Distinct Inter- & Intra-Muscular Features Observed by MR Imaging & Spectroscopy in Patients with FSHD Uncover Pathobiological Processes in Disease Development

Barbara H. Janssen¹, Rob J. W. Arts², Nicoline B. M. Voet³, Christine I. H. C. Nabuurs¹, Baziel G. M. van Engelen², Arend Heerschap¹

To assess muscular involvement and progression towards a diseased state in FSHD-patients we used fat infiltration and PCr/ATP measured by 1H-MRI and 31P-MRS of the thigh muscles as non-invasive biomarkers. Almost all investigated muscles were either not or entirely fat infiltrated. In muscles showing intermediate fatty infiltration we found that fat-content increased over the length of the muscle in the distal direction. Interestingly only the intermediately affected muscles also showed a change in fat-content over time. The fat-infiltration is inversely correlated with muscle strength. A decreased PCr/ATP ratio shows that energy metabolism is compromised in remaining muscles.