Sonography of fetal Dandy-Walker malformation: a reappraisal.

Thirty-four cases of fetal Dandy-Walker malformation recognized in utero with ultrasound between 16 and 37 weeks' gestation are reported. In each case a qualitative examination of the posterior fossa structures was performed, including the cerebellar hemispheres, cerebellar vermis, fourth ventricle and cisterna magna. In each case, the transverse cerebellar diameter and the depth of the cisterna magna were measured in a standard transcerebellar view of the fetal brain. The atrial width of the lateral ventricles was also assessed. The transverse cerebellar diameter was abnormal in 15 cases, the cisterna magna depth was abnormal in 33, and the atrial width was abnormal in 30. It is concluded that measurement of the transverse cerebellar diameter is unreliable in predicting fetal Dandy-Walker malformation. Measurements of the cisterna magna and atrium seem to be more valuable, although the real sensitivity remains unclear. In pregnancies at risk for fetal Dandy-Walker malformation, the sonographic examination should not be limited to the cerebral ventricles and transcerebellar view but should include a detailed evaluation of all the different anatomical components of the posterior fossa, especially the fourth ventricle and inferior cerebellar vermis.