This patient had a final diagnosis of an epidural abscess secondary to tuberculous spondylitis (also known as Pott disease or spinal tuberculosis). The lumbar plain-film radiographs revealed a compression fracture of the T11 vertebra (Figure 1). A subsequent MRI (Figure 2; sagittal T2-weighted image) revealed severe pathologic compression fractures, multilevel osteomyelitis, and an epidural abscess extending from T10 to T12. Although there was increased disk signal, particularly in the T10-T11 disk space, the signal was also present at uninvolved levels; this finding was believed to be secondary to normal hydration, as enhancement consistent with diskitis was not demonstrated in contrast-enhanced images (not available) of the involved disk spaces. These radiologic findings suggested tuberculous spondylitis, which was definitively diagnosed after cultures revealed pan-susceptible Mycobacterium tuberculosis (see final paragraph for details of diagnosis).
Tuberculous spondylitis results from the hematogenous spread of M tuberculosis. Percival Pott first described spinal tuberculosis in 1779; however, evidence of the disease can be seen even in ancient mummies from Egypt and Peru. Although rare in industrialized countries, this disease continues to be seen in developing countries. Tuberculosis is the world's most deadly infection; it affects roughly 2 billion people worldwide and causes nearly 3 million deaths annually. Because humans are the only carriers of M tuberculosis, eradication is possible, but tuberculosis control programs have had varied success. Not surprisingly, some of the more successful countries include the United States and other industrialized nations. Nations such as Cuba and the Dominican Republic are achieving commendable results as well. Slightly more than half of patients afflicted with tuberculosis in the United States are of foreign origin; therefore, it is particularly important to consider the diagnosis when examining patients from Southeast Asia, India, China, and other endemic regions.
Tuberculous spondylitis is seen in approximately 8-9% of cases of extrapulmonary tuberculosis. The vertebral bodies of the spine are susceptible to seeding from tuberculosis because of high blood flow throughout adult life. The distribution of the vertebral blood supply also allows multiple adjacent vertebrae to be affected.
Pott disease is more commonly associated with late reactivation of tuberculosis than with primary infection. In the United States, Pott disease primarily occurs in adults, and it most commonly affects the lower thoracic and lumbar regions. In approximately 10% of cases, the cervical region is affected. Cervical and upper thoracic involvement is potentially more disabling[1] and can present with dysphagia, stridor, torticollis, hoarseness, and other neurologic deficits.
In tuberculous spondylitis, the infection leads to inflammatory bone destruction and caseating necrosis within the vertebral body.[2] It then spreads via the anterior/posterior longitudinal ligaments to adjacent vertebral bodies; typically, 2 or more contiguous vertebrae are involved (which is unlike the bony lesions seen in most cancers). This destruction can cause collapse of the vertebral bodies, producing spinal instability, spinal cord compression, and herniation of the disk. Involvement of the anterior and lateral portions of the vertebral body typically causes vertebral collapse, with kyphosis and gibbous deformity; cavitation and extradural masses more often result when the posterior vertebral body is affected. A tuberculous abscess in the epidural region can also compress the spinal cord, frequently causing bilateral symptoms. Abscess formation and/or bony destruction carry the potential to cause serious morbidity and permanent neurologic deficits. Uncommonly, cervical involvement can result in extension of disease into the neck or retropharynx. Lumbar disease can similarly track along fascial planes and form calcifications within psoas abscesses or extradural abscesses[3]; this finding is nearly pathognomonic for tuberculous infection.
Pott disease typically presents with a 3- to 4-month history of achy back pain that gradually intensifies and is sometimes associated with muscle spasm or radicular pain. Fevers, weight loss, and elevated white blood cell counts are not typical, presenting in less than 40% of cases.[4] Neurologic abnormalities occur in 50% of patients and may include nerve root pain, cauda equina syndrome, sensory loss, or paresis. The most serious complication of tuberculous spondylitis is spinal cord compression that causes paraplegia; this condition is also known as Pott paraplegia.
