Marginal glioneuronal heterotopias in nine cases with and without cortical abnormalities

Nine cases of marginal glioneuronal heterotopias over the cerebral cortex were reviewed from the morphological point of view. There were developmental disabilities in all cases except one (case 8), who was stillborn. All subjects died before 1 year of age except one (case 5). The common features of small glioneuronal heterotopias and abundant heterotopic glioneuronal proliferation are described. The correlation of glioneuronal heterotopias with polymicrogyria and other cortical malformations, as well as their appearance over a normal cortex, are described. The glioneuronal heterotopias are considered to be a separate type of malformation that could arise during the second half of intrauterine life. A breach of the neuropial border seems to be the most acceptable pathomechanism for our presented cases. Their morphological features indicate that damage to this barrier leads to involvement of glioneuronal heterotopias in fusion of opposite cortical convolutions.