Neuronal migration disorders in man

A classification of neuronal migration disorders based on the gross morphol ogy of the disorder with subclassifications according to the cause of the u nderlying disorder as far as that is known is presented. Emphasis is on dis orders of the neocortex. The classical entities classical lissencephaly, co bblestone lissencephaly, polymicrogyria, neuronal heteropia within the whit e matter and leptomeningeal glial and glioneuronal heterotopia are describe d. Recent findings on the genetics of neuronal migration disorders are disc ussed. More subtle structural abnormalities such as cortical dysgenesis or dysplasia remain still more controversial as separate entities.