Abstracts

Rationale: Voltage-gated sodium channel subunit gene (SCN1A) mutations in patients may result in widespread clinical symptoms with generalized epilepsy with febrile seizures plus (GEFS+) on the mildest end and severe myoclonic epilepsy of infancy (SMEI) on the severest end of the spectrum. The presence of myoclonic seizures and generalized tonic clonic seizures associated with fever in childhood are first clinical signs of both syndromes. Our study aims to reveal clinical key symptoms in childhood and in adulthood to provide a more adequate diagnostic procedure in adult patients having intractable myoclonic and tonic clonic seizures. Methods: We assessed 15 patients having myclonic seizures before the age of one year and/or, fever related tonic clonic seizures in early childhood. All patients developed intractable generalized seizures in adulthood. Blood samples to analyze SCN1A gene were collected. Clinical signs of patients in childhood and in adulthood were described. Results: In 8 patients we found a SCN1A mutation of which 5 had a ‘de novo’ mutation. All 15 patients had intractable epilepsy with tonic clonic and myoclonic seizures. Normal MRI was present in all patients. EEG’s in patients having SCN1A mutation showed > 50 % epileptic activity in 7 of 8 patients and 5 of 8 patients developed decrease of muscular strength. We saw developmental delay in all patients. In patients with no mutation of SCN1A gene 1 of 7 had ataxia, 5 of 7 had behavior problems and EEG’s showed > 50 % epileptic activity in 2 of 7 patients. 4 patients with SCN1A mutation were SIBS. Conclusions: In patients having intractable epilepsy that started in early childhood testing for SCN1A mutation is relevant. The combination of fever induced seizures in childhood, normal MRI, increase of movement disorders and > 50% epileptic activity in EEG may lead to diagnose SCN1A mutation.