FIG 1. MR images from a case of coexistent Chiari II malformation and holoprosencephaly that occurred in a viable infant.

A, Stigmata of the Chiari II malformation. Sagittal T1-weighted MR image shows elongated caudally displaced effaced fourth ventricle and caudal herniation of the cerebellum.

B, Manifestations of holoprosencephaly. Axial T1-weighted MR image shows absent interhemispheric falx and partial fusion of frontal cortex and white matter.

C, Follow-up image obtained at 13 months of age. Sagittal T1-weighted MR image shows poor myelination and extensive polymicrogyria along the mesial surfaces of the cerebral hemispheres. Arrow indicates the large massa intermedia.