Spinal Epidural Abscess

Aka: Spinal Epidural Abscess, Epidural Abscess

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II. Epidemiology

  1. Incidence: 2 to 10 per 10,000 hospital admissions
  2. Mortality 2 to 20%

III. Precautions

  1. Spinal Epidural Abscess is frequently misdiagnosed on initial presentation
    1. Triad of back pain, fever and neurologic deficit is present in <15% of cases
    2. Fever is present in <50% of cases
  2. Be alert for red flag presentations (esp. with back pain)
    1. Unexplained fever (present in 86% of cases)
    2. Focal neurologic deficits with progressive or disabling symptoms (present in 82% of cases)
  3. References
    1. Bhise (2017) Am J Med 130(8): 975-81 +PMID: 28366427

IV. Pathophysiology: General

  1. Epidural Abscess occurs in the epidural space (between the dura and the Vertebral wall lining)
    1. Contiguous involvement is common (80% are found with Osteomyelitis or Discitis)
  2. Most cases involve thoracolumbar spine
    1. Larger space and higher fat content increase infection risk
  3. Seeding of the epidural space
    1. Hematogenous spread (esp. pediatric patients)
    2. Contiguous spread
    3. Direct inoculation (e.g. Lumbar Puncture, instrumentation)
  4. Most common organisms
    1. Staphylococcus aureus (>60% of positive cultures)
    2. Gram Negative Bacilli
    3. Stretococcus

V. Pathophysiology: Sites

  1. Anterior Epidural Abscess (20%)
    1. Associated infections
      1. Disk space infection (Discitis)
      2. Vertebral Osteomyelitis
    2. Blunt Trauma and associated Hematoma infection
    3. Direct extension from adjacent infection
      1. Retropharyngeal Abscess
      2. Retroperitoneal abscess
  2. Posterior Epidural Abscess (80%)
    1. Distant source (Cellulitis, dental, Pharyngitis)

VI. Risk Factors

  1. Immunocompromised states
    1. Diabetes Mellitus
    2. Chronic Corticosteroids
    3. Corticosteroid Injections
  2. Substance Abuse
    1. Alcohol Use Disorder
    2. Intravenous Drug Abuse
  3. Other infections
    1. Sepsis
    2. Cellulitis
    3. Osteomyelitis
    4. Septic Arthritis

VII. Findings

  1. Fever (<50% of cases)
  2. Back pain (70% of cases)
  3. Radiculopathy in a Dermatomal Distribution
  4. Neurologic deficits at or below the Epidural Abscess (may be slow and insidious, even over weeks to months)
    1. Motor deficits (may progress to irreversible paralysis within 1-2 days)
    2. Sensory deficits or Paresthesias
    3. Cauda Equina Syndrome (bowel or Bladder dysfunction, saddle Anesthesia, Foot Drop)

VIII. Labs

  1. Precautions
    1. Avoid Lumbar Puncture (may spread infection)
  2. Complete Blood Count (CBC) with differential
    1. Leukocytosis (60 to 90% of cases)
  3. Inflammatory Markers
    1. C-Reactive Protein (C-RP) >10 mg/L
    2. Erythrocyte Sedimentation Rate (ESR) >30 mm/h
  4. Blood Cultures (positive in >60% of cases)
    1. Staphylococcus aureus is most commonly isolated organism (>60% of positive cultures)

IX. Imaging

  1. Precautions
    1. Image the entire spine (skip lesions are common in Spinal Infections)
    2. Skip lesions are present in 15% of cases and have several associated risk factors
      1. Older age
      2. Bacteremia
      3. Very high Erythrocyte Sedimentation Rate (ESR) >95 mm/h
      4. High White Blood Cell Count >20k
      5. Concurrent area of infection outside the spine
      6. Longer symptom duration >7 days
  2. Gadolinium-enhanced Spine MRI (preferred)
    1. Test Sensitivity >90% for Spinal Epidural Abscess
    2. Abscess appears as an enhancing Lesion on T2-Weighted Images (chronic lesions may appear hypointense)
    3. MRI also differentiates Diskitis from Vertebral Osteomyelitis
  3. CT Spine with Myelography
    1. Similar Test Sensitivity for Epidural Abscess as MRI
      1. However, underestimates Spinal Epidural Abscess size
    2. Consider when MRI is contraindicated or unavailable
      1. However myelography risks spreading infection, and is relatively contraindicated
      2. Consult neurosurgery regarding imaging with CT myelography versus CT with IV contrast
  4. CT Spine with IV Contrast
    1. May be preferred when MRI is contraindicated due to the risks associated with Myelography
    2. Findings include soft tissue and Vertebral changes and disc narrowing
    3. False Negative results in early Epidural Abscess
  5. Spine XRay
    1. Typically non-diagnostic
    2. Advanced cases may demonstrate lytic lesions (Osteomyelitis) or disc space narrowing (Discitis)

