Complex Chiari Malformation: Proposal of a New Set of Diagnostic Criteria and Outcomes After fusion Surgery.

Background: The proposal of C1-C2 fusion as a better treatment option compared with foramen magnum decompression (FMD) for the treatment of Chiari 1 malformations has led to controversy. Although FMD is a time-tested treatment option, a group of patients exists who will benefit from C1-C2 fusion. We have proposed an objective system for defining complex Chiari malformations and studied the outcomes of fusion with decompression versus decompression alone for these patients.