Clinical Significance of Variable Clivus Gradients in Patients with Chiari Malformation Type I Following Surgical Decompression: a Retrospective Analysis.

OBJECTIVE: Previous studies have shown that the clivus angle gradient is significantly decreased in patients with Chiari malformation type I (CMI) with an associated syrinx compared with patients with CMI only and a healthy population. To date, the relationship between the clivus gradient and clinical outcomes has remained unclear. The objective of the present study was to investigate whether different clivus gradients (angle alpha) in CMI after posterior fossa decompression will lead to different clinical outcomes. METHODS: A total of 86 patients who had undergone surgical decompression at our institution from 2010 to 2016 were retrospectively divided into 2 groups: group A, with a gradient angle >44 degrees, and group B, with an angle <= 44 degrees. The patients' outcomes were determined using the Chicago Chiari Outcome Scale (CCOS). RESULTS: Direct comparisons were made between the 2 groups. No statistically significant differences were found between the 2 groups in demographic data, preoperative symptoms, postoperative complications, or radiographic characteristics (P > 0.05), except for the length of the postoperative hospital stay (P = 0.006). The mean overall CCOS score was 12.80 +/- 2.08. The total CCOS score was significantly different statistically between the 2 groups (P < 0.05). Moreover, group A demonstrated significantly better postoperative improvements compared with group B in the clinical outcome measures using the CCOS (P = 0.021). CONCLUSIONS: A direct comparison between the 2 groups revealed that a decreased clivus gradient was related to unsatisfactory clinical outcomes. Thus, clivus gradients might emerge as a predictor of clinical outcomes after surgical decompression in patients with CMI.