Table 6. Muscle MRI imaging of SMA type 2 and 3 patients.
| SMA type 2 | SMA type 3 | Overall (n = 20) 1 | Healthy controls | |||||
|---|---|---|---|---|---|---|---|---|
| Non-Sitter (n = 2) | Sitter (n = 6) | Non-Ambulant (n = 4) | Ambulant (n = 8) | |||||
| Arm | ||||||||
| Biceps Brachii | ||||||||
| CSA (cm2)* | 317 a, b (-) | 185 a (172–224) | 599 b (557–645) | 300 a, b (245–1052) | 281 (201–574) | |||
| C-CSA (cm2)* | 214 a, b (-) | 160 a (131–179) | 536 b (492–598) | 257 a, b (215–583) | 249 (163–502) | |||
| Fat Fraction (%)* | 45.9 a (-) | 24.5 a, b (19.1–32.2) | 15.5 a, b (10.0–17.9) | 11.9 b (8.2–13.4) | 18.5 (11.9–28.3) | |||
| Water T2 mean (ms) | 34.5 (-) | 35.2 (27.8–36.9) | 36.1 (35.4–38.0) | 36.4 (32.8–37.4) | 35.7 (33.4–36.7) | |||
| Abnormal T2 (%) | 25.8 (-) | 25.0 (8.7–28.8) | 18.1 (9.5–34.1) | 13.7 (4.5–27.2) | 19.6 (8.2–28.1) | |||
| Water T2 heterogeneity (CV) | 0.098 (-) | 0.126 (0.107–0.152) | 0.094 (0.082–0.114) | 0.108 (0.082–0.132) | 0.108 (0.086–0.130) | |||
| Triceps | ||||||||
| CSA (cm2)* | 339 a, b (-) | 180 a (124–201) | 632 b (517–707) | 308 b (236–308) | 279 (201–548) | |||
| C-CSA (cm2)* | 168 a, b (-) | 116 a (96–177) | 522 b (415–608) | 229 a, b (217–462) | 220 (151–426) | |||
| Fat Fraction (%) | 70.9 (-) | 19.8 (12.9–42.8) | 20.3 (13.6–36.5) | 12.9 (11.6–19.9) | 18.1 (12.9–39.0) | |||
| Water T2 mean (ms)* | 36.2 a, b (-) | 34.0 a (32.8–36.4) | 39.2 b (37.6–40.5) | 37.3 a, b (36.7–38.9) | 37.2 (34.4–38.8) | |||
| Abnormal T2 (%)* | 26.0 a, b (-) | 10.4 a (8.7–23.1) | 40.8 b (34.6–60.4) | 29.8 a, b (18.0–47.6) | 29.8 (17.7–37.0) | |||
| Water T2 heterogeneity (CV) | 0.130 (-) | 0.125 (0.092–0.150) | 0.080 (0.070–0.114) | 0.111 (0.079–0.111) | 0.111 (0.084–0.129) | |||
| Forearm | ||||||||
| Flexor group | n = 122 | |||||||
| CSA (cm2)* | 531 a, b (-) | 204 a (177–240) | 519 b (483–611) | 349 b (319–860) | 349 (229–554) | |||
| C-CSA (cm2)* | 183 a, b (-) | 143 a (119–200) | 435 b (392–513) | 325 a, b (271–499) | 269 (156–398) | |||
| Fat Fraction (%)* | 77.9 a (-) | 36.1 a, b (28.5–62.1) | 33.3 a, b (23.3–36.8) | 17.1 b (12.7–23.6) | 30.4 (19.8–50.9) | 3.7 (1.1) | ||
| Water T2 mean (ms) | 34.6 (-) | 36.1 (33.8–37.2) | 37.2 (36.5–38.0) | 36.9 (35.2–37.7) | 36.5 (35.0–37.7) | 35.1 (0.7) | ||
| Abnormal T2 (%) | 10.0 (-) | 20.1 (14.2–28.5) | 24.5 (16.5–32.2) | 20.5 (15.4–30.2) | 20.0 (15.4–30.2) | 10.0 (5.1) | ||
| Water T2 heterogeneity (CV) | 0.151 (-) | 0.138 (0.106–0.158) | 0.098 (0.089–0.108) | 0.104 (0.077–0.126) |
0.115 (0.091–0.115) |
0.10 (0.02) | ||
| Extensor group | n = 122 | |||||||
