The effects of MRI signal intensity changes and clinical manifestations on prognosis after surgical intervention for cervical spondylotic myelopathy

OBJECTIVE: To investigate whether the magnetic resonance (MR) T2 image signal intensity ratio and clinical manifestations can predict the prognosis in patients with cervical spondylotic myelopathy (CSM). METHODS: A total of 73 patients treated with anterior, posterior, or posterior-anterior combined surgery for compressive cervical myelopathy were enrolled retrospectively in this study. 1.5 T magnetic resonance imaging (MRI) was performed on all patients before surgery. T2-weighted images (T2WI) of sagittal signal intensity were obtained of the cervical spinal cord, and the regions of interest (ROI) were taken by 0.05 cm(2). MR T2WI of sagittal normal cord signal at the C7-T1 disc level were also obtained, and the ROI were taken by 0.3 cm(2). Signal value was measured by computer and the signal ratio between regions 0.05 cm(2) and 0.3 cm(2) calculated. Where no intramedullary high signal intensity was noted on MR T2WI, the ROI were taken by 0.05 cm(2) of the region of most severe spinal cord compression. The 73 patients were divided into three groups by hierarchical clustering analysis with signal intensity ratio (group 1: low signal intensity ratio; group 2: middle signal intensity ratio; group 3: high signal intensity ratio). Statistical analyses were performed with SPSS 11.0. RESULTS: There were significant differences between the three groups according to the recovery rate (P < 0.001), age (P= 0.003), duration of disease (P= 0.001), Babinski sign (P < 0.001), pre- and postoperative Japanese Orthopaedic Association (JOA) score (P= 0.006). With increases in both signal intensity ratio grade and age, the recovery rate and pre- and postoperative JOA scores gradually decreased, and the incidence of Babinski sign increased. There was no significant difference in sex among the three groups (P= 0.387). Multiple comparison tests further supported the above-mentioned results. CONCLUSION: Patients with light or no intramedullary signal changes on T2WI had a good surgical outcome. However, increase of signal intensity ratio and occurrence of the pyramidal sign were associated with a poor prognosis after surgery.