Spinal epidural abscess

Darouiche RO. Current Concept: Spinal epidural abscess NEJM 35;19 2012 Nov 9 2006

Article concentrates on bacterial causes. Most patients have predisposing risk factors: DM, ETOH, HIV, drug abuse intravenous, DJD, surgery with instrumentation, placement of stimulators, or potential local source of infection (skin, soft tissue, indwelling catheter, UTI, sepsis). Entry is contiguous spread (1/3) or hematogenous (1/3). Two thirds are staph aureus, 40 % of those Methicillin resistant (MRSA). These are especially common a few weeks after implantation of devices.

Other causes: St epidermidis, e coli, Ps aer., rarely actinomyces, nocardia, mycobacteria, fungi, (candida, aspergillus) parasites (echonococcus and dracunculus). A letter writer added brucellosis as a cause in Spain, Italy and the Near East.

Spinal cord injury can occur either by mechanical compression of vascular occlusion due to septic thrombophlebitis.

Clinical staging system: stage 1, back pain at level; stage 2, nerve root pain of affected level; stage 3, motor weakness, sensory loss, or B/B dysfunction at affected level; stage 4, paralysis. 3/4 have back pain, fever present in half, neurologic dysfunction in one third. Stage 2 is "enigmatic" in thoracic cases. Duration/rate of progression is highly variable but can be extremely rapid.

Abscesses favor large epidural spaces with infection prone fat, and therefore are more common in posterior than anterior and thoracolumbar than cervical. Lumbar even more common due to epidural injections. Generally they extend over 3-4 levels or more.

Diagnosis is by drainage. Sed rate is always high. Differential diagnostic conditions ( osteomyelitism discitis, sepsis, endocarditis) also have S aureus bacteremia. CSF cultures are negative in 75%. Blood cultures are usually positive. Risks of LP includes causing meningitis by introducing infection through the meninges or causing deterioration if tapped below a block.

MRI with contrast is preferred procedure although myelography has > 90 % sensitivity. Spine CT can be done in conjunction with and may suggest changes of osteopmyelitis.

Frequent misdiagnoses include: osteomyelitism discitis, meningitis, UTI, sepsis, endocarditis, disc prolapse, DJD, spinal tumor, transverse myelitis, spinal hematoma. These are made because patient is neurologically intact.

Treatment: medical v. surgical. No trials done. Medical treatment indicated if patient has high risk of surgery, has panspinal infection, or paralysis for more than 24 hours, or if agent is identified and his condition is monitored closely. Surgery can be a limited laminectomy if patient has a panspinal infection. Empiric coverage should include coverage against MRSA, against gram negative bacilli (with a third or fourth generation cephalosporin such as ceftazidime). Letter writer added that medical management was safe as long as the patient didnot deteriorate.

Statistics: 4-22% get irreversible paralysis. 11-75 % are initially misdaignosed.

The most important predictor of outcome is patient's status just before surgery. Patients who undergo surgery in stage 1 or 2 are expected to remnain neurologically intact.