Rhombencephalosynapsis: association with single umbilical artery.

A 6-year-old girl who presented with developmental delay and non-progressive ataxia is described. MRI of brain showed agenesis of cerebellar vermis with fusion of cerebellar hemispheres and dentate nuclei. MRI findings were characteristic of rhombencephalosynapsis. Partial agenesis of corpus callosum and absent septum pellucidum were also seen. The child had also been noted to have a single umbilical artery at birth: a hitherto undescribed association.