| CSA (cm2)* | 229 a, b (-) | 120 a (94–153) | 453 b (319–474) | 159 a, b (137–772) | 203 (133–432) | |||
| C-CSA (cm2)* | 101 a, b (-) | 93 a (65–130) | 397 b (263–412) | 142 a, b (120–402) | 130 (95–325) | |||
| Fat Fraction (%)* | 64.6 (-) | 26.5 (9.3–38.3) | 12.8 (7.6–16.9) | 10.2 (6.3–12.9) | 12.8 (9.2–28.2) | 4.5 (2.8) | ||
| Water T2 mean (ms) | 34.5 (-) | 35.0 (33.8–36.1) | 36.6 (35.6–38.7) | 36.2 (34.2–36.7) | 35.5 (34.2–36.7) | 34.1 (1.9) | ||
| Abnormal T2 (%) | 10.4 (-) | 15.3 (9.9–26.1) | 12.4 (6.1–35.32) | 11.1 (8.7–24.8) | 12.2 (9.2–23.4) | 6.7 (6.9) | ||
| Water T2 heterogeneity (CV)* | 0.145 (-) | 0.136 (0.111–0.147) | 0.083 (0.069–0.105) | 0.108 (0.081–0.127) | 0.116 (0.088–0.137) | 0.10 (0.02) | ||
| Thigh 3 | n = 0 | n = 1 3 | n = 0 | n = 7 3 | n = 8 | |||
| Quadriceps | n = 33 4 | |||||||
| CSA (cm2) | 626 | 840 (653–2029) | 838 (633–1977) | |||||
| C-CSA (cm2) | 507 | 774 (543–1270) | 772 (516–1159) | |||||
| Fat Fraction (%) | 31.9 | 27.3 (19.5–79.4) | 29.1 (19.9–67.3) | 1.8 (0.4) | ||||
| Water T2 mean (ms) | 41.3 | 39.8 (35.3–41.0) | 39.9 (36.0–41.2) | 35.0 (0.9) | ||||
| Abnormal T2 (%) | 68.1 | 53.5 (16.5–66.1) | 55.7 (21.6–67.6) | 4.0 (4.5) | ||||
| Water T2 heterogeneity (CV) | 0.094 | 0.095 (0.085–0.103) | 0.095 (0.087–0.101) | 0.058 (0.009) | ||||
| Hamstring | ||||||||
| CSA (cm2) | 344 | 560 (462–225) | 547 (435–2056) | |||||
| C-CSA (cm2) | 282 | 524 (409–1987) | 500 (372–1734) | |||||
| Biceps Femoris | ||||||||
| Fat Fraction (%) | 18.9 | 15.5 (10.2–27.5) | 17.0 (10.6–25.3) | |||||
| Water T2 mean (ms) | 38.4 | 36.4 (35.0–38.7) | 36.9 (35.2–38.6) | |||||
| Abnormal T2 (%) | 42.0 | 18.1 (7.6–40.7) | 25.5 (8.4–41.7) | |||||
| Water T2 heterogeneity (CV) | 0.068 | 0.091 (0.065–0.125) | 0.087 (0.065–0.117) | |||||
| Semi Membranosus | ||||||||
| Fat Fraction (%) | 14.4 | 12.8 (8.0–27.5) | 13.6 (8.6–25.3) | |||||
| Water T2 mean (ms) | 37.3 | 36.0 (35.5–36.8) | 36.1 (35.6–36.8) | |||||
| Abnormal T2 (%) | 32.4 | 15.9 (10.7–28.2) | 19.0 (11.4–29.1) | |||||
| Water T2 heterogeneity (CV) | 0.095 | 0.103 (0.098–0.110) | 0.103 (0.095–0.108) | |||||
| Semi Tendinosus | ||||||||
| Fat Fraction (%) | 21.0 | 20.1 (10.6–58.9) | 27.8 (11.2–49.5) | |||||
| Water T2 mean (ms) | 34.4 | 35.1 (34.3–35.5) | 35.0 (34.3–35.4) | |||||
| Abnormal T2 (%) | 13.1 | 5.6 (3.8–14.7) | 7.5 (4.0–14.3) | |||||
| Water T2 heterogeneity (CV) | 0.111 | 0.089 (0.064–0.099) | 0.093 (0.070–0.108) | |||||
| Leg 3 | n = 0 | n = 1 3 | n = 0 | n = 7 3 | n = 8 | |||
| Extensor | ||||||||
| CSA (cm2) | 125 | 203 (178–872) | 197 (175–810) | |||||
| C-CSA (cm2) | 102 | 186 (168–709) | 185 (163–655) | |||||
