Dandy Walker Malformation

Etiology: abnormality of ventral induction
Imaging: triad is agenesis of the cerebellar vermis / cystic dilation of the 4th ventricle / enlargement of posterior fossa, often associated with hydrocephalus

Radiology Cases of Dandy Walker Malformation

MRI of Dandy Walker malformation — Sagittal T1 MRI without contrast of the brain (upper left) shows an enlarged posterior fossa containing a dilated fourth ventricle resulting in a large midline cyst that is causing elevation of the superior cerebellum and torcular inversion. Axial (upper right) and coronal (below) T1 MRI without contrast of the brain show agenesis of the cerebellar vermis. A mild-moderate amount of hydrocephalus is present.