Dandy-Walker syndrome: incidence in a defined population of Tabuk, Saudi Arabia.

Dandy-Walker syndrome (DWS) is characterized by cystic dilatation of the 4th ventricle and absence of the cerebellar vermis. There may also be posterior fossa enlargement, hydrocephalus, hypoplastic cerebellar hemispheres and other malformations within and outside the central nervous system (CNS). The condition is uncommon, and the incidence is unknown. We studied the incidence of DWS in a defined Saudi Arabian population of military personnel and their dependants. We identified all patients diagnosed with DWS during an 11-year period (1989-1999) from a cohort of 45,274 live births. The incidence of DWS was 1.0 per 100,000 live births per year. The incidence by sex per 100,000 live births per year was 1.24 for males and 0.78 for females. DWS formed 3.5% of our cases of infantile hydrocephalus.