Evaluation of the diagnostic utility of spinal magnetic resonance imaging in axial spondylarthritis

Abstract

Objective. Magnetic resonance imaging (MRI) is increasingly used for the diagnosis of axial spondylarthritis (SpA), but it is unknown whether characteristic lesions are actually specific for SpA. This study was undertaken to compare MRI patterns of disease in active SpA, degenerative arthritis (DA), and malignancy.Methods. Fat-suppressed MRI of the axial skeleton was performed on 174 patients with back pain and 11 control subjects. Lesions detected by MRI, including Romanus lesions (RLs) and end-plate, diffuse vertebral body, posterior element, and spinous process bone marrow edema (BME) lesions, were scored in a blinded manner. An imaging diagnosis was given based on MRI findings alone, and this was compared with the goldstandard treating physician's diagnosis.Results.The physician diagnosis was SpA in 64 subjects, DA in 45 subjects, malignancy in 45 subjects, other diagnoses in 20 subjects, and normal in 11 subjects. There was 72% agreement between the imaging diagnosis and physician diagnosis. End-plate edema, degenerative discs, and RLs were frequently observed in patients with any of the 3 major diagnoses. Single RLs were of low diagnostic utility for SpA, but >3 RLs (likelihood ratio [LR] 12.4) and severe RLs (LR infinite) in younger subjects were highly diagnostic of SpA. Posterior element BME lesions of mild or moderate grade were also highly diagnostic of SpA (LR 14.5). The most common diagnostic confusion was between SpA and DA, since both had RLs present and the presence/ absence of degenerative discs did not change the diagnostic assessment.Conclusion. This study confirms the high diagnostic utility of MRI in axial SpA, with severe or multiple RLs evident on MRI being characteristic in younger patients and mild/moderate posterior element lesions being specific for SpA. However, MRI lesions previously considered to be characteristic of SpA could also be found frequently in patients with DA and patients with malignancy, and therefore such lesions should be interpreted with caution, particularly in older patients.In recent years, magnetic resonance imaging (MRI) has become established as a diagnostic tool for spondylarthritis (SpA), particularly in early sacroiliac (SI) joint disease. This is principally because the diagnostic radiographic changes in the SI joints and spine usually develop slowly (1). Fat-suppressed MRI enables identification of osteitis at disease presentation and has the potential to transform the diagnosis of axial SpA, since much of the axial pathology is related to a diffuse perifibrocartilage osteitis, either in the SI joints or at the entheses in the spine (2-4).Many features of SpA that have been identified on MRI, including Romanus lesions (RLs), end-plate lesions, diffuse vertebral body lesions, posterior element (facet and pedicle) lesions, and spinous process bone marrow edema (BME) lesions, are recognized as characteristic of SpA (5-7). It is generally assumed that these MRI patterns of disease can be used to distinguish SpA Dr. Hensor's work is supported in part by an ARC ...

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