Dandy-Walker syndrome is a congenital malformation of the cerebellum with maldevelopment of the fourth ventricle and is associated with which features?

• A. Ventriculomegaly, enlarged posterior fossa, splaying of the cerebellar hemispheres, and cisterna magna > 1.0 cm
• B. Cerebral hemispheric atrophy with intact posterior fossa
• C. Isolated hydrocephalus without posterior fossa changes
• D. Normal posterior fossa with isolated ventriculomegaly

Answer: (A)

Dandy-Walker malformation involves maldevelopment of the cerebellar vermis with cystic dilation of the fourth ventricle and enlargement of the posterior fossa. This combination creates several characteristic imaging features: ventriculomegaly from hydrocephalus, an enlarged posterior fossa, and splaying or separation of the cerebellar hemispheres by an enlarged cisterna magna (often with the cisterna magna measuring more than 1 cm). These findings reflect the vermian hypoplasia/agenesis and the cystic fourth ventricle that define the condition.

Other scenarios lack this posterior fossa involvement or vermian abnormality, such as intact posterior fossa with cerebral hemispheric atrophy, isolated hydrocephalus without posterior fossa changes, or normal posterior fossa with isolated ventriculomegaly.