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Updated: Jul 6 2021

Spinal Tuberculosis

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  • summary
    • Spinal Tuberculosis, also known as Pott's Disease, is a spinal infection caused by tuberculosis that can lead to osteomyelitis, kyphotic deformity, and spinal mechanical instability.
    • Diagnosis is made with a CT-guided biopsy sent for acid-fast bacilli.
    • Treatment is usually bracing and anti-tuberculosis antibiotics in the absence of neurological defects or mechanical instability. Surgical management is indicated in the presence of neurological deficits, progressive kyphosis, and/or mechanical instability. 
  • Epidemiology
    • Incidence
      • increasing incidence of TB in United States due to increasing immunocompromised population
    • Demographics
      • HIV positive population (often seen in patients with CD4+ count of 50 to 200)
    • Anatomic location
      • 15% of patients with TB will have extrapulmonary involvement
      • the spine, and specifically, the thoracic spine is the most common extrapulmonary site
      • 5% of all TB patients have spine involvement
  • Etiology
    • Pathoanatomy
      • early infection
        • begins in the metaphysis of the vertebral body
        • spreads under the anterior longitudinal ligament and leads to
          • contiguous multilevel involvement
          • skip lesion or noncontiguous segments (15%)
          • paraspinal abscess formation (50%)
            • usually anterior and can be quite large (much more common in TB than pyogenic infections)
        • initially does not involve the disc space (distinguishes from pyogenic osteomyelitis, but can be misdiagnosed as a neoplastic lesion)
      • chronic infection
        • severe kyphosis
          • mean deformity in nonoperative cases is 15°
            • in 5% of patients, deformity is >60°
            • higher rate of progression of kyphosis when involvement of the vertebral body and posterior elements
          • infection is often diagnosed late, there is often much more severe kyphosis in granulomatous spinal infections compared to pyogenic infections
          • in adults
            • kyphosis stays static after healing of disease
          • in children
            • kyphosis progresses in 40% of cases because of growth spurt
          • classification of progression (Rajasekaran)
            • Type-I, increase in deformity until cessation of growth
              • should be treated with surgery
            • Type-II, decreasing progression with growth
            • Type-III, minimal change during either active / healed phases.
  • Presentation
    • Symptoms
      • onset of symptoms of tuberculous spondylitis is typically more insidious than pyogenic infection
        • constitutional symptoms
          • chronic illness
          • malaise
          • night sweats
          • weight loss
        • back pain
          • often a late symptom that only occurs after significant boney destruction and deformity.
    • Physical exam
      • kyphotic deformity
      • neurologic deficits (present in 10-47% of patients with Pott's Disease)
        • mechanisms
          • mechanical pressure on cord by abscess, granulation tissue, tubercular debris, caseous tissue
          • mechanical instability from subluxation/dislocation
            • paraplegia from healed disease can occur with severe deformity
          • stenosis from ossification of ligamentum flavum adjacent to severe kyphosis
  • Imaging
    • CXR
      • 66% will have an abnormal CXR
      • should be ordered for any patients in which TB is a possibility
    • Spine radiographs
      • early infection
        • shows involvement of anterior vertebral body with sparing of the disc space (this finding can differentiate from pyogenic infection)
      • late infection
        • shows disk space destruction, lucency and compression of adjacent vertebral bodies, and development of severe kyphosis
      • risk factors for buckling collapse ("spine at risk signs")
        • retropulsion
        • subluxation
        • lateral translation
        • toppling
    • MRI with gadolinium contrast
      • indications
        • remains preferred imaging study for diagnosis and treatment
        • diagnose adjacent levels
          • multiple levels involved in 16-70%
      • findings
        • low signal on T1-weighted images, bright signal on T2-weighted images
        • presence of a septate pre-/ paravertebral / intra-osseous smooth walled abscess with a subligamentous extension and breaching of the epidural space
        • end-plate disruption
          • sensitivity 100%, specificity 81%
        • paravertebral soft tissue shadow
          • sensitivity 97%, specificity 85%
        • high signal intensity of the disc on the T2-weighted image
          • sensitivity 81%, specificity 82%
        • spinal cord
          • edema
          • myelomalacia
          • atrophy
          • syringomyelia
    • CT
      • indications
        • demonstrates lesions <1.5cm better than radiographs
          • inaccurate for defining epidural extension
      • findings
        • types of destruction
          • fragmentary
          • osteolytic
          • subperiosteal
          • sclerotic
    • Nuclear medicine studies
      • obtain with combination of technetium and gallium
