Spinal Epidural Abscess
A spinal epidural abscess is an accumulation of pus in the epidural space that can mechanically compress the spinal cord. Diagnosis is by MRI or, if unavailable, myelography followed by CT. Treatment involves antibiotics and sometimes drainage of the abscess.
(See also Overview of Spinal Cord Disorders.)
Spinal epidural abscesses usually occur in the thoracic or lumbar regions. An underlying infection is often present; it may be remote (eg, endocarditis, furuncle, dental abscess) or contiguous (eg, vertebral osteomyelitis, pressure ulcer, retroperitoneal abscess). In about one third of cases, the cause cannot be determined. The most common causative organism is Staphylococcus aureus, followed by Escherichia coli and mixed anaerobes. Occasionally, the cause is a tuberculous abscess of the thoracic spine (Pott disease). Rarely, a similar abscess occurs in the subdural space.
Symptoms of spinal epidural abscess begin with local or radicular back pain and percussion tenderness, which become severe; pain may be worsened by recumbency. Fever is common. Spinal cord compression may develop; compression of lumbar spinal roots may cause cauda equina syndrome, with neurologic deficits resembling those of conus medullaris syndrome (eg, leg paresis, saddle anesthesia, bladder and bowel dysfunction—see Table: Spinal Cord Syndromes). Deficits progress over hours to days.
Because rapid treatment is necessary to prevent or minimize neurologic deficits, clinicians should consider spinal epidural abscess if patients have significant atraumatic back pain, particularly when there is focal percussion tenderness over the spine, or if they have a fever or have had a recent infection or dental procedure. Characteristic neurologic deficits are more specific but may occur later, so delaying imaging until these neurologic deficits are present can make a poor outcome more likely.
Diagnosis of spinal epidural abscess is by MRI; myelography followed by CT may be used if MRI is not available. Samples from blood and infected areas are cultured.
Lumbar puncture is contraindicated because it may trigger cord herniation if the abscess completely obstructs CSF flow. Plain x-rays are not routinely indicated but show osteomyelitis in about one third of patients. ESR is elevated, but this finding is nonspecific.
Antibiotics with or without parenteral needle aspiration may be sufficient; however, abscesses causing neurologic compromise (eg, paresis, bowel or bladder dysfunction) are surgically drained immediately. Pus is gram-stained and cultured. Pending culture results, antibiotics to cover staphylococcus and anaerobes are given as for brain abscess. If the abscess developed after a neurosurgical procedure, an aminoglycoside is added to cover gram-negative bacteria.