Differentiating tubercular from pyogenic causes of spine involvement on Magnetic Resonance Imaging

Based on clinical parameters alone, it is difficult to differentiate between tubercular (TB) and pyogenic spondylodiscitis. Therefore, this study aimed to identify imaging features that can help to differentiate these two entities.

This retrospective observational study included microbiologically confirmed cases of TB and pyogenic spondylitis over three years. Magnetic resonance imaging of included cases was reviewed for a predefined set of imaging findings. A multivariable logistic regression analysis was done to compare the radiological features of both groups. A scoring system was created using the features that were significant in univariate and multivariable analysis.

Of the 90 included cases, 44 were TB and 46 were pyogenic. Involvement of the thoracic vertebra, paravertebral abscess, epidural abscess, posterior element involvement, loss of height, spine deformity, nerve compression, destruction of the disc and larger abscess size were more common in patients with TB. Involvement of the thoracic spine, posterior element involvement and spine deformity were independent predictors of diagnosing TB spine. At a score of 7 (out of 11) or above, the scoring system had a sensitivity and specificity of 86% and 94%, respectively, in diagnosing the TB spine.

In the presence of relevant clinical findings, specific MRI findings can help to differentiate TB from pyogenic spondylitis.