Diagnostic challenges in pyogenic spinal infection: an expanded role for FDG-PET/CT

Abstract

In a preliminary investigation of FDG-PET/CT for assessment of therapy response of pyogenic spine infection, it was concluded that activity confined to the margins of a destroyed or degenerated joint with bone-on-bone contact represents nonseptic inflammation, regardless of the intensity of uptake. Only activity in bone, soft tissue, or within the epidural space represents active infection. The purpose of this investigation was to assess the performance of these pattern-based interpretation criteria in a series of problem cases of proven or suspected spine infection. Eighty-two FDG-PET/CTs were done for initial diagnosis because other imaging failed to provide a definitive diagnosis and 147 FDG-PET/CTs were done to assess treatment responses. Pattern-based interpretations were compared with the clinical diagnosis based on bacterial cultures and outcomes after cessation or withholding of antibiotic therapy. Pattern-based interpretation criteria achieved a sensitivity and specificity of 98 and 100%, respectively, for initial diagnosis and a specificity of 100% for assessment of treatment response. The same data was analyzed using intensity of activity as the primary factor. Sensitivity and specificity using the intensity-based criteria were 93 and 68%, respectively, for initial diagnosis, and the specificity of a negative interpretation for therapy response was 55%. Differences from pattern-based criteria are highly significant. Pattern-based criteria perform well in problem cases with equivocal MR and for treatment response because they correctly eliminate activity from nonspecific inflammation associated with destroyed joints with bone-on-bone contact. Response occurs within a timeframe that is useful for managing antibiotic therapy.

Clinical and Radiological Analysis of Pyogenic Vertebral Osteomyelitis Immediately after Successful Antimicrobial Therapy: Considerations for Assessing Therapeutic Response

“…FDG-PET showed a significantly higher frequency of grade II than MRI with predominant grade III, which means that FDG-PET has the ability to show the recovery of PVO lesion earlier than MRI. Unfortunately, we did not identify an image of grade I in both FDG-PET and MRI, which is perhaps because our FDG-PET/MRIs were performed relatively earlier (on 42.28 ± 14.58 (21–89) days of parenteral antibiotics) than in previous studies [ 14 ]. We assume that it will take more time to obtain a higher frequency of the typical pattern of FDG-PET as grades I or II after antimicrobial therapy.…”

“…Distribution patterns were interpreted using the criteria presented by Yu et al [ 14 ], which were based on the distribution pattern of FDG uptake on FDG-PET, contrast enhancement on T1-weighted contrast MRI (T1C), and high signal intensity implying edema on T2-weighted fat saturation MRI (T2FS) in PVO lesion. If a PVO lesion had more than two levels, the most advanced lesion was evaluated.…”

Validity of Clinical Assessment Using Clinical Symptoms and C-Reactive Protein for Therapeutic Response in Pyogenic Vertebral Osteomyelitis: Analysis Based on 18F-FDG-PET

“…PVO shows non-specific symptoms and may not necessarily present with fever [ 3 , 4 ]. Usually, PVO would have already progressed with spondylodiscitis and abscess of epidural or paravertebral structures before diagnosis [ 5 ]. Approximately half of PVO cases are still treated with empirical antibiotics because of culture-negative for causative microorganism despite several culturing attempts [ 6 ].…”

Pattern-Based Interpretation Criteria for 18F-Fludeoxyglucose Positron Emission Tomography/Computed Tomography in the Assessment of Pyogenic Spine Infection

“…18 F-fludeoxyglucose positron emission tomography/ computed tomography ( 18 F-FDG PET/CT) is the procedure of choice for investigation of pyogenic spine infection (PSI) when other imaging fails to provide a definitive diagnosis, and for assessment of treatment response when patients are not responding as expected to antibiotic therapy [1].…”

“…We have recently reported on the performance of the pattern-based interpretation criteria in a series of problem cases [1]. Eighty-two scans were done for initial diagnosis because other imaging failed to provide a definitive consistent answer, often because of unexplained enhancement on magnetic resonance (MR), and 147 scans were done for assessment of treatment response.…”