Preserved thenar muscles in non‐ambulant Duchenne muscular dystrophy patients

Background Clinical trials in Duchenne muscular dystrophy (DMD) focus primarily on ambulant patients. Results cannot be extrapolated to later disease stages due to a decline in targeted muscle tissue. In non‐ambulant DMD patients, hand function is relatively preserved and crucial for daily‐life activities. We used quantitative MRI (qMRI) to establish whether the thenar muscles could be valuable to monitor treatment effects in non‐ambulant DMD patients. Methods Seventeen non‐ambulant DMD patients (range 10.2–24.1 years) and 13 healthy controls (range 9.5–25.4 years) underwent qMRI of the right hand at 3 T at baseline. Thenar fat fraction (FF), total volume (TV), and contractile volume (CV) were determined using 4‐point Dixon, and T2water was determined using multiecho spin‐echo. Clinical assessments at baseline (n = 17) and 12 months (n = 13) included pinch strength (kg), performance of the upper limb (PUL) 2.0, DMD upper limb patient reported outcome measure (PROM), and playing a video game for 10 min using a game controller. Group differences and correlations were assessed with non‐parametric tests. Results Total volume was lower in patients compared with healthy controls (6.9 cm3, 5.3–9.0 cm3 vs. 13.0 cm3, 7.6–15.8 cm3, P = 0.010). CV was also lower in patients (6.3 cm3, 4.6–8.3 cm3 vs. 11.9 cm3, 6.9–14.6 cm3, P = 0.010). FF was slightly elevated (9.7%, 7.3–11.4% vs. 7.7%, 6.6–8.4%, P = 0.043), while T2water was higher (31.5 ms, 30.0–32.6 ms vs. 28.1 ms, 27.8–29.4 ms, P