Your browser does not support javascript:   Search for gard hereSearch for news-and-events here.


Genetic and Rare Diseases Information Center (GARD)

Print friendly version

Bilateral perisylvian polymicrogyria

Other Names for this Disease
  • CBPS
  • Congenital bilateral perisylvian syndrome
  • Perisylvian syndrome
  • Perisylvian syndrome, congenital bilateral
  • PMGX
More Names
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.


Newline Maker

What causes bilateral perisylvian polymicrogyria?

The exact cause of bilateral perisylvian polymicrigyria (BPP) is not completely understood. The symptoms and findings associated with the condition are believed to be due to improper development of the outer surface of the brain (cerebral cortex) during embryonic growth. The cerebral cortex, which is responsible for conscious movement and thought, normally consists of several deep folds (gyri) and grooves (sulci). However, in cases of BPP, newly developed embryonic cells (neuroblasts) fail to migrate to their destined locations in the outer portion of the brain (neuronal dysmigration). As a result, the cerebral cortex does not develop the normal number of cellular layers, and the deep grooves that normally develop on the sides of both cerebral hemispheres may form improperly, resulting in an abnormally increased number of folds that are unusually small (hence the name, bilateral perisylvian polymicrogyria).[1]

The condition appears to occur randomly for unknown reasons (sporadically) in the absence of a family history, in most cases. However, a few families have been reported in which more than one member has been affected.[1]

Specific non-genetic causes of polymicrogyria have been recognized, including exposure to cytomegalovirus infection (CMV) during pregnancy. Polymicrogyria has also been associated with certain complications in twin pregnancies.[2]
Last updated: 5/6/2011

  1. Perisylvian Syndrome, Congenital Bilateral. NORD. December 31, 2010; Accessed 5/6/2011.
  2. Cassandra L. Kniffin et al. POLYMICROGYRIA, BILATERAL PERISYLVIAN; BPP. OMIM. February 6, 2009; Accessed 5/6/2011.