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Chiari malformations

Chaouki Khoury, MD, MS
Section Editor
Marc C Patterson, MD, FRACP
Deputy Editor
John F Dashe, MD, PhD


Chiari malformations are a heterogeneous group of disorders that are defined by anatomic anomalies of the cerebellum, brainstem, and craniocervical junction, with downward displacement of the cerebellum, either alone or together with the lower medulla, into the spinal canal [1].

This topic will review anatomic and clinical aspects of the various types of Chiari malformations.


Chiari malformations were first described by John Cleland in 1883 [2,3]. They were later classified by Hans Chiari in 1891, into four groups [1,4].

Chiari I malformation (CM-I) is characterized by abnormally shaped cerebellar tonsils that are displaced below the level of the foramen magnum (image 1).

Chiari II malformation (CM-II), also known as Arnold-Chiari malformation, is characterized by downward displacement of the cerebellar vermis and tonsils, a brainstem malformation with beaked midbrain on neuroimaging, and a spinal myelomeningocele (image 2 and image 3 and figure 1).

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Literature review current through: Nov 2017. | This topic last updated: Sep 27, 2017.
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