For patients who have ankylosing spondylitis (AS), radiographic assessment of the sacroiliac joint with MRI is the cornerstone of evaluation and treatment. Erosions alone—rather than bone marrow edema or contrast medium enhancement—are the most disease-specific measurable imaging findings in sacroiliac MRI of patients with AS in clinical practice.
Wick and coworkers retrospectively reviewed laboratory data, clinical findings, and MRI scans from 179 patients who presented with sacroiliac pain. They attempted to determine whether any other findings might be more relevant for differentiating AS from other causes of sacroiliac pain.
Only 27 (15%) of the study participants unequivocally had AS. Everyone else had another condition, such as a degenerative disease, a rheumatologic disease, or a spondyloarthropathy. Of all the MRI findings, including bone cysts, bone marrow edema, and contrast medium enhancement, only erosions consistently and strongly identified AS. Patients with erosions who received a diagnosis of AS also had the highest C-reactive protein levels, although these elevated levels were nonspecific for AS.
The authors noted that rapid identification of patients with AS at early clinical disease stages, showing only discrete sacroiliac changes, provides an important window of treatment opportunity before irreversible damage occurs.
