Table 1 Muscle MRI scores and muscle parameters in ASS patients and controls

  Edema extent score (0–18)

3.2 (5.3)

0.4 (1.4)

<0.001

  Edema signal intensity score (0–18)

3.1 (5.0)

0.5 (1.7)

<0.001

  Fascial edema score (0–6)

1.3 (2.1)

0.1 (0.4)

<0.001

  Fatty replacement score (0–30)

5.8 (4.3)

1.8 (2.4)

<0.001

  Muscle volume reduction score (0–6)

0.6 (1.6)

0.1 (0.6)

<0.036

Total MRI score (activity + damage; 0–78)

14.1 (14.1)

3.0 (4.2)

<0.001

  Median CK, U/L (range)

95 (24–1344)

98 (35–839)

<0.676

  CK > 2 × ULN, n/N (%)

4/67 (6)

1/65 (2)

<0.366

  Median MMT14 score (25th, 75th centile)

139 (133, 140)

140 (138, 140)

<0.001

  Median MMT4 score (25th, 75th centile)

40 (36, 40)

40 (39, 40)

<0.004

  Median FI2 score (25th, 75th centile)

211 (116, 301)

324 (281, 330)

<0.001