[Diffuse subcortical heterotopias of the gray matter].

Three cases of diffuse subcortical gray matter heterotopias in children are reported. Generalised seizures and mild mental retardation were the most frequent signs. No specific electroencephalographic pattern was recognized. Magnetic resonance imaging scans showed the thick diffuse layer of heterotopic gray matter which was surrounded by normal white matter. Gyration was normal, and no associated malformation was observed. This neuronal migrational disorder happens between the 10th and 16th gestational week. Nineteen observations (17 girls) are reported in the literature. The filiation with agyria-pachygyria and the possible genetic transmission are discussed.