Syringomyelia Resolution Following Chiari Surgery: A Novel Scale for Communication and Research

BACKGROUND The pathophysiological connection between Chiari malformation and syringomyelia is accepted. Debate remains, however, how can we best define changes in syringomyelia following surgery. OBJECTIVE To introduce a grading system focusing on syrinx reduction based on routinely and reproducible radiological information, and provide a suggestion of the application of this scale for prediction of patient's prognoses. METHODS Data from 48 patients with Chiari malformation and syringomyelia were compiled. We calculated syrinx cross-sectional area by approximating an ellipse in the largest axial plane. We compared the percentage of reduction or enlargement following surgery. The percentage change was grouped into four grades: Grade 0 = Increasing size, grade I <= 50% reduction, grade II = 50% to 90% reduction, grade III >= 90% reduction. RESULTS A total of 89.6% of patients had syrinx improvement after surgery. A total of 5 patients were grade 0, 14 were grade I, 20 patients were grade II, and 9 patients met criteria for grade III. The mean postoperative syrinx area was 24.1 mm(2) (0-169 mm(2)()) with a mean syrinx reduction of 62.7%. CONCLUSION Radiological improvement of syringomyelia can be mathematically defined and standardized to assist in communication in outcome-based trials. Radiological resolution is expected most patients.