Martin et al. showed that double heterozygous mice for both Scn1a and Scn8a had a higher threshold for drug-induced seizures and outlived heterozygous Scn1a only mice, suggesting Scn8a acts as a genetic modifier in Scn1a mouse model of Dravet syndrome [74]. This evidence concerns the gene SCN8A and encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.