Congenital central nervous system anomalies.

Magnetic resonance imaging, because of its multiplanar capabilities and exquisite contrast differentiation, has risen above all other forms of in vivo imaging for the classification and determination of congenital central nervous system (CNS) anomalies. We briefly discuss pertinent aspects of CNS embryology and, using a recently proposed classification of central nervous system anomalies, present examples of a spectrum of abnormalities that one may encounter in practice. These anomalies include: the Chiari malformations, encephaloceles, holoprosencephaly, septooptic dysplasia, Dandy-Walker variant, hydranencephaly, phakomatoses, schizencephaly, agyria or pachygyria, and dysgenesis of the corpus callosum.