Challenges in the imaging and diagnosis of chronic non-bacterial osteomyelitis (CNO)

Chronic non-bacterial osteomyelitis (CNO) is a benign skeletal disorder of childhood and adolescence characterised by sterile bone inflammation that results in chronic insidious bone pain. Although it is increasingly recognised, many challenges remain in its diagnosis with patients waiting 15-24 months for diagnosis from the time of symptom onset. Prompt identification and treatment are key to reducing morbidity from CNO, which affects school attendance and can result in chronic limb or spine deformities. Identifying its imaging features, particularly its characteristic lesion distribution on whole-body MRI, remains key to diagnosis. Image-guided biopsy is also required in many cases, particularly those with clinical uncertainty around the diagnosis. We present a review of the challenges encountered in the diagnosis of CNO from a critical appraisal of the literature and our experience as a national paediatric sarcoma, rheumatology and orthopaedic centre. This review hopes to inform radiology colleagues involved in the evaluation of potential CNO patients by discussing its imaging appearances, typical MRI phenotypes, potential mimics and the role of image-guided biopsy.