= DANDY-WALKER VARIANT (nonpreferred term)

Genetics: usually no recurrence risk

• mild deficits in fine motor activity + receptive language
• partial absence of inferior vermis (best on midsagittal image)
• remainder of vermis + cerebellar hemispheres + 4^th ventricle + posterior fossa of normal size and architecture

OB-US: diagnosis reliable >18–20 weeks GA

Cave: high false-positive rate (~ 30%)

Prognosis: favorable outcome in 75%