Non-cystic Anomalies of the Posterior Fossa

Non-cystic posterior fossa abnormalities constitute a heterogeneous group of cerebral lesions of diverse primary or secondary etiologies. The incidental finding suspicious for these groups of conditions is usually the late discovery of a transverse cerebellar diameter below the fifth centile. Investigation of the personal and family medical history combined with detailed morphological evaluation of fetal supra- and infratentorial cerebral structures may help in the diagnosis as the presence of specific signs is suggestive of certain specific pathophysiological mechanisms. Fetal MRI, possibly repeated, and genetic analysis according to updated indications, is also mandatory for a better understanding of these complex situations.