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Discitis

Summary

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  • Inflammatory condition affecting the intervertebral disc space and adjacent vertebral endplates
  • Typically presents with severe back pain, fever, and neurological symptoms
  • Diagnosis relies on clinical presentation, laboratory findings, and imaging studies, particularly MRI

Pathophysiology

  • Usually results from hematogenous spread of infection to the avascular intervertebral disc
  • Common causative organisms:
    • Staphylococcus aureus (most frequent)
    • Streptococcus species
    • Escherichia coli
    • Mycobacterium tuberculosis (in endemic areas)
  • Infection leads to:
    • Inflammation of the disc space
    • Destruction of cartilaginous endplates
    • Potential spread to adjacent vertebral bodies

Demographics

  • Can affect all age groups, but bimodal distribution:
    • Young children (< 5 years)
    • Adults > 50 years
  • Risk factors:
    • Immunocompromised states
    • Intravenous drug use
    • Recent spinal surgery or invasive procedures
    • Diabetes mellitus
    • Chronic renal failure

Diagnosis

  • Clinical presentation:
    • Severe, localised back pain
    • Fever (may be absent in chronic cases)
    • Neurological deficits (in advanced cases)
  • Laboratory findings:
    • Elevated inflammatory markers (ESR, CRP)
    • Leukocytosis
  • Microbiological studies:
    • Blood cultures (positive in 50-70% of cases)
    • CT-guided biopsy for culture and sensitivity

Imaging

  • Plain radiographs:
    • Often normal in early stages
    • Later findings: disc space narrowing, endplate erosions, vertebral body destruction
  • Computed Tomography (CT):
    • Better visualisation of bony changes
    • Useful for guiding biopsy procedures
  • Magnetic Resonance Imaging (MRI):
    • Modality of choice for early diagnosis and follow-up
    • Findings:
    • T1-weighted: low signal intensity in disc space and adjacent vertebral bodies
    • T2-weighted: high signal intensity in disc space and adjacent vertebral bodies
    • Contrast enhancement of disc space and adjacent vertebral bodies
    • Potential epidural or paraspinal abscesses

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  • A 60-year-old patient presented was midtoracic back pain with elevated inflammatory markers.
  • MRI showed enplate erosion, vertebral body oedema and enhancing paraspinal soft tissue.
  • Discitis secondary to Staphlococcus Aureus infection was diagnosed based on blood culture and CT-guided biopsy.

Treatment

  • Antimicrobial therapy:
    • Empiric broad-spectrum antibiotics initially
    • Tailored based on culture and sensitivity results
    • Prolonged course (6-12 weeks) typically required
  • Conservative management:
    • Bed rest and immobilisation in early stages
    • Gradual mobilisation as symptoms improve
  • Surgical intervention:
    • Indicated for:
    • Neurological deficits
    • Spinal instability
    • Failure of conservative treatment
    • Procedures may include:
    • Debridement and fusion
    • Abscess drainage
  • Pain management:
    • Analgesics and anti-inflammatory medications
  • Follow-up:
    • Regular clinical and radiological assessment to monitor treatment response

Differential diagnosis

Differential Diagnosis Differentiating Feature
Degenerative disc disease Disc space narrowing with osteophytes and vacuum disc phenomenon on CT; no T1 hypointensity or STIR hyperintensity crossing the disc space
Vertebral compression fracture Vertebral body height loss without disc space involvement or end-plate erosion; preserved disc signal
Spinal metastasis Focal vertebral body lesions without crossing the disc space; preserved disc height; T1 hypointense and STIR hyperintense
Epidural abscess Rim-enhancing epidural collection separate from disc; posterior epidural location; may occur without disc involvement
Osteomyelitis without discitis Vertebral body involvement without significant disc signal change or end-plate erosion
Ankylosing spondylitis Shiny corners and syndesmophytes on CT; sacroiliac joint fusion; no fluid signal crossing disc space
Herniated disc Disc protrusion with preserved end-plate signal; no T1 or STIR signal change in adjacent vertebral bodies
Spinal tuberculosis Gibbus deformity; paraspinal and psoas abscess with rim enhancement; relative preservation of disc until late stage