Polymicrogyria is a condition characterized by abnormal development of the brain before birth. The surface of the brain normally has many ridges or folds, called gyri. In people with polymicrogyria, the brain develops too many folds, and the folds are unusually small. The name of this condition literally means too many (poly-) small (micro-) folds (-gyria) in the surface of the brain.

In most people with polymicrogyria, the cause of the condition is unknown. However, researchers have identified several environmental and genetic factors that can be responsible for the disorder. Environmental causes of polymicrogyria include certain infections during pregnancy and a lack of oxygen to the fetus (intrauterine ischemia).

The prevalence of isolated polymicrogyria is unknown. Researchers believe that it may be relatively common overall, although the individual forms of the disorder (such as bilateral generalized polymicrogyria) are probably rare.

Isolated polymicrogyria can have different inheritance patterns. Several forms of the condition, including bilateral frontoparietal polymicrogyria (which is associated with mutations in the ADGRG1 gene), have an autosomal recessive pattern of inheritance. In autosomal recessive inheritance, both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Published Date: June 01, 2009
Published By: National Institutes of Health