Cystic Posterior Fossa Anomalies

The prenatal diagnosis of cystic malformation of the posterior fossa represents a critical aspect of antenatal care, offering valuable insights into the early identification and management of these congenital anomalies. The diagnosis of these malformations has traditionally been performed in the second trimester of pregnancy. However, the introduction of high-frequency probes has allowed to explore in detail the anatomy of the posterior cranial fossa already from the first trimester of pregnancy, opening new perspectives on the diagnostic classification of these pathologies and on prenatal counseling. This chapter reviews current methodologies and technologies employed in the prenatal assessment of cystic posterior fossa malformations, emphasizing the role of advanced imaging modalities such as ultrasound and fetal neurosonography. The diagnostic challenges associated with distinguishing between different types of cystic malformations, such as Dandy–Walker malformation, vermian hypoplasia, Blake’s pouch cyst, mega cisterna magna, and arachnoid cysts, are discussed. Moreover, we will describe the new markers for cystic malformation of posterior fossa that may allow the identification of these anomalies already from the first trimester and the natural evolution of the pathology from the first to the second trimester, with related sonographic appearance. As prenatal diagnostic techniques advance, we emphasize the importance of understanding the relevance of emerging technologies to enhance the precision and effectiveness of diagnosing fetal cystic posterior fossa malformations.