Quantitative MRI reveals decelerated fatty infiltration in muscles of active FSHD patients

Objective: To investigate the effects of aerobic exercise training (AET) and cognitive-behavioral therapy (CBT), directed towards an increase in daily physical activity, on the progression of fatty infiltration and edema in skeletal muscles of patients with facioscapulohumeral muscular dystrophy (FSHD) type 1 by T2 MRI. Methods: Quantitative T2 MRI (qT2 MRI) and fat-suppressed T2 MRI of the thigh were performed at 3T on 31 patients, 13 of whomreceived usual care (UC), 9 AET, and 9 CBT. Muscle-specific fat fractions (%), derived from qT2 MRI, were recorded pretreatment and posttreatment. Intervention effects were analyzed by comparing fat fraction progression rates of the UC with the treated groups using Mann-Whitney tests, and intermuscle differences by a linear mixed model. Edematous hyperintense lesions were identified on the fat-suppressed T2 MRI. Results: The intraclass correlation coefficient for reproducibility of qT2 MRI fat assessment was 0.99. In the UC group, the fat fraction increased by 6.7/year (95% confidence interval [CI] 4.3 to 9.1). This rate decreased to 2.9/year (95% CI 0.7 to 5.2) in the AET (p = 0.03) and 1.7/year (95% CI 20.2 to 3.6) in the CBT group (p = 0.00015). The treatment effect differed among individual muscles. Fewer new edematous lesions occurred after therapy. Conclusions: Fat fraction derived from qT2 MRI is a reproducible and sensitive biomarker to monitor the effects of increased physical activity in individual muscles. This biomarker reports a favorable effect of AET and CBT on the rate of muscular deterioration in FSHD as reflected in decelerated fat replacement. Classification of evidence: This study provides Class II evidence that for patients with FSHD type 1, both AET and CBT decrease the rate of fatty infiltration in muscles.