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A retrospective imaging study of 73 patients who underwent surgery for cervical spondylotic myelopathy (CSM) between April 2005 and July 2007.To investigate whether magnetic resonance (MR) T2 image signal intensity (SI) ratio and clinical manifestation can assess the prognosis in patients with CSM.The association between intramedullary high SI on T2-weighted MR images and surgical outcome in CSM remains controversial. The means of quantizing SI ratio for the disease has not been discussed.A total of 73 patients with cervical compressive myelopathy were retrospectively enrolled and were treated with anterior, posterior, and posterior-anterior united decompression. A total of 1.5-T magnetic resonance imaging was performed in all patients before surgery. T2-weighted images of sagittal increased SI on the cervical spinal cord were obtained, and the regions of interest (ROIs) are taken by 0.05 cm2. T2-weighted MR images of sagittal normal cord SI on the cervical between C7-T1 disc levels were obtained, and the ROIs are taken by 0.3 cm2. SI value is measured by computer, and the SI ratio between the regions 0.05 cm2 and 0.3 cm2 has been calculated. If no intramedullary high SI was noted on T2-weighted MR images, the ROIs were taken by 0.05 cm2 of the severe compression cord. All patients had been divided into 3 groups by hierarchical clustering analysis with SI ratio (Group 1: low SI ratio, Group 2: middle SI ratio, and Group 3: high SI ratio). Statistical analyses were performed with SPSS 11.0.There are significant differences between 3 groups by comparing the recovery rate (P < 0.001), age (P = 0.003), duration of disease (P = 0.001), Babinski sign (P < 0.001), preoperative JOA score (P = 0.006), and postoperative JOA score (P < 0.001). There are no significant differences on sex among 3 groups (P = 0.387). By using the multiple comparison analysis, the above results are further shown.Patients with low SI ratio who were not too old and had a shorter duration of disease experienced a good surgical outcome. However, with the increase of SI ratio and the occurrence of pyramidal sign, a poor prognosis after surgery will show. SI ratio and clinical manifestation can be a predictor of surgical outcome.