The Infectious Diseases Society of America (IDSA) has published a new guideline dealing with the diagnosis and treatment of native vertebral osteomyelitis (NVO) in adults. The guideline contains a total of 38 recommendations that were rated using the GRADE system, and while the strength of the recommendations was variable, many were based on low-level evidence — a result of the fact that there are so few comparative clinical trials in this field. In the GRADE system, low-level evidence is defined as “Evidence for at least one critical outcome from observational studies, RCTs with serious flaws, or indirect evidence” — not exactly a booming endorsement. For assessment of the strength and quality of evidence for the recommendations contained in this narrative summary, please examine the original document.
The diagnosis of NVO, which often results from unrecognized episodes of bacteremia, is often delayed with resultant severe adverse consequences. The first set of recommendations revolve around the critical need for early consideration of the diagnosis in patients with new or worsening neck or back pain, especially in the presence of fever (which, unfortunately, frequently may be absent). Examination of such patients should include a directed motor and sensory neurologic examination and laboratory studies to include blood cultures, erythrocyte sedimentation rate, and C-reative protein. If clinical or epidemiological evidence points to the need, blood cultures and serological tests for Brucella or fungi may be indicated. For those with a subacute presentation or appropriate epidemiological history, a purified protein derivative (PPD) or interferon gamma release assay (IGRA) should be performed.
Magnetic resonance imaging (MRI) is the recommended diagnostic imaging procedure, with combined spinal gallium/Tc99 bone scan or PET scan in those in whom MRI cannot be performed. Unless blood cultures or serological tests for an undisputed pathogen are positive, patients should undergo an imaging-guided aspiration biopsy for microbiological studies (including fungal and/or mycobacterial, when indicated) and, if sufficient material is recovered, for histopathological examination. In the absence of neurological compromise, sepsis, or hemodynamic instability, antibiotic therapy may be temporarily withheld prior to the procedure. In the presence of such findings, however, empiric antibiotic therapy should be initiated immediately (blood cultures should be obtained first) and, in the case of neurological compromise, immediate surgical intervention is indicated, regardless of the presence or absence of sepsis or hemodynamic instability.
If no etiology is determined from blood or aspiration specimens, a second aspiration biopsy should be performed — alternatively, a specimen may be obtained by percutaneous endoscopy discectomy and drainage or by an open surgical procedure. If cultures of specimens from a first or second procedure remain negative, nucleic acid amplification testing for bacterial, mycobacterial, and fungal etiologies should be performed on appropriately stored specimens.
Antibiotic treatment, either parenterally or orally, should be continued for a total duration of 6 weeks, with 3 months of therapy indicated for patients with brucellosis. Inflammatory makers, along with a clinical assessment, should be performed approximately 4 weeks after initiation of therapy. There is no indication for a routine follow-up MRI in the patient with a favorable and laboratory response to antibiotic therapy. In those with a poor clinical response, repeat MRI can be performed to evaluate epidural and paraspinal soft tissue changes. If there is clinical evidence of treatment failure and imaging indicates evidence of failure of improvement in epidural or paraspinal infection, specimens for further microbiological evaluation should be obtained.
Surgical debridement, with or without a stabilization procedure, should be performed in patients receiving appropriate antibiotic therapy who have persistent or recurrently positive blood cultures for whom no alternative source of the microbemia is present. Patients who suffer from worsening neurological deficits, vertebral deformity, and instability of the spine should also undergo surgical intervention. In the absence of one of these indications, patients who have clinical improvement and a decrease in the levels of inflammatory markers, but who have worsened bony changes on imaging at 4-6 weeks do not have an indication for surgical intervention.