Tuberculosis

Tuberculosis is the most common granulomatous infection of the spine. The three patterns of spinal involvement are peridiscal (commonest), central, and anterior. Peridiscal occurs adjacent to the vertebral endplate and spreads around a single intervertebral disc as the abscess material tracks beneath the anterior longitudinal ligament (the disc is usually spared unlike in pyogenic infections). Central involvement occurs in the middle of the vertebral body and eventually leads to vertebral collapse and kyphotic deformity. This pattern of involvement can be mistaken for a tumor. Anterior infections begin beneath the anterior longitudinal ligament, causing scalloping of the anterior vertebral bodies, and extend over multiple levels. The presentation is highly variable. Mild back pain is the most common symptom. Patients with tuberculous infections may present with malaise, fevers, night sweats, and weight loss. In addition, chronic infections may result in cutaneous sinuses, neurologic deficits (in up to 40% of patients), and kyphotic deformities. Certain factors define the high-risk population and should raise suspicion. Patients from countries with a high incidence of tuberculosis, such as Southeast Asia, South America, and Russia are considered high risk. Patients who live in confinement with others, such as homeless centers and prisons, are also at risk. Elderly adults, chronic alcoholics, patients with AIDS, and patients with a family member or a household contact with tuberculosis are additional high-risk groups. The leukocyte count may be normal or mildly elevated. The ESR is mildly elevated (typically < 50), but may be normal in up to 25% of cases. Although the purified protein derivative (PPD) skin test may detect active infection or past exposure, this test is unreliable because false-negative results may occur in malnourished and immunocompromised patients. Anergy panel testing should be included for this reason. Urine cultures, sputum specimens, and gastric washings may be helpful for diagnosis if the primary source is unknown. The most reliable test for diagnosis is CT-guided biopsy. The characteristic finding on histology is a granuloma, which is described as a multinucleated giant-cell reaction surrounding a central region of caseating necrosis. Molecular detection of mycobacterium DNA or RNA is useful for rapid diagnosis and for determining drug resistance. Radiographs: A clue to diagnosis is the presence of extensive vertebral destruction out of proportion to the amount of pain. Typically, the intervertebral discs are preserved in the early stages of this disease. Chest radiographs can be useful in demonstrating pulmonary MRI: The imaging modality of choice for diagnosis of spinal TBCT: Plays a role in defining the extent of bony destruction and localization for biopsies. Chemotherapy (four-drug regimen, for a minimum of 6-month duration, includes isoniazid, rifampin, pyrazinamide, and ethambutol) and brace immobilization are the initial treatment except in patients presenting with neurologic deficit or progressive deformity. The indications for surgery and the principles of surgical reconstruction are similar to those advised for pyogenic spinal infections.