What does Dandy Walker malformation typically involve?

Dandy Walker malformation is characterized primarily by cystic dilation of the fourth ventricle, which is a key feature of this condition. In individuals with Dandy Walker malformation, there is an abnormal development of the cerebellar vermis, which results in an enlargement of the fourth ventricle. This malformation often leads to associated anomalies, such as hydrocephalus due to obstruction of cerebrospinal fluid (CSF) pathways, but the hallmark is the cystic enlargement of the fourth ventricle itself.

The condition can also involve dysgenesis or agenesis of the cerebellar vermis and the presence of a large posterior fossa. However, the presence of cystic dilation of the fourth ventricle remains the most defining aspect of this malformation. Recognition of these features is crucial for evaluation and management in affected individuals.