Chronic nonbacterial osteomyelitis — clinical and magnetic resonance imaging features

Abstract

Background Chronic nonbacterial osteomyelitis (CNO) is a rare autoinflammatory bone disorder. Little information exists on the use of imaging techniques in CNO. Materials and methods We retrospectively reviewed clinical and MRI findings in children diagnosed with CNO between 2012 and 2018. Criteria for CNO included unifocal or multifocal inflammatory bone lesions, symptom duration >6 weeks and exclusion of infections and malignancy. All children had an MRI (1.5 tesla) performed at the time of diagnosis; 68 of these examinations were whole-body MRIs including coronal short tau inversion recovery sequences, with additional sequences in equivocal cases. Results We included 75 children (26 boys, or 34.7%), with mean age 10.5 years (range 0–17 years) at diagnosis. Median time from disease onset to diagnosis was 4 months (range 1.5–72.0 months). Fifty-nine of the 75 (78.7%) children presented with pain, with or without swelling or fever, and 17 (22.7%) presented with back pain alone. Inflammatory markers were raised in 46/75 (61.3%) children. Fifty-four of 75 (72%) had a bone biopsy. Whole-body MRI revealed a median number of 6 involved sites (range 1–27). Five children (6.7%) had unifocal disease. The most commonly affected bones were femur in 46 (61.3%) children, tibia in 48 (64.0%), pelvis in 29 (38.7%) and spine in 20 (26.7%). Except for involvement of the fibula and spine, no statistically significant differences were seen according to gender. Conclusion Nearly one-fourth of the children presented with isolated back pain, particularly girls. The most common sites of disease were the femur, tibia and pelvic bones. Increased inflammatory markers seem to predict the number of MRI sites involved.

Assessment of disease activity using a whole-body MRI derived radiological activity index in chronic nonbacterial osteomyelitis

“…The low prevalence of bone hyperintensity within these sites in our cohort and the relevant change after treatment argue against over-reading. Further studies are warranted to compare the minimal changes detected in children with CNO with those from healthy children in order to identify the key difference that would be specific to active disease in CNO and to determine the minimum clinically significant difference of MRI findings by using external validation measurements [ 42 ].…”

The Pediatric Spine

“…66 MRI allows an early identification of findings related to acute sacroiliac joint inflammation. 68 The main MRI findings of active sacroiliitis include hyperintensity of the sacroiliac joint with adjacent subchondral bone marrow edema or osteitis depicted by water-sensitive sequences, enthesitis, capsulitis, and synovitis (seen on contrast-enhanced images). 64 Despite many controversial published studies about the utility of contrast agents to detect active sacroiliitis, gadolinium contrast-enhanced images still have a main role in the identification of synovitis.…”

“…Chronic nonbacterial osteomyelitis (CNO) is an inflammatory sterile musculoskeletal condition occurring in children and adolescents, with a broad clinical spectrum characterized by recurring episodes of multifocal chronic osteomyelitis and/or asymptomatic inflammation of single bones. 68 The exact incidence is still unknown in relation to the great variability of presentation and the presence of nonspecific findings. It manifests usually with localized or multifocal bone pain and swelling, mostly of the long bones, but pathologic fractures of affected vertebrae can occur and lead to kyphosis and vertebra plana.…”

“…MRI, in particular whole-body MRI, is largely used in the diagnosis and follow-up of CNO because it allows the detection of both symptomatic and asymptomatic sites of the disease. 68 Typical bone marrow edema and collapse of the involved vertebra are well recognized using water-sensitive sequences (i.e., short tau inversion recovery) and T1-weighted images (►Fig. 14).…”

“…9 Sacroiliac joints involvement is often multifocal, and despite sacroiliitis in JIA, typical lesions may not be localized just at the subchondral marrow, but they can extend to the inner parts of the sacrum. 68…”