Last updated on:September 9th, 2021
A spinal epidural abscess (SEA) is a suppurative infection of the central nervous system that is enclosed within the bony confines of the spinal column. While rare, the incidence of SEA has increased over time due to an aging population, increasing use of spinal instrumentation and vascular access, and the spread of injection-drug use.
The epidural space is the vertical area between the dura mater and the vertebral wall; this contains fat, arteries, and a venous plexus. SEAs are most commonly located posteriorly, and in the thoracolumbar region (where the epidural space is larger). Abscesses that begin at one level often extend longitudinally; and may also extend locally into the paravertebral tissue or spinal musculature, giving rise to an iliopsoas abscess.
Bacteria reach the epidural space via contiguous spread (e.g., pyogenic infectious discitis or vertebral osteomyelitis), hematogenous dissemination, or direct inoculation into the spinal canal (e.g., via surgery or spinal or epidural procedures such as contaminated insertion of catheters). Spinal cord injury subsequently results due to direct compression, exposure to bacterial toxins and mediators of inflammation, and infectious vasculitis and spinal artery thrombosis.
Staphylococcus aureus causes about two-thirds of cases. This is because most predisposing factors allow for invasion by skin flora. Some of these cases are due to methicillin-resistant S. aureus (MRSA); the incidence varies by setting. In order of frequency, the other pathogens encountered include Gram-negative bacilli, Streptococci, coagulase-negative Staphylococci; and rarely, anaerobes, fungi, parasites, and in resource-limited settings, Mycobacterium tuberculosis. Note that post-neurosurgical patients are more likely to have resistant Gram-negative organisms.