MCDs. Malformation of cortical developments are a frequent cause of intractable epilepsies and, if appropriate, surgical resection may be warranted. Malformations represent a wide range of cortical lesions resulting from derangements of normal intrauterine developmental processes affecting the formation of the cortical mantle. Polymicrogyria (PMG) is one of the most common malformations of cortical development. However, while somatic mutations affecting the mTOR pathway are a known cause of certain subtypes of MCD, the polymicrogyrias have remained elusive. The underlying cause remains unknown in more than 80% of cases and, if identified, may be due to a wide range of underlying genetic causes. In a recent publication, mosaic trisomy 1q was identified as a novel and relatively frequent cause of polymicrogyria, emphasizing the role of somatic mutation detection in malformation of cortical development. Continue reading →