Three cases of typical polymyalgia rheumatica with effusion of the atlantoaxial joint found on MRI

Abstract

Polymyalgia rheumatica（PMR）is an inflammatory disorder of unknown origin which affects elderly individuals. The diagnosis of PMR is based on the association of clinical and therapeutic signs, and non-specific laboratory markers of inflammation. Therefore, a number of different diseases can mimic PMR. We found that some cases of typical PMR might be due to the synovitis of atlantoaxial joint by MR image analysis. We report three representative cases. Three elderly females came to our hospital for acute severe pain and stiffness of their neck, nape, and shoulders. Physical examination showed typical symptoms of PMR. The erythrocyte sedimentation rate and CRP were markedly increased. MRI showed effusion of the atlantoaxial joint. Oral corticosteroid therapy resulted in dramatic improvement in their condition. CRP became negative and follow-up MRI showed disappearance of the effusion. PMR is a kind of clinical diagnosis. Therefore, it can contain many pathogenesis, such as crowned dens syndrome and giant cell arthritis. This finding of joint synovitis may be useful for finding out the differential diagnosis and pathologic clarification of PMR. We named the sign of the synovitis of atlantoaxial joint on MRI “Buffalo sign”, as it looks like a buffalo with horns. The sign should also be utilized to efficiently establish the diagnosis of PMR.