Indeed, a possible manifestation of neuronal overmigration, cortical polymicrogyria (Squier & Jansen, 2014), is found in Weaver syndrome, which is caused by mutations in the EZH2 gene (Tatton-Brown et al, 2013), and in a neuroactive drug embryopathy, fetal hydantoin syndrome (Al-Shammri et al, 1992). This evidence concerns the gene EZH2 and Weaver syndrome.