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Neuroradiology Case of the Week

Case 338

Iris Young, RPA-C and Per-Lennart Westesson, MD, PhD, DDS

Clinical Presentation: An 83-year-old male with a 3-month history of low back pain. The patient has a history of +PPD and completed a 6 month course of INH. He has known exposure to TB when his brother- in-law was treated for active TB many years ago and he has a remote history of international travel.

Imaging Findings: Sagittal CT images through the lumbar spine (Figs. 1 & 2) demonstrate severe degeneration of the L5-S1 disc space with a very irregular destructive appearance and adjacent endplate changes. Following contrast administration, the L5 and S1 vertebral bodies reveal heterogeneous enhancements. Surrounding paraspinal soft tissue enhancement extends superiorly to L4/5 level and inferiorly to S2 level with epidural involvement around the nerve roots bilaterally. The lateral view of the L5 bone biopsy (Fig. 3) demonstrates bone sample being taken from the anterior 1/3 of the vertebral body from a posterior approach. The A-P view of the disc aspiration (Fig. 4) demonstrates good positioning within the disc space. The chest x-ray (Fig. 5) showed calcified hilar lymph nodes, but no findings suggestive of pulmonary tuberculosis.

Diagnosis: Tuberculous spondylitis, Pott's disease

Differential Diagnosis: Degenerative disc disease vs. Infectious disc disease

Discussion: Tuberculosis (TB) is a common disease in developing countries, and sporadic in well-developed countries. The incidence of tuberculosis infection in the U.S. declined during the 20th century, then increased in the late 1980’s to a peak of 27 cases per 100,000 in 1992. The incidence has since declined to 5.2 cases per 100,000 in 2002. In developed countries, a greater percent of cases are associated with antimicrobial resistance, drug and alcohol addiction, HIV infection, and therapeutic immunosupression. Twenty percent of patients with TB have multiple lesions. Spinal Tuberculosis is always a secondary disease from another primary site.
     Spinal TB is an indolent granulomatous infection, most often in the lower thoracic region, but can be at any spinal level.The infection can spread by vascular supply (hematogenous spread) or from surrounding tissues (contiguous spread). The intervertebral disc may be involved (discitis), as well as most of the vertebral body and posterior elements (osteomyelitits). As the vertebrae degenerate and collapse along the anterior spine, the gibbus or kyphotic deformity results, characteristic of Pott’s disease. Most commonly, spinal TB involves the disc with 2 adjacent vertebral bodies and opposing endplates. There is destruction of the disc space, and/or development of an epidural or paravertebral (psoas) abscess. Destruction of the skeletal components can lead to neurologic damage including paresis, paraplegia or quadriplegia.
     MRI findings aides in demonstrating the disc infection with destruction of the disc space, and extension into the vertebral bodies with a relative sparing of the vertebral endplates. The definitive diagnosis is achieved only through disc aspiration and/or bone biopsy. Biopsy is essential for diagnosis and prompt treatment.

Prognosis: Early diagnosis with better imaging and multi-drug regimens have improved prognosis without requiring surgery. Recurrence of disease occurs if the drug treatment is irregular or discontinues after a short time. These factors contribute to the emergence of drug resistant tuberculosis strains.

References:

1. Ahmadi J, Bajaj A, Destian S, Segall HD, Zee CS. Spinal tuberculosis: atypical observations at MR imaging. Radiology. 1993 Nov;189(2):489-93. [Medline]
2. Grossman RI, Yousem DM. Neuroradiology: The Requisites, vol. 2, Philadelphia: Mosby, 2003: 796, 798f, and 799t.
3. Hidalgo JA, Alangaden G. Pott's disease (tuberculous spondylitis). Emedicine, August 25, 2006. http://www.emedicine.com/med/topic1902.htm.
4. McLain RF, Isada C. Spinal tuberculosis deserves a place on the radar screen. Cleve Clin J Med. 2004 Jul;71(7):537-9, 543-9. [Medline]
5. Thamburaj AV. Spinal tuberculosis. Neurosurgery on the Web. http://www.thamburaj.com/spinal_tuberculosis.htm.