Radiology Quiz

MARTHA "MIMI" COTSEN, MD

aFall 1996

History: An eight-year-old female walked into the emergency room with lower back pain of six weeks duration.

Questions: Based on the plain film findings, what additional test should be ordered and why? Should this child be kept in an isolation room?

FIGURE 1. Plain films of the lumbosacral spine.
[Left] Posterior anterior view. [Right] Lateral view.

Radiologic findings: The plain films of the spine demonstrate focal erosion of the anterior inferior aspect of the third lumbar vertebral body and of the anterior inferior aspect of the fourth lumbar vertebral body, loss of the intervening disc height, fusiform swelling of the left psoas muscle and mild scoliosis of the lumbar spine. A contrast-enhanced CT scan was performed to further evaluate the extent of paraspinal, intraspinal, bone and disc disease. The CT scan demonstrates destruction of the vertebral body and an abscess with a thick enhancing rim within the psoas muscle bilaterally. The abscess extends posteriorly into the spinal epidural space.

Diagnosis: Tuberculosis of the spine.

Discussion

The plain film and CT findings of vertebral body destruction and/or collapse, paraspinal abscess formation, subligamentous spread of infection and extension into the spinal epidural space are consistent with tuberculosis spondylitis.

The vertebral column is the most frequent site of skeletal tuberculosis. The etiology is generally felt to be hematogenous, spread most commonly from a primary infection in the lung, with seeding of the anterior subchondral vertebral body adjacent to the disc. Infection can then spread to the adjacent disc and contiguous vertebral body and from there into adjacent ligaments and soft tissues including paraspinal muscles. Paraspinal extension is suggested by the fusiform swelling of the left psoas muscle on the plain film and is clearly seen on the CT scan. Posterior extension is infrequent but can occur as in this case with the associated epidural abscess. Subligamentous extension can produce bone and disc invasion at distant sites. Abscesses can also burrow long distances with subsequent extension into visceral organs (i.e. esophagus, liver, kidney, bladder) or emerge on the body’s surface as fistulae. Because of the indolent nature of tuberculosis, a radiographic abnormality can take from two to five months to develop. Patients frequently present late with dramatic, radiographic findings, as in this case.

FIGURE 2. CT scan (with contrast) at the level of the third lumbar vertebral body.
[Left] Axial plane. [Right] Coronal plane.

The findings, however, are not pathognomonic for tuberculosis spondylitis and can be seen in other infectious lesions of the spine. Pyogenic spondylitis presents with vertebral body destruction and/or collapse and loss of disc space but in contrast to tuberculosis spondylitis, it is rapidly progressive (one to three weeks). Radiographic features more commonly seen and, hence, suggestive of tuberculosis spondylitis include: a thick rim of enhancement around paraspinal abscesses, increased intensity or calcification of the psoas region, and visible sequestra. Definitive diagnosis, however is made by a positive PPD test, culture and acid-fast stain.

The incidence of tuberculosis in the United States has increased dramatically as a result of the resurgence of tuberculosis in patients with AIDS, the spread of tuberculosis among the homeless, and expanding immigration from high prevalence countries. This child, however, does not need to be considered infectious. It is our practice, however, to isolate such patients because their adult family members and visitors may have active tuberculosis. Because of the very low number of tubercle bacilli in pulmonary secretions and absent or weak cough, children with tuberculosis are rarely infectious. A family member with active, pulmonary tuberculosis more than likely transmitted it to this child. That adult and any child or adult in close contact with that person should be tuberculin skin tested and examined as soon as possible. Young children, especially infants, should receive priority testing because their risk of infection is greater, and they are more likely to develop severe forms of tuberculosis.

FOR FURTHER READING

1. Nelson W, Behrman R, Kleigman R, Arvin A: Nelson Textbook of Pediatrics> (ed 15), Philadelphia: W. B. Saunders, 1996, 834–847.

2. Resnick D: Diagnosis of Bone and Joint Disorders (ed 3), Philadelphia: W. B. Saunders, 1995, 2425–37; 2461–75.

3. Ozonoff MB: Pediatric Orthopaedic Radiology (ed 2), Philadelphia: W.B. Saunders, 1992, 109–110.

4. Shanley DS: Tuberculosis of the Spine; Imaging features. AJR 1995; 164:659–664.

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