Revision 28 for 'Dandy-Walker variant'

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Dandy-Walker variant

Dandy-Walker variant (DWV) is a less severe posterior fossa anomaly than the classic Dandy-Walker malformation (DWM) and is considered being on the lesser end of the disease spectrum in the Dandy-Walker continuum


This term was created to include those malformations that do not meet the criteria for Dandy Walker malformation, however some authors recommend to avoid it as there is a lack of specificity that may create some confusion. Instead, a more detailed anatomic description is recommended 4

Please refer on isolated inferior vermian hypoplasia for a broad discussion in this defined entity. 


There is usually partial vermian hypoplasia with partial obstruction to the fourth ventricle, but without enlargement of the posterior fossa.

Radiographic features

Antenatal ultrasound
  • the diagnosis of a Dandy-Walker variant can not be made definitely until 18th week of gestation as the inferior vermis does not form till then
  • may show a connection between the cisterna magna and fourth ventricle
  • the fourth ventricle is large but less dilated and better formed than the classic Dandy-Walker malformation 1
  • the cerebellar hemispheres are hypoplastic but there is less severe hypoplasia of the inferior vermis

Differential diagnosis

On antenatal ultrasound - consider

  • communication between the fourth ventricle and the cisterna magna can be a normal finding up to ~ 18 weeks of gestation
  • incorrect angluation of the scan may make the posterior fossa larger than usual

See also

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