Native Vertebral Osteomyelitis: New Treatment Guidelines for Rare Spinal Infection
When patients have recalcitrant low back or neck pain, it can be difficult for clinicians to make an appropriate clinical decision, especially if additional symptoms begin to point to a more serious ailment, like Native Vertebral Osteomyelitis (NVO). NVO is the most common form of hematogenous osteomyelitis in patients over 50 years of age.1
As pain clinicians who often assess and evaluate back pain, it is important to be aware of this rare, often overlooked but critical, diagnosis.
NVO is difficult to catch and tricky to treat. Radiographs of the spine do not detect the condition in its early stages. If the diagnosis is delayed, it can lead to permanent spinal cord injury or septicemia.
Fortunately, the Infectious Diseases Society of America (IDSA) recently published a clinical practice guideline for diagnosing and treating NVO.2 A comprehensive, detailed, consensus-based guideline, it was authored by the IDSA’s 11-member panel of experts in infectious diseases, spine orthopedic surgery, and neuroradiology. Click here for the full guidelines.
3 Signs for Diagnosing NVO
Diagnosing NVO can be difficult, given that idiopathic back and neck pain are such common symptoms. Because of this, NVO is often diagnosed much later, at around 2 to 4 months after incidence,3 or it is misdiagnosed altogether—sometimes as often as 34% of the time.4
According to the IDSA guidelines, NVO diagnosis should be expected in patients that exhibit these 3 signs:
- New or worsening back or neck pain with fever
- Elevated inflammatory markers: erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
- Blood stream infection with Staphylococcus aureus or infective endocarditis
Clinicians may suspect NVO in patients that have a fever and new neurologic symptoms, which may or may not be accompanied by back pain, or in patients that have had a recent infection of S. aureus within the previous year5-7 and suffer from new localized back or neck pain.
A proper diagnostic evaluation of a patient suspected of NVO should include giving “a pertinent medical and motor/sensory neurological examination,” obtaining bacterial blood cultures and baseline ESR and CRP, and performing a spine magnetic resonance imaging test (MRI), the guidelines said.
A thorough medical and neurological examinations of patients should be conducted to try to detect the entry point of infection. Patient histories can offer pertinent information for the diagnosis of NVO, such as antimicrobials use, surgical procedures, intravenous drug use, and infections of the urinary tract, bloodstream, skin, or soft tissue.
Image-Guided Aspiration Biopsy
To confirm infection, an image-guided aspiration biopsy should be performed under either computed tomographic (CT) or fluoroscopic guidance. Antimicrobial therapy must be avoided until doctors can confirm NVO, particularly when blood cultures and serologic tests have yet to confirm the diagnosis. However, the IDSA’s guidelines do not give a blanket endorsement of image-guided aspiration biopsy in every context.
The guidelines actually advise against image-guided biopsies in patients with sub-acute NVO and strongly positive Brucella serology and in “patients with S. aureus, S. lugdunensis, or Brucella species bloodstream infection suspected of having NVO based on clinical, laboratory, and imaging studies,” as these circumstances obviate the need for the biopsy.
However, there could be other species in the blood, like Candida, Enterobacter, Pseudomonas, or Streptococcus, in which case it’s the physician’s decision to use the biopsy if he or she feels it is necessary.
Using Discretion with Clinical Therapy
Most patients with bacterial NVO will require 6 weeks of parenteral or highly bioavailable oral antimicrobial therapy.8 However, most patients with NVO due to Brucella infection will require 3 months of antimicrobial therapy.
Some IDSA panelists do advocate a longer treatment regimen for patients at a high risk of failure, although doctors must be aware of the lack of data to support any efficacy of this. With longer treatment also comes higher risk of adverse reactions, particularly emerging pathogens like Clostridium difficile colitis.9-11
Despite inconclusive evidence,12 the IDSA panel believes that antimicrobial therapy should be withheld until a microbiologic diagnosis can be formally established, as this should improve the accuracy of culture results in patients that exhibit stable and normal neurologic examination and hemodynamics.
However, for patients that exhibit hemodynamic instability, sepsis, septic shock, or progressive or severe neurologic symptoms, empiric antimicrobial therapy could be started in conjunction with establishing microbiologic diagnoses. In certain contexts, surgical intervention also may be necessary, particularly “in patients with progressive neurologic deficits, progressive deformity, and spinal instability with or without pain despite adequate antimicrobial therapy.” Unfortunately, there have been no randomized clinical trials to evaluate a specific surgical approach, the guidelines noted.
How to Establish Treatment Failure
Defining treatment failure with NVO patients is difficult, given there is no established definition of failure. Patients can have symptoms suggesting a persistent or reoccurring infection, like recalcitrant pain, residual neurologic deficit, systemic inflammation, etc. However, the IDSA panel believes that the best measure for failure is a microbiologically confirmed persistent infection despite a targeted antimicrobial therapy.13,14
The IDSA panel also advocates monitoring inflammatory markers (ESR and CRP) 4 weeks after therapy, with MRI follow-up for patients that have a favorable response to antimicrobial therapy, as well for patients with poor response, as they could exhibit evolutionary changes of the epidural and paraspinal soft tissues.
The IDSA guidelines also provide detailed guidance of handling NVO patients who are suspected of treatment failure, including how to interpret systemic inflammatory markers, tissue samples, and follow-up MRIs.
The expert panel that composed these guidelines all complied with the IDSA’s policy concerning conflicts of interest, disclosing any relevant financial interests that could be construed as an actual, potential or apparent conflict of interest. No limiting conflicts of interest were identified.