# 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 **Laboratory Interpretation:** The blood tests show: - Anaemia of chronic disease (Hb 108) - consistent with chronic infection - Normal WCC - typical for TB (deceptively normal in indolent infection) - Mildly elevated CRP (28) with moderately elevated ESR (65) - chronic inflammatory pattern - Hypoalbuminaemia - catabolic state with weight loss - Positive QuantiFERON - indicates TB exposure (does NOT confirm active TB) **Imaging Interpretation:** The MRI demonstrates classic features of spinal tuberculosis: - Vertebral body destruction with subligamentous spread - Relative disc preservation (early disease) - key differentiator from pyogenic infection - Bilateral psoas abscess formation - Epidural extension with cord compression **Differential Diagnosis:** | Diagnosis | Supporting Features | Against | |-----------|---------------------|---------| | **Spinal tuberculosis** | Endemic area, constitutional symptoms, subligamentous spread, disc preservation, psoas abscess | - | | Pyogenic spondylodiscitis | Vertebral destruction, back pain | Disc relatively preserved, indolent course, normal WCC | | Spinal metastasis | Back pain, weight loss, vertebral destruction | Disc preservation, psoas abscess, positive QuantiFERON | | Brucellosis | Similar endemic regions, spondylodiscitis | Less common, different imaging pattern | **Leading diagnosis: Spinal tuberculosis (Pott's disease)** based on endemic origin, constitutional symptoms, characteristic MRI with subligamentous spread and disc preservation, and psoas abscess formation. > **Key Point:** TB SPARES discs early (spreads under ligaments). Pyogenic infection DESTROYS discs early. **Tissue Diagnosis is Essential:** - MUST have microbiological/histological confirmation before starting treatment - Empiric anti-TB therapy without tissue diagnosis is NOT acceptable **Biopsy Options:** | Method | Advantages | Yield | |--------|------------|-------| | CT-guided percutaneous biopsy | Minimally invasive, can target psoas abscess | 70-90% | | Surgical biopsy | Higher yield, can decompress/stabilise if needed | >90% | **Samples to Send:** 1. **Microscopy:** Ziehl-Neelsen stain for acid-fast bacilli (AFB) 2. **Culture:** Lowenstein-Jensen medium (takes 6-8 weeks) 3. **TB PCR (GeneXpert):** Rapid result (2 hours), detects rifampicin resistance 4. **Histopathology:** Caseating granulomas 5. **Routine MC&S:** Don't forget pyogenic organisms **Histological Features of TB:** - Caseating granulomas (central necrosis) - Langhans giant cells (horseshoe-shaped nuclei) - Epithelioid macrophages - Lymphocytic infiltrate > **Consultant Tip:** Send MULTIPLE samples. Request ZN stain, TB culture, PCR, AND histology. Never start treatment without tissue confirmation. **Important Principle:** Medical treatment is CURATIVE for spinal TB. Surgery is for specific complications, NOT for debulking bacterial load. **Absolute Surgical Indications:** | Indication | Rationale | |------------|-----------| | Progressive neurological deficit | Urgent decompression required | | Spinal instability | Mechanical failure, progressive kyphosis | | Large abscess requiring drainage | Facilitates antibiotic penetration | | Failed medical treatment | Worsening despite 4-6 weeks antibiotics | | Need for tissue diagnosis | If CT-guided biopsy unsuccessful | **Relative Surgical Indications:** - Severe kyphosis >40° (prevent progression) - Persistent pain despite medical treatment - Significant epidural abscess with cord compression **Surgical Approaches:** | Approach | When to Use | |----------|-------------| | Anterior (thoracotomy/retroperitoneal) | Debridement, grafting, anterior column reconstruction | | Posterior | Stabilisation, instrumentation | | Combined anterior-posterior | Severe instability, significant kyphosis correction | **Hong Kong Procedure (Historical):** - Radical anterior debridement + strut grafting - High fusion rates reported - Now modified with instrumentation for stability > **Consultant Tip:** Surgery is for COMPLICATIONS (neurology, instability, drainage) - not for reducing bacterial load. Chemotherapy handles the infection. **Standard RIPE Regimen:** **Intensive Phase (2 