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Infectious spondylodiscitis is an infection of the intervertebral disc and adjacent vertebral bodies, most commonly caused by hematogenous spread of bacteria.
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| Cause Category | Examples |
|---|---|
| Bacterial (Pyogenic) | Staphylococcus aureus (most common), E. coli, Streptococcus spp. |
| Mycobacterial | Mycobacterium tuberculosis (→ Pott disease) |
| Fungal | Candida, Aspergillus, endemic fungi (esp. immunocompromised) |
| Iatrogenic | Post-surgical or post-injection (e.g., epidural steroid injection) |
| Direct inoculation | Trauma, spine surgery |
| Contiguous spread | From adjacent abscess or soft tissue infection |
Risk Factors:
| Category | Examples |
|---|---|
| Immunocompromised | Diabetes mellitus, HIV, malignancy, CKD |
| IV drug use | Common cause of hematogenous spread |
| Older age | Reduced immunity and vascularity |
| Spinal instrumentation | Recent surgery, implants |
| Chronic infection | UTIs, dental infections, endocarditis |
| Symptom | Description |
|---|---|
| Back pain | Severe, focal, and progressive |
| Fever | Present in only ~50% of cases |
| Neurologic deficit | Weakness, paresthesia, bowel/bladder involvement |
| Constitutional symptoms | Malaise, weight loss (especially in TB/fungal) |
| Localized tenderness | Over infected spinal level |
| Structure | Pathological Process |
|---|---|
| Disc space | Initial site in pyogenic infection |
| Adjacent vertebral endplates | Rapid destruction |
| Paravertebral soft tissue | Phlegmon, abscess formation |
| Epidural space | Can lead to abscess and cord compression |
| Facet joints | Less commonly involved |
| Modality | Imaging features |
|---|---|
| MR | • T1: ↓ signal in disc and adjacent vertebral bodies |
| • T2/STIR: ↑ signal due to marrow edema and disc inflammation | |
| • Contrast enhancement: Irregular enhancement of disc, vertebrae, and abscesses | |
| • Epidural/paraspinal abscess Seen as rim-enhancing collections | |
| CT | • Bone destruction: Vertebral endplate erosion, disc space narrowing |
| • Guided biopsy: CT useful for image-guided aspiration | |
| XR | Late findings (2–4 weeks): Disc space narrowing, endplate erosion, vertebral collapse |
| Nuclear medicine | Functional diagnosis (e.g., technetium-99m, gallium scans) |
| Condition | Differentiating Features |
|---|---|
| Modic Type 1 degeneration | MRI: no abscess, less enhancement, typically avascular disc |
| Andersson lesion | Seen in ankylosing spondylitis; sterile discovertebral lesion |
| Malignancy/metastasis | Spares disc space early, often involves multiple non-contiguous levels |
| Tuberculous spondylitis | Subligamentous spread, large paraspinal abscess, skip lesions |
| Brucellar spondylitis | Slow course, preserved disc early, endemic areas |