Spinal epidural abscess diagnosis

● fever, sweats or rigors are common, but normal WBC and temperature can occur

● classical presentation of a skin boil (furuncle) occurs in only ≈ 15% somewhere on the body

Changes on plain radiographs appear at least 3 to 4 weeks after the onset of disease. Bone scan is a sensitive but not a specific test. Computed tomography provides structural details in the bone and intervertebral disc but magnetic resonance imaging is a superior imaging test for diagnosing infections earlier and more accurately. In many patients, percutaneous or open biopsy is required to make the definitive diagnosis of discitis or osteomyelitis and the organism responsible for the infection. Early and accurate diagnosis of spinal infections will lead to less invasive treatment for the patient ¹⁾.

Inflammatory parameters in the blood are generally elevated, but not specific.

Gadolinium-enhanced magnetic resonance imaging is the most sensitive, specific and accurate imaging method.

Magnetic resonance imaging has permitted earlier diagnosis, although significant delays in diagnosis are common due to the nonspecific symptoms that frequently attend the disorder.

Imaging study of choice. Diferentiates other conditions (especially transverse myelitis or spinal cord infarction) better than myelo/CT, and doesn’t require LP.

Typical findings: T1WI→hypo- or iso-intense epidural mass, vertebral osteomyelitis shows up as reduced signal in bone. T2WI →high intensity epidural mass that often enhances with gadolinium (3 patterns of enhancement: 1) dense homogeneous, 2) inhomogeneous with scattered areas of sparse or no uptake, and 3) thin peripheral enhancement ²⁾ ) but may show minimal enhancement in the acute stage when comprised primarily of pus with little granulation tissue. Vertebral osteomyelitis shows up as increased signal in bone, associated discitis produces increased signal in disc and loss of intranuclear cleft. Unenhanced MRI may miss some SEA, ³⁾ gadopentetate dimeglumine enhancement may slightly increase sensitivity ⁴⁾.

They could have high morbidity and mortality if left untreated.

If patients present with acute neurological deficits and evidence of a multilevel ventral spine abscess on neuroimaging, blood cultures should be taken and the abscess emergently evacuated in patients able to tolerate surgical interventions.

CBC: leukocytosis common in acute group (average WBC= 16,700/mm3), but usually normal in chronic (ave. WBC= 9,800/mm3) ⁵⁾

ESR elevated in most, ⁶⁾ usually >30, ⁷⁾ CRP.

LP: performed cautiously in suspected cases at a level distant to the clinically suspected site (C1– 2 puncture may be needed to do myelogram) with constant aspiration while approaching thecal sac to detect pus (danger of transmitting the infection to subarachnoid space); if pus is encountered, stop advancing, send the fluid for culture, and abort the procedure. CSF protein & WBC usually elevated; glucose normal (indicative of parameningeal infection). 5 of 19 cases grew organisms identical to an abscess.

Blood cultures: may be helpful in identifying organism in some cases.

Anergy battery: (e.g. mumps and Candida) to assess immune system.

Usually normal unless there is osteomyelitis of adjacent vertebral bodies (more common in infections anterior to dura). Look for lytic lesions, demineralization, and scalloping of endplates (may take 4–6 weeks after onset of infect ion).

Usually shows findings of extradural compression (e.g. “paintbrush appearance” when complete block is present). In the event of complete block, C1–2 puncture may be needed to delineate upper extent (unless post-myelographic CTshows dye above the lesion). See cautions above regarding LP.

Intraspinal gas has been described on plain CT ⁸⁾. Post-myelographic CT is more sensitive.