Korean J Radiol.  2016 Oct;17(5):565-580. 10.3348/kjr.2016.17.5.565.

Magnetic Resonance Imaging Findings of Early Spondylodiscitis: Interpretive Challenges and Atypical Findings

• Yeom JA
• Lee IS
• Suh HB
• Song YS
• Song JW

• KMID: 2458049
• DOI: http://doi.org/10.3348/kjr.2016.17.5.565

Abstract

MR findings of early infectious spondylodiscitis are non-specific and may be confused with those of other conditions. Therefore, it is important to recognize early MR signs of conditions, such as inappreciable cortical changes in endplates, confusing marrow signal intensities of vertebral bodies, and inflammatory changes in paraspinal soft tissues, and subligamentous and epidural spaces. In addition, appreciation of direct inoculation, such as in iatrogenic spondylodiscitis may be important, because the proportion of patients who have undergone recent spine surgery or a spinal procedure is increasing. In this review, the authors focus on the MR findings of early spondylodiscitis, atypical findings of iatrogenic infection, and the differentiation between spondylodiscitis and other disease entities mimicking infection.

Keyword

Spine infection; Magnetic resonance imaging; Spondylodiscitis; Iatrogenic infection

MeSH Terms

Diagnosis, Differential
Discitis/*diagnostic imaging/microbiology
Early Diagnosis
Humans
Infection/*diagnostic imaging
Magnetic Resonance Imaging/methods

Figure

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  Fig. 1 Pyogenic discitis. 9-year-old girl received chemotherapy for leukemia. Sagittal fat-suppressed, contrast-enhanced T1-weighted image showed peripheral rim enhancement (arrows) of L4–5 and L5–S1 discs.

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  Fig. 2 Pyogenic (enterococcal infection) spondylodiscitis. 75-year-old man with back pain and absence of fever. Focal cortical discontinuity (arrow) was visualized on sagittal T1-weighted imaging (WI) (A). Subtle marrow signal changes (arrowheads) were noted in anterior subchondral areas of L2 and L3 bodies on fat-suppressed, sagittal T2WI (B). Also, faint subligamentous enhancement (arrows) was observed on fat-suppressed, contrast-enhanced sagittal T1WI (C), representing high degree of suspicion of early infectious condition. However, formation of multiple spurs (arrows), representing more degenerative changes, were prominent on axial T2WI (D). On sagittal fat-suppressed, contrast-enhanced T1WI (E) obtained 2 weeks later, infectious process was found to be aggravated.

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  Fig. 3 Pyogenic spondylodiscitis. 68-year-old man with lower back pain. Fat-suppressed sagittal T2-weighted image (A) showed bright high signal intensity (arrow) of L1–2 disc, which was well enhanced (arrow) on fat-suppressed, contrast-enhanced sagittal T1-weighted imaging (B). Fat-suppressed, contrast-enhanced axial T1-weighted image (C) demonstrated enhancement of paraspinal soft tissue and peripheral portion of disc (arrows).

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  Fig. 4 Schematic illustrations representing vertebral arterial system. A. Axial schematic figure of lumbar vertebra: 1, aorta; 2, segmental artery; 3, direct vertebral body feeding artery; 4, intercostal/muscular artery; 5, dorsal spinal artery; 6, radicular artery; 7, nutrient artery. B. Sagittal schematic figure of lumbar vertebra: 1, segmental artery; 2, metaphyseal anastomosis; 3, intermetaphyseal anastomosis.

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  Fig. 5 Pyogenic spondylodiscitis. 67-year-old woman with lower back pain. Axial T1-weighted imaging (T1WI) showed abnormal low signal intensity (arrow) (A), and axial T2-weighted imaging showed corresponding high signal intensity (arrow) (B) in right paraspinal area. Fat-suppressed, contrast-enhanced axial T1WI showed diffusely enhanced lesion (arrow) (C). Fat-suppressed, contrast-enhanced sagittal T1WI showed linear subligamentous enhancement (arrows) at L5–S1 level (D).

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  Fig. 6 Pyogenic spondylodiscitis with epidural abscess. 72-year-old woman with lower back pain and underlying hepatocellular carcinoma. Axial diffusion-weighted imaging (A) showed high signal intensity in paraspinal area (arrows) and epidural area (arrowhead) at L5–S1 level. Epidural lesion demonstrated signal loss (arrowhead) on axial apparent diffusion coefficient (ADC) map (B) and had lower ADC value (0.93 x 10-3 mm2/s). Fat-suppressed, contrast-enhanced sagittal T1-weighted imaging (C) showed marked epidural enhancement (arrow) at L5–S1 level.

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  Fig. 7 77-year-old woman with erosive intervertebral osteochondrosis at L1–2 and L2–3 levels. Sagittal T1-weighted imaging showed numerous erosions (arrows) surrounded by low and high signal intensity bone marrow consistent with osteosclerosis and fat transformation.

