Fetal MRI of a severe Dandy-Walker malformation with an enlarged posterior fossa cyst causing severe hydrocephalus

We present a case of severe Dandy-Walker malformation with enlarged posterior fossa cyst extruding through the incisura of the tentorium and causing severe hydrocephalus. A posterior fossa malformation was suspected by ultrasonography and was further evaluated by fetal magnetic resonance imaging (MRI). Fetal MRI demonstrated that there were no associated anomalies and the decision was made to continue with labor instead of terminating the pregnancy. The precise diagnosis and absence of associated anomalies revealed by MRI aided in parent counseling and obstetrical management.