Tuberculosis, Spinal (Pott Disease)

Essentials of Diagnosis

• Seen primarily in immigrants from developing countries or immunocompromised patients

• Back pain and gibbus deformity

• Radiographic evidence of vertebral involvement

• Evidence of Mycobacterium tuberculosis in aspirates or biopsies of spinal lesions

General Considerations

• Typically seen in adult immigrants from countries where tuberculosis is prevalent

• May develop in the setting of immunosuppression (eg, HIV infection, therapy with biologic agent)

• Spinal tuberculosis accounts for about 50% of musculoskeletal infection due to M tuberculosis

• Seeding of the vertebrae may occur through

  • Hematogenous spread from the respiratory tract at the time of primary infection, with clinical disease developing years later as a consequence of reactivation

  • Lymphatics from infected foci in the pleura or kidneys

• The thoracic and lumbar vertebrae are the most common sites of spinal involvement

• Vertebral infection is associated with paravertebral cold abscesses in 75% of cases

Symptoms and Signs

• Patients complain of back pain, often present for months and sometimes associated with radicular pain and lower extremity weakness

• Constitutional symptoms are usually absent, and < 20% have active pulmonary disease

• Destruction of the anterior aspect of the vertebral body can produce the characteristic wedge-shaped gibbus deformity

Differential Diagnosis

• All subacute and chronic bacterial infections of bone, eg, Brucella

• Gonococcal arthritis

• Mycotic bone infection

• Pyogenic osteomyelitis or septic arthritis

• Rheumatoid arthritis

• Sporotrichosis

• Metastatic cancer

• Osseous dysplasia

Laboratory Tests

• Most patients have a positive reaction to purified protein derivative (PPD) or a positive interferon-gamma release assay

• Cultures of paravertebral abscesses and biopsies of vertebral lesions are positive in up to 70–90%

Imaging Studies

• Radiographs can reveal lytic and sclerotic lesions and bony destruction of vertebrae but are normal early in the disease course

• CT scanning can demonstrate paraspinal soft tissue extensions of the infection

• MRI is the imaging technique of choice to detect compression of the spinal cord or cauda equina

Diagnostic Procedures

• Biopsies reveal characteristic caseating granulomas in most cases

• Isolation of M tuberculosis from an extraspinal site is sufficient to establish the diagnosis in the proper clinical setting

• Recovery of the acid-fast organism from joint fluid, pus, or tissue specimens using culture or polymerase chain reaction

Medications

• Antimicrobial therapy should be administered for 6–9 months, usually in the form of isoniazid, rifampin, pyrazinamide, and ethambutol for 2 months followed by isoniazid and rifampin for an additional 4–7 months

• Medical management alone is often sufficient

Surgery

• Surgical intervention, however, may be indicated when there is neurologic compromise or severe spinal instability

Complication

• Paraplegia due to compression of the spinal cord or cauda equina