There is some evidence from animal models of monogenic epilepsies that delivery of gene therapies (or other means of normalisation of target gene expression) after symptom onset can rescue the disease phenotype, including in mouse models of SCN1A-related Dravet syndrome [180], UBE3A-associated Angelman syndrome [181], and MECP2-associated Rett syndrome [182]. The gene discussed is SCN1A; the disease is encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.