Rhombencephalosynapsis associated with Dandy-Walker malformation.

Coexistence of rhombencephalosynapsis and Dandy-Walker malformation has previously been documented in a fetus by autopsy. In addition, there are three cases in the imaging literature suggesting this combination. This paper reports an 8-month-old girl with clear MR imaging evidence of association of these two anomalies. The vermis was absent, and there was fusion of the cerebellar hemispheres, characteristic for rhombencephalosynapsis. The fourth ventricle showed cystic dilatation associated with an enlarged posterior fossa, characteristic for Dandy-Walker malformation. These findings suggest that rhombencephalosynapsis and Dandy-Walker malformation can coexist.