Epidermal naevus syndrome belongs to a group of neurocutaneous diseases conditioned by a developmental defects in the early period of embryonic development. The critical period is that of forming a neurocutaneous tube, migration of neuroblasts and period of developing cerebral vascularization and organogenesis. The defects of development in these periods are clinically manifested by dermal, cerebral, skeletal as well as organ abnormalities. The most frequent neurological clinical manifestation is epilepsy and mental retardation that usually have their correlate even in a MRI finding such as lissencephaly, heterotopia, dysplasia of the brain tissue and, very often, vascular anomalies. Dermal symptomatology is also usually various but always present. The report has presented four cases in which MRI findings showed the disturbed migration of neuroblasts as well as vascular dysplasia. These disorders are not so rare, however, they must be supposed especially in the diagnostics of the so-called idiopathic epilepsy and/or mental retardation.

        Key words: epidermal naevus syndrome, neurocutaneous diseases, idiopathic epilepsy, heterotopia