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Cortical Malformations
Other cortical malformations
Polymicrogyria (PMG): this may also be a neuronal migration disorder, but the exact nature of the condition is unclear. It is likely to be more common than lissencephaly. PMG is characterised by more frequent and smaller convolutions on the surface of the brain. It often appears in distinct patterns, and the most common is Perisylvian Polymicrogyria. Intrauterine infection (cytomegalovirus - CMV) is a known cause for PMG; intrauterine hypoperfusion has also been implicated. Familial occurrences and association with a number of different chromosome anomalies also point to a genetic aetiology in some cases. PMG is associated with a number of different chromosome anomalies; 22q11 deletions are the most common. A rare form of PMG has been associated with mutations in the GPR56 gene; causes for a number of syndromes with PMG as a feature have also be identified (Goldberg-Shprintzen syndrome (see entry), Joubert syndrome (see entry))
Schizencephaly (SCH): this describes a cleft from the cerebral cortex to ventricle, usually lined with polymicrogyria. The causes for SCH are thought to be similar to PMG; familial occurrences appear uncommon.
Congenital microcephaly and cortical malformations: Lissencephaly, polymicrogyria, or simplified (not fully formed) gyri (SG) can also be seen in association with severe congenital microcephaly (very, very small head at birth). In these conditions autosomal recessive inheritance has been observed The general term 'Microlissencephaly' is often used, but is unfortunately inadequate to describe the variation in cortical anomalies mentioned above (like PMG and SG).
Related neuronal migration disorders
| Inheritance patterns and prenatal diagnosis 
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