High Yield Overview
Spinal Epidural Abscess
A Surgical Emergency: Delay in diagnosis leads to permanent paralysis.
15%Have Classic Triad
50%Missed on initial visit
S. aureusMost Common Organism
MRIStudy of Choice
Anatomical Location
Lumbar
PatternMost common (48%).
TreatmentDecompression
Thoracic
Pattern31%. Higher risk of cord compression.
TreatmentUrgent Decompression
Cervical
Pattern21%. Highest risk (Tetraplegia).
TreatmentUrgent Decompression
Critical Must-Knows
- The 'Classic Triad' (Fever, Back Pain, Neurology) is rarely present (less than 15%).
- Back pain is the most consistent symptom (greater than 70%).
- Any patient with Back Pain + Fever + Risk Factors needs an MRI.
- Neurological deficit is an indication for EMERGENCY surgery.
- Paralysis can become permanent within hours.
Examiner's Pearls
- "Paralysis is due to mechanical compression AND venous thrombosis (venous stasis).
- "Once paralysis sets in, less than 50% recover function even with surgery.
- "CRP is almost always elevated (greater than 90%), unlike WCC.
- "Lumbar Puncture is CONTRAINDICATED (risk of meningitis spreading).
Critical Errors
Delaying MRI
Negligence. Do not wait for neurological signs. Any high-risk patient with severe back pain needs an urgent MRI.
LP Contraindicated
Major Safety Violation. Do NOT puncture an infected site. Risk of seeding meningitis.
Medical Management
Strict Criteria. Only for: Neurologically Intact AND Identified Organism AND Stable. Close monitoring essential.
At a Glance
SEA vs Discitis
| Feature | Epidural Abscess | Discitis / Osteomyelitis |
|---|---|---|
| Urgency | Emergency (Hours) | Urgent (Days) |
| Main Risk | Cord Compression (Paralysis) | Instability / deformity |
| Location | Epidural Space | Disc & Endplate |
| Surgery | Decompression (Laminectomy) | Biopsy / Debridement / Fusion |
Mnemonics
Mnemonic
RISKRisk Factors
R
Renal / Diabetes
Immunocompromised state
I
IV Drug Use
Direct inoculation / S. aureus
S
Skin / Spine
Recent infection or procedure
K
Known Infection
Distant site (UTI, Pneumonia)
Memory Hook:Who gets SEA?
Mnemonic
Pain - Shoot - Weak - ParalyzedHeusner's Stages
1
Pain
Focal back pain
2
Shoot
Radicular pain (nerve root irritation)
3
Weak
Motor weakness / Sensory loss
4
Paralysis
Complete paraplegia (Irreversible)
Memory Hook:Progression of disease.
Mnemonic
SECCommon Pathogens
S
Staph aureus
Most common (greater than 60%) (MSSA/MRSA)
E
E. coli
Gram negatives from UTI
C
Coag-neg Staph
Skin flora (epidermidis)
Memory Hook:Bugs.
Overview and Epidemiology
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.
Pathophysiology and Mechanisms
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).
Classification Systems
Anatomical Classification Based on location relative to the Dura.
- Posterior: Behind the cord. (Majority). Easier to decompress via laminectomy.
- Anterior: In front of the cord. Harder to access. Often requires corpectomy or transpedicular approach.
- Circumferential: Surrounds the cord. High risk of ischemia.
Clinical Assessment
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.
Imaging and Investigations
Diagnostic Protocol
LabsScreening
- WCC: Elevated in ~60% (Unreliable).
- CRP/ESR: Elevated in greater than 95% (Highly Sensitive).
- Blood Cultures: Positive in ~60%. Guide antibiotic therapy.
MRIGold Standard
- T1: Iso/Hypointense.
- T2: Hyperintense (High signal) fluid collection.
- T1+Gad: Peripheral enhancement (Ring enhancement) with central non-enhancing pus.
- Cord Signal: Look for T2 hyperintensity in the cord (Edema/Myelomalacia).
CTAlternative
- Used if MRI contraindicated (Pacemaker).
- CT Myelogram is the alternative.
- Shows compression but misses cord signal changes.
Imaging Gallery
Click to expand
Management Algorithm
📊 Management Algorithm
Click to expand
Clinical Algorithm— SEA Management
Loading flowchart...
Treatment Protocols
Medical Management
- Reserved for:
- Neurologically intact patients.
- Known organism (Blood Cx or Biopsy positive).
- Too unfit for surgery.
- 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.
Surgical Technique
Laminectomy
- Goal: Evacuate pus and decompress the neural elements.
- Technique:
- Midline approach.
- Wide Laminectomy (remove spinous process and lamina).
- Identifying the abscess (often epidural fat is inflamed/indurated).
- Irrigation and gentle suction.
- Drains: Leave large bore drains.
- Note: Culture the pus!
Complications
| Complication | Rate | Impact |
|---|---|---|
| Permanent Paralysis | 4-22% | Devastating. Predictor: Pre-op deficit severity. |
| Death | 5-15% | Due to Sepsis / Multi-organ failure. |
| Recurrence | 10% | Inadequate drainage or short antibiotic course. |
| Meningitis | Rare | Due to dural tear during surgery. |
Postoperative Rehab
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.
Outcomes and Prognosis
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.
