Background A positive MRI at baseline is a strong predictor for a positive follow-up MRI1. But many questions about the volatility of the lesions over short follow-up periods remain unsolved. Is it possible for lesions to disappear, occur or move localisation? Or is their location rather consistent over time?
Objectives To describe if and how the location of active inflammatory lesions change and if lesions can occur or disappear after 3 months without changing treatment.
Methods 90 patients with chronic back pain (≥3 months, ≤2 years, onset ≤45 years) who were included in the SPondyloArthritis Caught Early (SPACE)-cohort underwent an MRI of the SI joints (MRI-SIJ) at baseline and after 3 months follow-up.
Results Out of all patients 66/90 (73.3%) did not show any lesions at any of the time points. In 12 patients no difference was found between baseline and follow-up MRI with respect to the SI joint (only left side affected in 7 patients, only right side in 2 and in 3 patients both SIJs were affected). In 5 patients without lesions at baseline new inflammation occurred (4 times only in the right SIJ and once in both SIJs). In 4 patients with inflammation at baseline the inflammation was no longer present at follow-up. In 3 out of 6 patients with inflammation in both SIJs at baseline, the inflammation was only present in the left SIJ after 3 months. The other 3 patients presented inflammation in both SIJs at baseline as well as follow-up (see table).
24/90 (26.7%) patients had a positive MRI at baseline or follow-up, or both. The quadrant in which the lesion was present did not change over time in 6 patients. Lesions disappeared from quadrants in 9 patients (lesion disappeared in only 1 quadrant in 7 patients and in 3 quadrants in 2 patients) and occurred in 7 patients (MRI changed from negative to positive in 5 and remained positive in 2 patients). The lesions moved between quadrants in 2 patients. In these 2 patients lesions disappeared from one quadrant and occurred in another. In 20/24 patients the medication between baseline MRI and follow-up did not change (18 patients used NSAIDs and 2 of them did not use any medication) and 4 patients changed medication (2 patients switched NSAID type and the other 2 started NSAID treatment in that period). Out of the patients that changed from a negative to positive MRI (n=5) or vice versa (n=4), only 1 patient also changed medication, by switching to another NSAID.
Conclusions BME lesions on MRI occur or disappear at SIJ level in 9% of the patients with chronic back pain after 3 months. From all patients with a positive MRI at baseline, lesions did not change location in 50% of them at SIJ level, while at quadrant level less than 30% of the patients showed stability in the location of lesions. So, there is quite some volatility of lesions over a short follow-up period of 3 months only.
Disclosure of Interest None Declared
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