Dandy-Walker Syndrome

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Background  Neuroimaging Gross Pathology  Histopathology & Immunohistochemistry  Differential Diagnosis


Summary: The three essential features are: agenesis of the vermis, cystic dilatation of the fourth ventricle and enlargement of the posterior fossa. Hydrocephalus is a frequent but inconstant finding.

Clinical features: The clinical manifestations of Dandy-Walker syndrome are mainly those of hydrocephalus. Therefore, the diagnosis is made in 75% of cases after 3 months of age and often only by the first birthday, as hydrocephalus usually becomes apparent by 1 year of age. Remarkably, there is no cerebellar sign or disturbances of stance. Mental retardation is present in 30-50% of patients.

Prognosis: Prognosis is guarded and the mortality is about 27%.

Other cerebral and visceral anomalies: it is the presene or absence of other cerebral and viseral abnormalies that determines the prognosis of individuals. About 68% of all cases have other developmental abnormalities of the CNS. Facial abnormalities may also be seen.

Pathogenesis: agenesis of the vermis and cystic dilatation of the fourth ventricle may be the two primary events. Obstruction of the foramina of Magendie and Luschka may not be present in every cases. Other features may be secondary to the primary events.

Prognosis: Mortality varies from 12.6% to 57%; IQ of 71% of patients are less than 83 with no significant relationship between retardation and associated anomalies.

Genetics: no constant chromosomal abnormalities have been identified. The recurrent rate is only 1-5%.


Posterior fossa cyst in communication with the fourth ventricle, absence of vemian tissue, and an abnormally high insertion of the tentorium.


Dandy-Walker syndrome as defined by Benda (1954), the person who introduced the term "Dandy-Walker syndrome", it has six features. Not all six features are found in each case.

In most cases, the supreior vermis may be present but the inferior vermis is attenuated and blends with the membranous roof of the cystic fourth ventricle.

Dilatation of the lateral and third ventricle (but to a lesser extent the fourth ventricle.

Widely separated, hypoplastic cerebellar hemispheres, with a small  hypoplastic vermis, and rostral displacement.

Enlarged posterior fossa with high tentorium cerebelli and transverse sinuses.

Thin transparent membrane containing ependymal cells and occasionally cerebellar tissue in the fourth ventricle which replaces the vermis.

Associated with the agenesis of corpus callosum.


The cyst membrane has two layers: an outer fibrous leptomeningeal layer and an inner glio-ependymal layer sometimes including cerebellar remnants.


May be confused with a posterior fossa cyst. Identification of vermian agenesis or hypoplasia will be helpful for diagnosing Dandy-Walker syndrome.

NeuroLearn NeuroHelp Malformations  For Comment: KarMing-Fung@ouhsc.edu

Background  Neuroimaging Gross Pathology  Histopathology & Immunohistochemistry  Differential Diagnosis