MR imaging characteristics of tuberculous spondylitis vs vertebral osteomyelitis

Retrospective evaluation was made of four patients with tuberculous spondylitis who had been studied by MR with T1- and T2-weighted images in the sagittal plane and spin-density-weighted images in the axial plane. Evaluation was made of the distribution of abnormal signals within the body and posterior elements of the vertebrae, the intervertebral disk, and the associated paraspinal and epidural areas. In two of the cases, three-level involvement was seen with noninvolvement of intervening disks; metastases were misdiagnosed. One patient had anterior/inferior erosion of the vertebral body without visualization of the disk. The last patient had the more typical MR characteristics of intervertebral disk infection. Plain film examination showed only degenerative changes in three of the four cases. MR revealed more extensive involvement than the plain films did. Involvement of the posterior element and posterior vertebral body was prominent in three of the four cases. This is a significant finding since these patients are more likely to have neurologic symptoms and require laminectomy. Follow-up examinations in two cases showed increased signal on T1-weighted images, suggesting infiltration of hemopoietic marrow with fat, as has been described for degenerative osteoarthritis. The anatomy of the microcirculation of the vertebral body is related to the patterns of vertebral osteomyelitis, and discrepancies can be seen between the findings in our cases and the MR criteria previously noted for pyogenic vertebral osteomyelitis. The MR findings in our patients generally were more typical of neoplasm than of infection. These findings may reflect the characteristics of the tuberculous organism relative to the age-dependent pattern of vertebral microcirculation. Correct diagnosis of tuberculous spondylitis in young to middle-aged adults requires correlation of MR and clinical findings.