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Lissencephaly is a malformation of cortical development, where there is deficient gyration (folding) in the cerebral cortex, resulting in absent gyri (agyria) and/or broad simple gyri (pachygyria).

There are two major types of lissencephaly:

  • Classical lissencephaly (also known as type 1 lissencephaly), with reduced gyration and cerebral cortical thickening, this may occur in isolation or with other congenital abnormalities, for example as part of a 17p microdeletion - Miller-Dieker syndrome
  • Cobblestone lissencephaly (also known as type 2 lissencephaly), with reduced gyration and a nodular appearance to the cortex, is associated with structural abnormalities of the cerebellum and brainstem, and commonly occurs with eye and muscle involvement - Fukuyama congenital muscular dystrophy, muscle-eye-brain disease, and Walker-Warburg syndrome

Lissencephaly may co-occur with any of a large number of other structural brain abnormalities, such as abnormality in ventricular appearance, of the corpus callosum, of the septum pellucidum and hypoplasia of the pyramidal tracts

Clinical Context

Classical lissencephaly

The clinical presentation of classical lissencephaly depends on the extent of the malformation, and whether associated with other structural abnormalities within the brain, or with involvement of other systems. Epilepsy is present in nearly all individuals (more than 90%), often with onset of seizures in the first year of life. Developmental, cognitive and motor impairments are frequent and significant in most cases. Many children have bulbar difficulties that result in difficulty with feeding and respiratory function.

Cobblestone lissencephaly

The clinical presentation of cobblestone lissencephaly predominantly relates to the co-occurring severe congenital muscular dystrophy.

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