What is the pathophysiology of spinal epidural abscess?

Updated: Jul 12, 2018
  • Author: J Stephen Huff, MD, FACEP; Chief Editor: Niranjan N Singh, MBBS, MD, DM, FAHS, FAANEM  more...
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The spinal epidural space is not a uniform space. Posteriorly, the epidural space contains fat, small arteries, and the venous plexus. Infections in this space may spread over several vertebral levels. Anteriorly, the epidural space is a potential space with the dura tightly adherent to the vertebral bodies and ligaments. Abscesses occur more frequently in the larger posterior epidural space. Most spinal epidural abscesses occur in the thoracic area, which is anatomically the longest of the spinal regions.

Some series suggest that dorsal spinal epidural abscesses are much more likely to present with weakness and severe neurologic deficit than ventral spinal epidural abscesses. [4]

Hematogenous spread with seeding of the epidural space is the suspected source of infection in most children and is thought to occur in many adults as well. Reported sources of infection are numerous and include bacterial endocarditis, infected indwelling catheters, urinary tract infection, peritoneal and retroperitoneal infections, and others.

Direct extension of infection from vertebral osteomyelitis occurs in adults and rarely in children.

Epidural catheters and injections may lead to direct inoculation of the epidural space. The source of infection is not identified in many patients. There was a recent outbreak of fungal infections including epidural abscesses associated with injection of methylprednisolone that was contaminated with environmental molds. [5]

The more clinically significant effects of the epidural abscess may be from involvement of the vascular supply to the spinal cord and subsequent infarction rather than direct compression. Staphylococcus aureus is the most commonly reported pathogen [6] , though many other bacteria have been implicated, including Staphylococcus and Pseudomonas species, Escherichia coli, Brucella, and Mycobacterium tuberculosis. Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly reported particularly in patients with a history of MRSA abscesses, spinal surgery, or implanted devices. Immunosuppressed patients may have infections from unusual bacterial or fungal organisms. Fungal infections may also occur. Environmental mold Exserohilum rostratum was the unusual pathogen associated with the outbreak of contaminated methylprednisolone.

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