Your diagnosis? - Healio

n radiologic case study

Section Editor: Terrence C. Demos, MD

Enhance your diagnostic skills with this “test yourself” monthly column, which features a radiograph and challenges you to make a diagnosis.

The case: A

12-year-old boy presented to the spine clinic with a significant spinal deformity.

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Figure 1: Pre- (A) and postoperative (B) lateral radiographs of the thoracolumbar spine.

Your diagnosis?

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infection S P OT L I G H T O N

Diagnosis: Pott’s Disease Michael P. Silverstein, BS; Isador H. Lieberman, MD; Selvon St. Clair, MD, PhD; Mark Kayanja, MD, PhD; Laura W. Bancroft, MD

Answer to Radiologic Case Study

Pott’s disease, or tuberculous spondylitis, is a consequence of the hematogenous spread of Mycobacterium tuberculosis.1 Tuberculosis continues to be the world’s most lethal and prevalent infectious disease, with .3 million deaths annually, and spinal tuberculosis accounts for approximately 5% of all tuberculosis cases.2-4 An increasing incidence, likely resulting from an aging population, is found in association with acquired immune deficiency syndrome (AIDS) and increased immigration.

The presentation of Pott’s disease depends on the stage of the disease, the affected location, and the presence of complications. Pulmonary involvement is typically the primary focus, with secondary involvement causing destruction of the vertebrae and intervertebral disks and gross spinal deformity. In addition, prevertebral and paravertebral abscesses can form.5 The traditional treatment approach involved surgical intervention for debridement of the abscess, reconstruction of

Mr Silverstein and Dr Bancroft are from the College of Medicine, Florida State University, Tallahassee, Florida; Dr Lieberman is from the Scoliosis and Spine Tumor Center, Texas Back Institute, Plano, Texas; Dr St. Clair is from the Orthopaedic Institute of Ohio, Lima, and Dr Kayanja is from the Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio. Dr Bancroft is also from the Department of Radiology, Florida Hospital, Orlando, Florida. Mr Silverstein and Drs Lieberman, St. Clair, Kayanja, and Bancroft have no relevant financial relationships to disclose. Correspondence should be addressed to: Laura W. Bancroft, MD, Department of Radiology, Florida Hospital, 601 E Rollins, Orlando, FL 32803 ([email protected]). doi: 10.3928/01477447-20120327-02

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the deformity, and protection of the neurological elements. With advanced antibiotic regimens, the disease can be controlled and cured prior to the advent of the osteolytic spinal deformity.5

lesions more often resulting in kyphosis.2 Spinal tuberculosis remains a potentially crippling disease and is one of the most common worldwide causes of kyphotic deformity.7,8

Pathogenesis

Clinical features of spinal tuberculosis include an insidious, gradual onset of back pain, local tenderness, and anorexia. Night sweats and fever may also be present. Oguz et al6 reported that .50% of patients had some element of a neurologic deficit. Thoracic involvement is associated with more severe sequelae compared with lumbar manifestations; complications include sensory deficits, motor loss, and changes in bowel and bladder function. Skin breakdown over severe curves can lead to local and systemic infections. The most severe complications of spinal tuberculosis are paraplegia, tetraplegia, hemiplegia, or monoplegia.1 Paraplegia can result from impingement on the spinal cord

When Mycobacterium tuberculosis involves the spine, an inflammatory process results in the formation of granulomatous lesions affecting the diskovertebral segments. Bone destruction and sclerosis can be seen, as well as osseous fragmentation. Nutrient supply to the disk is impaired from the destruction of the vertebra, and caseous necrosis causes the diskovertebral unit to collapse. The osseous destruction is progressive, leading to vertebral collapse. Kyphosis and scoliosis can result. Granulation tissue and abscess formation around the spinal canal can result in neurologic symptoms.6 Tubercular lesions can be present in the thoracic and lumbar spine, with thoracic

Clinical Presentation

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due to abscesses, caseous debris, and granulation tissue. Mechanical instability and spinal deformity can result in paraplegia from stretching of the spinal cord, resulting in cord impairment.9 Although spinal tuberculosis is primarily treated medically, severe complications may require surgical intervention.

