SCN1A and encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy: Furthermore, Dravet syndrome, one of the most severe forms of childhood epilepsy, is caused by mutations in SCN1A encoding Nav1.1 [reviewed in (Eijkelkamp et al., 2012)], or a mutation in SCN1B encoding Nav channel β1 subunit (Patino et al., 2009).