Epilepsy in 9 (22%) of 37 members of a family with maternally inherited mitochondrial disease is reported from the Department of Neurology, University Hospital, Tromsö, Norway. The epilepsy began in infancy or childhood in 3 patients and during adult life in the remainder. The different clinical expressions of epilepsy in the family were myoclonus, partial epilepsy and generalized tonic-clonic seizures. The neuropsychiatric disorders included intellectual deterioration, muscle weakness, pigmental retinal degeneration, progressive hearing loss, cerebellar ataxia and in 1 patient a hemiplegia and paranoid psychosis. The CT scan showed cerebral atrophy, cerebellar atrophy and calcification in the basal ganglia. The EEG abnormalities included slowing and spikes, sometimes focal, and a bilateral paroxysmal response to photic stimulation. A muscle biopsy from the proband revealed a mild defect in the NADH-ubiquinone oxidoreductase step (complex 1) in the respiratory chain. 
COMMENT. The various clinical manifestations of epilepsy including partial motor and/or complex partial epilepsy in different branches of this family were remarkable and worthy of publication. The authors postulate that mitochondrial dysfunctions may be the cause of some epileptic syndromes of undetermined etiology.