      • shown to have highest sensitivity for detecting infection
  • Studies
    • CBC
      • relative lymphocytosis
      • low hemoglobin
    • ESR
      • usually elevated but may be normal in up to 25%
    • PPD (purified protein derivative of tuberculin)
      • positive in ~ 80%
    • Diagnosis
      • CT guided biopsy with cultures and staining effective at obtaining a diagnosis
        • should be tested for acid-fast bacilli (AFB)
          • mycobacteria (acid-fast bacilli) may take 10 weeks to grow in culture
        • PCR allows for faster identification (95% sensitivity and 93% accuracy)
        • smear positive in 52%
        • culture positive in 83%
  • Differential
    • Other etiologies of granulomatous infection may have similar clinical picture as TB and include
      • atypical bacteria
        • Actinomyces israelii
        • Nocardia asteroides
        • Brucella
      • fungi
        • Coccidioides immitis
        • Blastomyces dermatitidis
        • Cryptococcus neoformans
        • Aspergillosis
      • spirochetes
        • Treponema pallidum
  • Treatment
    • Nonoperative
      • pharmacologic treatment +/- spinal orthosis
        • indications
          • no neurological deficit
          • drugs are the mainstay of treatment in most cases
        • pharmacologic
          • agents
            • isoniazid (H), rifampin (R), ethambutol (E) and pyrazinamide (Z) therapy
          • regimen
            • RHZE for 2 months, then RH for 9 to 18 months
        • spinal orthosis
          • indications
            • may be used for pain control and prevention of deformity
    • Operative
      • anterior decompression/corpectomy, strut grafting ± posterior instrumented stabilization ± posterior column shortening
        • indications
          • neurologic deficit
            • worsening neurological deficit
            • acute severe paraplegia
            • with panvertebral involvement with/without subluxation/dislocation
          • spinal instability
          • kyphosis correction
            • > 60° in adult
            • progressive kyphosis in child
            • ≥3 vertebrae involved with loss of ≥1.5 vertebral bodies in thoracic spine
            • children ≤ 7 years with ≥3 vertebral bodies affected in T/TL spine and ≥ 2 at risk signs are likely to have progression and should undergo correction
            • late onset paraplegia (from kyphosis)
              • cosmetic correction of kyphosis controversial
          • advanced disease with caseation preventing access by antibiotics
          • failure of nonoperative treatment after 3 to 6 months
          • diagnosis uncertain
          • panvertebral lesion
        • advantages of surgical treatment
          • less progressive kyphosis
          • earlier healing
          • decreased sinus formation
          • in patients with neurologic deficits, early debridement and decompression led to improved neurologic recovery
        • technical aspects
          • autogenous and allograft strut grafts are acceptable with good results
          • continue medical management with isoniazid, rifampin, and pyrazanamide
          • chronic implant colonization is less common in TB and other granulomatous infections compared to more common pyogenic infections
      • Halo traction, anterior decompression, bone grafting, anterior plating
        • indications
          • cervical kyphosis
      • Pedicle subtraction osteotomy
        • indications
          • lumbar kyphosis
      • Direct decompression / internal kyphectomy
        • indications
          • correction of healed thoracic/thoracolumbar kyphosis
          • allows spinal cord to transpose anteriorly
  • Technique
    • Anterior decompression/corpectomy, strut grafting ± posterior instrumented stabilization ± posterior column shortening
      • indications (see above)
        • kyphosis
        • active disease
      • techniques
        • single-stage transpedicular
        • 2-stage
          • anterior decompression with bone grafting
          • posterior kyphosis correction and instrumentation
        • single-stage extrapleural anterolateral
  • Complications
    • Deformity (kyphosis/gibbus)
      • highest risk
        • after anterior decompression and grafting alone
          • slippage and breakage of graft (especially if ≥ 2 levels)
      • lowest risk
        • after both anterior and posterior fusion
    • Retropharyngeal abscess affects swallowing/hoarseness
    • TB arteritis and pseudoaneurysm
    • Respiratory compromise if there is costopelvic impingement
    • Sinus formation
    • Pott's paraplegia
      • spinal cord injury can be caused by abscess/bony sequestra or meningomyelitis
      • abscess/bony sequestra has a better prognosis than meningomyelitis as the cause of spinal cord injury
  • Atypical Spinal Tuberculosis
    • definition
      • compressive myelopathy without visible spinal deformity, without typical radiological appearance
    • etiology
      • intraspinal granuloma, neural arch involvement, concertina collapse of vertebra body , sclerotic vertebra with bridging of vertebral body
    • treatment
      • laminectomy
        • indications
          • extradural extraosseous granuloma
          • subdural granuloma
      • decompression and myelotomy
        • indications
          • intramedullary granuloma
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