The Dandy-Walker malformation is a term that represents not just a single entity, but rather several abnormalities of brain development that exist simultaneously. It was first described by Dandy and Blackfan in 1914.
This malformation is typically characterized by incomplete formation of the cerebellar vermis, dilation of the fourth ventricle and enlargement of the posterior fossa. Although earlier, traditional descriptions of this complex include the incomplete formation of several fourth ventricular outlet pathways for the cerebrospinal fluid, it is now known that this occurs in only a minority of affected individuals.
The above-noted developmental abnormalities generally result in the formation of posterior fossa cysts that communicate with an enlarged fourth ventricle. The mean incidence of this complex in individuals with hydrocephalus is estimated to be 3 percent. There is no statistically significant sex prevalence.
Eighty 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, ocular abnormalities and cleft palate.
After placement of a shunt, expected results include an appropriate decrease in size of the shunted compartment with resolution of the child's pre-operative signs and symptoms. Dandy-Walker patients with successfully shunted hydrocephalus can do very well and are frequently in the mainstream at school. Statistics in the literature citing a high rate of mental retardation most likely reflect injury due to inadequate management of the associated hydrocephalus, something that is less likely to occur today than in the past.
Nearly 40 percent of Dandy-Walker individuals who have received a single compartment shunt will subsequently compartmentalize another CSF space and ultimately require a second shunt. Infrequent complications of lateral and posterior fossa shunts include infection, hemorrhage and malfunction. The failure rate of shunts in Dandy-Walker patients is comparable to that documented for shunted patients with other hydrocephalus syndromes.
Conclusion
Dandy-Walker malformations have variable features and, therefore, no single treatment option is universally appropriate. Individualized, aggressive treatment with careful long-term surveillance of these patients will lead to excellent outcomes.