Beyond Cord Compression: Instability as a Major Driver for Neurological Deficit in Active Thoracic Spinal Tuberculosis

Study Design Retrospective. Objective To evaluate the association between mechanical instability and neurological deficit in spinal tuberculosis (TB), and compare it against previously recognized radiological parameters. Methods Clinical and radiological data of patients with active thoracic spinal TB were evaluated. Instability was assessed using the Spinal Tuberculosis Instability Scoring System (STISS) by Rajasekaran et al. Neurological status and radiological parameters were analysed to identify the factors associated with neurological deficit. Results A total of 122 patients were included. The average age was 51 ± 18 years, and 54.9% were males. 40 (32.8%) patients had neurological deficits at presentation. Based on the STISS, 71 (58%) patients were categorised as stable, 10 (8.2%) as potentially unstable, and 41 (34%) as definitely unstable. On MRI, cord signal changes and epidural compression were noted in 18% and 64% of the patients, respectively. Definite instability was found to be the strongest independent association of neurological deficit (OR 9.77, 95% CI 2.85-38.9, P < 0.001), followed by greater canal encroachment area (CEA) (OR 1.08, 95% CI 1.03-1.13, P = 0.002). In a stable spine with epidural compression, the predicted probability of neurological deficit is 27%. In an unstable spine, the likelihood of neurological deficit is 50% even without epidural compression, and highest (63%) when instability was associated with epidural compression. Conclusion Mechanical instability is the strongest independent association of neurological deficit in spinal TB, even in the absence of epidural compression. Incorporating the Spine Instability Scoring System into routine clinical evaluation improves risk stratification, enables timely decision-making, and can prevent irreversible neurological deficits.