P125 Quantitative MRI in upper limb muscles of patients with dysferlinopathy: 6-months and 12-months longitudinal data from the natural history Jain COS 2 project.

In dysferlinopathy patients, the upper limb muscles are affected in the later stages of the disease, and muscle fat replacement of arm and forearm muscles follows thigh and leg involvement. Additionally, increased disease activity (such as inflammation) in lower limb muscles has been reported to be a feature in patients with dysferlinopathy. Adding to the COS1 results, a longitudinal quantitative MRI study in upper limbs was set up in four clinical centers (UK, France, Italy, USA), investigating both muscle fat fraction (FF; reflecting the extent of muscle fat replacement) and water T2 (reflecting the extent of muscle inflammation). The MRI data presented here were acquired in two of the four sites, at baseline, 6-months, and/or 12-months. The MRI acquisitions included FF and water T2 mapping at the level of the upper arm (deltoid, triceps and biceps brachialis) and forearm (extensor, flexor). Student's t-tests were performed (P<0.05). Patients in this cohort (17 female, 10 male, 89% ambulant, 70% LGMD R2 diagnosis) were 46.1±12.1 years old and had symptoms for 14.9±7.7 years. At baseline, the lowest FF values were found in forearm muscles (23.5±14.6% in flexor, 24.1±16.1% in extensor). FF values in upper arm muscles were 30.1±18.6%, 31.1±21.4% and 35.1±24.1% in deltoid, biceps brachialis and triceps muscles, respectively. Per 6 months, FF increased, on average, by 2 to 3% in forearm muscles and 2 to 5% in upper arm muscles (P>0.05). Biceps brachialis and extensor muscles showed normal water T2 values (<37.0 ms), whereas elevated water T2 values were found in flexor and triceps muscles (≥38.7 ms) across the three visits. These quantitative MRI data showed that the upper arm muscles were somewhat more involved than forearm muscles. A high inter-patient heterogeneity of disease progression was observed, resulting in non-significant results for changes in FF. The persistent disease activity in some muscles (reflected by elevated water T2 values across the entire study) was earlier shown in thigh and leg muscles in dysferlinopathy. [ABSTRACT FROM AUTHOR]