MR imaging of the lower spine. Differentiation between infectious and malignant disease.

The findings on MR imaging of 28 patients with spinal infection and 40 patients with spinal malignant disease were compared. Spinal infections involved one to 4 vertebrae, usually (23/28) 2 vertebrae. The posterior elements were involved with certainty in 26/40 patients with malignancy but in none with infection. In the latter group, the posterior elements might have been involved in 3/28. The intervertebral disk between the infected vertebrae was involved in 26/28 patients and 21/28 had a paravertebral mass. Spinal malignancies affected the vertebrae alone in 19 patients and paravertebral extension was found in 21/40 patients. The intervertebral disk was involved only in one patient with malignancy. The differences in the distribution of the MR findings between spinal infection and spinal malignancy were highly significant (p < 0.001). The highest signal intensity of the infectious lesions on T2-weighted images was equal to or higher than that of the cerebrospinal fluid (CSF) in 26/28 patients. In contrast, the signal intensity of the malignant lesions was hypointense as compared to the CSF in 29/40 patients (p < 0.001). MR is a useful method for differentiating between infection and malignancy in the lower spine; T2-weighted images are especially valuable for differentiation.