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.

Methods: A total of 26 patients with complex Chiari malformations were identified using our criteria (any 4 of 7 clinicoradiological parameters). Of the 26 patients, 13 had undergone C1-C2 fusion with FMD and 13 had undergone FMD alone. They had also undergone pre- and postoperative clinicoradiological evaluations, and the outcomes were assessed using the Chicago Chiari outcome score.

Results: Of the 13 patients in the fusion group, 12 (92.3%) showed improvement compared with only 6 of 13 patients (46.2%) in the nonfusion group using the Chicago Chiari outcome score, a statistically significant difference (P = 0.036, χ test). The mean hospital length of stay was longer for the fusion group (6.15 ± 1.46 days) than for the nonfusion group (4.38 ± 2.22 days; P = 0.02).

Conclusions: We have proposed a novel set of criteria for defining complex Chiari malformations. Fusion with decompression provided better outcomes than decompression alone.