Whole-body patterns of muscle degeneration and progression in sarcoglycanopathies

MRI studies were performed following standard protocols, either WB(Carlier & Quijano-Roy, 2019; Chardon et al., 2019; Quijano-Roy et al., 2012) or combination of UB and LB MRI(Tasca et al., 2012, 2014), using different 1.5T or 3T scanners, and T1-weighted images were analyzed.A total of 65 muscles on both sides were independently evaluated for each scan by two independent observers, a radiologist and a pediatric neurologist with experience in muscle imaging (AS and LC). In case of discrepancy between the evaluators, agreement was reached by consensus (AS, DGA and LC). The median scores from both sides were used for data analysis. A four-point modified Lamminen scale was used to evaluate signal abnormalities representative of the extent of intramuscular fatty replacement in each muscle as follows: 0= normal signal intensity, 1=slightly hyperintense, patchy intramuscular signal changes 2=markedly hyperintense and widespread intramuscular signal changes, 3= total, homogeneous hyperintense signal change in whole muscle, equaling the signal intensity of the adjacent subcutaneous or paramuscular fat, or atrophy(Chardon et al., 2019; Lamminen, 1990; Wattjes et al., 2010). The scores of muscles that were not adequately visualized were considered as missing values (NA). The lower limb scans analyzed in the previous imaging study(Tasca et al., 2018) with a 5-point scoring system were re-scored to address the limitations in assessing some of the small and flat muscles in the head, trunk, neck and arms, ensuring uniformity across all body regions.