Colpocephaly is present. A severe migrational anomaly is almost certain. The distinction between lissencephaly and band heterotopia is made by the relatively preserved sulcation seen with heterotopia in this case. The images shown simulate markedly thickened cortex, but there is a thin subcortical rim of white matter.
Migrational anomalies can coexist.
Gray matter heterotopia is a migrational anomaly of variable severity which occurs between 2-5 months of gestation. It is the most common migrational anomaly. Heterotopia may be divided into nodular and band types, the nodular type being much more common than band heterotopia. Other migrational anomalies include lissencephaly, pachygyria, schizencephaly, and polymicrogyria.