills, and ataxia [110,111]. Here, SCN1A is linked to encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.