What is Polymicrogyria?

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 polymicrogyria, the brain develops too many folds, and the folds are unusually small. The name of this condition means too many (poly-) small (micro-) folds (-gyria) in the surface of the brain.

Polymicrogyria can affect part of the brain or the whole brain. When the condition affects one side of the brain it is described as unilateral. When it affects both sides of the brain, it is described as bilateral.

Polymicrogyria most often occurs as an isolated feature, although it can occur with other brain abnormalities. It is also a feature of several genetic syndromes characterized by intellectual disability and multiple birth defects. These include 22q11.2 deletion syndrome, Adams-Oliver syndrome, Aicardi syndrome, Galloway-Mowat syndrome, Joubert syndrome, and Zellweger spectrum.


The signs and symptoms associated with polymicrogyria depend on how much of the brain, and which particular brain regions, are affected. Bilateral forms of polymicrogyria tend to cause more severe neurological problems. Signs and symptoms can include recurrent seizures (epilepsy), delayed development, crossed eyes, problems with speech and swallowing, and muscle weakness or paralysis. The most severe form of the disorder, bilateral generalized polymicrogyria, affects the entire brain. This condition causes severe intellectual disability, problems with movement, and seizures that are difficult or impossible to control with medication.


Treatment is generally based on the manifestations of symptoms and may include physical therapy, pharmacologic management, orthotic devices, and surgery for those with spastic motor impairment; speech therapy for language impairment; occupational therapy for fine motor difficulties; antiepileptic drugs for seizures; assessment of educational needs and evaluations for speech, vision, and hearing difficulties in infancy and preschool years.


Individuals with milder forms of polymicrogyria survive into adulthood, while those with the most severe forms may die at a young age as a result of such complications as seizures or pneumonia.

1. Chang B, Walsh C, Apse K, Bodell A. Polymicrogyria Overview. Gene Reviews. August 6, 2007. http://www.ncbi.nlm.nih.gov/books/NBK1329/
2. Polymicrogyria. Genetics Home Reference (GHR). 2014; http://ghr.nlm.nih.gov/condition/polymicrogyria. Accessed 6/23/2014.