Discovertebral lesion in ankylosing spondylitis: differential diagnosis with discitis by magnetic resonance imaging.

Abstract  Ankylosing spondylitis (AS) is occasionally accompanied by erosive changes in the vertebral endplate at one or more restricted levels (Andersson lesions). The radiographic findings of this lesion are similar to those of bacterial discitis, and a differential diagnosis between them is often difficult. These diseases must be diagnosed correctly because they require different treatments. In order to evaluate the prevalence of Andersson lesions in the Japanese population, we examined 31 cases of AS which were treated in our department, and Andersson lesions were found in three (9.7%) of them. All these three cases developed Andersson lesions in the earlier phase of the AS, and differentiating the lesions from bacterial discitis was difficult. The details of these three cases are reviewed, and the importance of differentiating between Andersson lesions and bacterial discitis is discussed. Plain radiographs showed no clear difference between these conditions, but magnetic resonance imaging (MRI) was found to be more efficient.