Associated Disorders
The migration of cells from the ventricular zone to their intended destination and the success of their differentiation can be interrupted in many different ways, including interference with mechanical motors or an alteration of molecular signals that initiate movement, lead the cell in migration, and terminate its migration. The function of the molecules that affect migration are not confined to cell movement, overlapping considerably with the events associated with neurogenesis. As a result, neuronal migration syndromes are difficult to classify. The largest class of neuronal migration syndroms is lissencephaly. This includes a spectrum of simplified cortex ranging from agyria (a total absence of cortical convolutions) to pachygyria (broadened gyri) with unusually thick cortex.
Mis-migration of neurons can also result in Bilateral Periventricular Nodular Heterotopia, a disease recognized by neuronal heterotopia lining the lateral ventricles. Zellweger Syndrome is characterized by a cortical dysplasia similar to polymicrogyria of cerebral and cerebellar cortex, occasionally with pachygyria surrounding the Sylvian fissure, and focal/subependymal heterotopia. Kallmann syndrome is recognized by anosmia due to mental retardation, hypogonadism, and the failure of the olfactory bulb to develop.
Disorders of axonal projection and assembly are rarely pure, but closely related to neuronal migration genes. This notably includes agenesis of the corpus callosum.
Disturbances in the genesis of neural elements can result in cortical dysplasia. Examples include ectopic neurogenesis, microencephaly, and altered cell survival resulting in areas of hyperplasia, reduced apoptosis, and heterotopia.
Read more about this topic: Ganglionic Eminence
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