The findings, in this case, are consistent with rhombencephalosynapsis which is thought to be caused by a failure of vermian differentiation which is required in order to form separate cerebellar hemispheres or by vermian agenesis which allows cerebellar hemispheres to become apposed and then fuse in the midline.

Rhombencephalosynapsis is sometimes associated with midline supratentorial abnormalities as seen in this case where posterior corpus callosal dysgenesis is observed.

Case courtesy of Dr Guillermo Bolivar