Many brain malformations are closely related to neuronal migration disorders1. Neuronal migration disorders include focal cerebro cortical dysgenesis, heterotopia, polymicrogyria, lissencephaly or pachygyria, and schizencephaly. These disorders are caused by the abnormal migration of neurons in the developing brain and nervous system. Neurons must migrate from their origin areas to their final anatomic location within the central nervous system (CNS) where they must settle into proper neural circuits. Neuronal migration, which occurs as early as the second month of gestation, is controlled by a complex assortment of chemical guides and signals. When these signals are absent or incorrect, neurons do not migrate appropriately.
Fetal neuroimaging, through advances in ultrasound and MR imaging, has contributed to the field of fetal medicine in prenatal detection of many congenital CNS anomalies, such as prosencephalic disorders, neurulation disorders, intracranial tumors, cysts, and brain damage attributable to intrauterine insults. In addition, prenatal imaging assessment of the fetal CNS contributes to more effective prenatal/postnatal management. Although migration disorders occur during early gestational stage, their phenotypic expression appears in late pregnancy, when sonoraphic assessment of the cortical development is difficult because of fetal cranial ossification. Antenatal cortical assessment is, at present, one of the most challenging fields of fetal medicine.