Lissencephaly

In general, lissencephaly describes the shape of a brain as being smooth, as opposed to gyrified. This means that cortical fissures being less pronounced than, for instance, in the adult human brain (a condition known as pachygyria), or even totally absent (agyria).

In humans, lissencephaly represents a neurodevelopmental disorder due to disturbed neuronal migration during the development of the cerebral cortex, resulting in disturbed cortical connectivity.

In other mammals, particularly those with small brains, lissencephaly may be the normal state of an adult brain, as is the case with beavers, manatees and platypuses, for instance.