MR Classification System Based on Axial Images for Cervical Compressive Myelopathy

Abstract

Purpose: To propose a new magnetic resonance (MR) classification system based on axial images for cervical compressive myelopathy (CCM) (Ax-CCM system), to assess the interobserver agreement with the Ax-CCM system, and to evaluate the relationship between Ax-CCM patterns and the baseline severity of CCM and the subsequent surgical outcome. Materials and Methods: The institutional review board approved this retrospective study. A total of 202 patients (male-to-female ratio, 128:84; mean age 6 standard deviation, 56.3 years 6 11.9; age range, 24–83 years) with CCM who underwent preoperative MR imaging and decompression surgery were retrospectively evaluated. The Ax-CCM pattern was based on the margin and extent of intramedullary hyperintensity on axial T2-weighted images, as follows; type 0 = normal, type 1 = diffuse, type 2 = fuzzy focal, and type 3 = discrete focal. Interobserver variability was analyzed by using the intraclass correlation coefficient across three readers. The modified Japanese Orthopedic Association (JOA) score and the postoperative improvement (good vs little improvement) were evaluated according to the AxCCM pattern by using one-way analysis of variance, the x2 test, and the Fisher exact test. Results: The intraclass correlation coefficient for the Ax-CCM system was 0.83. The preoperative JOA score was significantly different according to Ax-CCM pattern across all readers (P , .05), with the type 2 pattern showing the worst preoperative JOA score (mean, 11.6 6 3.1 for readers A and C and 11.7 6 2.9 for reader B). The proportion of good improvement was significantly lower with the type 2 pattern (27 of 72 patients, 37%) than with the other patterns (64 of 123 patients, 52%) (P = .034). Conclusion: The Ax-CCM system showed good interobserver agreement, and the type 2 pattern was correlated with poor preoperative neurologic status and less postoperative improvement.