SPINAL TUBERCULOSIS (POTT'S DISEASE)
Diagnosis | Imaging | Medical Management | Surgical Indications
ANATOMICAL PATTERNS
Critical Must-Knows
- Thoracolumbar junction (T10-L2) is most common site
- Disc preservation early distinguishes from pyogenic infection
- Cold abscess does not contain pus - caseous material
- MRI is gold standard - sensitivity 96%, specificity 93%
- Medical treatment first - surgery for specific indications
Examiner's Pearls
- "Paradiscal type is most common - adjacent vertebrae + disc involvement
- "Skip lesions in 10-15% - always image whole spine
- "Psoas abscess is pathognomonic when combined with spine findings
- "Neurological deficit from granulation tissue, abscess, or kyphosis
Clinical Imaging
Imaging Gallery
Critical Spinal TB Exam Points
Disc Preservation
Early TB preserves the disc while pyogenic infection destroys it early. This is a key differentiating feature. However, late-stage TB can involve the disc. Always compare with clinical tempo - TB is insidious, pyogenic is acute.
Cold Abscess
Cold abscess is characteristic of TB - it lacks acute inflammatory features and contains caseous neite, not pus. It can track along fascial planes (psoas abscess). The absence of local warmth and systemic toxicity distinguishes it from pyogenic abscess.
Imaging Sensitivity
MRI is essential - 96% sensitivity, 93% specificity. Changes visible within 3-5 days. X-rays only positive when 50% trabecular bone destroyed (4-6 months delay). Always image whole spine for skip lesions (10-15%).
Medical First
Medical treatment is primary - 85-90% respond to antitubercular therapy (ATT) alone. Surgery reserved for: progressive neurology, instability, failure of medical treatment, severe kyphosis. Even with neurology, medical treatment often effective.
Spinal TB vs Pyogenic Spondylitis
| Feature | Tuberculosis | Pyogenic |
|---|---|---|
| Onset | Insidious (weeks-months) | Acute (days-weeks) |
| Disc involvement | Late or spared | Early destruction |
| Vertebral bodies | Multiple, skip lesions | Usually contiguous |
| Abscess wall | Thin, smooth | Thick, irregular |
| Posterior elements | Spared early | Often involved |
| Calcification | Present (pathognomonic) | Rare |
COLD ABSCESS - TB Features
Memory Hook:COLD ABSCESSES lack heat, redness, and acute toxicity - unlike pyogenic
SPINE TB - Imaging Findings
Memory Hook:MRI is imaging modality of choice - sensitivity 96%
SURGERY - Indications for Surgery
Memory Hook:Most patients (85-90%) respond to medical treatment alone
Overview and Epidemiology
Spinal tuberculosis (Pott's disease) is the most common form of skeletal tuberculosis, first described by Percivall Pott in 1779. It represents a significant cause of morbidity, particularly in endemic regions, and remains important in the Australian context due to immigration patterns.
Epidemiology:
- Spinal TB accounts for 50% of all skeletal TB cases
- Second most common form of extrapulmonary TB
- Thoracolumbar junction (T10-L2) is most commonly affected
- Approximately 10-15% have skip lesions (non-contiguous involvement)
- Male to female ratio approximately 1.5:1
- Can occur at any age but peaks in second and third decades
Global Burden:
| Region | Estimated Incidence | Risk Factors |
|---|---|---|
| High endemic | More than 100/100,000 | Crowding, poverty, HIV |
| Intermediate | 10-100/100,000 | Immigration, immunosuppression |
| Low endemic | Less than 10/100,000 | Imported cases, reactivation |
Australian Context:
Australia has low TB incidence overall, but overseas-born individuals (particularly from high-burden countries) account for the majority of cases. Spinal TB may present in immigrants, refugees, or travelers, often as reactivation of latent infection years after initial exposure.
Immigration Pattern
In Australia, maintain high suspicion for spinal TB in patients from endemic regions (South Asia, Southeast Asia, Sub-Saharan Africa, Pacific Islands) presenting with chronic back pain and constitutional symptoms, even years after migration.
