Infective Spondylodiscitis: A Comparative Analysis of Magnetic Resonance Imaging Findings with Etiology

Abstract

Introduction: Spondylodiscitis in the Indian population is mostly tubercular and pyogenic. Gadolinium-enhanced magnetic resonance imaging (MRI) is currently most suited for radiological evaluation of the spine in patients with suspected vertebral osteomyelitis. Histology is highly sensitive in detecting the presence or absence of spondylodiscitis but fails in addressing the causative organism. The identification of organism is mainly through microbiological methods such as culture and tuberculosis (TB) polymerase chain reaction. The use of both pathologic examination and culture of the specimen along with imaging findings is paramount in establishing the diagnosis. Methodology: We performed prospective analysis of MR images obtained from patients with suspected spondylodiscitis who have undergone spinal biopsy for confirmation of diagnosis. T2- and T1-weighted images with and without contrast enhancement were subjected to assessment in coronal, axial, and sagittal planes. The sample obtained from biopsy was sent for microbiological and pathological analyses. Based on the final results, MRI findings and histopathological findings were correlated. Results: Out of 45 studied cases, 35 were confirmed to be infective spondylodiscitis, 5 were degenerative disc disease, 1 lymphoma, and 4 metastatic disease of the spine. Out of 35 confirmed cases, 17 (48.6%) were caused by TB and 18 (51.4%) by pyogenic organisms. The sensitivity and specificity of MRI for correctly diagnosing tuberculous spondylodiscitis were 70.6% and 77.8%, respectively, whereas the sensitivity and specificity of MRI for correctly diagnosing pyogenic spondylodiscitis were 44.4% and 85.2%, respectively. The statistically significant features specific for tuberculous spondylodiscitis for MRI were thin and smooth abscess wall, involvement of >2 vertebral bodies (52.9% in tuberculous vs. 44.4% in pyogenic), skip lesions (23.5% in tuberculous vs. 0% in pyogenic), and cold abscess (17.6% in tuberculous vs. 0% in pyogenic). Conclusion: It has been found that MRI is highly sensitive in detecting infective spondylodiscitis and has been widely accepted as the imaging modality of choice for the same. Although many imaging features have been identified to differentiate pyogenic and tuberculous etiologies, due to overlapping of these features, the sensitivity of MRI to conclusively diagnose the etiology needs further studies.