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  Fig. 8 Acute Schmorl's node. 36-year-old woman with lower back pain. Sagittal T1-weighted imaging (T1WI) (A) showed relatively well-defined, large concentric ring (arrow) located in subchondral area of L4 body and smaller ring (arrowhead) in L3 body. Fat-suppressed, contrast-enhanced sagittal T1WI showed irregular, well enhanced concentric rings (B).

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  Fig. 9 Type 1 Modic change. 66-year-old man with history of lung cancer and lower back pain. Findings of multifocal cortical discontinuities or erosions of endplates (arrows) on sagittal T2-weighted imaging (A) and paraspinal soft tissue enhancement (arrows) on fat-suppressed, contrast-enhanced axial T1-weighted imaging (B) were confused with infection. However, reformatted sagittal CT (C) findings of vacuum disc, well-defined sclerosis, and erosions of vertebral endplates reduced possibility of infection.

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  Fig. 10 46-year-old man with tuberculous spondylitis mimicking malignancy. Axial T1-weighted imaging (T1WI) (A) depicted ill-defined low signal intensity lesion (arrows) with subtle cortical disruption on left posterolateral aspect of T11 body and pedicle. Corresponding lesion showed diffuse enhancement (arrows) on contrast-enhanced axial T1WI (B). Prominent enhancement of adjacent epidural space (arrows) was observed on fat-suppressed, contrast-enhanced sagittal T1WI (C).

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  Fig. 11 Pyogenic (staphylococcal infection) spondylodiscitis. 73-year-old woman with mild fever and back pain. Fat-suppressed, contrast-enhanced sagittal T1-weighted imaging (T1WI) showed only thin linear enhancement of epidural space (arrows) without signal changes in bone marrow or cortical changes (A). However, fat-suppressed, contrast-enhanced axial T1WI (B) showed faint paraspinal (arrows) and epidural (arrowheads) enhancement. Two months later, follow-up MRI (not shown) demonstrated aggravation of infectious process.

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  Fig. 12 Epidural abscess (streptococcal infection) mimicking disc herniation. 54-year-old man with severe lower back pain and mild fever. Sagittal T2-weighted imaging showed mild collapse of L3–4 disc with high signal intensity continuous with epidural lesion showing similar signal intensity (arrow) (A). Fat-suppressed, contrast-enhanced axial T1-weighted imaging (B) showed diffusely enhanced epidural lesion (arrowhead) and faint paraspinal soft tissue enhancement (arrows). One month later, follow-up MRI (not shown) revealed that infectious changes had progressed.

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  Fig. 13 Acute compression fracture with bone marrow edema mimicking infection. 62-year-old man with history of medication for osteoporosis. Sagittal T1-weighted imaging (T1WI) (A) revealed L1 vertebral body with subchondral bone defect at its lower endplate with marked bone marrow edema (arrow). Fat-suppressed, contrast-enhanced axial T1WI (B) depicted paraspinal soft tissue edema (arrows). Sagittal T2-weighted imaging (C) exhibited faint fracture line (arrow) with low signal intensity, highly suspicious for compression fracture.

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  Fig. 14 Schematic showing spread of infectious changes after selective nerve root block (1) and therapeutic or diagnostic facet joint injection (2). Diffuse inflammatory changes can be seen along needle track (a) mainly in back muscles. These inflammatory changes can also occur at injection sites (b), around nerve root ganglions, and spread into paraspinal soft tissues (c) and into adjacent epidural space (d). More rarely, inflammation may begin at posterolateral aspect (e) of vertebral body adjacent to injection site.

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  Fig. 15 Pyogenic facet joint infection caused by procedure. 62-year-old female patient presented with lower back pain after facet joint prolotherapy at L3–4 level. Axial T2-weighted imaging raised suspicion of osteoarthritis of bilateral L3–4 facet joints (A). Soft tissue edema around facet joints with bone marrow edema (arrows) and linear thin epidural enhancement were observed on fat-suppressed, contrast-enhanced axial T1-weighted imaging (B).

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  Fig. 16 Pyogenic spondylodiscitis caused by procedure. 68-year-old male patient presented with lower back pain and fever 3 days after selective nerve root block. Fat-suppressed, contrast-enhanced axial T1-weighted imaging (T1WI) (A) showed mild inflammatory changes in right paraspinal soft tissue (arrow) and back muscle area (arrowheads) corresponding to needle track. Fat-suppressed, contrast-enhanced sagittal T1WI (B) showed faint epidural enhancement (arrows) and linear subligamentous enhancement (arrowheads). MRI (not shown) obtained 10 days later showed aggravation of infectious process.

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  Fig. 17 Pyogenic spondylodiscitis caused by operation. 29-year-old man presented with pain and fever after percutaneous discectomy. Seven days after discectomy for disc extrusion, sagittal T1-weighted imaging (T1WI) (A) showed focal cortical discontinuity (arrow) and faint marrow signal changes. Corresponding fat-suppressed, contrast-enhanced sagittal T1WI (B) showed prominent epidural enhancement (arrows). MRI (images not shown) performed 20 days after first post-operative MRI revealed aggravation of infectious changes.

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