Mondo Description The term lissencephaly covers a group of rare malformations sharing the common feature of anomalies in the appearance of brain convolutions (characterised by simplification or absence of folding) associated with abnormal organisation of the cortical layers as a result of neuronal migration defects during embryogenesis.

Disease Ontology Description A congenital nervous system abnormality characterized by the absence of folds in the cerebral cortex and caused_by defective neuronal migration during the 12th to 24th weeks of gestation.