ABSTRACT
The classification of cerebellar malformations is controversial; no widely accepted agreement has been reached, despite many attempts by neuroradiologists, geneticists and neuropathologists [1–4]. In particular, as far as the conditions associated with a defective vermis are concerned, there is no general consensus as to their categorization. In addition, cerebellar hemispheric and vermian malformations have been described but are poorly understood. Thus, the prognosis of patients with most cerebellar malformations is uncertain. Finally, it is often difficult to distinguish clearly, in an infant with signs and symptoms relating to the posterior fossa, between cerebellar or vermian atrophy, hypoplasia or malformation. In the fetus, the situation is understandably even more confused, due to difficulties in the prenatal assessment of posterior fossa, both by ultrasound (US) and MRI. However, based on a morphologic US approach, it is at least possible to differentiate posterior fossa anomalies into two broad categories:
Cystic malformations, characterized by the presence of an apparent cerebrospinal fluid (CSF) collection in the posterior fossa due to 4th ventricle/cisterna magna dilatation, or to true arachnoid loculations
Non-cystic malformations, in which there is no apparent CSF collection [4,5].
