Spinal Tuberculosis (Pott Disease)

In the developing world, children primarily bear the burden of musculoskeletal tuberculosis.

In the United States, however, musculoskeletal infection is more often seen in adults who have immigrated from countries where tuberculosis is prevalent, or it develops in the setting of immunosuppression (eg, HIV infection, therapy with biologic agent).

Spinal tuberculosis (Pott disease) accounts for about 50% of musculoskeletal infection due to M. tuberculosis (see Chapter 14).

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 due to reactivation, or through 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.

Diagnostic Essentials

• Seen primarily in individuals from developing countries or immunocompromised patients.
• Back pain and gibbus deformity with radiographic evidence of vertebral involvement.
• Less than 20% have active pulmonary tuberculosis.
• Evidence of Mycobacterium tuberculosis in aspirate or biopsies of spinal lesions.

Clinical Findings

Symptoms and Signs

Patients have 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 vertebral body anteriorly can produce the characteristic wedge-shaped gibbus deformity.

Laboratory Findings

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%.

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.

Imaging

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.

Differential Diagnosis

Spinal tuberculosis must be differentiated from subacute and chronic spinal infections due to pyogenic organisms, Brucella, fungi, and malignancy.

Complications

Paraplegia due to compression of the spinal cord or cauda equina is the most serious complication of spinal tuberculosis.

Treatment

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 (see also Chapter 14).

Medical management alone is often sufficient.

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