MRI of the posterior fossa demonstrates absence of the cerebellar vermis with complete fusion of the cerebellar hemispheres across the midline. Characteristic transverse folia inferiorly can be clearly seen crossing the midline. The fourth ventricle is abnormal in shape, elongated in the AP direction. Features are consistent with rhomboencephalosynapsis.
Additionally the corpus callosum is dysplastic and there is fusion of the cerebral hemispheres across the midline consistent with coexisting syntelencephaly.