[Prenatal ultrasound findings in Arnold-Chiari deformity]

The Arnold-Chiari malformation is a congenital deformity characterized by displacement of parts of the cerebellum, fourth ventricle, pons and medulla oblongata into the spinal canal. The ACM almost always is associated with a hydrocephalus and a myelomeningocele. The report demonstrates the sonographic findings of a ACM at 20 weeks' gestation. Clinical findings, aetiology and pathogenesis of the malformation are discussed.