Abnormalities in the development of the cerebral cortex. These include malformations arising from abnormal neuronal and glial cell proliferation or apoptosis (Group I); abnormal neuronal migration (Group ii); and abnormal establishment of cortical organization (Group iii). Many inborn metabolic brain disorders affecting cns formation are often associated with cortical malformations. They are common causes of epilepsy and developmental delay. [ http://id.nlm.nih.gov/mesh/D054220 ]