A Novel Magnetic Resonance Imaging Scoring System in Making Specific Diagnosis of Tubercular Spondylitis in Advanced Infection

Abstract

Objective: The diagnosis of tuberculous spondylitis by microbiological and histopathological analysis is time consuming. Non-invasive methods such as magnetic resonance imaging (MRI) are useful for early diagnosis of infective spondylitis; however, the usefulness of MRI in accurate prediction of tuberculosis rather than non-specific infections is still not elucidated. There is a lacuna in the literature with regard to this. Non-invasive identification of tubercular etiology help in initiation of appropriate treatment and thus a better therapeutic response. We intend to devise a novel MRI score in making a confident diagnosis of tubercular spondylitis rather than non-specific infective spondylitis. Materials and Methods: A retrospective observational analysis was performed on 125 biopsy-proven infective spondylitis patients which included 70 tubercular (Group A) and 55 pyogenic (Group B) patients. Tubercular spondylitis was confirmed by either positive result of tissue gene expert test, histopathology or culture results. Eight MRI findings described in literature to be favorable for tubercular spondylitis were selected and analyzed for their predictive value, and a scoring system is derived based on the observations. Results: Statistically significant differentiation was noted in six out of selected eight MRI parameters, namely, (1) involvement of more than two contiguous vertebrae, (2) presence of para or intraosseous abscess, (3) subligamentous spread, (4) vertebral collapse, (5) large collection with thin abscess wall, and (6) presence of hypointense debris/wall on T2WI. Positive predictive value for tubercular spondylitis was obtained for the following MRI parameters by multivariate regression analysis: (1) Sub-ligamentous spread, (2) vertebral collapse, (3) large collection with thin abscess wall, and (4) presence of T2 hypointense debris. These MRI parameters having an independent prediction of tuberculosis were given two points score for each. Less significant MRI findings of more than two contiguous vertebral involvement and presence of intraosseous abscess were given a score of one for each. A total score of 10 was formulated and scoring for both groups was tabulated and analyzed. Contrary to that available in literature, no significant statistical correlation for differentiation was observed in our group for the presence of skip lesions and absence of intervertebral disc involvement. Hence, these were not included in our scoring system. Distribution of scores among the subjects aged 53.4 ± 17 years showed P < 0.001 (t-test and Mann–Whitney U-test) with mean of 7.4 for tubercular and 2.9 for pyogenic group (SD of 1.9). A score of 6 or above suggested tuberculosis and score below 6 suggested pyogenic infection (Chi-square value of 87.67 and P < 0.00001). Conclusion: MRI can thus be used for accurate diagnosis of spinal tuberculosis, and our novel MRI scoring system can be applied to exclude non-specific spondylodiscitis, help in reducing the burden of additional invasive investigations, expenditure and the time delay for initiating antitubercular treatment.