Pathophysiology and Anatomy
Route of Infection
Primary Infection:
- Haematogenous spread from pulmonary focus (most common)
- Arterial dissemination to vertebral bodies
- Paradiscal arteries supply adjacent vertebrae (paradiscal type)
- Batson's venous plexus may facilitate spread
Secondary Spread:
- Subligamentous extension under ALL
- Epidural spread causing cord compression
- Paravertebral spread forming cold abscess
- Psoas tracking along muscle sheath
Anatomical Patterns of Involvement
1. Paradiscal Type (50-75%):
- Most common pattern
- Involves adjacent vertebral bodies and intervening disc
- Arterial spread via paradiscal arteries
- Late disc destruction (unlike pyogenic)
- May extend to multiple levels
2. Central Type:
- Isolated vertebral body involvement
- Concertina collapse
- May produce ivory vertebra
- Spares disc initially
3. Anterior Subligamentous Type:
- Spreads under anterior longitudinal ligament
- Multi-level involvement with anterior scalloping
- Can produce skip lesions
- Extensive yet may spare vertebral integrity initially
4. Posterior Type (2-10%):
- Involves neural arch (pedicle, lamina, spinous process)
- More common in lower lumbar spine
- May cause early neurological deficit
Pathological Changes
Bone Changes:
- Granulomatous inflammation
- Caseous necrosis
- Bone destruction and sequestration
- Minimal new bone formation (unlike pyogenic)
Soft Tissue:
- Cold abscess formation (paravertebral, epidural, psoas)
- Granulation tissue proliferation
- Fibrosis with healing
Neurological Compression:
- Early: Epidural granulation tissue, abscess
- Late: Bony compression from kyphotic deformity
Classification Systems
Kumar Classification (Neurological Status)
| Stage | Description | Neurological Findings |
|---|---|---|
| I | No deficit | Normal |
| II | Sensory | Sensory loss only |
| III | Motor - ambulatory | Motor weakness, can walk |
| IV | Motor - non-ambulatory | Cannot walk |
| V | Complete paraplegia | No function below lesion |
Tuli Classification (Paraplegia Type)
Type A: Active Disease with Paraplegia
- A1: Minimal bone loss, severe deficit
- A2: Moderate bone loss, severe deficit
- A3: Extensive bone loss with deficit
Type B: Healed Disease with Paraplegia
- B1: Cord compression from healed kyphosis
- B2: Reactivation in previously healed lesion
This classification guides surgical approach and prognosis for neurological recovery.
Clinical Assessment
History
Presenting Symptoms:
| Symptom | Frequency | Characteristics |
|---|---|---|
| Back pain | 90-95% | Insidious, localized, constant |
| Constitutional | 50-70% | Weight loss, night sweats, fever |
| Neurological | 20-30% | Weakness, sensory changes |
| Deformity | 30-40% | Visible kyphosis (gibbus) |
| Abscess | 20-30% | Swelling (groin, flank) |
Key History Elements:
- Duration of symptoms (typically weeks to months)
- Constitutional symptoms (weight loss, night sweats, low-grade fever)
- Neurological symptoms (weakness, numbness, bowel/bladder)
- Contact history (TB exposure)
- Country of origin and travel
- Immunocompromise (HIV, diabetes, immunosuppressants)
- Previous TB treatment
Physical Examination
Spinal Assessment:
- Gibbus deformity (angular kyphosis)
- Localized tenderness
- Paraspinal muscle spasm
- Restricted range of motion
- Cold abscess (paravertebral, groin, flank)
Neurological Examination:
- Motor power (myotomes)
- Sensory level
- Reflexes
- Long tract signs (spasticity, clonus, Babinski)
- Bladder/bowel function
- Gait assessment
Systemic Examination:
- Lymphadenopathy
- Pulmonary findings (primary TB)
- Peripheral cold abscess
- Signs of other organ involvement
Cold Abscess Features
A cold abscess lacks the cardinal signs of inflammation (calor, rubor, dolor, tumor). It presents as a non-tender, fluctuant swelling that may track to distant sites (groin in psoas abscess). The absence of acute inflammatory features is characteristic.
