Abnormalities in the process of neuronal migration during embryogenesis result in CNS structures that are dysfunctional, architecturally abnormal, or totally absent. Several distinct mechanisms can be operative in the pathogenesis of clinical disorders related to disrupted neuronal migration. Some neuronal migrational disorders are heritable, and others are presumed to be the result of ischemic, toxic, or metabolic damage during the perinatal period.
Cortical Neurons in Neuronal Migration Disorders
The most common neuronal migration abnormalities involve the neocortex. In humans, normal neuronal migration to the cerebral cortex takes place mostly during the 8th to the 24th week of gestation. Neurons originating deep in the brain along the surface of the ventricles migrate to the cortex along a network of extensions of glial cells known as radial glia. The first neurons to arrive populate the deepest layer of the cortex, and successive groups of arriving cells occupy progressively more...