MRI of shoulder girdle in polymyalgia rheumatica: inflammatory findings and their diagnostic value

BackgroundNon-synovial inflammation as detected by MRI is characteristic in polymyalgia rheumatica (PMR) with potentially high diagnostic value.ObjectiveThe objective is to describe inflammatory MRI findings in the shoulder girdle of patients with PMR and discriminate from other causes of shoulder girdle pain.MethodsRetrospective study of 496 contrast-enhanced MRI scans of the shoulder girdle from 122 PMR patients and 374 non-PMR cases. Two radiologists blinded to clinical and demographic information evaluated inflammation at six non-synovial plus three synovial sites for the presence or absence of inflammation. The prevalence of synovial and non-synovial inflammation, both alone and together with clinical information, was tested for its ability to differentiate PMR from non-PMR.ResultsA high prevalence of non-synovial inflammation was identified as striking imaging finding in PMR, in average 3.4±1.7, mean (M)±SD, out of the six predefined sites were inflamed compared with 1.1±1.4 (M±SD) in non-PMR group, p