Herniation of part of cerebellum into the foramen Magnum which cause obstruction of the flow of cerebral spinal fluid causing hydrocephalus. It occurs due to genetic mutations and lack of maternall diet Symptoms: - dizziness - muscle weakness - numbness - vision problems - headache - problems with balance and coordination Chiari malformation occur in newborns but they may occur later in life due to drainage of CSF caused by: - injury - infection - exposure to toxic substances