Prenatal diagnosis of cerebellar vermis aplasia

The observation of the posterior cranial fossa of the fetus, and the visualization and measurement of the cerebellum, offer an accurate parameter useful for biometry and permit the diagnosis of malformation. We report a case of cerebellar vermis aplasia detected by ultrasound at the 36th week of pregnancy in a fetus with no other morphological anomalies. Echographic picture showed an enlargement of the posterior cranial fossa, which was occupied by two cerebellar hemispheres not joined together on the midline and floating in a large amount of liquor. Differential diagnostic criteria are here discussed with particular regard to prognosis and obstetrical management.