Table 1
Participants descriptives of demographics, clinical and neuropsychological variables.
| DIAGNOSIS | p-VALUE | |||
|---|---|---|---|---|
| HC | ET | ETrt | ||
| Age | 64 ± 4.5a | 67 ± 5.9a | 68.5 ± 12.6a | .651 |
| Gender | 15 M – 12 F | 34 M – 29 F | 17 M – 21 F | .602 |
| Disease Duration | / | 5.0 ± 5.2a | 8.0 ± 7.4a | .133 |
| Education | 8.0 ± 4.5a | 9.5 ± 5.2a | 8.0 ± 4.5a | .211 |
| Fahn Tolosa Marin-A | / | 8.0 ± 2.9a | 12.0 ± 5.9a | .683 |
| Postural items | / | 4.0 ± 1.48a | 4.0 ± 2.22a | .983 |
| Kinetic items | / | 3.0 ± 1.48a | 3.0 ± 1.48a | .713 |
| Rest items | / | / | 4.0 ± 1.48a | / |
| MMSE | 27.7 ± 1.9b | 27.6 ± 1.6b | 27.0 ± 1.3b | .154 |
| COWAT | 29.7 ± 8.9b | 26.2 ± 4.6b | 24.9 ± 8.2b | .154 |
| RAVLT_IR | 41.6 ± 5.5b | 39.5 ± 8.7b | 36.4 ± 11.1b | .744 |
| RAVLT_DR | 8.1 ± 2.1b | 7.2 ± 2.6b | 5.9 ± 3.4b | .604 |
| Digit Span F | 5.8 ± 1.1a | 5.2 ± 1.2a | 4.9 ± 0.9a | .091 |
| Digit Span B | 4.0 ± 0.6a | 3.0 ± 0.7a | 3.0 ± 0.7a | .221 |
[i] a values are reported as median ± mad; bmean ± sd; 1Kruskal-Wallis rank sum test; 2Pearson’s Chi-squared test; 3 Wilcoxon rank sum test;4ANalysis Of VAriance.
Table 2
Comparison of Thickness, MD and FA descriptives between the three groups.
| DIAGNOSIS | p-VALUE | |||
|---|---|---|---|---|
| HC | ET | ETrt | ||
| Genu Thickness (mm)a | 5.73 ± 0.81 | 3.66 ± 0.67 | 3.66 ± 1.01 | HC vs ET p < .001 HC vs ETrt p < .001 ET vs ETrt p = 1 |
| Body Thickness (mm)a | 4.72 ± 0.81 | 2.95 ± 0.57 | 3.16 ± 0.90 | HC vs ET p < .001 HC vs ETrt p < .001 ET vs ETrt p = 1 |
| Splenium Thickness (mm)b | 5.83 ± 0.89 | 4.40 ± 1.04 | 4.42 ± 0.89 | HC vs ET p < .001 HC vs ETrt p < .001 ET vs ETrt p = 1 |
| Genu MD (mm2/s)b | 1.7 · 10–3 ± 2.3 · 10–4 | 1.6 · 10–3 ± 2.5 · 10–4 | 1.7 · 10–3 ± 2.9 · 10–4 | HC vs ET p = .129 HC vs ETrt p = 1 ET vs ETrt p = 1 |
| Body MD (mm2/s)b | 1.3 · 10–3 ± 1.3 · 10–4 | 1.5 · 10–3 ± 1.6 · 10–4 | 1.4 · 10–3 ± 2.4 · 10–4 | HC vs ET p = .029 HC vs ETrt p = .07 ET vs ETrt p = 1 |
| Splenium MD (mm2/s)a | 1.3 · 10–3 ± 1.2 · 10–4 | 1.3 · 10–3 ± 1.6 · 10–4 | 1.3 · 10–3 ± 2 · 10–4 | HC vs ET p = 1 HC vs ETrt p = 1 ET vs ETrt p = 1 |
| Genu FAa | 0.35 ± 0.05 | 0.39 ± 0.06 | 0.38 ± 0.07 | HC vs ET p = .033 HC vs ETrt p = 1 ET vs ETrt p = 1 |
| Body FAa | 0.43 ± 0.05 | 0.43 ± 0.05 | 0.44 ± 0.07 | HC vs ET p = 1 HC vs ETrt p = 1 ET vs ETrt p = 1 |
| Splenium FAa | 0.55 ± 0.05 | 0.55 ± 0.05 | 0.54 ± 0.06 | HC vs ET p = 1 HC vs ETrt p = 1 ET vs ETrt p = 1 |
[i] avalues are reported as mean ± sd; a regression model included Age and white matter volume as necessary covariates;
bregression model included Age and Gender and white matter volumes as necessary covariates.
Figure 1
Mean thickness values in different regions of corpus callosum.
a) Boxplots representing mean thickness in different regions of corpus callosum in all groups; b) Comparison of mean thickness along all the 50 CC ROIs between the three groups.
