Causes / typical injury mechanism: Spinal epidural abscesses (SEAs) are inflammatory masses or localized collections of purulent material that occur due to infections, most often bacterial, in the epidural space between the dura mater and vertebral column. These can occur via hematogenous spread of a pathogen, spread from a contiguous infection (eg, osteomyelitis), or direct inoculation (eg, spinal steroid injection). Staphylococcal aureus is the most common pathogen, implicated in two-thirds of cases.

Classic history and presentation: The classic triad of a SEA is acute onset of back or neck pain, fever, and neurologic deficits. Neurologic symptoms may include weakness, sensory changes, radiculopathy, and/or bladder and bowel dysfunction, depending on the location and size of the abscess. Having all aspects of the triad is relatively rare (approximately 10% of patients) but very specific. Symptoms may present acutely within hours or days (usually in cases secondary to hematogenous spread or direct inoculation of a pathogen) or can present chronically over weeks to months (usually occurs with spread of contiguous infection).

Prevalence: An estimated 2-8 cases per 10 000 hospital admissions.

• Age – Mean age is 50 years, with the majority of cases occurring between the ages of 30 and 70 years.
• Sex / gender – Incidence may be higher in men according to a few studies.

Risk factors:

• Intravenous (IV) drug use
• Alcohol use disorder
• Smoking
• Diabetes mellitus
• Renal insufficiency
• Malignancy
• Immunocompromise
• Concurrent infection
• Recent spinal trauma or injection

Pathophysiology: Pathogens may enter the epidural space via contiguous spread from vertebral osteomyelitis or a psoas abscess (about 30% of cases), hematogenous dissemination (about 25%-50% of cases), or direct inoculation (eg, during spinal or epidural anesthetic procedures or surgery). Local extension of infection from the spinal epidural space can occur or can disseminate to other sites via the bloodstream. S aureus causes approximately 50%-90% of cases. Less common pathogens include coagulase-negative Staphylococci, aerobic gram-negative rods, and Pseudomonas aeruginosa. Polymicrobial infection occurs in about 5%-10% of cases.

Grade / classification system: A 4-stage grading system based on clinical symptoms has been described to assess severity of SEAs:

• Stage 1 – Back pain, fever, tenderness.
• Stage 2 – Radicular pain, nuchal rigidity / stiffness, decreased deep tendon reflexes.
• Stage 3 – Muscle weakness, sensory abnormalities, bladder / bowel dysfunction.
• Stage 4 – Complete paralysis.