A spinal epidural abscess is an accumulation of pus in the space between the spine and outer layer (dura mater) of tissue covering the spinal cord (epidural space). These abscesses can put pressure on (compress) the spinal cord.
- Epidural abscesses are often caused by bacteria from another infection in the body.
- They may cause back pain, which may become severe, and weakness or partial paralysis of the legs, loss of bladder and bowel control, fever, and other serious symptoms.
- Doctors use magnetic resonance imaging (MRI) to diagnose an epidural abscess in the spinal cord or, if MRI, is unavailable, myelography followed by computed tomography.
- Doctors treat abscesses with antibiotics, and if the abscess is causing serious problems, they drain it immediately.
(See also Overview of Spinal Cord Disorders.)
Epidural abscesses in the spinal cord are often caused by another infection, most often in the skin or tissues near the spinal cord. However, sometimes epidural abscesses result from an infection of the heart valves (endocarditis), pressure sores, an infection in the bones of the spine (osteomyelitis), or a dental abscess. Epidural abscesses may also develop after an invasive procedure such as spinal surgery or placement of an catheter in the epidural space.
The bacteria that usually cause these abscesses are Staphylococcus aureus (60%), Escherichia coli or other gram-negative bacteria (15%), or streptococci (10%). Occasionally, the abscess is caused by tuberculosis that affects the spine (Pott disease) or IV drug use. In about one third of people, the cause cannot be determined.
Symptoms of a spinal epidural abscess begin with back pain. The back over the abscess is tender to the touch. Pain may become severe and is worsened by lying down. Fever is common.
The abscess may put pressure on (compress) the spinal cord. If an epidural abscess occurs in the lower back, it may compress the cauda equina, causing the cauda equina syndrome. People with cauda equina syndrome may lose sensation in the buttocks, genital area, bladder, and rectum (called the saddle area). Their legs may become weak or partially paralyzed. They may retain urine or lose control of the bladder (urinary incontinence) or bowel (fecal incontinence). They may have problems walking. Symptoms may progress over hours to days.
- Magnetic resonance imaging (MRI)
Doctors may suspect a spinal epidural abscess if people have significant, unexplained back pain, particularly when the spine is tender to the touch or when they have a fever or have had a recent infection or dental procedure.
Spinal epidural abscess is diagnosed using MRI. If MRI is not available, myelography followed by computed tomography (CT) may be used. Samples of blood and, when possible, samples from the infected areas are taken and sent to a laboratory to be grown (cultured) so that the bacteria causing the abscess can be identified. Examination of the blood sample often detects evidence of infection, such as an elevated white blood cell count.
- If abscesses compress the spinal cord, immediate drainage
Rapid treatment of epidural abscesses is necessary to prevent or minimize problems.
Antibiotics may be sufficient. But if abscesses compress the spinal cord, causing weakness or paralysis in the legs, incontinence, or other serious problems, they are surgically drained immediately. A sample of pus from the abscess is sent to a laboratory to be analyzed and cultured to help identify the bacteria causing the abscess.
Antibiotics to treat the bacteria that are usually involved are given without waiting for test results. They are changed as needed when results of testing are available.