Arnold Chiari malformation is characterized by all except:

- Hypoplasia of cerebellar vermis is seen in DANDY WALKER SYNDROME: Arnold Chiari malformation It is the most common malformation of the posterior fossa and hindbrain. It consists of herniation of the cerebellar tonsils though the foramen magnum. Often, there is associated abnormality of the bones of the skull base leading to a small posterior fossa Type I typically produces symptoms during adolescence or adult life and is usually not associated with hydrocephalus. Type II Chiari malformation is characterized by progressive hydrocephalus with a myelomeningocele.