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Neuroradiology Case of the Week

Case 371

December 2008

Daniel Giant, MD, MS and Per-Lennart Westesson, MD, PhD, DDS

Clinical Presentation: Patient is a 20-year-old female with a 5 month history of axial predominant low back pain, with radiation to the proximal lower extremities. The patient has undergone antibiotic treatment for L1 osteomyelitis.

Imaging Findings:
Lumbar spine radiographs demonstrate a region of lucency involving the disc space of L1-L2, with surrounding sclerosis of the inferior aspect of L1 and the superior endplate of L2.

Non-contrast Head CT: There is endplate depression and lytic changes of L1 and L2 vertebral bodies with associated disc space loss and vertebral body sclerosis. No paravertebral or epidural soft tissue swelling or abscess is seen.

MRI: Altered marrow signal intensity in the opposing endplates and vertebral bodies of L1 and L2 vertebra with involvement of intervening discs. These lesions appear hyperintense on T2 and STIR and hypointense on T1-weighted images. There is enhancement on post-contrast images within the disc as well as within the end plates. A very small right paravertebral soft tissue component is also noted.

Diagnosis: Chronic lumbar spondylodiscitis

Discussion: Spondylodiscitis most commonly involves the lumbar spine [1]. The main organisms implicated in spondylodiscitis include Staphylococcus, Streptococcus, Peptostreptococcus, Brucella, tuberculosis, and E. coli [1, 2]. In adults, since the disc is an avascular structure, discitis usually results from extension of osteomyelitis, direct trauma, and following disc surgery in 1 to 2% of cases [3]. Other risk factors include immunosuppressive conditions, drug use, and alcoholism.
     MRI is the modality of choice for evaluating spondylodiscitis due to its high sensitivity and specificity, particularly in identifying paravertebral involvement [4]. Initially, in the acute setting, the disc and the vertebral bodies are hypointense on T1 and hyperintense on T2 [2]. Usually, pyogenic spondylodiscitis demonstrates high-signal on T2 and low-signal on T1 in the affected portions of the disc and vertebral bodies. However, tuberculous spondylodiscitis is associated with shorter T1 [2]. With Gd administration, there is enhancement of the disc, osteolytic areas, and paravertebral components, if present [2].
     Differential diagnosis of infectious spondylodiscitis includes degenerative disc disease associated with Modic type 1 changes, pseudoarthrosis in ankylosing spondylitis, dialysis spondyloarthropathy, and neuropathic spondyloarthropathy [5].

References:

1. Grossman R. Yousem D. Neuroradiology, The Requisites. 2nd Ed. Philadelphia: Mosby, 2003: 795-796.
   
2. Maiuri F, Iaconetta G, Gallicchio B, Manto A, Briganti F. Spondylodiscitis. Clinical and magnetic resonance diagnosis. Spine. 1997 Aug 1;22(15):1741-6. [PubMed]
   
3. Canale ST. Beaty JH. Campbell's Operative Orthopaedics, 11th ed. , 4 volume set, Elsevier, Online Version, 2007. [MD Consult]
   
4. Jevtic V. Vertebral infection. Eur Radiol. 2004 Mar;14 Suppl 3:E43-52. [PubMed]
5. Forrester DM. Infectious spondylitis. Semin Ultrasound CT MR. 2004 Dec;25(6):461-73. [PubMed]