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