Spinal Tuberculosis (Pott's Disease)
CIM Case: Spinal Tuberculosis (Pott's Disease)
Clinical Scenario
Patient: 45-year-old man from India Presentation: 4 months of progressive back pain, weight loss (8kg), and night sweats Relevant history: Immigrated to Australia 2 years ago. No known TB contacts or previous treatment. Non-smoker, no HIV risk factors disclosed. Examination findings:
- Tender thoracolumbar junction with localised kyphosis at T12-L1
- No gibbus deformity palpable
- Full power in lower limbs (MRC 5/5)
- Sensation intact, reflexes normal, plantar responses flexor
- No bladder or bowel symptoms
Investigations Provided
Laboratory Results
| Test | Result | Normal Range | Interpretation |
|---|---|---|---|
| Hb | 108 g/L | 130-170 g/L | ↓ Anaemia of chronic disease |
| WCC | 8.2 ×10⁹/L | 4-11 ×10⁹/L | Normal |
| Platelets | 385 ×10⁹/L | 150-400 ×10⁹/L | Normal |
| CRP | 28 mg/L | <5 mg/L | ↑ Mildly elevated |
| ESR | 65 mm/hr | <20 mm/hr | ↑↑ Elevated |
| Albumin | 28 g/L | 35-50 g/L | ↓ Hypoalbuminaemia |
| QuantiFERON Gold | Positive | Negative | Indicates TB exposure |
| HIV | Negative | Negative | Important to exclude |
Imaging
Image 1: Lateral Radiograph of Thoracolumbar Spine
Radiological features:
- Anterior vertebral body destruction at T12 and L1
- Reduced disc height at T12-L1 (late finding)
- Localised kyphotic angulation at T12-L1
- Bilateral paravertebral soft tissue shadow (psoas shadow widening)
- No obvious calcification
Image 2: Chest X-ray PA
Findings:
- No active pulmonary TB changes visible
- No upper lobe cavitation or consolidation
- Normal cardiac silhouette
Image 3: MRI Thoracolumbar Spine (T1, T2/STIR, Post-contrast)
MRI findings:
- Destruction of T12 and L1 vertebral bodies with low T1, high STIR signal
- Relative preservation of T12-L1 disc in early images (classic for TB)
- Subligamentous spread along anterior longitudinal ligament extending to T11 and L2
- Large bilateral psoas abscesses (5cm right, 4cm left)
- Epidural soft tissue extending into spinal canal causing mild cord compression
- No myelomalacia signal within cord
- Kyphotic deformity measuring 25°
Questions & Model Answers
Describe the investigation findings and differential diagnosis
How would you confirm the diagnosis?
What are the indications for surgery in spinal TB?
The biopsy confirms TB with ZN-positive AFB. What is your antibiotic regimen?
At 3 months, the patient develops new bilateral lower limb weakness. What is your management?
What is the prognosis and follow-up for spinal TB?
Key Teaching Points
Pattern Recognition
This pattern suggests Spinal Tuberculosis:
- Patient from TB-endemic area with constitutional symptoms
- Insidious onset back pain with weight loss and night sweats
- Thoracolumbar junction involvement (most common site)
- Deceptively normal inflammatory markers (WCC often normal)
- MRI: Subligamentous spread with relative disc preservation
Distinguish from Pyogenic Spondylodiscitis:
| Feature | TB | Pyogenic |
|---|---|---|
| Onset | Insidious (months) | Acute (days-weeks) |
| WCC/CRP | Often normal/mildly elevated | Usually markedly elevated |
| Disc involvement | Preserved early | Destroyed early |
| Spread pattern | Subligamentous (under ALL) | Direct disc destruction |
| Abscess | Common (psoas) | Less common |
| Calcification | May be present | Rare |
Distinguish from Spinal Metastasis:
- Metastasis: Usually posterior elements involved, no disc changes
- TB: Anterior vertebral body, subligamentous spread, disc relatively preserved
- Both can cause weight loss - look for primary tumour
Critical Management Points
- Tissue diagnosis before treatment - never treat empirically
- Medical treatment is curative - surgery for complications only
- RIPE regimen for 12-18 months - shorter courses have high failure rates
- Monitor for drug toxicity - especially hepatotoxicity
- Compliance is crucial - consider DOT if adherence concerns
Common Examiner Follow-ups
Q: "What is the most common site for spinal TB?"
The thoracolumbar junction (T12-L1) is most commonly affected, followed by lower thoracic and upper lumbar spine. Cervical involvement is less common but carries higher risk of neurological complications.
Q: "What is a 'cold abscess' and why is it called that?"
A cold abscess is a collection of caseous material and pus that forms without the classical inflammatory signs of warmth and erythema. It occurs because TB produces a granulomatous rather than acute inflammatory response. Can track along fascial planes (e.g., psoas abscess presenting in groin).
Q: "What is Frankel grading and how would you use it?"
Frankel grading assesses spinal cord function:
- A: Complete motor and sensory loss
- B: Incomplete - sensation present, no motor function
- C: Motor function present but not useful (power <3)
- D: Motor function useful (power ≥3)
- E: Normal motor and sensory function
Used for documenting baseline deficit and monitoring improvement.
Q: "What are the risk factors for kyphosis progression?"
- Age <10 years (greatest risk)
- Loss of >2 vertebral bodies
- Thoracic spine involvement
- Pan-vertebral disease
- Initial kyphosis >30°
- Posterior element involvement
Children with >2 vertebral bodies destroyed may need prophylactic fusion to prevent severe kyphosis.
Related Topics
- Pyogenic Spondylodiscitis
- Spinal Cord Compression
- Psoas Abscess
- Kyphosis Correction Surgery
- TB in Orthopaedics