months):** | Drug | Dose | Maximum | Key Toxicity | |------|------|---------|--------------| | **R**ifampicin | 10 mg/kg daily | 600 mg | Hepatotoxicity, orange secretions | | **I**soniazid (INH) | 5 mg/kg daily | 300 mg | Hepatotoxicity, peripheral neuropathy | | **P**yrazinamide | 25 mg/kg daily | 2 g | Hepatotoxicity, hyperuricaemia | | **E**thambutol | 15 mg/kg daily | 1.2 g | Optic neuritis | **Continuation Phase (10-16 months):** - Rifampicin + Isoniazid only - Total duration for spinal TB: **12-18 months** **Essential Adjuncts:** - **Pyridoxine (Vitamin B6) 25mg daily** - prevents INH-induced peripheral neuropathy - Nutritional support **Monitoring Schedule:** | Test | Frequency | Drug Monitored | |------|-----------|----------------| | LFTs | Baseline, 2 weeks, then monthly | INH, rifampicin, pyrazinamide | | Visual acuity & colour vision | Monthly | Ethambutol | | Uric acid | Monthly | Pyrazinamide | | FBC | Monthly | Rifampicin | **Drug Resistance Considerations:** - Multi-drug resistant TB (MDR-TB): Resistant to INH AND rifampicin - Requires ID specialist and second-line agents (fluoroquinolones, aminoglycosides) - Extended treatment duration (18-24 months) > **Consultant Tip:** Remember RIPE. Spinal TB needs 12-18 months total. Add pyridoxine for ALL patients on INH. **Urgent Assessment:** **Possible Causes:** 1. Disease progression despite treatment (drug resistance?) 2. Expanding epidural abscess/granulation tissue 3. Developing mechanical instability with cord compression 4. Paradoxical reaction (immune reconstitution) **Immediate Actions:** 1. **Full neurological examination** - document power, sensation, reflexes 2. **Urgent MRI spine** - assess cord compression, abscess, instability 3. **Review drug sensitivities** - check for MDR-TB 4. **ID consultation** - consider treatment modification **If Imaging Shows Cord Compression:** | Surgical Approach | Details | |-------------------|---------| | Anterior decompression | Remove abscess, debride, strut graft | | Posterior instrumentation | Stabilise with pedicle screws | | Combined approach | For severe instability or kyphosis | **Paradoxical Reaction:** - Worsening despite appropriate treatment - Immune-mediated phenomenon - Consider corticosteroids (with ID input) - More common in HIV co-infection **Post-operative Care:** - Continue anti-TB medications - Rehabilitation and physiotherapy - Serial imaging to assess fusion - Watch for late complications (kyphosis progression) > **Consultant Tip:** New neurology in a patient on treatment = urgent MRI and surgical assessment. Don't wait - cord compression is a surgical emergency. **Prognosis:** - Excellent with early diagnosis and appropriate treatment - 95% cure rate with full course of chemotherapy - Neurological recovery depends on duration and severity of deficit - Residual kyphosis may require late correction **Follow-up Protocol:** | Timeframe | Assessment | |-----------|------------| | Weekly initially | Clinical response, drug tolerance | | Monthly | LFTs, visual acuity, symptoms | | 3-monthly | Inflammatory markers (ESR, CRP), clinical exam | | 6-monthly | Imaging if indicated | | End of treatment | Confirm clinical and radiological cure | **Markers of Response:** - Clinical: Resolution of pain, weight gain, improved mobility - Laboratory: Falling ESR and CRP - Radiological: Healing of lesions, no new lesions **Late Complications to Monitor:** - Progressive kyphosis (especially in children) - Late-onset paraplegia (rare) - Non-union of graft - Recurrence (if treatment incomplete) **Duration of Follow-up:** - Minimum 2 years after treatment completion - Longer if residual deformity or risk factors > **Consultant Tip:** TB is curable but requires completing the full course. Compliance is critical - consider DOT (directly observed therapy) if concerns. --- ## 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 1. **Tissue diagnosis before treatment** - never treat empirically 2. **Medical treatment is curative** - surgery for complications only 3. **RIPE regimen for 12-18 months** - shorter courses have high failure rates 4. **Monitor for drug toxicity** - especially hepatotoxicity 5. **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