Abstract
Microstructural changes of White Matter (WM) associated with aging have been widely described through Diffusion Tensor Imaging (DTI) parameters. In parallel, White Matter Hyperintensities (WMH) as observed on a T2-weighted MRI are extremely common in older individuals. However, few studies have investigated both phenomena conjointly. The present study investigates aging effects on DTI parameters in absence and in presence of WMH. Diffusion maps were constructed based on 21 directions DTI scans of young adults (n = 19, mean age = 33 SD = 7.4) and two age-matched groups of older adults, one presenting low-level-WMH (n = 20, mean age = 78, SD = 3.2) and one presenting high-level-WMH (n = 20, mean age = 79, SD = 5.4). Older subjects with low-level-WMH presented modifications of DTI parameters in comparison to younger subjects, fitting with the DTI pattern classically described in aging, i.e., Fractional Anisotropy (FA) decrease/Radial Diffusivity (RD) increase. Furthermore, older subjects with high-level-WMH showed higher DTI modifications in Normal Appearing White Matter (NAWM) in comparison to those with low-level-WMH. Finally, in older subjects with high-level-WMH, FA, and RD values of NAWM were associated with to WMH burden. Therefore, our findings suggest that DTI modifications and the presence of WMH would be two inter-dependent processes but occurring within different temporal windows. DTI changes would reflect the early phase of white matter changes and WMH would appear as a consequence of those changes.
Highlights
Aging is associated with widespread brain structural modifications both in gray matter (GM) and in white matter (WM) compartments
Mean Diffusivity (MD) represents a global measure of water diffusion, Fractional Anisotropy (FA) represents the degree of directionality of water diffusivity, Axial Diffusivity (AD) describes the principal direction of fibers and Radial Diffusivity (RD) describes the perpendicular diffusion of the principal direction
Relationships between White Matter Hyperintensities (WMH) burden and diffusion values of the Normal Appearing White Matter (NAWM) were found in older subjects with high-level-WMH
Summary
Aging is associated with widespread brain structural modifications both in gray matter (GM) and in white matter (WM) compartments. DTI is an established method for studying in vivo the WM pathways and has the ability to reveal structural properties of the WM (Basser et al, 2000; Le Bihan et al, 2001; Behrens et al, 2003) by measuring water. Age-Related White Matter Changes diffusion at mesoscopic resolution in brain tissue. DTI is sensitive to the magnitude and orientation of water displacement throughout tissue, and such information can be exploited through a tensor model to calculate several diffusion parameters. In studies including older subjects, a consistent pattern of DTI parameters modifications has been described: a decrease of FA and an increase of both MD and RD were observed in the major WM tracts (Head et al, 2004; Pfefferbaum et al, 2005; Salat et al, 2005a,b; Sullivan and Pfefferbaum, 2006). The pattern of FA decrease/RD increase, observed in pathological conditions such as multiple sclerosis (Roosendaal et al, 2009; Liu et al, 2012), certainly reflects demyelination process, whereas the pattern of FA decrease/AD decrease reflects axonal degeneration as observed in callosotomy condition (Concha et al, 2006)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
