[Cortical dysgenesis: current classification, MRI diagnosis, and clinical review]

Cortical dysgenesis comprises a heterogenous group of genetic or acquired disturbances of cortical development which, due to progress in modern neuroimaging techniques, are increasingly recognized in association with a variety of clinical disorders. The spectrum of clinical manifestations, depending on type and extent of the alterations, includes severe mental retardation and epilepsy as well as neuropsychological deficits and psychiatric disorders. Up to now, the nomenclature of cortical malformations has been difficult and ambiguous. Recently, the understanding and terminology of these disorders has been facilitated by the proposal of a new classification scheme based on pathophysiological as well as pathogenetic mechanisms. This proposal has been elaborated by a group of experts and is not yet well-known in the German literature. Magnetic resonance imaging (MRI) allows diagnosis and classification in many cases of cortical dysgenesis during lifetime, thereby helping to identify prognostic and therapeutic options. Early diagnosis of cortical malformations is of particular importance in patients with drug-resistant epilepsy, as they can either be cured or benefit from epilepsy surgery. This review gives examples of the most relevant cortical malformations using the new classification scheme and summarizes their clinical as well as MRI characteristics. Besides routine MRI applications, some experimental techniques are discussed which may help to identify even subtle alterations.