Diagnostic imaging of posterior fossa anomalies in the fetus and neonate: part 1, normal anatomy and classification of anomalies.

This article is the first portion of a two-part review that illustrates the normal appearance of the cerebellum and posterior fossa on prenatal ultrasound and MRI and on postnatal diagnostic imaging studies. Classification and terminology of posterior fossa abnormalities in the literature are confusing due to evolution of concepts and sometimes lack of consensus. Accurate classification of posterior fossa anomalies is important for predicting fetal outcome and for appropriate counseling. In Part 1 of this review, prenatal and postnatal imaging techniques for assessing the posterior fossa will be discussed, followed by a discussion of how cerebellar malformations may be classified.