Complex Chiari Malformations: Diagnosis, Evaluation, and Treatment.

The term "complex Chiari malformation" (CCM) refers to a subset of clinical and radiographic findings that describe a subpopulation of Chiari patients with craniocervical kyphosis and secondary brainstem compression. These patients are at a greater risk for unsuccessful surgical treatment with standard Chiari surgical decompressive procedures and may require craniocervical fusion and/or odontoid resection. This article reviews concepts related to the diagnosis, management, and treatment of CCM and discusses possible directions for future research.