Discitis Osteomyelitis Diagnosis and Management

Epidemiology and Pathophysiology

Native vertebral osteomyelitis occurs most commonly through hematogenous seeding of the adjacent disc space from a distant infectious focus, as the disc itself is avascular 1
The infection typically begins with a septic embolus to the vertebral endplate, then spreads to the adjacent disc 3

Recalcitrant back or neck pain unresponsive to conservative measures is the most common presenting symptom 1
Fever may or may not be present 1, 2
Elevated inflammatory markers are typically present 1, 2
Neurologic symptoms may occur if there is extension to the epidural space 4
Diagnosis is often delayed by several months and initially misdiagnosed as a degenerative process 1

Recent bloodstream infection, particularly Staphylococcus aureus, is a risk factor 1, 2
Infective endocarditis is a risk factor 2
Immunocompromised state is a risk factor 5
Advanced age is a risk factor 5
Diabetes, long-term steroid use, liver failure, and renal failure are risk factors 5

MRI is the imaging modality of choice, with sensitivity of 97%, specificity of 93%, and accuracy of 94% 4
Characteristic MRI findings include inability to distinguish margins between disc space and adjacent vertebral marrow on T1-weighted images, with increased signal intensity on T2-weighted images 4
Blood cultures should be obtained in all patients 4
Image-guided aspiration biopsy is recommended in patients with suspected discitis osteomyelitis 1, 6

Definitive therapy should be based on culture results and susceptibility testing 1
Empiric antibiotics should be withheld until microbiologic diagnosis is established, except in patients with hemodynamic instability, sepsis, or severe neurologic symptoms 3, 5, 6
Surgical intervention is indicated for progressive neurologic deficits, progressive deformity, or spinal instability with or without pain despite adequate antimicrobial therapy 5, 7

Monitor systemic inflammatory markers after approximately 4 weeks of antimicrobial therapy 8
ESR values >50 mm/hour and CRP values >2.75 mg/dL after 4 weeks of treatment may indicate higher risk of treatment failure 8
Routine follow-up MRI is not recommended in patients with favorable clinical and laboratory response 8

Mortality rates have improved from approximately 25% in the pre-antibiotic era to 0-11% in contemporary cohorts 8
Factors associated with worse outcomes may include multidisc disease, concomitant epidural abscess, lack of surgical therapy when indicated, infection with S. aureus, and significant comorbidities 2, 5, 6, 7