TABLE 2.
Principal characteristic and main results of diffusion imaging studies in Down syndrome.
| Paper | Groups | Sample n | Sample age | Main results |
| (Mean; SD) | ||||
| Gunbey et al. 2017 | DS | 10 | 2,6; ± 0,69 | Voxel-wise TBSS analysis (DS > HC) |
| ● FA decrease of IFOF, ILF, UF, right cerebral peduncle, corpus callosum body, right anterior limb of internal capsule. | ||||
| ● MD increase of right IFOF, right ILF, UF, ATR, right cerebral peduncle, left external capsule, left anterior thalamic radiation, anterior corona radiata. | ||||
| ROI analyses (DS > HC) | ||||
| ● Lower FA in right cerebellar peduncle, right ILF, UF. | ||||
| HC | 10 | 2,5; ± 0,7 | ● Volumetric reduction of corpus callosum and right cerebellar white matter in DS as compared to HC. | |
| Lee et al. 2020 | DS | 15 | 17,0; ± 5.5 | Voxel-wise TBSS analysis (DS > HC) |
| ● FA decrease in only 1% of total voxels: cerebellar (inferior and middle) and cerebral peduncles, external and internal capsule, anterior corona radiata, fornix, and medial lemniscus. No difference in MD. | ||||
| TBM analyses (DS > HC) | ||||
| ● Hypoplasia of several areas (cerebellar area, pons, and fornix). | ||||
| ROI analysis (DS > HC) | ||||
| ● Hypoplasia transverse pontine fibres, cerebellar and cerebral peduncles, fornix, frontal white matter, anterior limb of internal capsule, and cingulum. | ||||
| Tractography analysis (passing though most affected ROIs) with continuous negative Ln-J voxel (DS) | ||||
| HC | 15 | 17,8; ± 6,1 | ● Hypoplasia of the fronto-pontine-cerebellar and temporo-occipito-parietal-pontine-cerebellar pathways, as well as of the fibres connecting the olives to the contralateral cerebellar cortex (thought he inferior cerebellar peduncles). | |
| Romano et al., 2018 | DS | 17 | 23,7; (range 15–27) |
Voxel-wise TBSS analysis (DS > HC) |
| ● FA decrease of IFOF, ILF, ATR, CST. | ||||
| HC | 17 | 21,6; (range 14–27) | ● MD, Axial and Radial diffusivity increase of IFOF, ILF, UF, Cingulum, ATR, CST, Splenium of corpus callosum, as well as MD and Axial diffusivity increase of SLF. | |
| Koenig et al., 2019 | DS | 10 | 29,4; (range 26–32) | Voxel-wise volumetric MRI analyses (DS > HC) |
| ● Reduced WM volume in bilateral ACC and PCC. | ||||
| Diffusion ROI analysis (DS > HC) | ||||
| ● Radial diffusivity in right IPL and right precuneus was related with attention scores in DS. | ||||
| HC | 10 | 28,7; (range 24–33) | ● Radial diffusivity in right rostral MFG, right ACC and left PCC was related with plasma inflammatory markers. | |
| Fenoll et al., 2017 | DS | 45 | 35,3; (range 18–52) | Voxel-wise TBSS analysis (DS > HC) |
| ● FA reduction in frontal lobes, semiovale centrum, corpus callosum, external capsule, internal capsule, putamen, thalamus, pyramidal tracts, brainstem. Alterations were more severe in the frontal-subcortical circuits. | ||||
| HC | 45 | 34,6; (range 19–51) | ● Positive correlation between FA and semantic fluency in several regions (frontal lobes, corpus callosum, semioval centres, arcuate fasciculus, caudate nucleus, external capsule, thalamus, and hippocampus). | |
| Patrick et al. 2019 | DS | 25 | – | Voxel-wise TBSS analysis (DsAD > DS) |
| DsAD | 8 | – | ● MD increase of ILF, SLF, corona radiata, and fronto-occipital fasciculus. | |
| Bazydlo et al. 2021 | DS | 46 | 39,1; ± 7,7 | Voxel-wise TBSS analysis and Pearson’s partial correlation analyses (across all groups) |
| ● FA in SLF and ILF positively correlates with measures of episodic memory. | ||||
| ● MD in SLF and ILF negatively correlates with measures of episodic memory. | ||||
| ● The results didn’t change after removing the participants with preclinical/prodromal AD and AD from the analyses. | ||||
| DS preclinical/prodromal AD | 3 | 45,5; ± 3,5 | ||
| DsAD | 3 | 50,5; ± 5,2 | ||
| Powell et al. 2014 | DS | 10 | 50,6; ± 5,5 | Voxel-wise TBSS analysis (DS > HC) |
| ● FA reduction of IFOF, ILF, SLF, UF, Cingulum, Splenium of corpus callosum, Thalamic Radiation. The largest number of significantly lower FA voxels were found in the frontal lobes. Positive correlation between FA and frontal executive function in several areas. | ||||
| DS preclinical/prodromal AD | 10 | 52,1; ± 7,5 | Voxel-wise TBSS analysis (DsAD > DS) | |
| HC | 10 | 51,7; ± 2.1 | ● No statistically significant results after multiple comparison correction. | |
| Rosas et al. 2020 | DS | 11 | 48.5; ± 6.1 | Voxel-wise TBSS analysis (DsAD > Ds with preclinical/prodromal AD > DS) |
| ● Average FA values tend to decrease (as a trend) in the progression from DS to DS with preclinical/prodromal AD to DsAD in Genu, Splenium, Cingulum bundle, UN, and ILF. Diffusion metrics of Genu, Splenium and Cingulum bundle correlates with measure of general cognitive functioning and memory across groups. | ||||
| Voxel-wise TBSS analysis (Ds with preclinical/prodromal AD > DS) | ||||
| ● FA decrease of Genu, Splenium, Cingulum bundle, ILF in DS with preclinical/prodroma AD as compared to DS. | ||||
| Voxel-wise TBSS analysis (DsAD > DS) | ||||
| ● FA decrease and MD, Axial and Radial diffusivity increase Genu, Splenium, Cingulum bundle, ILF, UN, SLF, Cingulum angular bundle in DsAD as compared to DS. | ||||
| DS preclinical/prodromal AD | 12 | 51.5; ± 5.2 | Partial Spearman correlation analysis between ROI’s FA and amyloid SURV scaling (across all groups) | |
| DsAD | 8 | 54.3; ± 7.7 | ● Low Genu FA correlate with amyloid burden in frontal region and low Splenium FA correlate with amyloid burden in precuneus and parietal regions. Low Cingulum bundle FA correlate with amyloid burden in entorhinal cortex and parietal cortical region. |
DS, Down syndrome; DsAD, Down syndrome with Alzheimer disease; HC, healthy control; SD, standard deviation; TBSS, tract-base spatial statistic; ROI, region of interest; FA, fractional anisotropy; MD, mean diffusivity; SURV, standardised uptake value ratio; Ln-J, Logarithm of the determinant of the Jacobian; IFOF, inferior fronto-occipital fasciculus, ILF, inferior longitudinal fasciculus; SLF, superior longitudinal fasciculus; UF, uncinate fasciculus; ATR, anterior thalamic radiation; CST, corticospinal tract.