lissencephaly definition
MRI scan showing the characteristic smooth brain of an individual with 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 Î»Î¹ÏÏÏÏ lissos meaning smooth and encephalos meaning brain. 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.