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Dandy-Walker variant (DWv) is a less severe posterior fossa anomaly than the classic Dandy-Walker malformation (DWM), characterized as partial vermian hypoplasia with partial obstruction to the fourth ventricle. It is considered 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 to isolated inferior vermian hypoplasia for a broad discussion in this defined entity.
- the diagnosis of a Dandy-Walker variant can not be made definitely until the 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
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 angulation of the scan may make the posterior fossa larger than usual
- 1. Estroff JA, Scott MR, Benacerraf BR. Dandy-Walker variant: prenatal sonographic features and clinical outcome. Radiology. 1992;185 (3): 755-8. Radiology (abstract) - Pubmed citation
- 2. Ecker JL, Shipp TD, Bromley B et-al. The sonographic diagnosis of Dandy-Walker and Dandy-Walker variant: associated findings and outcomes. Prenat. Diagn. 2000;20 (4): 328-32. Prenat. Diagn. (link) - Pubmed citation
- 3. Entezami M, Albig M, Knoll U et-al. Ultrasound Diagnosis of Fetal Anomalies. Thieme. (2003) ISBN:1588902129. Read it at Google Books - Find it at Amazon
- 4. Bosemani T, Orman G, Boltshauser E et-al. Congenital abnormalities of the posterior fossa. Radiographics. 2015;35 (1): 200-20. doi:10.1148/rg.351140038 - Pubmed citation