ABSTRACT
Chiari malformations are hindbrain herniation syndromes that occur in children and adults. The classification scheme (i.e., Chiari I, II, III, and IV) describes the relationship of the posterior fossa contents to the foramen magnum (Table 1). This classification scheme does not imply a spectrum of increasing severity of the anatomical abnormality or the clinical significance (i.e., a Chiari I does not progress to a Chiari II). Chiari I and II are the only clinically relevant types.
