The chronic structural changes of fatty deposition, erosions, and syndesmophytes are also characteristic findings [123]. One study showed that the presence of two or more corner inflammatory lesions had a sensitivity of 69% and specificity of 94% for AS and that lateral vertebral inflammatory lesions had high specificity of 97% [120]. The presence of multiple lesions in the spine has shown to be useful; specifically the presence of at least 5 inflammatory lesions or 5 fatty lesions in the spine has been shown to have a specificity of 95% for axSpA [89]. One study shows that the corner sign in the lumbar spine on T1- weighted or T2-weighted images without fat saturation has a sensitivity of 62% and specificity of 96% for AS [12]. Furthermore, it has been shown that the presence of multiple fatty corner lesions in the spine has a high specificity of 98% and can be useful in the absence of active inflammatory lesions [11]. The ASAS considers a spine MRI positive for axSpA if there are three or more sites of inflammatory spondylitis and considers fatty corner deposition at several sites suggestive of axSpA especially in younger adults [123]. A subsequent study confirmed that the presence of multiple corner lesions has high specificity for axSpA, although it showed a low diagnostic utility because of low sensitivity [121]. Importantly, the findings on spine MRI should be interpreted alongside sacroiliac joint MRI to ensure the highest diagnostic utility. Additionally, MRI findings should be interpreted with specific Inflammatory Back Pain attention to identify associated morphologic findings such as disc degeneration or osteophytes that favor degenerative changes rather than axSpA, because both inflammatory and fatty lesions can occur in degenerative changes [124].
Inflammatory Back Pain Known or Suspected Axial Spondyloarthropathy PCAs. The chronic structural changes of fatty deposition, erosions, and syndesmophytes are also characteristic findings [123]. One study showed that the presence of two or more corner inflammatory lesions had a sensitivity of 69% and specificity of 94% for AS and that lateral vertebral inflammatory lesions had high specificity of 97% [120]. The presence of multiple lesions in the spine has shown to be useful; specifically the presence of at least 5 inflammatory lesions or 5 fatty lesions in the spine has been shown to have a specificity of 95% for axSpA [89]. One study shows that the corner sign in the lumbar spine on T1- weighted or T2-weighted images without fat saturation has a sensitivity of 62% and specificity of 96% for AS [12]. Furthermore, it has been shown that the presence of multiple fatty corner lesions in the spine has a high specificity of 98% and can be useful in the absence of active inflammatory lesions [11]. The ASAS considers a spine MRI positive for axSpA if there are three or more sites of inflammatory spondylitis and considers fatty corner deposition at several sites suggestive of axSpA especially in younger adults [123]. A subsequent study confirmed that the presence of multiple corner lesions has high specificity for axSpA, although it showed a low diagnostic utility because of low sensitivity [121]. Importantly, the findings on spine MRI should be interpreted alongside sacroiliac joint MRI to ensure the highest diagnostic utility. Additionally, MRI findings should be interpreted with specific Inflammatory Back Pain attention to identify associated morphologic findings such as disc degeneration or osteophytes that favor degenerative changes rather than axSpA, because both inflammatory and fatty lesions can occur in degenerative changes [124].