[Pachygyria and laminar heterotopic tissue. A rare case of unique expression of a neuronal migration disorder in twins].

We report of 16 year old twinsisters with a neuronal migration disorder, twin I with mental retardation and focal epileptic seizures on MRI showed general pachygyria, laminar subcortical heterotopia and mildly dilated lateral ventricles, whereas twin II whose first symptom was a cerebral seizure only showed a focal pachygyria and laminar subcortical heterotopia; the location of pachygyria corresponded to the epileptogenic focus. The morphological expression seems to correspond with the severeness of the clinical features. Genetic as well as exogenic factors must be assumed to be causative for the migration anomalies.