This exhibit features sagittal and axial sections of Dandy-Walker malformations in an infant. Dandy-Walker malformation is a congenital defect of the brain, involving the cerebellum and the fluid filled spaces surrounding it. In both renditions, a large occipital meningocele is seen in continuity with a posterior fossa cyst and ventricular fluid accumulations. Excessive fluid presence (hydrocephalus) increases intracranial pressure and raises the tentorium cerebelli, encroaching upon the cerebrum. Maldevelopment of the cerebellar hemispheres and agenesis (developmental failure) of the cerebellar vermis are also seen.