Search

Background Myositis is an autoimmune disease which can cause a decrease in quality of life and increased mortality, presenting with muscle weakness, raised muscle enzymes and myalgia. Diagnosis is reliant on subjective clinical examinations, blood tests, conventional MRI and invasive muscle biopsies. Quantitative T2 MRI offers a non-invasive measurement of muscle oedema which could help improve the understanding of muscle pathology and potentially inform diagnosis. The aim of this study was to evaluate whether quantitative T2 MRI of muscles is sensitive enough to detect differences in myositis patients compared to healthy controls, and how it compares with current radiologist scoring methods. Methods 16 myositis patients were recruited (10/16 female, 10 polymyositis, 6 dermatomyositis, mean age 50 ± 26), median CK 1000IU/L ± 3100IU/L, and 16 age and gender matched healthy controls were recruited. MRI of the dominant thigh were performed. Imaging was performed using a fat-suppressed turbo-spin echo sequence. Quantitative T2 measurements were obtained from regions of interest (ROI) drawn manually within the individual muscles that make up the quadriceps and hamstrings with no distinction made between affected and unaffected muscles. A mono-exponential fit was used to obtain an estimate of the T2 from each ROI. Two radiologists blinded to the diagnosis, semi-quantitatively scored by consensus the muscles on a 4-point visual scale as either no oedema (0), mild oedema (1), moderate oedema (2) or severe oedema (3). Muscle strength was assessed using an isokinetic dynamometer. Results T2 values were higher in myositis patients compared to healthy controls [mean (SD) hamstring myositis 47.8ms (7.7ms), healthy 39.9ms (1.5ms), p < 0.001; quadriceps myositis 53.8ms (12.1ms), healthy 42.1ms (2.1ms), p < 0.001]. Quantitative T2 correlated with the radiologists’ oedema scores with rs=0.7 in the hamstrings (p < 0.001) and rs=0.6 in the quadriceps (p < 0.001), with an upward trend in T2 as radiologist scored visible oedema increased. Patients who had been classified as normal by the radiologists were compared with matched healthy controls (n = 8), T2 values for patients with ‘normal muscle’ were still higher than those for healthy controls: mean T2 in the hamstrings (myositis 42.2ms, healthy controls 38.7ms, p = 0.004); mean T2 in the quadriceps (myositis 43.9ms, healthy controls 40.1ms, p = 0.001). T2 was inversely correlated with muscle strength in all participants. Conclusion Quantitative T2 measurements can detect muscle differences between myositis patients and healthy control groups, which suggests that this measurement could be used as an objective method to monitor muscles. They are also sensitive to differences that may not be detected by radiologists. This suggests that subtle systemic changes in muscle in myositis patients, which go undetected in semi-quantitative visual scoring, can be detected using quantitative T2 measurements. This shows the potential for T2 measurements to be a diagnostic measure in the diagnosis and management of myositis. Disclosures M. Farrow None. J. Biglands None. A. Grainger None. E. Hensor None. P. O'Connor None. A. Ladas None. S. Tanner None. A. Aslam None. P. Emery None. A. Tan None.

Background Rheumatoid arthritis (RA) can present with the loss of muscle mass and a decrease in strength and functional capability. Quantitative MRI offers a non-invasive measurement of muscle status which could improve the understanding of muscle pathology in RA. The purpose of this study was to assess whether MRI-based measurements of T2, fat fraction (FF), diffusion tensor imaging and muscle volume can detect differences between the muscles of RA patients and healthy controls in the thigh; and to assess how different stages of the disease present differently. Methods 39 RA patients were recruited, comprised of 3 groups: 13 newly diagnosed treatment naïve (Group 1 - New RA: 10/13 female, mean age 63 years, mean CRP 31.5, mean EMS 71 minutes), 13 in clinical remission DAS28 3.2 ± raised CRP/ESR ± DMARD/targeted therapy escalation ± requiring steroid therapy (Group 3 - Resistant RA: 10/13 female, mean age 65, mean CRP 17.4, mean disease 123 months, mean EMS 63 minutes). 13 healthy controls were also recruited. All 4 groups were age and gender matched. MRI of the dominant thigh was performed using a STEAM-EPI imaging sequence to assess diffusion: mean diffusivity (MD) and fractional anisotropy (FA), 2-point Dixon imaging to assess FF and a fat-suppressed turbo-spin echo sequence to measure T2. All participants had knee extension/flexion and grip strength torque measured using isokinetic dynamometer. Results A one-way ANOVA analysis demonstrated significant differences in T2, FF and muscle volume between RA patients and healthy controls, but no difference in MD or FA. There was no significant difference between the RA groups. T2 and FF were higher in RA patients whilst muscle volume was lower. Muscle volume was significantly correlated with early morning stiffness (rs = 0.4, p = 0.001), DAS28 (rs = 0.4, p = 0.001) and grip strength (rs = 0.5, p < 0.001). All RA patients showed weaker strength compared to the healthy controls. Although the patients in remission (group 2) had better results compared to New (group 1) and Resistant RA patients (group 3), they performed worse than the healthy controls in all strength assessments. Conclusion Quantitative MRI can detect changes in the muscles of RA patients, whether they are newly diagnosed, in remission or with persistently active disease. Difference in T2, FF and muscle volume were apparent even at diagnosis, suggesting muscle changes in RA occur early. Despite effective RA therapy, patients in remission show worse MRI parameters and strength compared to healthy individuals. These warrant attention in improving the muscle strength and quality throughout the spectrum of the RA continuum. Disclosures M. Farrow: None. J. Biglands: None. S. Tanner: None. E. Hensor: None. M. Buch: None. P. Emery: None. A. Tan: None.