Adult chronic non-bacterial osteitis (CNO): An illustrated CT-based radiological guideline

Chronic non-bacterial osteitis (CNO) is a rare chronic auto-inflammatory bone disease. In adults, it primarily affects the axial skeleton, especially the anterior chest wall, followed by the spine and the mandible. Whole Body-MRI (WB-MRI) or computed tomography (CT) combined with nuclear imaging are the preferred imaging techniques for the diagnosis and monitoring of adult CNO. However, WB-MRI has several important limitations when addressing adult CNO, due to the difficult evaluation of bone marrow edema in areas of marked sclerosis.Extensive sclerosis is one of the most important radiological manifestations of the disease, together with hyperostosis, calcification of capsules and ligaments, ankylosis, erosions, and secondary degenerative changes, all easily assessable with CT, which also represents a technique available in the majority of hospitals and countries.CNO disease course is generally chronic, relapsing and remitting over time. For the evaluation of the disease activity, CT alone is insufficient, but it can be combined with sodium fluoride-18 positron emission tomography/computed tomography ([18F]NaF-PET/CT), which gives multiple advantages and strongly correlates with clinical disease activity, qualifying the imaging tool as a disease-monitoring instrument.This manuscript provides a comprehensive overview of characteristic CT features of adult CNO in different "target" locations of the axial skeleton, thereby helping to differentiate them from pitfalls, providing guidance in the (early) detection of the disease.