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DA: 401

Developmental anomaly information

Definition: Lissencephaly is part of a spectrum of brain malformations, which are referred to as the agyria pachygyria-band spectrum and are caused by abnormalities in neuronal migration, a critical process in brain development that leads to the gross appearance of a smooth brain.The malformed brain lacks the characteristic convolutions of the normal cerebral cortex and is abnormally thick.These disorders range from complete absence of folds (agyria) to milder forms such as subcortical band heterotopia or double cortex syndrome, a neurological disorder where the malformed brain has two distinct layers of cerebral cortex. In pachygyria, there are localized areas of abnormally large folds and, in general, it is less severe than agyria. Scientific research on mice and humans has revealed several important genes responsible for causing lissencephaly. Lissencephaly can be divided into two main subtypes. Type I, also known as classical lissencephaly, is distinguished by the smooth surface of the cerebral cortex and an abnormal four-layered cortex. Classical lissencephaly can be associated with abnormalities of the rest of the brain, including malformation of the corpus callosum or cerebellum. Lissencephaly can also be associated with other developmental abnormalities such as facial deformities in a syndrome known as the Miller-Dieker syndrome. Type II, or "cobblestone" lissencephaly, is characterized by a bumpy appearance of the abnormal surface of the brain. The cortex in Type II lissencephaly is completely abnormal and there are no distinguishable layers. This subtype tends to be associated with genetic syndromes affecting muscles, as in the Walker-Warburg syndrome.


  • Smooth brain

Developmental anomaly parent: Neuronal migration anomaly

Topology: Human body > Head and neck > Head > Cranium > Brain

System: Human body > Nervous system > Central nervous system > Brain

Developmental anomaly category: Malformation

Case records
Observed in MDB cases
Observed in combinaisons (MDB)
Observed in malformative diseases (MDB)
Associated genes in profile
Associated genes in malformative diseases
Associated chromosomal diseases
Associated signaling pathways
Associated developmental anomalies

Last modified: 2008-12-22 20:18:02 by farideh

Created: 2008-06-13 04:57:57 by jcfournet

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