Epidural Abscess

Followup Rounds
12/11/15
Article inspired by: Dr. Anna Meyendorff

THE CASE

27 y/o M p/w left upper back pain x 10 days.

  • Felt a bump on his back for the last few weeks,
  • Swelling waxed and waned
  • Took ibuprofen and has been using a heating pad for the pain.
  • Last 3 days, has developed fevers/chills, nausea, vomiting, diarrhea, and poor appetite.
  • Entire body hurts, especially his muscles
  • Cannot walk secondary to the pain and general weakness
  • Denies numbness, paresthesias, incontinence, IVDU
  • ROS- mild headache with photophobia, some difficulty swallowing and a sensation of food getting stuck in his throat

PMHx: HIV/AIDS (last CD4 6, VL 119,520), Frequent skin abscesses

PSHx: Anal wart resection

Meds: Non-compliant (prescribed: Norvir, Reyataz, Truvada, Azithromycin, Bactrim)

Allergies: Denies

SHx: Smokes 1/2ppd, occasional cocaine, denies IVDU; multiple male partners, uses condoms

Physical Exam:

  • Vitals: BP: 118/50, HR: 116, RR: 20, Temp: 102.6F, SpO2: 97%
  • General: Lying on stretcher in no distress, Cachectic, Diaphoretic, Oral thrush
  • Chest: CTA b/l, No wheezes/rales/rhonchi
  • Cardiac: Tachycardic, No murmurs/rubs/gallops
  • Abdomen: Soft, NT/ND
  • Rectal: Tone intact, No saddle anesthesia
  • Back: No midline cervical/thoracic/lumbosacral tenderness; Large tender area with local induration and calor over the left paraspinal area at mid-thoracic level
  • Neuro: AAOx3; Unable to test gait (refusing 2/2 pain); Motor 5/5 in b/l UE, 5/5 in LLE hip flexion, knee flex/ext, plantar/dorsiflexion, 3/5 RLE hip flexion, 4/5 knee flex/ext, 5/5 plantar/dorsiflexion; Sensation symmetrically intact to light touch over face, trunk, and extremities; Reflexes 3+ b/l biceps, 2+ b/l ankle jerk, toes flex b/l
  • Extremities: Warm and well-perfused x 4, Several scars on right arm (from old-appearing, small, healed abscesses), Tenderness to light touch over R anterior thigh and L triceps

Labs

  • 7.8>10.8/33<322
  • 127/4.7/89/25/19/0.9<107
  • Lactate 1.9, Alb 3.0, T. Bili 1.5, AST 198, ALT 87, Alk Phos 84
  • Coags nl, CRP 391, ESR 117

Imaging

  • CT Chest & Thoracic Spine w/o contrast: Large lobulated collection at the lateral aspect of the left paraspinal musculature concerning for a soft tissue abscess measuring 2 x 6 x 11.7 cm. Small epidural collection along the left lateral aspect of the upper thoracic spine at the T3 level. Possible fluid collection in the neuroforamina at T3/4. No osseous erosions seen. Follow-up with contrast-enhanced MRI recommended.

THE TALK

  • Two types of epidural abscesses
    • Intracranial epidural abscess
    • Spinal epidural abscess (nine times more common)
      • Most common in thoracolumbar areas (larger epidural space and more infection-prone fat tissue)

Why is an epidural abscess dangerous?

  • Can expand and compress brain/spinal cord by
    • Direct compression
    • Thrombosis/thrombophlebitis of nearby veins
    • Interruption of arterial blood supply
    • Bacterial toxins and mediators of inflammation

What does the epidural abscess contain?

  • S. aureus (63%)
  • Mycobacterium tuberculosis (more frequent cause in developing world)
  • In acute cases, frank pus
  • More commonly, granulation tissue (when present > 2 weeks)

How can bacteria get into the epidural space?

  • Hematogenously
    • Skin/soft tissue infections
    • Bacterial endocarditis
    • PNA/UTI
  • Direct extension from infected contiguous tissue
    • Vertebral osteomyelitis
    • Retropharyngeal abscess
    • Psoas abscess
  • Direct inoculation into the spinal canal
    • Epidural injections or catheters
    • Penetrating injury
    • Spinal stimulators

Who is at risk for epidural abscesses?

  • IV drug users
  • Immunocompromised (diabetes, alcoholics, HIV)
  • Recent perispinal procedures (epidural, L.P., spinal surgery)
  • Infection of adjacent structures (vertebral osteomyelitis, infected pressure sores)

Is there a classic triad I should look out for?

  • Fever (50%)
  • Back Pain
  • Neurological deficits (usually absent early on so diagnosis missed at 1st presentation)

What is the classical progression of the disease, if left untreated?

  • Back pain (focal and severe), progressing to
  • Nerve root pain (“shooting” or “electric shocks”), progressing to
  • Motor weakness, sensory changes and bladder/bowel dysfunction, progressing to
  • Paralysis (quickly becomes irreversible)

Are there any lab tests I can order to help me?

  • Leukocyte count can be elevated or normal
  • ESR is usually elevated in both epidural abscess and vertebral osteomyelitis
  • Blood cultures

Hmm, I guess not. How about imaging?

  • MRI is the preferred test (image entire spinal column because multiple skip lesions are common)
    • May require pain management so they can lie flat/still for an MRI
    • MRI is important to distinguish epidural soft tissue edema VS epidural abscess
    • Fluid-equivalent signal intensity on T2-weighted images with rim enhancement and hypointense center
  • CT with IV contrast is an acceptable alternative, if no MRI available

Okay, what do I do if the MRI suggests an epidural abscess?

  • Diagnosis
    • 2 sets of blood cultures
    • Direct needle aspiration (usually under CT guidance) of abscess fluid/pus
    • Do NOT L.P. (risk of seeding subarachnoid space leading to meningitis)
  • Treatment
    • Reduce size and ultimate elimination of inflammatory mass
      • Early surgical decompression and drainage (within 24 hours)
      • Medical (conservative) approach only if lacking risk factors (such as advanced age, bacteremia, WBC > 12,500 cell/L, diabetes, MRSA infection, in whom organism is known from aspiration and no neurological deficit)
    • Eradicate the causative organism
      • Empiric antibiotics against staphylococci, streptococci and gram-negative bacilli
        • Vancomycin (for empiric MRSA) +
        • Nafcillin OR Oxacillin (for optimal MSSA coverage as better than Vanc) +
        • Metronidazole +
        • Cefoxatime OR Ceftriaxone OR Ceftazidime (preferred if Pseudomonas considered)

REFERENCES

Meyendorff A. “Follow up Rounds: Epidural Abscess” Jacobi Medical Center. Jacobi/Montefiore Emergency Medicine Conference. Bronx. Dec 2015. Case Presentation

Sexton, Daniel J., and John H. Sampson. “Spinal Epidural Abscess.” Spinal Epidural Abscess. UpToDate, 4 Jan. 2016. Web.

Nickson, Chris. “Spinal Epidural Abscess.” Spinal Epidural Abscess. Life in the Fast Lane, Web.

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