| Peroneus Lateralis | ||||||||
| CSA (cm2) | 88 | 138 (89–397) | 119 (88–383) | |||||
| C-CSA (cm2) | 61 | 122 (82–316) | 108 (70–314) | |||||
| Fat Fraction (%) | 57.0 | 16.6 (14.1–17.0) | 16.8 (14.7–29.3) | |||||
| Water T2 mean (ms) | 36.2 | 35.0 (33.7–36.9) | 35.4 (33.8–36.7) | |||||
| Abnormal T2 (%) | 2.3 | 5.5 (2.7–20.4) | 4.1 (2.3–19.0) | |||||
| Water T2 heterogeneity (CV) | 0.046 | 0.068 (0.044–0.086) | 0.065 (0.044–0.082) | |||||
| Tibialis Anterior | ||||||||
| Fat Fraction (%) | 40.5 | 10.3 (6.5–17.6) | 13.5 (6.9–34.8) | |||||
| Water T2 mean (ms) | 38.0 | 35.0 (34.4–37.2) | 35.3 (34.5–37.7) | |||||
| Abnormal T2 (%) | 46. | 6.4 (2.1–22.7) | 11.3 (2.7–29.4) | |||||
| Water T2 heterogeneity (CV) | 0.080 | 0.080 (0.059–0.082) | 0.080 (0.064–0.082) | |||||
| Triceps Surae | ||||||||
| CSA (cm2) | 192 | 768 (607–2774) | 735 (554–2581) | |||||
| C-CSA (cm2) | 122 | 717 (572–2624) | 697 (516–2351) | |||||
| Fat Fraction (%) | 67.4 | 13.6 (12.7–16.6) | 14.1 (12.7–42.0) | |||||
| Water T2 mean (ms) | 34.8 | 35.5 (34.9–37.0) | 35.7 (34.9–36.8) | |||||
| Abnormal T2 (%) | 14.6 | 16.0 (8.3–20.7) | 15.3 (9.5–20.7) | |||||
| Water T2 heterogeneity (CV) | 0.112 | 0.062 (0.055–0.0121) | 0.062 (0.056–0.119) | |||||
Abbreviations: CSA: Cross Section Area; C-CSA: Contractile-Cross Section Area; Abnormal T2: percentage of voxels with abnormal T2 (>39ms); SD: Standard Deviation
Values are median (IQR) and overall population size is n = 19 unless otherwise indicated
1 Twenty patients were evaluated for MRI, seventeen during baseline visit and three during month-6 visit
2 Forearm Flexors and Extensors fat fraction, water T2 mean, abnormal T2 and water T2 heterogeneity were previously measured in n = 12 healthy controls aged 7–18 years [38]. Values are mean (SD)
3 Lower limb muscles were assessed in seven ambulant patients with SMA type 3 and one sitter patient with SMA type 2. This latter patient was evaluated although the initial protocol imaging design did not include non-ambulant patients in lower limb MRI acquisition. Since then it has been amended in order to be able to capture these data
4 Quadriceps fat fraction, water T2 mean, abnormal T2 and water T2 heterogeneity were previously measured in n = 33 healthy boys aged 19–27 years[37]. Values are mean (SD).
* p ≤ 0.05
a, b Subscript letters represent Post-hoc tests results. In a row, a same subscript letter indicates subset of categories (non-sitter SMA type 2, sitter SMA type 2, non-ambulant SMA type 3 and ambulant SMA type 3) which do not differ significantly from each other at level 0.05.