MRI in differential diagnosis between tuberculous and pyogenic spondylodiscitis

The aim of the study was to investigate whether MRI findings together with epidemiological data could help in differentiating between tuberculous and pyogenic spondylodiscitis.

Clinical records of 260 patients with a suspicion of spondylodiscitis were analysed. Patients were selected using the following inclusion criteria: confirmed diagnosis of spondylodiscitis either from pyogenic bacteria or from Mycobacterium tuberculosis and contrast-enhanced MRI performed before treatment. Clinical data concerning age, sex and country-of-origin were also collected. For each patient, several MRI-features were evaluated by two-expert musculoskeletal radiologists. A chi-squared test and a multiple logistic regression were used to find the best predictors of tuberculous or pyogenic spondylodiscitis.

114 patients were retrospectively enrolled, 30 with tuberculous and 84 with pyogenic spondylodiscitis. We found 18 MRI-features, significantly different between the two groups. Among these, the most strongly associated with tuberculous spondylodiscitis were: heterogeneous vertebral signal on T1w-sequences (Odds Ratio(OR) = 205.759-p < 0.001), presence of epidural abscess (OR = 86.221-p < 0.001), severe vertebral destruction (OR = 10.017-p < 0.001) and absence of epidural phlegmon (OR = 86.221-p < 0.001). Moreover, patients coming from countries with a middle-high prevalence of tuberculosis were more frequently affected by tuberculous spondylodiscitis than others were (OR = 229.136-p < 0.001). The best prediction model demonstrated a correct classification rate of 94.7%.

To the best of our knowledge this is the largest study comparing MRI-features of tuberculous and pyogenic spondylodiscitis. The above-mentioned MRI-features and epidemiological data are crucial in the differential diagnosis between these two entities, guiding the choice of the appropriate therapy, especially when a pathogen cannot be clearly identified with other modalities.