[Neuronal migration disorders]

Neuronal migration disorders represent a group of congenital nervous system malformations that affect the process whereby millions of neuroectodermic cells move from germinal matrix to the loci, where they will reside for life. They produce important changes in cytoarchitecture, lamination and normal neuronal physiology, particularly in cerebral cortex. These disorders appear as sporadic cases, genetically determined or caused by external agents as infections, intoxications and radiations, etc. The better identified nosological entities include: schizencephaly, lissencephaly, pachygyria, polymicrogyria, neuronal heterotopias and agenesis of corpus callosum. Patients usually present early symptoms and signs of disease and epilepsy is a dominant manifestation. By means of studies of craneal computed tomography (CCT), magnetic resonance (MR), positron emission tomography (PET), single-photon emission computed tomography (SPECT) and immunohistochemical and Golgi studies (IHG), it has been recently shown that nervous system dysgenesis can be a frequent cause of many refractory epilepsies and epileptic syndromes considered as cryptogenic. When these disorders are associated with dismorphic stigmas, genetics syndromes such as Miller-Dieker, Zellweger and Aicardi should be suspected.