New MRI Grading System for the Cervical Canal Stenosis

OBJECTIVE. The purpose of this study was to propose a new MRI grading system for cervical canal stenosis and to evaluate the reproducibility of the system. MATERIALS AND METHODS. Cervical canal stenosis was classified according to the T2-weighted sagittal images into the following grades: grade 0, absence of canal stenosis; grade 1, subarachnoid space obliteration exceeding 50%; grade 2, spinal cord deformity; and grade 3, spinal cord signal change. The MRI scans of 82 patients (37 men and 45 women; mean age, 65.2 years; range, 60-86 years) were independently analyzed by six radiologists. Interobserver and intraobserver agreements were analyzed using intraclass correlation coefficient (ICC), along with the percentage agreement and kappa statistics. RESULTS. The ICC for interobserver agreement was 0.716-0.802, indicating good-to-excellent agreement. For the distinction among the four grades, the percentage of agreement was 63-64% (kappa = 0.60-0.62). The percentage of agreement for the presence of cervical canal stenosis (grade 0 vs grades 1, 2, and 3) was 79-85% (kappa = 0.51-0.59). The percentage of agreement for insignificant (grade 0-1) or significant (grade 2-3) stenosis was 81-85% (kappa = 0.57-0.66). The percentage of agreement for the presence of spinal cord signal change (grade 0-2 vs grade 3) was 92-95% (kappa = 0.70-0.73). The overall intraobserver agreement was excellent, as determined by an ICC of 0.768. CONCLUSION. The new grading system provides a reliable assessment of cervical canal stenosis.