Dandy-Walker syndrome is a congenital brain malformation involving the fourth ventricle and cerebellum.
It is defined as an enlargement of the fourth ventricle, an absence (partial or complete) of the cerebellar vermis (the narrow middle area between the two cerebral hemispheres), and cyst formation in the posterior fossa (the internal base of the skull). Hydrocephalus (increased intracranial pressure) may also be present.
Eigthy percent of cases are diagnosed before the age of one year, typically as a result of the associated hydrocephalus. The malformation may have a number of other, associated anomalies in the brain's development including agenesis of the corpus callosum, occipital encephalocele, occular abnormalities and cleft palate.
