epidural abscess

see also:

• acute spinal cord compression
• Spinal cord syndromes and lesions

• spinal infections such as bacterial vertebral osteomyelitis / discitis or epidural abscess are not only neurologic emergencies for potential acute spinal cord compression, but are life threatening, particularly once infection spreads to the CSF
• this should be considered in ANY patient with midline back pain and fever, especially if they have risk factors such as intravenous drug users (IVDU) or injection drug use (IDU)
• a low index of suspicion is required to detect this condition early

• Spontaneous epidural abscess is rare, accounting for 0.2–1.2 cases per 10 000 hospital admissions per year
• some patients have a pre-existing haematoma from an injury in the preceding weeks which then becomes infected.
• usually are haematogenous spread and seeding in patients with either:
  • intravenous drug users (IVDU) or injection drug use (IDU)
  • recent staphylococcal infection within the past few weeks - this may be on the skin or elsewhere
  • infective endocarditis (including SBE)
• may spread from bacterial vertebral osteomyelitis / discitis
  • most are from haematogenous seeding as for epidural abscesses (see above), but in this case they may be from UTIs or respiratory infections
  • discitis occurs in 1-2% of post-op spinal surgery patients in which case they are generally skin flora
  • some cases are due to tuberculosis (TB)
• rarely, they may result from direct inoculation of bacterial such as with:
  • complication of dry needling or acupuncture of the spine
    • epidural haematomas are uncommon complications of dry needling of the spine ¹⁾²⁾, and when these occur, they may develop into abscesses
  • complication of central nerve blocks such as epidural blocks or epidural steroid injections ^{3) 4) 5)}
    • incidence 1:1000 to 1:100 000
    • most patients have risk factors such as compromised immunity, spinal column disruption, source of infection
    • risk increases with duration of epidural > 2 days
    • even with aseptic technique and 10% povidone iodine skin prep, 18% of the used epidural or spinal needles end up contaminated with bacteria suggesting that there is a risk of inoculation of skin or nasal flora into the epidural space.

• in the developed world, the main bacterial causes are:
  • Staph. aureus 57-93% of cases
  • streptococcus / streptococcal infections in 18% of cases
  • Gram negatives in 13%
• less commonly, and especially in the immunocompromised, a range of other organisms may be the cause, including Listeria monocytogenes / Listeriosis, tuberculosis (TB) and fungi

• usually present with progressive midline spine pain
• usually have fever and this is usually the first clinical feature, but fever may also be a late feature
• some may have clinical evidence of acute spinal cord compression, although only around 13% have the classic triad of fever, back pain and new neurology
• some may develop meningism, especially if cervical

• fever, midline back pain and spinal tenderness:
  • spinal tuberculosis (TB)
  • vertebral osteomyelitis / discitis and other infections around the spine
  • neoplasia / cancer / tumours
  • vascular causes
  • spinal gout +/- epidural involvement (rare)

• clinical history and examination, particularly looking for risk factors and for evidence of focal spinal tenderness and neurology
• FBE, U&E, CRP, ESR, 2 sets of blood cultures
• if sepsis is possible based upon clinical features or WCC or raised CRP, then consider emergent MRI scan that day and referral to neurosurgery
• consider empirical broad spectrum antibiotics with staph coverage after discussion with neurosurgery
• definitive management will probably require laminectomy and drainage at a neurosurgical center
  • some patients may be medically managed
    • if organism not detected on cultures, consider CT guided needle aspirate to determine organism and sensitivities
  • all patients usually required many weeks of iv antibiotics
• use of corticosteroids is inconclusive

• irreversible neurology
• seeding or spread of infection to other sites:
  • vertebral osteomyelitis
  • endocarditis
  • psoas muscle abscess
  • meningitis
• severe sepsis

• many factors determine prognostic outcome:
  • age - probability of a worse outcome doubles with each decade of age
  • degree of thecal sac compression
  • duration of symptoms
  • severity of sepsis
  • presence of neurology (especially if persistent for > 36hrs)
  • location - in general, thoracic ones cause more neurology than lumbar ones