Ketogenic Diet vs.Antiepileptic Drug Treatment in Drug Resistant Epilepsy

Inclusion Criteria: * The patient is mentally retarded * The patient has tried at least 3 different AED:s including one combination with two or more different AED:s. * The parents are willing to include their child in the study after written and verbal information. * Patients with all types of epilepsy can be included. * The patient has at least 6 seizures/month. * The patient is submitted to our epilepsy center. * The seizures are possible to count * The patient has either generalized epilepsy, multifocal epilepsy or an epilepsy where it is undetermined whether it is localized or generalized such as Dravet syndrome classified as G40.3-G40.9 in ICD X. Exclusion Criteria: * The family is expected to have compliance problems with treatment and/or seizure registration. * The hospital which have submitted the patient is not willing to accept the inpatient stays and the procedures that are necessary for the project. * The patient's seizures are under acceptable control. * The patient has got a vagus nerve stimulator implanted within the last 18 months, has started a new antiepileptic drug within the last 2 months or has changed his antiepileptic drugs the last month. * The patient has a medical condition, for example a metabolic disease, where ketogenic diet is contraindicated. * The patient has a localized epilepsy classified as G40.0-G40.2 in ICD X. * The patient's nutritional status is not good enough or intake of fluid is to small to permit treatment with ketogenic diet. * The patient has within the last 2 months been using medications or herbal medications that has a considerable effect on glucose metabolism, such as oral glucocorticoids. * The patient has within the last 2 months been using medications or herbal medications that has a considerable effect on metabolism of AED:s. * The patient uses herbal medicine which can interact with AED or Ketogenic diet.