The diagnosis of Pott disease can be challenging to make because of the indolent nature of the disease and the extensive differential diagnosis. A comprehensive history that includes questions about the patient's country of origin, history of tuberculosis exposure, and family history of tuberculosis must be performed. A complete physical examination should also be performed, with careful assessment of the spine, skin, abdomen (looking for a flank mass), and lungs. A complete neurologic examination, including assessment of strength, rectal tone, perineal sensation, and lower-extremity reflexes, is vital. A chest radiograph can be obtained to visualize apical scarring, cavitary disease, or infiltrates; however, the diagnosis should still be investigated despite a negative chest radiograph, especially if there is a strong clinical suspicion.
Tuberculin skin testing (purified protein derivative [PPD]) should be performed because it is positive in 90% of immunocompetent patients with skeletal tuberculosis. Nonetheless, a negative tuberculin skin test does not exclude a diagnosis of tuberculosis. In particular, patients who are immunocompromised are more likely to have a false-negative PPD test; such patients are the most susceptible to Pott disease.[5] The erythrocyte sedimentation rate should also be checked, as it is frequently elevated (>100 mm/h) in patients with Pott disease. A biopsy of the affected area with positive acid-fast bacillus stain or cultures is diagnostic. Unfortunately, the tubercle bacillus is notably difficult to isolate, with only 50% of biopsies yielding positive cultures.
MRI and computed tomography (CT) scanning are both excellent studies for visualizing the typical findings of Pott disease. Plain radiographs can also show evidence of tuberculous spondylitis, including osteolytic destruction of the vertebral body, collapse of the vertebral body, increased anterior wedging, and reactive sclerosis. CT scans can reveal the bony detail of irregular osteolytic lesions, disk collapse, sclerosis, or disruption of bone circumference. MRI is effective at demonstrating neural compression, the presence of epidural abscesses, and differentiating tuberculous spondylitis from pyogenic spondylitis (pyogenic spondylitis is characterized by a thick and irregular enhancement of the abscess wall, whereas enhancement is typically smooth and thin in tuberculous spondylitis).[6] Additionally, tuberculous spondylitis differs radiologically from pyogenic spondylitis in that the disk space is usually secondarily involved or not involved at all; vertebral body involvement with disk-space sparing may be seen. As a result of this pattern of involvement, tuberculous spondylitis may exhibit skip lesions from subligamentous extension, whereas pyogenic spondylitis almost always involves a disk and adjacent vertebral bodies.
Treatment of Pott disease consists of at least a 3-drug and, frequently, a 4-drug regimen of antituberculous medications. A 6-month course of therapy is recommended for tuberculosis involving all sites (except the meninges) by The American Thoracic Society, the Centers for Disease Control and Prevention, and the Infectious Diseases Society of America.[7] In one study, routine surgery was not shown to be beneficial for the treatment of Pott disease[8]; however, if used judiciously, surgery may improve early mobilization and reduce mortality.[9] Surgery is more clearly indicated for decompression of the spinal cord if the patient has advanced neurologic deficits, neurologic deficits that progress or persist despite medical therapy, if there is concern about the patient's spinal stability (with kyphosis greater than 40°), or if there is a need to drain an epidural abscess. Subsequent to treatment, patients should be closely followed for their response to therapy and medication compliance, as these issues can significantly affect their individual outcomes.
The patient in this case was admitted to the hospital, where he underwent diskectomies of T10 to L1, corpectomy of T11 and T12, drainage of the epidural abscess, and fusion of T11 and T12. He was definitively diagnosed with tuberculous spondylitis (Pott disease) after cultures revealed pan-susceptible M. tuberculosis. He was discharged to home with a 9-month course of rifampin, isoniazid, pyridoxine, and pyrazinamide. He was able to ambulate at the time of discharge.
CME/CE Test
16% 
