Cystic Malformations Within the Posterior Fossa

Cystic malformations within the posterior fossa are rather common findings in pediatric neuroimaging. They may be divided in two main groups based on their location and size: large extra-cerebellar and small intra-cerebellar cystic malformations. Both groups include various diseases: Dandy–Walker malformation, Blake’s pouch cyst, posterior fossa arachnoid cysts, and mega cisterna magna are extra-cerebellar posterior fossa cystic malformations, while α-dystroglycanopathies, GPR56-related fronto-parietal polymicrogyria, and Poretti–Boltshauser due to LAMA1 mutations are intra-cerebellar posterior fossa cystic malformations. These diseases may be differentiated based on the neuroimaging pattern. Differentiation between the various diseases associated with extra- and intra-cerebellar cystic malformations is important in terms of diagnosis, management, prognosis, and counseling of the affected families.