SCN1A and encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy: The most severe and often life-limiting seizure disorders associated with SCN1A mutations include epileptic encephalopathies (EE) such as Dravet syndrome (DS, also known as severe myoclonic epilepsy in infancy), intractable childhood epilepsy with generalized tonic–clonic seizures (ICE-GTC), epilepsy of infancy with migrating focal seizures (EIMFS), and myoclonic astatic epilepsy (MAE)3,4.