In 1954, Benda introduced the term Dandy-Walker syndrome to indicate the association of (1) ventriculomegaly of variable degree, (2) a large cisterna magna, and (3) a defect in the cerebellar vermis through which the cyst communicates with the fourth ventricle. Currently, the following findings are included in the Dandy-Walker syndrome or malformation: (4) cystic dilatation of the fourth ventricle, (5) dysgenesis of the cerebellar vermis, and (6) a high position of the tentorium. The Dandy-Walker malformation has prevalence of about 1 in 30,000 live births and found in 4–12% of infantile hydrocephalus.