X. Differential Diagnosis

  1. See Spinal Cord Syndrome
  2. See Spinal Infection
  3. Vertebral Osteomyelitis
  4. Spinal Epidural Abscess

XI. Management

  1. Emergent Neurosurgery or Spine SurgeryConsultation
  2. Surgical decompression of Epidural Abscess (first-line, preferred management)
    1. Indications
      1. Phlegmon
      2. Developing or worsening neurologic deficits
        1. However, pre-surgical paralysis may not benefit from surgery
      3. Cervical or Thoracic Spine involvement
        1. Higher risk for neurologic complications than Lumbar Spine (except Cauda Equina Syndrome)
    2. Methods
      1. Open decompression such as with Laminectomy (preferred)
        1. May be performed with endoscopy-assisted surgery
      2. Percutaneous drainage (aspiration under CT guidance)
        1. Consider in posterior Spinal Epidural Abscess AND
        2. Lack of neurologic deficit OR high surgical risk patient
        3. May also be preferred in children
      3. References
        1. Epstein (2015) Surg Neurol Int 6(suppl 19): S476-86 [PubMed]
    3. Alternative: Non-surgical, conservative management
      1. Indications
        1. Early presentation
        2. No neurologic deficit
        3. Poor candidate for surgery
        4. Full paralysis for >36 to 48 hours (surgery may have low efficacy)
      2. Precaution: Risk of failed conservative management in some cohorts
        1. Age over 65 years
        2. Diabetes Mellitus
        3. Prolonged symptoms
        4. Extraspinal infection
        5. C-Reactive Protein (C-RP) >115 mg/L
        6. White Blood Cell Count elevated
        7. Methicillin Resistant Staphylococcus Aureus on culture
      3. Precautions: Reassess frequently
        1. Acute deterioration may occur in <48 hours
        2. Address any neurologic changes with neurosurgery
  3. Empiric Antibiotics
    1. Start early empiric therapy and modify based on culture results
      1. Discuss with neurosurgery (may ask to withhold Antibiotics until surgical culture obtained)
      2. Typical IV Antibiotic duration: 6 weeks (up to 16 weeks for associated Discitis or Vertebral Osteomyelitis)
    2. Drug 1: MRSA Coverage (Staphylococcus aureus is most common cause, used with drug 2 below)
      1. Vancomycin 15-20 mg/kg IV every 8-12 hours (dosing must be calculated based on weight, levels)
      2. Alternatives: Linezolid, Daptomycin
    3. Drug 2: Gram Negative, esp. IVDA, Immunosuppression, UTI (used in combination with MRSA Drug 1 coverage)
      1. Gram Negative Coverage without Pseudomonas coverage
        1. Ceftriaxone 2 g IV every 24 hours
        2. Cefepime 2 g IV every 8 hours
        3. Levofloxacin 750 mg IV every 24 hours
      2. Gram Negative With Pseudomonas coverage as indicated (e.g. IV Drug Abuse, recent hospitalization)
        1. Ceftazidime 1-2 g IV every 8-12 hours
        2. Ciprofloxacin 400 mg IV every 12 hours
        3. Piperacillin-Tazobactam 4.5 g IV every 6 to 8 hours
        4. Meropenem 1 g IV every 8 hours
    4. Drug 3: Anaerobe Coverage
      1. Metronidazole 500 mg IV every 6 hours
    5. Candida Coverage Indications
      1. Immunocompromised State
      2. Recent Spine Surgery
    6. Other modified Antibiotic coverage
      1. Mycobacterium tuberculosis suspected

XII. Prognosis

  1. Mortality 2 to 20%
  2. Neurologic outcome may not be clear for the first year
  3. Poor Prognostic Indicators
    1. Delayed surgical intervention (when indicated)
    2. Long symptom duration
    3. Paralysis at the time of presentation
    4. Extensive spine involvement (esp. Thoracic Spine)
  4. Positive Prognostic Indicators
    1. Intact or only mild neurologic symptoms prior to intervention
      1. Most accurate prognostic indicator
      2. Neurologic symptoms progress with delayed diagnosis
      3. Residual deficits persist after surgery in 50% of cases (paralysis is often irreversible)
    2. Age under 60 years
    3. Cord symptoms (e.g. Bladder dysfunction) <24 hours
    4. No comorbid conditions
    5. Thecal sac compression <50%

XIII. Complications

  1. Cauda Equina Syndrome
    1. Results from direct mechanical compression of cord
  2. Meningitis (or overwhelming Sepsis)
    1. Results from spread into subarachnoid space
  3. Mortality
    1. Mortality rate: 5%

XIV. References

  1. Dasburg (2020) Crit Dec Emerg Med 34(6): 28-9
  2. Della-Giustina (2014) Crit Dec Emerg Med 28(3): 2-9
  3. Long and Carlson in Swadron (2022) EM:Rap 22(7): 7-9
  4. Uke and Bronckman (2024) Crit Dec Emerg Med 38(5): 4-8
  5. Bond (2016) Biomed Res Int 2016:1614328 +PMID: 28044125 [PubMed]
  6. Chao (2002) Am Fam Physician 65(7):1341-6 [PubMed]
  7. Tompkins (2010) J Emerg Med 39(3): 384-90 [PubMed]

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