Definition: Suppurative infection enclosed within the epidural space
Incidence: 2-3 cases per 10,000 hospitalized patients (Sendi 2008).
- Rate is increasing given the rise in number of spinal procedures and anesthesia techniques
- Mortality is low at 5%, however, if untreated paralysis may occur
- Can occur at any age but most patients are between 50 and 70 years old.
Classified as either primary or secondary:
Primary: Hematogenous spread from a distant focus to the epidural space
- Usually from skin and soft tissue infections
- Often located in the posterior/dorsal aspect of the spinal canal due to the presence of infection prone adipose tissue.
Secondary: Direct inoculation from recent spinal procedure, trauma or contiguous spread from adjacent discitis or osteomyelitis
- Typically develops in the anterior/ventral epidural space
- Primary: Hematogenous spread from a distant focus to the epidural space
- Organism: Most commonly Staph Aureus (MSSA and MRSA) with Coagulase-negative Staph and gram negative bacilli as the second and third most common, respectively
- Enlarging abscess may lead to spinal cord compromise via direct compression or interruption of blood supply
History and Physical
Risk Factors – The presence of certain comorbidities places patients at increased risk for developing disease. However, 20% of patients with SEA will have no predisposing factors. Risk factors include:
- Immunocompromised: DM, HIV, Malignancy, chronic steroids or immunosuppressant medication use
- Recent Soft Tissue Infection with Bacteremia (OR = 13.5) (Davis 2020)
- Spinal Abnormality: trauma, surgery, arthritis
- Substance Abuse: Alcoholism, IVDU
- Presence of an indwelling catheter
Spinal epidural abscess is known for its nonspecific presentation, and can be easily missed. Adding it to the differential is often the critical step in making the diagnosis.
Classic triad of fever, back pain and neurologic symptoms is only present in 15% of patients. (Darouiche 2006)
Back pain is the most common symptom (75% patients).
- Described as localized, severe and midline with tenderness to percussion.
- Fever is an inconsistent finding (50% of patients). Normothermia should not deter further workup.
- Neurologic symptoms (33% of patients) may indicate spinal cord compromise. These patients require rapid work-up and management. Once paralysis develops, it is often irreversible.
- Back pain is the most common symptom (75% patients).
- Classic triad of fever, back pain and neurologic symptoms is only present in 15% of patients. (Darouiche 2006)
4 Stages of Progression (Heusner 1948) – stepwise symptomatology of spinal epidural abscesses
- Pain: back pain at the spinal level affe3cted (however, lesions may be distant to location of pain)
- Radiculopathy: nerve root pain radiating from involved spinal region
- Weakness: motor weakness, sensory deficit, bladder and bowel dysfunction (retention or incontinence)
Skip lesions – lesions present in noncontiguous vertebrae.
Increased risk if patient has 2 or 3 of the following symptoms (Ju 2015):
- Delay in presentation (symptoms for ≥7 days)
- Concomitant area of infection outside the spine and paraspinal region
- ESR >95 mm/h at presentation.
- If a patient displays symptoms not localized to a certain spinal level, consider imaging the entire spine.
- Increased risk if patient has 2 or 3 of the following symptoms (Ju 2015):
Labs – routine labs are unhelpful in diagnosis but are drawn to assist inpatient management
- CBC: Leukocytosis is present in 66% of cases (Davis 2004), however a normal WBC count is insufficient to rule out SEA.
ESR/CRP: sensitive, however very nonspecific.
- ESR normal values vary by age, and are frequently elevated in patients with neoplastic disease, regardless of the presence of infection.
- CRP normalizes quicker than ESR, and may be used in post-op patients or trended as an indicator of treatment success.
- Recently, a treatment guideline suggested incorporating ESR/CRP elevation in the decision to pursue imaging (Davis 2011). It is important to note that this treatment guideline was based on a small set (n =86) of patients. Currently, neither the presence nor the degree of elevation should be used to rule-in or rule-out SEA
- Provides assistance in tailoring antibiotic therapy
- Isolates have excellent correlation with the organism later found during surgical drainage
Gadolinium enhanced MRI: gold standard for diagnosis, over 90% sensitive (Darouiche 2006). MRI is able to detect an abscess in early disease, show the extent of inflammatory changes and identify thecal sac compression.
- (Image 2)
CT with IV contrast – indicated only when MRI is contraindicated
- Cannot readily distinguish early findings of infection from typical soft tissue, disk and osseous changes
- Gadolinium enhanced MRI: gold standard for diagnosis, over 90% sensitive (Darouiche 2006). MRI is able to detect an abscess in early disease, show the extent of inflammatory changes and identify thecal sac compression.
Empiric Antibiotics: directed against Staphylococcus and Gram Negative Bacilli.
- Vancomycin (30-60 mg/kg divided into two daily doses) PLUS
- 3rd Generation Cephalosporin: Cefotaxime (2 g IV every 6 hrs), Ceftriaxone (2 g IV every 12 hours) or Ceftazidime (2 g IV every 8 hours)
Operative drainage: Not all epidural abscesses are surgically drained. Decision is determined by:
- Those with developing neurologic deficits are often drained given risk of rapid development to paralysis.
- Patients whom have already progressed to paralysis with low likelihood of improvement are often treated with antibiotics alone.
Presence of a drainable abscess versus a phlegmon on imaging
- A phlegmon is granulomatous-thickened tissue without a significant purlent collection. It is noted as a homogenously enhancing lesion on MRI.
- A liquid abscess is displayed as a central hypointense region with hyperintense peripheral enhancement.
- Location – given small amount of epidural space, and thus increased risk of developing neurologic sequelae, cervical or thoracic epidural abscesses are more likely to be surgically drained
- Neurologic deficits
Take Home Points
- Spinal Epidural Abscess may present insidiously and patients often lack the classic triad of fever, back pain and neurologic symptoms
- Empiric Antibiotics should cover Staphylococcus (including MRSA) and Gram negative Bacilli
- All patients with clinical suspicion require rapid evaluation with MRI as the diagnostic study of choice
- Although not all patients will go to the operating room, surgical consult (Neurosurgery or Orthopedics) should be obtained immediately
Guest Post By: Latrice Triplett, MD
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- Ju K, et al. Predicting patients with concurrent noncontiguous spinal epidural abscess lesions. Spine J. 2015 Jan 1; 15(10):95-101. PMID: 24953159
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- Winters ME, Kluetz P et al. Back Pain Emergencies. Med Clin North Am, 2006 May;90(3):505-23. PMID: 16473102
Post Peer Reviewed By: Salim R. Rezaie, MD (Twitter: @srrezaie)
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