Table 2.
The quantitative MRI parameters (volume, fat fraction and T2water-) for all individual extra-ocular muscles for the MG groups recently diagnosed, chronic and seronegative, for the disease controls chronic progressive external ophthalmoplegia (CPEO), oculopharyngeal muscular dystrophy (OPMD) and Graves’ orbitopathy (GO), and the healthy controls. For volume, fat fraction and T2water the amount of patients with zero, one or more than one muscle higher or lower than 2 standard deviations (SD) above and below the mean of healthy controls are mentioned. Per quantitative MRI parameter an ANOVA was performed and for the group comparison a post-hoc testing was performed using Dunnett’s multiple comparisons test to correct for multiple testing
| MG Recently diagnosed n = 19 | MG Chronic n = 18 | MG Seronegative n = 11 | CPEO n = 6 | OPMD n = 6 | GO n = 5 | Healthy controls n = 16 | p-value with MG groups combined | |
| Volume | ||||||||
| Lateral rectus (mm3) | 753.5±126.7 | 753.5±187.6 | 685.0±145.7 | 531.0±116.8* | 662.6±158.5 | 918.6±186.2* | 728.1±116.8 | < 0.0001 |
| Medial rectus (mm3) | 664.8±117.6 | 691.5±154.0 | 569.5±101.5 | 497.1±121.3* | 618.0±103.8 | 775.6±188.5* | 629.8±142.2 | 0.0002 |
| Inferior rectus (mm3) | 517.3±121.3 | 565.4±156.8* | 408.9±124.4 | 432.4±134.5 | 546.3±164.9 | 857.1±424.0* | 480.4±134.5 | < 0.0001 |
| Superior rectus plus levator palpebrae (mm3) | 953.1±252.8 | 1028.0±267.7* | 972.4±298.5 | 602.0±192.9*† | 739.8±199.8† | 1419.0±457.1* | 883.8±153.7 | < 0.0001 |
| 0 muscles out of 2 SD range (n [% ]) | 13 (68%) | 8 (44%)* | 5 (46%) | 2 (33%)* | 3 (50%) | 0 (0%)* | 11 (69%) | < 0.01 |
| 1 muscles out of 2 SD range (n [% ]) | 2 (11%) | 4 (22%)* | 4 (36%) | 0 (0%)* | 2 (33%) | 0 (0%)* | 5 (31%) | |
| 2 + muscles out of 2 SD range (n [% ]) | 4 (21%) | 6 (33%)* | 2 (18%) | 4 (67%)* | 1 (17%) | 5 (100%)* | 0 (0%) | |
| Fat fraction | ||||||||
| Lateral rectus | 0.142±0.032 | 0.147±0.040 | 0.114±0.022 | 0.226±0.104* | 0.181±0.029* | 0.160±0.033 | 0.131±0.031 | < 0.0001 |
| Medial rectus | 0.135±0.028 | 0.140±0.030* | 0.137±0.026 | 0.202±0.061* | 0.163±0.018* | 0.142±0.028 | 0.123±0.019 | 0.0075 |
| Inferior rectus | 0.174±0.052 | 0.187±0.046 | 0.151±0.042 | 0.223±0.057* | 0.194±0.035 | 0.199±0.077 | 0.169±0.045 | < 0.0001 |
| Superior rectus plus levator palpebrae | 0.167±0.050 | 0.170±0.055* | 0.140±0.030 | 0.199±0.077*† | 0.233±0.028*† | 0.194±0.052* | 0.142±0.026 | < 0.0001 |
| 0 muscles out of 2 SD range (n [% ]) | 10 (53%) | 9 (50%)* | 7 (64%) | 2 (33%)* | 1 (17%)* | 2 (40%) | 13 (81%) | < 0.01 |
| 1 muscles out of 2 SD range (n [% ]) | 5 (26%) | 4 (22%)* | 4 (36%) | 0 (0%)* | 0 (0%)* | 2 (40%) | 3 (19%) | |
| 2 + muscles out of 2 SD range (n [% ]) | 3 (16%) | 5 (28%)* | 0 (0%) | 4 (67%)* | 5 (83%)* | 1 (20%) | 0 (0%) | |
| T2 water | ||||||||
| Lateral rectus (ms) | 28.4±2.2 | 28.7±2.5 | 28.0±3.1 | 27.1±3.7 | 29.1±3.3 | 27.0±4.0 | 28.0±2.5 | n.s. |
| Medial rectus (ms) | 26.3±2.9 | 28.3±3.3 | 28.3±3.3 | 28.5±3.2 | 26.4±1.8 | 26.6±4.9 | 27.0±2.6 | n.s. |
| Inferior rectus (ms) | 24.5±3.6 | 25.8±3.4 | 26.8±3.9 | 24.7±3.0 | 29.3±2.7* | 25.1±6.2 | 24.3±4.0 | 0.0053 |
| Superior rectus plus levator palpebrae (ms) | 27.7±2.1 | 29.1±2.5 | 29.5±2.7 | 28.9±3.2 | 28.0±2.4 | 27.7±3.4 | 28.7±2.1 | n.s. |
| 0 muscles out of 2 SD range (n [% ]) | 13 (68%) | 12 (67%) | 5 (46%) | 1 (16.5%) | 4 (67%) | 1 (20%) | 11 (69%) | n.s. |
| 1 muscles out of 2 SD range (n [% ]) | 6 (32%) | 4 (22%) | 4 (36%) | 4 (67%) | 2 (33%) | 2 (40%) | 5 (31%) | |
| 2 + muscles out of 2 SD range (n [% ]) | 0 (0%) | 2 (11%) | 2 (18%) | 1 (16.5%) | 0 (0%) | 2 (40%) | 0 (0%) |
*The bold values are significantly different from healthy controls after post-hoc testing. †Two of the CPEO and one of the OPMD patients had surgery involving the levator palpebrae to correct for their ptosis and excluded from the mean.