Red Flags
- Rapidly progressive neurological deficit
- Complete paraplegia
- Bladder/bowel dysfunction
- Respiratory compromise (cervical lesions)
- Signs of MDR-TB or treatment failure
Investigations
Laboratory Investigations
Essential Tests:
| Test | Expected Finding | Notes |
|---|---|---|
| ESR | Elevated (often more than 50) | Useful for monitoring |
| CRP | Elevated | Less specific than ESR |
| Mantoux/IGRA | Usually positive | Does not confirm active disease |
| Sputum AFB | May be positive | If pulmonary involvement |
| HIV serology | Rule out coinfection | Important for management |
Imaging Protocol
Plain Radiographs:
- First-line imaging
- Positive only when 50% trabecular bone destroyed
- May take 4-6 months to show changes
- Shows: vertebral destruction, collapse, kyphosis
MRI (Gold Standard):
- Sensitivity 96%, Specificity 93%
- Changes visible within 3-5 days
- Essential for soft tissue assessment
- Detects epidural extension and cord compression
- Identifies skip lesions
MRI Findings:
- T1: Hypointense marrow signal
- T2/STIR: Hyperintense marrow edema
- Contrast: Rim enhancement of abscess
- Epidural extension
- Skip lesions
- Psoas/paravertebral abscess
CT Scan:
- Superior bone detail
- Calcification within soft tissue (pathognomonic)
- Bony destruction pattern
- CT-guided biopsy assistance
Tissue Diagnosis
Biopsy Indications:
- Atypical presentation
- Negative Mantoux/IGRA
- MDR-TB suspected
- Exclude malignancy
- Failed empirical treatment
Methods:
- CT-guided percutaneous biopsy
- Open surgical biopsy
- Abscess aspiration
Histopathology:
- Caseous necrosis
- Epithelioid granulomas
- Langhans giant cells
- AFB staining
- PCR (GeneXpert)
Management
Antitubercular Therapy (ATT)
Standard Regimen (WHO):
| Phase | Duration | Drugs |
|---|---|---|
| Intensive | 2 months | HRZE (4 drugs) |
| Continuation | 4-10 months | HR (2 drugs) |
Drug Dosages:
- H (Isoniazid): 5 mg/kg (max 300 mg)
- R (Rifampicin): 10 mg/kg (max 600 mg)
- Z (Pyrazinamide): 25 mg/kg (max 2 g)
- E (Ethambutol): 15 mg/kg (max 1.2 g)
Duration Controversy:
- Standard: 6-9 months
- Extended: 12-18 months (complex cases)
- WHO recommends 6 months for uncomplicated
- Many centers use 9-12 months for spinal TB
Monitoring:
- Baseline: LFTs, uric acid, visual acuity
- Monthly: LFTs during intensive phase
- Clinical response assessment
- Radiological healing (MRI at 6 months)
- ESR trending
Drug-Resistant TB:
- MDR-TB requires specialist management
- Second-line drugs (fluoroquinolones, injectables)
- Extended duration (18-24 months)
- Specialist input essential
Hepatotoxicity Risk
Monitor LFTs closely during ATT. Risk factors for hepatotoxicity include age more than 35, pre-existing liver disease, alcohol use, and concurrent hepatotoxic medications. Stop ATT if ALT rises more than 5x ULN or symptoms develop.
Medical therapy alone achieves good outcomes in 85-90% of cases when neurological deficit is not severe.
