RÉSUMÉ
Abstract Epilepsy is a common manifestation of mitochondrial disease. In a large cohort of children and adolescents with mitochondrial disease (n = 180), over 48% of patients developed seizures. The majority (68%) of patients were younger than 3 years and medically intractable (90%). The electroencephalographic pattern of multiregional epileptiform discharges over the left and right hemisphere with background slowing occurred in 62%. The epilepsy syndrome, infantile spasms, was seen in 17%. Polymerase ? mutations were the most common genetic etiology of seizures, representing Alpers-Huttenlocher syndrome (14%). The severity of disease in those patients with epilepsy was significant, as 13% of patients experienced early death. Simply the loss of energy production cannot explain the development of seizures or all patients with mitochondrial dysfunction would have epilepsy. Until the various aspects of mitochondrial physiology that are involved in proper brain development are understood, epilepsy and its treatment will remain unsatisfactory.