A 38-year-old man from rural Bihar presents with a 6-month history of progressive thoracic back pain, kyphosis, and lower limb weakness. Clinical examination reveals paraparesis and a palpable gibbus deformity. Plain radiographs show anterior vertebral body collapse with loss of disc space. Which investigation is most appropriate to confirm the diagnosis of Pott disease and guide management?

Explanation

## Investigation of Choice in Pott Disease ### Why MRI with Contrast is the Gold Standard **Key Point:** MRI is the investigation of choice for diagnosis and staging of Pott disease because it provides superior soft tissue contrast, detects early disease, assesses spinal cord compression, and evaluates epidural involvement. ### MRI Findings in Pott Disease | Finding | Significance | |---------|-------------| | Anterior vertebral body involvement (most common) | Pathognomonic for TB of spine | | Disc space preservation (early) | Distinguishes TB from pyogenic spondylitis | | Kyphotic deformity | Indicates structural instability | | Epidural abscess/granulation tissue | Assesses cord compression risk | | T2 hyperintense signal in vertebral body | Edema and inflammation | | Contrast enhancement | Confirms active disease | **High-Yield:** MRI is superior to CT for: - Early detection of disease (before radiographic changes) - Assessment of spinal cord compression and myelopathy - Evaluation of epidural involvement and abscess formation - Detection of multi-level disease - Monitoring response to anti-TB therapy ### Clinical Pearl **Clinical Pearl:** While plain radiographs show structural changes (vertebral collapse, kyphosis), they appear late in disease. MRI detects Pott disease in the early inflammatory phase when intervention can prevent irreversible neurological damage and severe deformity. ### Role of Other Investigations - **TST/IGRA:** Supports diagnosis but not confirmatory (high false negatives in active TB, positive in latent TB) - **ESR:** Non-specific marker of inflammation; useful for monitoring but not diagnostic - **CT scan:** Better for assessing bony anatomy and surgical planning but inferior to MRI for soft tissue and cord assessment - **Biopsy:** Reserved when MRI findings are inconclusive or to exclude malignancy; not first-line **Warning:** Do not rely on TST or ESR alone — they lack specificity and sensitivity for diagnosis. Microbiological confirmation (culture, GeneXpert MTB/RIF from biopsy/aspirate) is the gold standard, but MRI is the best imaging modality for initial diagnosis and management planning. ### Mnemonic for Pott Disease Workup **MRI-FIRST:** **M**RI for imaging, **R**adiographs for baseline, **I**GRA/TST for TB status, **F**ull spine assessment, **I**nflammatory markers (ESR/CRP), **R**adiological follow-up, **S**pinal cord status, **T**reatment monitoring.