Long-term clinical and radiological magnetic resonance imaging outcome of abscess-associated spontaneous pyogenic vertebral osteomyelitis under conservative management.

OBJECTIVES: Management of abscess-associated spontaneous pyogenic vertebral osteomyelitis (PVO) is controversial. The role of magnetic resonance imaging (MRI) in follow-up and its relation with clinical outcome is often unclear. This study evaluates the clinical and MRI outcome of abscess-associated PVO under conservative treatment. METHODS: Prospective study and retrospective review of patients with spontaneous PVO in whom the initial MRI showed soft-tissue involvement (STI). Treatment according to a medical protocol, clinical and MRI follow-up at diagnosis, and at 2 later time points: early response (ER, at the end of antibiotic therapy) and late response (LR, >or=6 months after therapy). MRI classified STI as soft-tissue edema (STE) or abscess. RESULTS: Of the 27 patients (20 men, 74%, age 65+/-14), all had pain, 17 (63%) had fever, and 6 (22%) had mild neurological impairment. The main etiology was Staphylococcus sp (11, 41%). Twenty-one (81%) had bacteremia and 18 (67%) had epidural/paraspinal abscess. Patients received antibiotics for 9 weeks, administered orally for 6 weeks. ER: Three cases failed and general improvement was seen in the remainder. MRI showed persistent STI, which diminished in all cases except 1, whereas bone/disc findings remained. LR: All patients were cured; 8 reported mild sequelae (30%). MRI still revealed bone/disc abnormalities, but residual STE was infrequent. Median follow-up was 29 months. CONCLUSION: Most patients with abscess-associated spontaneous PVO are cured with a conservative approach. MRI shows STI reduction at ER evaluation. Repeat MRI is probably unnecessary if clinical and laboratory outcomes are satisfactory. The persistence of bone/disc MRI findings alone does not represent therapeutic failure.