Spinal epidural abscess (SEA) is missed half of the time on initial presentation. The incidence is 1 case per 10,000 hospital admissions and has been increasing. Common risk factors include diabetes, end-stage renal disease, HIV infection, malignancy, morbid obesity, long-term corticosteroid use, intravenous drug abuse (IVDA), alcoholism, infection, indwelling catheters and invasive spinal procedures. Staphylococcus aureus is implicated in 2/3rds of cases and Streptococcus species in approximately 7%. Gram negative bacteria is common in IVDA. The infection is due to hematogenous spread in 25%–50% and direct extension from an infected contiguous structure in 15%–30%. Iatrogenic inoculation is also a common cause. Epidural catheterization has an estimated incidence of epidural abscess of 1 in 2000 and a catheter present for more than 2 days has a 4.3% infection rate.
Back pain is the most common presenting complaint and is present in approximately 75% of patients, it is often described as relentless and severe. Other findings include: Fever (60–70%), spinal tenderness (33%), radicular complaints (12–47%), and weakness (26-60%). A motor deficit is a poor prognostic indicator and usually does not improve with treatment. The classic triad of back pain, fever, and neurologic deficit is seen in less then 15% of cases.
The white blood cell count is elevated above 12,000 cells/mm³ in only 60% of cases. ESR is almost always elevated. Lumbar puncture should not be performed in the ED if SEA is suspected. The imaging test of choice is MRI with gadolinium contrast. CT myelography should be used if MRI is contraindicated. A search for causes of hematoenous spread should be undertaken (ie blood cultures, urine cultures, possible sputum, and ECHO if endocarditis is suspected – think IVDA).
It is important to consult spine surgery for emergent surgical management. If the patient is stable and consultants (spine surgery/infectious disease) are available a discussion about timing of antibiotics is recommended. It is common practice to delay antibiotics until intraoperative cultures are obtained. Empiric broad spectrum antibiotics for SEA include: vancomycin, metronidazole, and a 3rd/4th generation cephalosporin. Non-operative management and medical treatment is described for patients with minimal disease, poor surgical candidates and those with complete paralysis.
CLINICAL PEARL: IVDA and back pain is an epidural abscess until proven otherwise.
READ THIS ARTICLE IT MAY CHANGE YOUR PRACTICE: Davis et al. developed an ED decision algorithm incorporating risk factor assessment followed by ESR/CRP that was found to be highly sensitive in identifying ED patients with SEA. The algorithm lead to earlier diagnoses, less morbidity and less imaging.