A congenital anomaly in which the cerebellum and medulla oblongata, which is elongated and flattened, protrude down into the spinal canal through the foramen magnum. It may be associated with many other defects, including spina bifida occulta and meningomyelocele. ... (12 Dec 1998) ... 
(ahr´nәld ke-ah´re) Arnold-Chiari malformation (ahr´nәld ke-ah´re) Arnold-Chiari syndrome a condition in which the cerebellum and medulla oblongata protrude down into the spinal canal through the foramen magnum. It is present at birth and is almost always accompanied by meningomyelocele and hydrocep...
Type: Term Pronunciation: ar′nŏld kē-ah′rē Synonyms: Arnold-Chiari malformation
[n] - deformity in which part of the brain protrudes through the skull
noun deformity in which part of the brain protrudes through the skull