Diagnostic Imaging Tuberculosis of the spine is a relatively indolent process compared with pyogenic diskiitis because M tuberculosis does not produce proteases. However, marked destructive changes can occur, particularly with delayed treatment (Figures 2, 3). The features most commonly seen on computed tomography are bone and disk destruction with variable bone production or sequestra formation, multilevel involvement, and paraspinal abscesses that may be large and contain calcifications (Figure 4).10 Spinal tuberculosis tends to seed the thoracolumbar junction and may extend several vertebral levels away beneath the anterior and posterior longitudinal ligaments. This may result in classic gouging deformities of the anterior vertebral bodies above or below the level of primary involvement. Magnetic resonance imaging is the choice imaging method due to its planar capabilities and soft tissue contrast resolution.11 The predominant findings on magnetic resonance images are hypointensity on T1-weighted sequences, variable signal intensity depend-

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Figure 2: Preoperative lateral radiograph showing destruction of a vertebral body at the thoracolumbar junction, with gibbus deformity (A). Lateral spine radiograph obtained on postoperative day 2 showing reduction of the gibbus deformity, posterior decompression, and pedicle screw fixation (B). Clinical photograph showing the patient standing upright on postoperative day 2 (C).

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Figure 3: Anteroposterior (A) and lateral (B) radiographs of the thoracolumbar spine showing a large area of calcification involving several destroyed vertebral bodies at the thoracolumbar junction (asterisks), with gibbus deformity. Note the tear-drop extension of calcification into the right psoas muscle (arrows). T1-weighted sagittal magnetic resonance image showing the underlying chronic destruction at the thoracolumbar junction (asterisk) and marked kyphosis. Note the lack of visualization of the spinal cord at the involved level and the posterior cord displacement inferiorly (C).

ing on disease chronicity on T2-weighted sequences, and heterogeneous enhancement of the >1 involved vertebral bodies and disks (Figure 5).11-14 Paravertebral involvement may result in abscesses in the paravertebral or psoas muscles (Figure 5), which may contain calcification (better depicted on computed tomography scans).

The characteristic gibbus deformity seen in Figures 2 and 3 results from progressive bone necrosis leading to collapse and wedging in multiple anterior vertebral bodies.13 Low signal on T1-weighted and variable signal on T2weighted magnetic resonance images in affected vertebral bodies, delayed disk involve-

ment, and prevertebral and paravertebral or intraosseous abscesses with subligamentous and epidural extension are commonly seen in spinal tuberculosis (Figure 5).11

Surgical Management Multidrug antituberculous chemotherapy, including isoniazid, rifampin, pyrazin-



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Figure 4: Coronal reconstruction (A) and axial (B) computed tomography scans showing irregular fluid collection (asterisk) containing gas (arrow) in the right psoas muscle caused by tuberculosis. Note the relative indolent nature of the disease, with mild narrowing of the L2-L3 disk space and no vertebral destruction due to the lack of proteases by Mycobacterium tuberculosis.

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Figure 5: Coronal fluid-sensitive magnetic resonance image showing a large left paraspinal tubercular abscess (asterisk) (A). Axial T1-weighted enhanced fat-suppressed magnetic resonance image showing destruction of a lumbar vertebra (asterisk) with surrounding heterogeneously enhancing paraspinal abscess and phlegmon (arrows) (B).

amide, and ethambutol, is used to treat tuberculous spondylitis. However, when irreparable damage has occurred in chronic disease, surgical management may become necessary. A kyphotic curve >60° and curves likely to progress are candidates for surgical correction. Other surgical indications include paravertebral abscess, neurological deficit, lack of improvement or deterioration, and refractory disease.1 Surgical treatment consists of a combination of procedures depending on the spinal deformity. Anterior decompression, posterior shortening, bone grafting, and instrumen-

