summary Spinal tuberculosis, also known as Pott's disease, is a spinal infection caused by Mycobacterium tuberculosis that can lead to osteomyelitis, kyphotic deformity, and mechanical instability Diagnosis is made with a CT-guided biopsy evaluated 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 in the U.S. due to a growing immunocompromised population Demographics HIV-positive (often seen in patients with CD4+ counts of 50-200) 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 beneath the anterior longitudinal ligament, leading to contiguous multilevel involvement skip lesions or noncontiguous segments (15%) paraspinal abscess formation (50%) usually anterior and can be large (much more common in TB than in pyogenic infections) initially does not involve the disc space (distinguishing it 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 kyphosis progression when the vertebral body and posterior elements are involved granulomatous spinal infections are often diagnosed late and with more severe kyphosis compared to pyogenic infections in adults kyphosis stays static after healing in children kyphosis progresses in 40% of cases because of growth spurts 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 or healed phases Presentation Symptoms onset of symptoms is typically more insidious than that of pyogenic infections constitutional symptoms chronic illness malaise night sweats weight loss back pain often a late symptom that only occurs after significant bony destruction and deformity Physical exam kyphotic deformity neurologic deficits (present in 10-47% of patients with Pott's disease) mechanisms mechanical pressure on the cord by abscess, granulation tissue, tubercular debris, or caseous tissue mechanical instability from subluxation or dislocation paraplegia from healed disease can occur with severe deformity stenosis from ossification of the ligamentum flavum adjacent to severe kyphosis Imaging CXR 66% will have an abnormal CXR indicated for any patient in whom TB is a possibility Spine radiographs early infection involvement of the anterior vertebral body with sparing of the disc space (this can differentiate TB from a pyogenic infection) late infection lucency and compression of adjacent vertebral bodies, disc space destruction, and development of severe kyphosis risk factors for buckling collapse ("spine-at-risk signs") retropulsion subluxation lateral translation toppling MRI with gadolinium contrast indications preferred imaging study for diagnosis and treatment planning diagnosis of adjacent levels multiple levels involved in 16-70% findings low signal on T1-weighted images, bright signal on T2-weighted images presence of a septated prevertebral, paravertebral, and/or intraosseous, smooth-walled abscess with a subligamentous extension and breaching of the epidural space endplate disruption sensitivity 100% and specificity 81% paravertebral soft tissue shadow sensitivity 97% and specificity 85% high signal intensity of the disc on the T2-weighted image sensitivity 81% and specificity 82% spinal cord edema myelomalacia atrophy syringomyelia CT indications demonstrates lesions <1.5 cm better than radiographs inaccurate for detailing epidural extension findings types of destruction fragmentary osteolytic subperiosteal sclerotic Nuclear medicine studies obtain with a combination of technetium and gallium shown to have the 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 is 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 a clinical picture similar to TB 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 deficits medical therapy is 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 9-18 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 neurologic deficit acute severe paraplegia panvertebral involvement ± subluxation/dislocation spinal instability kyphosis correction >60° in adults progressive kyphosis in a child ≥3 vertebrae involved with loss of ≥1.5 vertebral bodies in the thoracic spine children ≤7 y/o with ≥3 affected vertebral bodies in the thoracic or thoracolumbar spine and ≥2 at risk signs are likely to have progression and should undergo correction late onset paraplegia (from kyphosis) cosmetic correction of kyphosis is controversial advanced disease with caseation preventing antibiotic access failure of nonoperative treatment after 3-6 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 can lead to improved neurologic recovery technical aspects autogenous and allograft strut grafts are acceptable with good results continued medical management with isoniazid, rifampin, and pyrazinamide chronic implant colonization is less common in TB and other granulomatous infections than in pyogenic infections Halo traction, anterior decompression, bone grafting, and anterior plating indications cervical kyphosis Pedicle subtraction osteotomy indications lumbar kyphosis Direct decompression/internal kyphectomy indications correction of healed thoracic or thoracolumbar kyphosis allows the spinal cord to be transposed anteriorly Technique Anterior decompression/corpectomy, strut grafting ± posterior instrumented stabilization ± posterior column shortening indications (see above) techniques single-stage transpedicular two-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 the graft (especially if ≥2 levels) lowest risk after both anterior and posterior fusion Retropharyngeal abscess can affect swallowing and cause hoarseness TB arteritis and pseudoaneurysm Respiratory compromise if there is costopelvic impingement Sinus formation Pott's paraplegia spinal cord injury can be caused by an abscess, bony sequestra, or meningomyelitis abscess/bony sequestra have a better prognosis than meningomyelitis Atypical Spinal Tuberculosis definition compressive myelopathy without visible spinal deformity or typical radiological appearance etiology intraspinal granuloma neural arch involvement concentric collapse of the vertebra body sclerotic vertebra with bridging of the vertebral bodies treatment laminectomy indications extradural extraosseous granuloma subdural granuloma decompression and myelotomy indications intramedullary granuloma