Lissencephaly

Lissencephaly is a set of rare brain disorders where the whole or parts of the surface of the brain appear smooth. The word lissencephaly is derived from the Greek λισσός lissos meaning “smooth” and encephalos meaning “brain”.

The lissencephaly-pachygyria spectrum is a useful way to describe the spectrum of diseases that cause relative smoothness of the brain surface and includes:

agyria: no gyri

pachygyria: broad gyri

lissencephaly: smooth brain surface

It is caused by defective neuronal migration during the 12th to 24th weeks of gestation resulting in a lack of development of brain folds (gyri) and grooves (sulci).

It is a form of cephalic disorder. Terms such as agyria (no gyri) and pachygyria (broad gyri) are used to describe the appearance of the surface of the brain. Children with lissencephaly generally have significant developmental delays, but these vary greatly from child to child depending on the degree of brain malformation and seizure control. Life expectancy can be shortened, generally due to respiratory problems.