Severe myoclonic epilepsy of infancy (Dravet syndrome): Recognition and diagnosis in adults

There is a group of adult patients with intractable epilepsy and intellectual disability in whom no etiologic diagnosis has been established. Determining the etiology is important for treatment and family counseling. Many families carry a burden of blame related to mistaken beliefs about causation. Severe myoclonic epilepsy of infancy (SMEI; Dravet syndrome) was described in 1978(1) but has only recently been widely recognized among childhood epilepsy populations, sparked by the discovery of mutations in the neuronal sodium channel alpha 1 subunit (SCN1A) gene.(2,3) Patients with SMEI typically present with recurrent febrile hemiclonic or generalized status epilepticus at around age 6 months. Between ages 1 and 4, other seizure types appear, including myoclonic and partial seizures. Psychomotor development is normal in the first year and then slows. The epilepsy is often intractable, developmental outcome is poor, and death in childhood is not rare.(4) "Borderline SMEI" (SMEB) refers to cases lacking some of the typical features such as myoclonic seizures.(5) Although SMEI has a characteristic presentation in childhood, adults with SMEI are underrecognized. To date, there are few data on long-term evolution or the phenotype in adults.(6,7) This study was performed to delineate the adult phenotype of SMEI and SMEB.