Spinal Epidural Abscess

Definition A collection of pus (purulent material) within the epidural space of the spinal canal.

Epidemiology

• Incidence is rising (aging population, IVDU, spinal procedures).
• Common in men (2:1).
• Peak age 50-70.

Pathophysiology

• Bacteria enter the epidural space via hematogenous spread (skin, UTI) or direct extension (discitis).
• The infection causes mechanical compression of the cord/cauda equina.
• It also causes septic thrombophlebitis of the epidural veins → Venous congestion → Cord ischemia → Infarction.

Epidural Space

• Potential space between the Dura Mater and the Periosteum/Ligamentum Flavum.
• Contains fat and the Batson's Venous Plexus.

Batson's Plexus

• Valveless venous system.
• Allows retrograde spread of infection from pelvic organs (e.g., during coughing/straining) to the spine.
• Explains why UTI is a common source.

Anterior vs Posterior

• Posterior: Most common in Thoracic/Lumbar spine (more epidural fat posteriorly).
• Anterior: Associated with Vertebral Osteomyelitis/Discitis (direct extension).

History

• Classic Triad: Fever + Back Pain + Neurology. (Only 10-15% sensivity).
• Back Pain: Most common symptom (greater than 75%). Severe, unrelenting, night pain.
• Fever: Only present in ~50%.
• History of: IVDU, Diabetes, Recent spinal injection, UTI.

Examination

• Spine: Focal percussion tenderness (Highly suspicious).
• Neurology:
  • Assess Power (Myotomes).
  • Assess Sensation (Fluid level? Saddle anesthesia?).
  • Assess PR Tone/Sensation (Cauda Equina).

Red Flags

• New onset back pain in an IV Drug User = SEA until proven otherwise.

Medical Management

• Reserved for:
  1. Neurologically intact patients.
  2. Known organism (Blood Cx or Biopsy positive).
  3. Too unfit for surgery.
  4. Complete paralysis greater than 48-72 hours (salvage unlikely).
• Antibiotics: Empiric (Vanc + Ceftriaxone) → Targeted.
• Monitoring: Daily neurological checks. Serial MRI if worsening.

Failure of Medical Management

• Defined as:
  • New neurological deficit.
  • Persistent fever/CRP elevation.
  • Increasing pain.
  • Enlargement of abscess on MRI.

Antibiotics

• Long term IV (usually 6-8 weeks).
• Oral suppression may be needed lifelong if implant retained (rare).

Rehabilitation

• Spinal Cord Injury protocol if deficit persists.
• Bladder/Bowel management.
• Pressure area care.

Prognostic Factors

• Pre-operative Neurology: The single most important factor.
• Duration of Deficit: Less than 36 hours has better prognosis.
• Age: Greater than 65 has worse outcome.
• Diabetes: Associated with higher mortality.

Recovery

• Complete recovery is rare if paralysis has set in.
• Early decompression (less than 24 hours) yields best results.

Global Epidemiology

• Incidence is rising worldwide: historically 0.2–2 per 10,000 hospital admissions (Reihsaus), now commonly quoted at 2–8 per 10,000 in tertiary centres, driven by an ageing population, diabetes, injection drug use and increasing spinal instrumentation.
• Male predominance (roughly 1.5–2:1); peak age 50–70 years.
• Staphylococcus aureus causes 60–70% of cases; the proportion of MRSA varies markedly by region and rises where community-acquired MRSA is endemic. Gram-negative organisms (e.g. E. coli) point to a urinary source; consider Mycobacterium tuberculosis (Pott disease) and Brucella in high-prevalence and limited-resource settings.

Guidance — Areas of Broad International Agreement

Where Practice Genuinely Varies

• Empirical regimen: vancomycin (MRSA cover) plus a broad Gram-negative agent (e.g. ceftriaxone, cefepime or an antipseudomonal in IVDU/healthcare-associated cases) is widespread, but local antibiograms and MRSA prevalence drive the exact choice. Where MRSA is rare, an anti-staphylococcal penicillin may suffice.
• Initial non-operative trial: more readily adopted in high-resource centres with rapid MRI access and the ability to monitor with frequent neuro-obs and serial imaging; risky where MRI and theatre access are limited, so earlier surgery is often favoured.
• Source-setting differences: in TB-endemic and limited-resource regions, tuberculous epidural abscess is a major differential and changes both imaging interpretation and drug therapy.

Registry & Outcome Notes

• SEA is not tracked in arthroplasty registries; the evidence base is retrospective cohorts and meta-analyses (Reihsaus; Curry; Kim) rather than RCTs. No high-quality randomised data compares medical vs surgical management — a key limitation acknowledged across guidelines.