Since Dravet syndrome patients typically present with febrile seizures that then progress to spontaneous afebrile seizures, we model this progression by priming F1.Scn1a+/- mice with a hyperthermia-induced seizure at P18 and then measuring subsequent spontaneous seizure frequency (Fig 3B). Here, SCN1A is linked to encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.