Spinal epidural abscess

I. What every physician needs to know.

Spinal epidural abscess, while uncommon, has potentially grave consequences. While initial symptoms may be mild or vague, the disease may progress quickly. Sequelae may include permanent neurological deficit, sepsis and death. A detailed physical examination followed by targeted and appropriate imaging is critical.

II. Diagnostic Confirmation: Are you sure your patient has Epidural Abscess?

While physical examination may help localize and/or raise the suspicion of epidural abscess, confirmation needs to be made by imaging.

A. History Part I: Pattern Recognition:

There is no absolute single pattern of presentation for spinal epidural abscess. Back pain is the most common feature and is frequently quite severe. Fever along with tenderness to palpation/percussion over affected vertebrae in conjunction with limb weakness or bowel/bladder dysfunction are key indicators as well.

B. History Part 2: Prevalence:

Spinal epidural abscess is quite unusual, but may represent 0.2 to 1.2 cases per 10,000 hospital admissions. Immunosuppressed states, intravenous drug abuse, prior spine surgery, epidural steroid injection and underlying hardware increase the risk for abscess formation.

C. History Part 3: Competing diagnoses that can mimic Epidural Abscess.

Other processes that affect the neuraxis should be considered in the differential. Compressive neuropathies may be the result of disc disease, malignancy, granulomatous disease or a myriad of other possibilities. Other causes of limb weakness and sensory abnormality include multiple sclerosis, transverse myelitis, and other intrinsic cord abnormalities such as syrinx.

D. Physical Examination Findings.

The classic clinical triad of back pain, fever and neurologic findings is seldom present. Unfortunately, findings may be quite non-specific.

One must take care to thoroughly examine the patient. This includes palpating the spine to evaluate for areas of tenderness. Motor function should be tested in both axial and appendicular muscles. When combined with sensory testing, a level of spinal involvement may be established. One should check sensation in multiple modalities (e.g., pin prick and vibration). One must realize that patients may be neurologically intact, especially early in the disease course.

E. What diagnostic tests should be performed?

Modern imaging modalities have greatly simplified the diagnosis of epidural abscess. However, a high index of suspicion is necessary as such testing is not routinely done in cases of back pain.

1. What laboratory studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

Unfortunately, many of the laboratory studies that are used in the diagnosis are non-specific. Blood cultures may show Staphylococcus aureus or other bacterial infection, but this does not identify a source and may not be available on initial evaluation. Measures of inflammation such as C-reactive protein and an erythrocyte sedimentation rate are typically elevated. Rarely is cerebrospinal fluid available or evaluated in these cases, but is abnormal 75% of the time, and all usually have an aseptic meningitis pattern and be gram stain and culture negative.

2. What imaging studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

Imaging is critical in the diagnosis of epidural abscess. It may be difficult to establish an exact level of involvement. Therefore, many recommend a screening sagittal magnetic resonance imaging (MRI) with gadolinium initially. This would then be followed by axial sections of the areas identified on the screening or physical examination. MRI should be considered the first line test. Myelography followed by computed tomography (CT) imaging would be an alternate but is invasive. Plain X-ray or CT is of less value. Radionuclide scanning is nonspecific, but may show areas of increased uptake.

F. Over-utilized or “wasted” diagnostic tests associated with this diagnosis.

N/A

III. Default Management.

Given the nature of the disease process, there is no good prospective, randomized data on the treatment of epidural abscess. There is not clear guidance as to the role for medical as opposed to surgical management. However, if the imaging supports the diagnosis, immediate spine surgical evaluation should be sought. If surgical evaluation is not available, antibiotics should be administered and the patient transferred emergently.

A. Immediate management.

Given the potential for rapid progression, both surgical evaluation and antibiotic administration should be immediate.

B. Physical Examination Tips to Guide Management.

Evidence of neurologic compromise necessitates rapid intervention and, at times, re-evaluation of an initial approach. Patients who develop neurological dysfunction, even while on antibiotics, may need repeat imaging and consideration for intervention.

C. Laboratory Tests to Monitor Response To, and Adjustments in, Management.

Evaluation of blood cultures may be of some value and are frequently used to assist in determing resolution as imaging may not be able to do so definitively. Inflammatory markers (white blood cell count, C-reactive protein and erythrocyte sedimentation rate) are useful in monitoring response to therapy.

D. Long-term management.

A prolonged course of antibiotics is frequently necessary (4-6 weeks), with close followup. Further evaluation is appropriate for the source of the initial infection.

E. Common Pitfalls and Side-Effects of Management.

One must closely monitor the patient’s pain and neurological examination in case of worsening. Prolonged courses of intravenous antibiotics are typically necessary.

IV. Management with Co-Morbidities.

N/A