Spinal epidural abscess

OVERVIEW

• Spinal epidural abscess is considered a neurosurgical emergency
• morbidity and mortality is worse with delayed diagnosis, and the worse the neurological deficit at the time of surgery the worse the outcome
• surgery within 24 hours of symptom onset is associated with the best prognosis
• Absent fever and absent neurological deficit does not rule out spinal epidural abscess, an MRI may be indicated

PATHOPHYSIOLOGY

• The epidural space is between the dura and the vertebral column

Source of infection

• often unknown
• haematogenous spread
  • skin/ soft tissue infections
  • infected prostheses e.g. IV catheters
  • bacterial endocarditis
  • pneumonia
  • UTI
• contiguous spread
  • Vertebral osteomyelitis
  • Retropharyngeal abscess
  • Overlying skin infections or pressure sores
  • Psoas abscess
  • Penetrating injury
  • Epidural injections or catheters
  • Spinal stimulators

Complications

• death from generalized septicemia/ meningoencephalitis
• Adjacent spread: osteomyelitis, paraspinal abscess
• Spinal cord dysfunction including paralysis: direct compression, spinal ischemia from local thrombosis

CAUSE

Typical causative organisms:

• Staphylococci
• Streptococci
• Gram negative anaerobes

Risk factors

• IV drug abuse
• Immunocompromise, including diabetics, alcoholics and HIV
• Infection of adjacent structures (e.g, vertebral osteomyelitis, infected pressure sores)
• Recent perispinal procedures (e.g. epidurals, lumbar puncture, spinal operations)

CLINICAL FEATURES

Typical progression of symptoms is:

• Localized back pain with or without fever: 50% afebrile, most have local tenderness
• nerve root irritation corresponding to the involved segments
• early neurological deficits: motor weakness, sensory deficits, bowel or bladder dysfunction
• late neurological deficits: paralysis (very poor prognosis if complete paralysis >24 hours)
• other complications (see above)

The diagnosis is often missed at first presentation, when neurological deficits may be absent

INVESTIGATIONS

Laboratory tests

• FBC: WBC increased with neutrophilia
• CRP can be elevated before abnormalities in WBC are seen (suspect SEA if raised CRP and point tenderness in back)
• Blood cultures

Imaging

• Spine XR usually unhelpful
• CT scan: high false negative rate but may be diagnositc; can be used for CT-guided diagnostic aspirate for cultures
• MRI: gold standard for diagnosis; ideally perform before the onset of neurological symptoms; routinely scanning the entire spine is the safest approach although some radiologists prefer to image the preseumed affected segment and adjacent segments

MANAGEMENT

• IV antibiotics (typically prolonged for 4-6 weeks, due to associated osteomyelitis)
  • cefotaxime
  • flucoxacillin, or vancomycin if MRSA is suspected
• Urgent neurosurgical referral for consideration of early decompressive laminectomy and drainage
• Selected cases may be managed by aspiration and/ or medical management alone
• Supportive care and monitoring including analgesia, attention to bowel and bladder cares, pressure injury prophylaxis and other issue relevant to spinal cord compromise

References and Links

Journal articles

• Darouiche RO. Spinal epidural abscess. N Engl J Med. 2006 Nov 9;355(19):2012-20. PMID: 17093252.
• Sendi P, Bregenzer T, Zimmerli W. Spinal epidural abscess in clinical practice. QJM. 2008 Jan;101(1):1-12. PMID: 17982180.
• Shah NH, Roos KL. Spinal epidural abscess and paralytic mechanisms. Curr Opin Neurol. 2013 Jun;26(3):314-7. PMID: 23511442.
• Tompkins M, Panuncialman I, Lucas P, Palumbo M. Spinal epidural abscess. J Emerg Med. 2010 Sep;39(3):384-90. PMID: 20060254.