Dandy-Walker malformation is described by which features?

Dandy-Walker malformation is described by which features?

• A. Enlarged posterior fossa with cystic dilation of the fourth ventricle and vermian hypoplasia/agenesis
• B. Hydrocephalus with normal posterior fossa
• C. Vermian agenesis with normal posterior fossa
• D. Dandy-Walker malformation features: enlarged posterior fossa with cystic dilation of the fourth ventricle and vermian hypoplasia/agenesis

Answer: (D)

The main idea is recognizing the classic pattern that defines Dandy-Walker malformation: an enlarged posterior fossa with cystic dilation of the fourth ventricle and vermian hypoplasia or agenesis. The description that includes all three features—posterior fossa enlargement, cystic fourth-ventricle dilation, and vermian underdevelopment—matches this pattern precisely, so it best fits the diagnosis. The other options miss one or more elements: one describes hydrocephalus without the enlarged posterior fossa, another has vermian agenesis with a normal posterior fossa, so they don’t reflect the full characteristic triad.

The main idea is recognizing the classic pattern that defines Dandy-Walker malformation: an enlarged posterior fossa with cystic dilation of the fourth ventricle and vermian hypoplasia or agenesis. The description that includes all three features—posterior fossa enlargement, cystic fourth-ventricle dilation, and vermian underdevelopment—matches this pattern precisely, so it best fits the diagnosis. The other options miss one or more elements: one describes hydrocephalus without the enlarged posterior fossa, another has vermian agenesis with a normal posterior fossa, so they don’t reflect the full characteristic triad.