Complications
Disease-Related Complications
| Complication | Incidence | Management |
|---|---|---|
| Kyphosis | 30-50% | Surgical correction if severe |
| Paraplegia | 20-30% | Decompression ± steroids |
| Cold abscess | 20-30% | Drainage if large |
| Sinus formation | 5-10% | Debridement, prolonged ATT |
| Spinal instability | Variable | Instrumented fusion |
Neurological Complications
Pott's Paraplegia:
- Early onset (active disease): Better prognosis
- Late onset (healed disease): Worse prognosis
- Causes: Abscess, granulation tissue, bony compression
Prognosis Factors:
- Duration of deficit (shorter = better)
- Completeness (incomplete = better)
- Age (younger = better)
- Vertebral destruction extent
Treatment-Related Complications
Medical:
- Hepatotoxicity (2-10%)
- Drug reactions
- Drug interactions
- MDR development
Surgical:
- Infection
- Neurological injury
- Hardware failure
- Pseudarthrosis
- Recurrence
Long-Term Sequelae
- Residual kyphosis
- Chronic pain
- Residual neurological deficit
- Adjacent segment disease
- Growth disturbance (paediatric)
Kyphosis Prevention
Early recognition and appropriate treatment can prevent severe kyphosis. Children are at higher risk of progressive deformity. Consider early surgery in children with significant vertebral destruction to prevent late kyphotic deformity.
Outcomes and Prognosis
Neurological Recovery
Prognosis by Presentation:
| Presentation | Recovery Rate | Timeframe |
|---|---|---|
| Early/mild deficit | 70-80% | 3-6 months |
| Moderate deficit | 50-70% | 6-12 months |
| Complete paraplegia | 20-30% | Variable |
Favourable Factors:
- Short duration of deficit
- Incomplete paraplegia
- Younger age
- Compression by soft tissue (not bone)
- Early treatment initiation
Treatment Outcomes
Medical Treatment Alone:
- Success rate: 85-90%
- Healing time: 6-12 months
- Residual kyphosis: 30-50%
Combined Medical + Surgical:
- Neurological improvement: 70-90%
- Fusion rate: 90-95%
- Deformity correction maintained
Long-Term Prognosis
Factors Affecting Outcome:
- Extent of initial disease
- Timing of treatment
- Adequacy of ATT
- Surgical technique
- Patient compliance
Return to Activity:
- Light activities: 3-6 months
- Full activities: 6-12 months
- Depends on neurological status
Outcome Summary
With appropriate treatment, most patients with spinal TB achieve good outcomes. Medical treatment alone is sufficient in 85-90%. Neurological recovery is expected in 70-80% of those with incomplete deficits. Surgery improves outcomes in selected cases with specific indications.
Evidence and Guidelines
Duration of ATT for Spinal TB
- 6 months ATT as effective as longer regimens in uncomplicated cases
- No difference in relapse rates between 6 and 12 months
- Extended treatment may be warranted in complex cases
- Compliance is more important than duration
Surgery vs Medical Treatment Alone
- Medical treatment alone effective in 85-90% of uncomplicated cases
- Surgery improves neurological recovery in selected patients
- Earlier surgery may benefit those with significant neurological deficit
- Combination approach best for complex cases
MRI for Diagnosis and Monitoring
- MRI sensitivity 96%, specificity 93%
- Changes visible within 3-5 days
- Superior to CT for soft tissue and epidural assessment
- Whole spine imaging detects skip lesions (10-15%)
Neurological Recovery Predictors
- Duration of paralysis inversely correlates with recovery
- Incomplete lesions recover better than complete
- Early decompression improves outcomes in selected cases
- Age affects recovery potential
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Classic Pott's Disease Presentation
"A 35-year-old man from India presents with 4 months of progressive back pain, night sweats, and weight loss. He has low-grade fever and difficulty walking due to leg weakness. MRI shows T11-12 vertebral destruction with anterior soft tissue collection."
Spinal TB vs Pyogenic Infection
"A 50-year-old man presents with back pain and low-grade fever. MRI shows L3-4 vertebral body involvement with disc changes and paravertebral collection. Both TB and pyogenic infection are being considered."
Pott's Paraplegia Management
"A 28-year-old woman presents with complete paraplegia of 2 weeks duration. MRI shows T7-8 vertebral destruction with large epidural collection causing severe cord compression. She has confirmed pulmonary TB on sputum."
MCQ Practice Points
Most Common Location
Q: What is the most common location for spinal tuberculosis?
