 Individuals may also present with SMEI, characterized by generally tonic-clonic seizures, impaired psychomotor development, myoclonic seizures, ataxia, and poor response to many anticonvulsants.GEFS+ type 1 is a subtype of GEFS+ in which there are mutations in SCN1B, a gene encoding a sodium channel β subunit.The β subunit is required for proper channel inactivation.