Spinal Infection Overview¶

Introduction¶

Spinal infections account for 2–7% of all musculoskeletal infections and can involve any component of the spine — vertebral body, intervertebral disc, epidural space, facet joints, or paravertebral soft tissues. The incidence has been increasing due to an aging population, rising rates of immunosuppression, intravenous drug use, and spinal instrumentation.

Classification¶

By Anatomical Location¶

• Spondylodiscitis — Infection of the vertebral body and adjacent disc (most common)
• Vertebral osteomyelitis — Infection primarily of the vertebral body
• Discitis — Infection of the intervertebral disc (more common in children)
• Epidural abscess — Infection in the epidural space
• Paravertebral abscess — Infection in the paraspinal soft tissues
• Subdural empyema — Rare infection between the dura and arachnoid

By Organism¶

• Pyogenic — Staphylococcus aureus (most common overall, 50–60%), Streptococcus, Gram-negative bacilli (E. coli, Pseudomonas)
• Mycobacterial — Tuberculosis (Pott disease) — the most common cause worldwide
• Brucella — Endemic in Mediterranean, Middle East, Latin America
• Fungal — Aspergillus, Candida, Coccidioides — primarily in immunocompromised patients

Routes of Infection¶

1. Hematogenous spread — Most common route. Arterial seeding from a distant source (urinary tract, endocarditis, skin/soft tissue, respiratory). Batson venous plexus also provides a route.
2. Direct inoculation — Post-surgical, spinal injection, penetrating trauma
3. Contiguous spread — From adjacent retroperitoneal or mediastinal infection

Imaging Approach¶

MRI (Modality of Choice)¶

MRI with gadolinium is the most sensitive and specific imaging study:

• T1-weighted — Low signal in the affected vertebral bodies and disc (loss of normal fatty marrow signal)
• T2-weighted/STIR — High signal in the vertebral bodies, disc, and surrounding soft tissues
• Post-contrast T1 with fat saturation — Enhancement of the disc, vertebral endplates, epidural space, and paravertebral tissues. Essential for detecting epidural abscess.
• Disc involvement — Loss of the normal intranuclear cleft, increased T2 signal, and disc enhancement are hallmarks of infection

CT¶

• Endplate erosion and destruction
• Paravertebral soft tissue mass or abscess with rim enhancement
• CT-guided biopsy for tissue diagnosis and culture

Nuclear Medicine¶

• Bone scan — Sensitive but nonspecific
• Gallium-67 or labeled WBC scan — Can increase specificity
• FDG-PET/CT — Highly sensitive; useful for monitoring treatment response

Risk Factors¶

• Age >50 years
• Diabetes mellitus
• Immunosuppression (HIV, steroids, chemotherapy, organ transplant)
• Intravenous drug use
• Recent spinal surgery or injection
• Renal failure / hemodialysis
• Endocarditis
• Urinary tract infection

Key Points¶

• MRI with contrast is the imaging modality of choice for spinal infection
• Spondylodiscitis (vertebral body + disc involvement) is the most common presentation
• Staphylococcus aureus is the most common pyogenic organism
• Tuberculosis is the most common cause of spinal infection worldwide
• Disc involvement with endplate destruction is the hallmark of infection
• CT-guided biopsy provides tissue for culture and sensitivity

References¶

1. DeSanto J, Ross JS. Spine infection/inflammation. Radiol Clin North Am. 2011;49(1):105-127. https://pubmed.ncbi.nlm.nih.gov/21111132/
2. Diehn FE. Imaging of spine infection. Radiol Clin North Am. 2012;50(4):777-798. https://pubmed.ncbi.nlm.nih.gov/22643395/
3. Hong SH, Choi JY, Lee JW, Kim NR, Choi JA, Kang HS. MR imaging assessment of the spine: infection or an imitation? RadioGraphics. 2009;29(2):599-612. https://pubmed.ncbi.nlm.nih.gov/19325068/
4. Hall WA, Graeber A, Cecava ND. Vertebral Osteomyelitis. In: StatPearls. Treasure Island (FL): StatPearls Publishing; updated 2024 Nov 25. https://www.ncbi.nlm.nih.gov/books/NBK532256/
5. Expert Panel on Neurological Imaging. ACR Appropriateness Criteria® Suspected Spine Infection. J Am Coll Radiol. 2021. https://acsearch.acr.org/docs/3148734/Narrative/
6. Dhodapkar MM, Patel T, Rubio DR. Imaging in spinal infections: Current status and future directions. N Am Spine Soc J. 2023;16:100275. https://pmc.ncbi.nlm.nih.gov/articles/PMC10562850/
7. Spondylodiscitis. Radiopaedia.org. https://radiopaedia.org/articles/spondylodiscitis

Related Articles¶

• Pyogenic Spondylodiscitis
• Spinal Tuberculosis
• Epidural Abscess
• Infection vs Tumor