Dandy–Walker syndrome (DWS), is a congenital brain malformation involving the cerebellum and the fluid filled spaces around it. A key feature of this syndrome is the partial or even complete absence of the part of the brain located between the two cerebellar hemispheres (cerebellar vermis). The Dandy–Walker complex is a genetically sporadic disorder that occurs one in every 30,000 live births. Prenatal diagnosis and prognosis of outcomes associated with Dandy-Walker can be difficult.
The term Dandy–Walker represents not a single entity, but several abnormalities of brain development which coexist. There are, at present, three identified types of Dandy–Walker complexes. These represent closely associated forms of the disorder: DWS malformation, DWS mega cisterna magna and DWS variant.
Image: Variant DWS with dysplasia of the pons and cerebellum in a 8-year old. T2 weighted sagittal MRI.