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Start free with EleplanIsolated Dandy-Walker malformation
ORPHA:217Morphological anomaly
What it is
A rare non-syndromic central nervous system malformation characterized by the association of three signs: hydrocephalus, partial or complete absence of the cerebellar vermis, and posterior fossa cyst contiguous with the fourth ventricle, presenting early in life with hydrocephalus, bulging occiput and posterior fossa signs such as cranial nerve palsies, nystagmus and ataxia.
Key facts
- Prevalence
- 1-9 / 100 000 (Europe)
- Age of onset
- Antenatal, Neonatal
- Inheritance
- Multigenic/multifactorial
- Classified as
- Morphological anomaly
Prevalence figures describe populations, not individuals, and are often estimates from a single study. Where the figure is an incidence or a birth prevalence, it says so.
Signs and symptoms
Common30–79%
7Sometimes5–29%
6These ranges are how often a sign appears across everyone diagnosed, not a prediction for one person — most people have some of these and not others. Orphanet also records findings that are specifically absent in this disease; those are in the data but not listed here.
Genes
ICD-10 codes
ICD-10 has no distinct code for most rare diseases, so many are filed under the nearest available one. A shared code identifies the group, not this disease — the ORPHAcode above is what identifies it.
Related health topics
Reached through the ICD-10 categories this disease is filed under, so these describe the broader group rather than this disease specifically.
Cross-references
Orphadata Science: Free access data from Orphanet. © INSERM 1999. Data version 2026-06-23. Available under CC BY 4.0. This is a reference, not medical advice.
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