Neuronal Migration Disorders Information Page
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What are Neuronal Migration Disorders?
Is there any treatment?
What is the prognosis?
What are Neuronal Migration Disorders?
Neuronal migration disorders (NMDs) are a group of disorders caused by the abnormal migration of nerve cells (neurons) very early in the development of the fetal nervous system. Neuronal migration is the process in which neurons move from their place of origin to their permanent location. When this process is disrupted, the result is a structurally abnormal brain involving the cerebral hemispheres, cerebellum, brainstem, and/or hippocampus.
NMDs may include: schizencephaly, porencephaly, lissencephaly, agyria, macrogyria, pachygyria, microgyria, micropolygyria, neuronal heterotopias (including band heterotopia), agenesis of the corpus callosum, and agenesis of the cranial nerves. These disorders may be associated with other abnormalities, including other NMDs. Symptoms vary and may include hypotonia (reduced muscle tone), seizures, developmental delay, mental retardation, growth failure, feeding difficulties, lymphedema (puffiness of the extremities because of poor fluid drainage), microcephaly, and motor dysfunction. NMDs may be associated with early death. Most individuals with NMDs have a normal physical appearance, however, there may be variations in facial appearance which can be noticed by trained professionals.
NMDs may be caused by genetic or biochemical abnormalities (e.g., Zellweger syndrome). Several genetic abnormalities have been identified, including a deletion of a gene on chromosome 17p13.3-which causes lissencephaly-and a mutation of a gene on chromosome Xq22.3,which causes lissencephaly in males and band heterotopia in females. The Reelin gene on chromosome 7q22 causes microcephaly, lissencephaly, cerebellar hypoplasia (small cerebellum), and lymphedema. Abnormalities on a number of other genes have been identified as the cause of NMDs, yet their roles in neuronal migration are not well-understood.
Is there any treatment?
Treatment is symptomatic, and may include anti-seizure medication and special or supplemental education consisting of physical, work-related, and speech therapies.
What is the prognosis?
The prognosis for individuals with NMDs varies depending on the specific disorder and the degree of neurological deficit and brain malformation.
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