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Dandy-Walker malformation is a congenital brain defect characterized by abnormal development of the cerebellum and fourth ventricle, resulting in cerebellar hypoplasia, cystic dilatation of the fourth ventricle, and enlargement of the posterior fossa. This rare condition affects approximately 1 in 25,000-35,000 births and can present with varying degrees of severity from mild developmental delays to severe neurological impairment.
The malformation occurs due to failed or incomplete development of the cerebellar vermis during early embryogenesis, typically between 6-12 weeks of gestation. This developmental failure leads to obstruction of normal cerebrospinal fluid flow through the fourth ventricle, causing progressive cystic enlargement and secondary hydrocephalus. The underlying genetic mechanisms involve disruption of multiple developmental pathways controlling hindbrain formation, though most cases are sporadic.
Diagnosis is typically made through prenatal ultrasound or postnatal neuroimaging showing the classic triad of cerebellar vermis hypoplasia, cystic fourth ventricle enlargement, and enlarged posterior fossa. Clinical presentation varies widely from asymptomatic cases to those with developmental delays, motor dysfunction, seizures, and signs of increased intracranial pressure requiring surgical intervention. Management focuses on treating associated hydrocephalus with ventriculoperitoneal shunting when indicated and providing supportive developmental therapies.