A: The thoracolumbar junction (T10-L2) is the most common site for spinal TB. The thoracic spine is involved in approximately 50% of cases, lumbar in 35%, and cervical in 15%. The paradiscal region is the most common pattern of involvement.
Disc Preservation
Q: Which feature distinguishes spinal TB from pyogenic spondylitis?
A: Early disc preservation distinguishes TB from pyogenic infection. In pyogenic spondylitis, the disc is destroyed early as bacteria can survive in disc tissue. In TB, the avascular disc is relatively resistant to mycobacterial infection, though late TB can involve the disc.
Imaging Sensitivity
Q: What is the sensitivity of MRI for detecting spinal tuberculosis?
A: MRI has 96% sensitivity and 93% specificity for spinal TB. Changes are visible within 3-5 days of infection onset. Plain radiographs only become positive when 50% of trabecular bone is destroyed, which may take 4-6 months.
Skip Lesions
Q: What percentage of spinal TB patients have skip lesions?
A: 10-15% of patients have skip lesions (non-contiguous vertebral involvement). This is why whole spine imaging with MRI is recommended in all suspected cases of spinal TB to detect all levels of involvement.
Treatment Response
Q: What percentage of patients with uncomplicated spinal TB respond to medical treatment alone?
A: 85-90% of patients with uncomplicated spinal TB respond to antitubercular therapy alone without surgery. Surgery is reserved for specific indications including progressive neurology, instability, and failure of medical treatment.
Australian Context
Epidemiology in Australia
Australia has low overall TB incidence (approximately 5.5 per 100,000 population), but overseas-born individuals account for more than 85% of TB cases. Countries of origin with high TB burden include India, Philippines, Vietnam, China, and Sub-Saharan African nations.
Spinal TB typically presents as reactivation of latent infection, sometimes decades after initial exposure. Clinicians should maintain high suspicion in patients from endemic regions presenting with chronic back pain and constitutional symptoms.
Diagnostic Approach
Australian guidelines recommend tissue diagnosis when possible, particularly given the low prevalence and need to confirm diagnosis before prolonged treatment. GeneXpert PCR is widely available and provides rapid results with drug susceptibility information.
Treatment Considerations
ATT in Australia follows WHO guidelines with modifications for local resistance patterns. Standard regimens of 6-9 months are typically prescribed, with extension to 12 months for complex cases. Rifampicin interactions with other medications require careful management.
Multidisciplinary Care
Management of spinal TB in Australia typically involves infectious disease physicians, orthopaedic or neurosurgeons with spinal expertise, radiologists, and public health teams. Notification to public health authorities is mandatory for all TB cases, and contact tracing is essential.
Follow-up and Monitoring
Patients require long-term follow-up to ensure treatment completion, monitor for complications, and detect relapse. DOT (Directly Observed Therapy) programs are available for patients at risk of non-compliance. Rehabilitation services assist with functional recovery following neurological involvement.
SPINAL TUBERCULOSIS (POTT'S DISEASE)
High-Yield Exam Summary
Key Facts
- •50% of skeletal TB is spinal
- •T10-L2 most common location
- •Paradiscal type most common (50-75%)
- •Skip lesions in 10-15% - image whole spine
TB vs Pyogenic
- •TB: Insidious onset, low-grade fever, disc spared early
- •Pyogenic: Acute onset, high fever, early disc destruction
- •TB: Thin smooth abscess wall, calcification
- •Pyogenic: Thick irregular wall, no calcification
Imaging
- •MRI gold standard: 96% sensitivity, 93% specificity
- •Changes visible on MRI in 3-5 days
- •X-ray: positive only when 50% bone destroyed (4-6 months)
- •Always image whole spine for skip lesions
Management
- •Medical first: 85-90% respond to ATT alone
- •ATT: HRZE 2 months, then HR 4-10 months
- •Surgery: progressive neurology, instability, large abscess
- •Combined approach for complex cases
Surgical Indications (SURGERY)
- •Severe kyphosis (more than 40-50 degrees)
- •Unstable spine
- •Resistant (MDR) TB
- •Granulation tissue compressing cord
- •Extensive abscess
- •Regressing neurology despite ATT