Dandy-Walker malformation is a congenital condition characterized by three main features: complete or partial absence of the cerebellar vermis, the structure connecting the two halves of the cerebellum; enlargement of the fourth ventricle; and an enlarged posterior fossa. On prenatal ultrasound, the key finding is a large, fluid-filled space in the back of the fetal brain where the cerebellar vermis should be, giving the cerebellum an abnormal, separated appearance. This condition is often associated with hydrocephalus and may be accompanied by other brain abnormalities. Detection on ultrasound prompts further evaluation with fetal MRI and genetic counseling, as the severity and prognosis can vary significantly depending on the extent of the malformation and associated anomalies.
Sonography Term