A spinal epidural abscess is a potentially life-threatening bacterial infection of the epidural space, due to its insidious onset and nonspecific symptoms of fever, back pain and malaise. The diagnosis is often delayed, and radiculopathy accompanied by severe disability or even paralysis are seen in severe stages of the disease. Laboratory, imaging, and microbiological studies are mandatory during workup.
The development of a spinal epidural abscess (SEA) is commonly a result of a bacterial infection occurring in other sites, most notably the heart (endocarditis), skin (abscesses and furuncles), throat (pharyngitis, retropharyngeal abscess), or dental infections, and the pathogenesis of bacterial dissemination in the epidural space remains incompletely understood [1] [2] [3]. Contiguous infections of the adjacent tissues, such as osteomyelitis, spondylitis, and/or discitis, on the other hand, are important sources of infection as well, whereas medical procedures involving the epidural space (administration of anesthesia) has been reported prior to its appearance in a minority of patients [3]. Several risk factors have been identified - diabetes mellitus, underlying immunosuppression (for eg. acquired immunodeficiency syndrome, or AIDS), intravenous drug abuse, alcoholism, but also trauma, which precede signs and symptoms in up to 35% of cases [1] [2] [3] [4]. SEA most frequently develops in the thoracic and lumbar spine, and the two principal complaints are nonspecific back pain and fever [1] [3]. Radiculopathy, muscle weakness, sphincter incontinence and various sensory and motor deficits are encountered in many individuals, as the diagnosis is often delayed [1] [3]. In up to a third of patients, paralysis may ensue, whereas a fatal onset of sepsis has been documented, strengthening the need for early recognition [1] [4].
Workup of patients in whom SEAs are the cause of symptoms should start with a thorough patient history that will evaluate the course of illness and assess whether risk factors for a SEA are present. Exclusion of previous trauma, recent dental treatment, drug or alcohol abuse, as well as confirmation of diabetes mellitus or other immunosuppressive diseases is imperative during patient history. The role of the physical examination must be emphasized, as percussion of the back may reveal local tenderness and pain, which can be an important clue in making a presumptive diagnosis, especially if accompanying signs of fever, malaise or neurological deficits are present [3]. A complete blood count (CBC) often reveal anemia, leukocytosis, and a high erythrocyte sedimentation rate (ESR) [1]. Blood cultures are positive in about 60% of patients, and staphylococcus aureus is identified as the principal causative agent, followed by actinomyces spp., various anaerobic bacteria and mycobacterium tuberculosis (known as Pott disease) [1] [3]. Imaging studies, however, are the cornerstone of SEA diagnosis [2]. Magnetic resonance imaging (MRI) of the thoracolumbar spine will reveal an abscess in the posterior epidural space in more than two-thirds of cases and is depicted as a homogenous enhancement [3]. Gadolinium-enhanced MRI is frequently implemented in order to obtain an even better view of the epidural space [3] [4]. When the lesion is identified, biopsy, either open or needle aspiration (guided by computed tomography), is usually performed to solidify the diagnosis, as it provides a viable sample for cultivation and confirmation of the causative agent [3].