Evidence Base
Diagnosis Pitfalls
Davis et al • J Emerg Med (2004)
Key Findings:
- Classic Triad (Fever, Pain, Neuro) seen in only 13% of patients.
- Back pain is the only consistent symptom (100%).
- ESR was elevated in 98% (Sensitivity).
- Delays in diagnosis led to significantly worse neurological outcomes.
Clinical Implication: Do not rely on the triad. Screen with ESR/CRP and MRI.
Surgical Timing
Patel et al • Spine J (2014)
Key Findings:
- Studied 128 patients with SEA.
- Patients treated medically vs surgically.
- Those failing medical management who then had surgery had worse outcomes than early surgery.
- Recommended early surgery for minimal deficits.
Clinical Implication: Aggressive early surgery prevents deterioration.
Medical vs Surgical
Arko et al • Neurosurgeon (2014)
Key Findings:
- Medical management failure rate is ~40%.
- Predictors of failure: Age greater than 65, Diabetes, MRSA, Neurological deficit.
- Conclusion: Medical management only for highly selected cases.
Clinical Implication: Medical management only for highly selected cases.
Conservative Failure
Curry et al • Neurosurgery (2005)
Key Findings:
- Age greater than 65, Diabetes, and MRSA are independent predictors of medical management failure.
- Failure rate of medical management was 41%.
- Neurological deterioration occurred in 32% of medical patients.
Clinical Implication: High risk patients should have surgery.
MRI Sensitivity
Tang et al • AJR (2002)
Key Findings:
- MRI with Gadolinium is superior to non-contrast MRI.
- Sensitivity greater than 90% for detecting epidural collections.
- Can differentiate abscess (ring enhancing) from phlegmon (solid).
Clinical Implication: Order Gadolinium.
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
VIVA SCENARIOStandard
The Missed Diagnosis
EXAMINER
"A 50M IVDU presents with severe back pain. Afebrile. Neuro intact. GP gave NSAIDs. Returns 2 days later with urinary retention. What happened?"
EXCEPTIONAL ANSWER
This is a classic missed SEA.
1. **Risk Factor**: IVDU is a major red flag.
2. **Symptom**: 'Severe back pain' out of proportion to mechanics.
3. **Error**: Relying on temperature (Afebrile). 50% are afebrile.
4. **Progression**: Urinary retention indicates Cauda Equina compression (Stage 3/4).
5. **Action**: Urgent MRI. Urgent Decompression. Prognosis is now guarded.
KEY POINTS TO SCORE
Red Flags mandate MRI
Fever is unreliable
CRP is rarely normal
COMMON TRAPS
✗Thinking 'Mechanical Back Pain' in an IVDU
✗Waiting for MRI in the morning
VIVA SCENARIOStandard
Medical Management
EXAMINER
"65F with L3 SEA. S. aureus. Neuro intact. Unfit for surgery (Severe COPD). Can you treat medically?"
EXCEPTIONAL ANSWER
**Yes, but with extreme caution.**
**Criteria for Medical Rx**:
1. Neurologically Intact (Strict requirement).
2. Known Organism (S. aureus).
3. High Surgical Risk.
**Management**:
- IV Antibiotics.
- Close monitoring (q4h neuro obs).
- Serial MRI (Day 7 or if pain worsens).
- Counsel regarding risk of sudden paralysis.
KEY POINTS TO SCORE
Must be intact
High failure rate (40%)
Requires vigilant monitoring
COMMON TRAPS
✗Treating medically because 'abscess is small' (can expand rapidly)
✗Treating medically without a known bug (empiric failure)
MCQ Practice Points
Diagnosis
Q: Most sensitive screening test for SEA? A: ESR / CRP (greater than 95% sensitivity). WCC is often normal.
Anatomy
Q: Which venous system facilitates spread from the pelvis to the spine? A: Batson's Venous Plexus (Valveless).
Management
Q: Absolute indication for surgery in SEA? A: Neurological Deficit (e.g., foot drop, retention).
Pathogen
Q: Most common causative organism? A: Staphylococcus aureus (greater than 60%).
Contraindication
Q: Which procedure is contraindicated in suspected SEA? A: Lumbar Puncture. Risk of introducing infection to the subarachnoid space (Meningitis).
Australian Context
Epidemiology
- High rates of S. aureus skin infections in indigenous communities (community acquired MRSA).
- IVD use rates in urban centers.
Exam Day Cheat Sheet
SEA Summary
High-Yield Exam Summary
Classic Triad
- •Back Pain (100%)
- •Fever (50%)
- •Neurology (Late)
- •Tenderness (Focal)
Workup
- •MRI Gadolinium (Gold Std)
- •Blood Cx x3
- •ESR/CRP (Sensitive)
- •Look for Source (Echo)
Management
- •Decompression (If Neuro Deficit)
- •Antibiotics (6w+)
- •Monitor CRP
- •Stabilize if needed
Red Flags
- •IV Drug Use
- •Diabetes
- •Recent Procedure
- •Night Pain
Image Manifest
- [4-sagittal-view-of-t2-diffusion-mri-lumbar-spine-sho.png]: Lumbar Abscess T2
- [1-sagittal-t2-weighted-magnetic-resonance-imaging-mr.png]: Cervical Abscess T2
- [sea_algorithm.png]: Management Algorithm