Congenital posterior fossa malformations: An imaging review for the practicing radiologist

Congenital malformations of the posterior fossa represent a heterogeneous group of malformations affecting the cerebellum, fourth ventricle, and related structures, with improved implications for embryologic considerations, clinical management, and neurodevelopment. Evolving imaging, especially fetal MRI and high-resolution postnatal MRI, has cemented the responsibility of the radiologist in correct diagnosis, classification, and differentiation of these malformations. This imaging review attempts to present a synthesis concerning the embryological basis, diagnostic criteria, and characteristic radiological findings of important posterior fossa anomalies: Dandy–Walker malformation, Blake’s pouch cyst, Chiari malformations, rhombencephalosynapsis, and mega cisterna magna. It further discusses critical diagnostic pitfalls and modality-specific imaging recommendations for prenatal and postnatal evaluations. The embryological underpinnings of the hindbrain are explored to set a developmental perspective for understanding these malformations, followed by a system of classification based on neuroimaging pattern. Multimodality imaging techniques from prenatal ultrasound all the way to fetal and neonatal MRI have been examined with regard to their merits, demerits, and clinical applications. The discussion also deals with radiologic-pathologic correlations, promising approaches involving machine learning to segment the posterior fossa, and current trends in prediction of outcome. Tables and diagrams have been provided to help the practising radiologist to navigate through this complex diagnostic terrain. Based upon recent neuroimaging literature, this article aims to bring together all available evidence, synthesizing it with clinical insights to provide the modern-day radiologist with a hands-on guide for daily interpretation and interdisciplinary cooperation within pediatric and prenatal contexts. Above all, it stresses the need for swift and accurate classification and communication by the radiologist, which, in turn, facilitates proper prognostication, parental counseling, and therapeutic decision-making.