MRI findings in a neonate with cerebellar agenesis.

Cerebellar agenesis is a rarely observed malformation that is frequently associated with other defects. We describe a neonate with an isolated cerebellar agenesis. In addition to the absence of recognizable cerebellar tissue, cranial magnetic resonance imaging demonstrated a hypoplastic base of the pons and absence of the normal outline of the inferior olives. Other major cerebral malformations were not found. As a developmental defect, cerebellar agenesis is heterogeneous because it occurs either as an anatomically isolated anomaly or as part of a more complex cerebral malformation. The pathogenesis and molecular basis of isolated cerebellar agenesis is unknown.