Lissencephaly

**Definition:** A smooth brain malformation of the CEREBRAL CORTEX resulting from the abnormal location of developing neurons during corticogenesis. It is characterized by an absence of normal convoluted indentations on the surface of the brain (agyria), or fewer and shallower indentations (pachygryia). There is a reduced number of cortical layers, typically 4 instead of 6, resulting in a thickened cortex, and reduced cerebral white matter that is a reversal of the normal ratio of cerebral white matter to cortex.

**Tree numbers:** - C10.500.507.450.499 - C16.131.666.507.450.499

**Synonyms:** - Lissencephalia