Figure 2
Mean MD in different regions of corpus callosum.
a) Boxplots representing mean MD in different regions of corpus callosum; b) Comparison of mean MD along all the 50 CC ROIs between the three groups.
Table 3
Effect sizes for the best model in regression analyses.
| MRI PARAMETER REGION | PARTIAL ETA SQUARED (η2) THICKNESS, MD AND FA | |||
|---|---|---|---|---|
| DIAGNOSIS | AGE | GENDER | WHITE MATTER VOLUMES | |
| Thickness | ||||
| Genu | 0.53 (0.43, 1) | 0.09 (0.03, 1) | / | 0.05 (0.01, 1) |
| Body | 0.48 (0.37, 1) | 0.09 (0.03, 1) | / | 0.04 (0.01, 1) |
| Splenium | 0.31 (0.19, 1) | 0.09 (0.02, 1) | 0.07 (0.01,1) | 0.03 (0.00, 1) |
| MD | ||||
| Genu | 0.06 (0.01,1) | 0.30 (0.20, 1) | 0.06 (0.01, 1) | 0.09 (0.03, 1) |
| Body | 0.10 (0.02, 1) | 0.25 (0.14, 1) | 0.09 (0.03, 1) | 0.10 (0.03, 1) |
| Splenium | 0.03 (0, 1) | 0.24 (0.14, 1) | / | 0.05 (0.01, 1) |
| FA | ||||
| Genu | 0.07 (0.01, 1) | 0.20 (0.10, 1) | / | 0.13 (0.05, 1) |
| Body | 0.01 (0, 1) | 0.12 (0.04, 1) | / | 0.12 (0.04, 1) |
| Splenium | 0.02 (0, 1) | 0.18 (0.09, 1) | / | 0.09 (0.03, 1) |
[i] η2 (95% CI).
Figure 3
Mean FA values in different regions of corpus callosum.
a) Boxplots representing mean FA in different regions of corpus callosum; b) Comparison of mean FA along all the 50 CC ROIs between the three groups.
Table 4
Clusters descriptives.
| C1-ET CLUSTER | C2-HC CLUSTER | p-VALUE | |
|---|---|---|---|
| Cluster composition | 56 ET 30 ETrt | 27 HC 7 ET 8 ETrt | <.0011 |
| Age | 68 ± 6.7a | 62.5 ± 6.67a | .022 |
| Gender | 39 F 47 M | 23 F 19 M | .411 |
| Genu Thickness | 3.4 ± 0.6b | 5.4 ± 0.9b | <.0013 |
| Body Thickness | 2.8 ± 0.5b | 4.5 ± 0.8b | <.0013 |
| Splenium Thickness | 4.2 ± 0.9b | 5.8 ± 0.8b | <.0013 |
| Genu Mean Diffusivity | 1.7 · 10–3 ± 2.4 · 10–4 b | 1.6 · 10–3 ± 3 · 10–4 b | .203 |
| Body Mean Diffusivity | 1.5 · 10–3 ± 1.7 · 10–4 b | 1.3 · 10–3 ± 1.7 · 10–4 b | <.0013 |
| Splenium Mean Diffusivity | 1.4 · 10–3 ± 1.6 · 10–4 b | 1.2 · 10–3 ± 1.5 · 10–4 b | <.0013 |
| Genu Fractional Anisotropy | 0.37 ± 0.06b | 0.38 ± 0.07b | .413 |
| Body Fractional Anisotropy | 0.43 ± 0.05b | 0.45 ± 0.06b | .033 |
| Splenium Fractional Anisotropy | 0.53 ± 0.05b | 0.57 ± 0.05b | <.0013 |
| Disease Duration | 7.0 ± 5.9a | 4.0 ± 4.5a | .222 |
| Fahn Tolosa | 9.0 ± 4.5a | 8.0 ± 4.5a | .282 |
| MMSE | 27.1 ± 1.6b | 27.9 ± 1.8b | .0493 |
| COWAT | 25.6 ± 5.1b | 29.1 ± 9.7b | .123 |
| RAVLT_IR | 38.9 ± 9.3b | 41.4 ± 7.1b | .213 |
| RAVLT_DR | 6.9 ± 2.8b | 8.0 ± 2.6b | .103 |
| Digit Span F | 5.1 ± 0.8b | 5.6 ± 0.9b | .033 |
| Digit Span B | 3.2 ± 0.8b | 3.6 ± 0.8b | .143 |
[i] avalues are reported as median ± mad; b values are reported as mean ± sd;
1Chi-squared test; 2Wilcoxon rank sum test; 3Two sample t-test.
Figure 4
Silhouette plot of clustering analysis.
The silhouette plot displays the distribution of silhouette coefficients across clusters, indicating the quality of clustering for each data point.
Figure 5
Multidimensional Scaling representing clusters distributions.
The Multidimensional Scaling represents the spatial distribution of participants based on structural callosal similarity. The dashed line indicates the cluster separation. Each point corresponds to an individual case. The distance between points reflects the degree of dissimilarity. Red dots represent HC, blue dots ET, and green dots ETrt.