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tation for stabilization may be used (Figure 2B).7 Anterior debridement of tubercular debris is usually necessary because anterior vertebral body involvement is responsible for the collapse of the vertebral bodies, forming a kyphotic curve. Inflexible scoliosis with ,25% flexibility and curves .80°, pedicle subtraction osteotomy, and vertebral column resections can be useful to gain correction.15 Pedicle subtraction osteotomy can allow for a 20° to 30° deformity correction at a single level.15,16 The SmithPeterson extension osteotomy technique is commonly used

for reconstruction of sagittal imbalance in patients with a deformity above the thoracolumbar junction. Total correction over several spinal segments from 20° to 40° is achievable.16 The SmithPeterson technique requires multiple osteotomies and the occasional use of anterior osteotomy for effective posterior compression. Vertebral correction osteotomy is beneficial in severely angulated kyphotic thoracic curves and large thoracic scoliosis curves. Surgery type depends on the need for degrees of correction, the location of the curve, the need for anterior release, the need for anterior or posterior instrumentation for stabilization, and the use of multilevel osteotomies. The Smith-Peterson osteotomy, pedicle subtraction osteotomy, and vertebral body resection are excellent correction procedures; however, significant risks include neurological impairment and blood loss.

Conclusion Tuberculous spondylitis is a worldwide disease that occurs in up to 5% of all cases of tuberculosis as a consequence of the hematogenous spread of pulmonary M tuberculosis. Because of the increasing incidence of tuberculosis in the aging population, patients with AIDS, and recent immigrants, orthopedic surgeons must consider this diagnosis in the event of multilevel spinal involvement or destruction at the thoracolumbar junction with kyphosis. Surgical intervention is required for debride-

ment of vertebral and paravertebral abscesses, reconstruction of the deformity, and protection of the neurological elements.

References 1. Jain AK. Tuberculosis of the spine: a fresh look at an old disease. J Bone Joint Surg Br. 2010; 92(7):905-913. 2. Khoo LT, Mikawa K, Fessler RG. A surgical revisitation of Pott distempter of the spine. Spine J. 2003; 3(2):130-145. 3. Weinberg J, Silber JS. Infections of the spine: what the orthopedist needs to know. Am J Orthop. 2004; 33(1):1317. 4. James SL, Davies AM. Imaging of infectious spinal disorders in children and adults [published online ahead of print January 18, 2006]. Europ J Radiol. 2006; 58(1):27-40. 5. Tuli SM. Tuberculosis of the spine. Clin Orthop Relat Res. 2007; 460:29-38. 6. Oguz E, Sehirlioglu A, Altinmakas M, et al. A new classification and guide for surgical treatment of spinal tuberculosis [published online ahead of print January 6, 2007]. Int Orthop. 2008; 32(1):127-133. 7. Issack PS, Boachie-Adjei O. Surgical correction of kyphotic deformity in spinal tuberculosis [published online ahead of print June 15 2011]. Int Orthop. 2012; 36(2):353-357. 8. Dursun AB, Guler ZM, Budak K, Ceylan O, Atas E. Pott’s disease and different clinical presentations [in Turkish]. Tuberk Toraks. 2003; 51(4):416-423. 9. Jain AK, Jain S. Instrumented stabilization in spinal tuberculosis [published online ahead of print July 1, 2011). Int Orthop. 2012; 36(2):285-292. 10. Kirchner TH, Kirchner J, Schneider M, et al. Computed tomography and magnetic renance tomography in tuberculous spondydlitis. A review of the literature and the authors’ own observations [in German]. Radiologe. 2000; 40(10):963969.

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11. Currie S, Galea-Soler S, Barron D, Chandramohan M, Groves C. MRI characteristics of tuberculous spondylitis [published online ahead of print May 12, 2011]. Clin Radiol. 2011; 66(8):778-787. 12. Zaidi H, Akram MH, Wala MS. Frequency and magnetic resonance imaging patterns of tuberculous spondylitis lesions in adults. J Coll Physicians Surg Pak. 2010; 20(5):303-306. 13. Jain AK, Sreenivasan R, Saini N, Kumar S, Jain S, Dhammi IK. Magnetic resonance evaluation of tubercular lesion in spine [published online ahead

of print October 29, 2011]. Int Orthop. 2012; 36(2):261-269. 14. Mahboubi S, Morris MC. Imaging of spinal infections in children. Radiol Clin North Am. 2001; 39(2):215-222. 15. Bezer M, Kucukdurmaz F, Guven O. Transpedicular decancellation osteotomy in the treatment of posttuberculous kyphosis. J Spinal Disord Tech. 2007; 20(3):209-215. 16. Bridwell KH. Decision making regarding Smith-Peterson vs. pedicle subtraction osteotomy vs vertebral column resection for spinal deformity. Spine. 2006; 31(19 suppl):S171-S178.
