Common causes of intracranial epidural abscess include paranasal sinusitis, osteomyelitis of the skull, and extension of infection from concurrent otitis or mastoiditis. Common causes of spinal epidural abscess include spinal instrumentation, vascular access, and IV drug use. Irrespective of cause, epidural abscess is a life-threatening, but treatable, condition.

Staphylococcus aureus is responsible for almost two thirds of the reported cases.^[1][2] Due to the generalized use of antibiotics through the years, the number of reported cases of spinal epidural abscess due to MRSA has increased exponentially, reaching up to 40% of the cases in some institutions, particularly in patients with spinal or vascular implanted devices.^[1] Other less common, but still important organisms are:^[1][3][4]

• Escherichia coli
• Pseudomonas aeruginosa
• Anaerobic bacteria
• Mycobacteria
• Fungi
• Parasites

Although some infectious organisms might be responsible for either type of epidural abscess, others are more common of one of those.^{[1][5][6][7][8][9]}

• If infection following sinusitis case:

• Microaerophilic organisms
• Anaerobic streptococci
• Propionibacterium
• Other anaerobic bacteria and fungi

• If infection following neurosurgery:

• Staphylococcus aureus
• Gram-negative bacteria

• Osteomyelitis of the skull

• Staphylococcus aureus
• MRSA
• Mycobacterium tuberculosis