Department of Neuroradiology, Istituto Nazionale Neurologico C. Besta, Milan, Italy
Malformations of cortical development are classified on the basis of imaging features and stages of cortical development. They are grouped by causes of the malformation: abnormal glial and neuronal proliferation, abnormal neuronal migration and abnormal cortical organisation. Focal or multifocal and generalised forms are recognised in each of these groups. In the first group, generalised forms include microlissencephalies. Among focal‐multifocal abnormalities, neoplastic forms include ganglioglioma and dysembryoplastic neuroepithelial tumours. Non‐neoplastic forms include focal cortical dysplasia and tuberous sclerosis. Malformations due to abnormal migration include lissencephalies; cortical heterotopias are recognised in both focal and generalised forms. Abnormal cortical organisation includes polymicrogyria, in generalised or focal forms, and schizencephalies among the focal forms.