Imaging recommendation · Neuro · Head & Neck

Suspected Dandy-Walker malformation (posterior fossa cyst, vermian agenesis)

Q: What's the alternative imaging for suspected dandy-walker malformation (posterior fossa cyst, vermian agenesis) when prenatal detection?

MRI — Fetal MRI in 3rd trimester (no contrast).

Recommended: MRI Brain is the preferred imaging study for suspected dandy-walker malformation (posterior fossa cyst, vermian agenesis). Spectrum: Dandy-Walker malformation, Dandy-Walker variant, mega-cisterna magna, Blake's pouch cyst.

Recommended study

MRI Brain

MRI No contrast Preferred Neuro · Head & Neck Outpatient Reviewed 2026-05

Spectrum: Dandy-Walker malformation, Dandy-Walker variant, mega-cisterna magna, Blake's pouch cyst.

If the default doesn't apply

Prenatal detection

MRI Fetal MRI in 3rd trimester No contrast

Watch-outs

Hydrocephalus is common

Up to 80% develop hydrocephalus; serial imaging for ventricular size and shunt evaluation.

Pearls

Dandy-Walker: enlarged posterior fossa + vermian hypoplasia + cystic dilation of 4th ventricle + elevated tentorium.
Associated with chromosomal anomalies, callosal agenesis, and other CNS malformations.
Distinguish from Blake's pouch cyst (normal vermis, communicates with 4th ventricle).