Arnold-Chiari malformation /är″nəldkē·är″ē/ [Julius Arnold, German pathologist, 1835–1915; Hans Chiari, French pathologist, 1851–1916] , a congenital herniation of the brainstem and lower cerebellum through the foramen magnum into the cervical vertebral canal. It is often associated with meningocele and spina bifida. See also neural tube defect.
