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Abstract
To study the integrity of hemispheric subcortical white matter by comparing normal young and elderly subjects using quantitative fractional anisotropy (DTI-FA).MethodsSubjects of two different age groups (young=12, elderly=12) were included. MR - GE Signa Horizon - 1.5T scans were performed. Cases with Fazekas scores =3 were assessed on FLAIR sequence. Standard parameters for DTI-FA were used. ROIs were placed at various sites of the subcortical white matter, and the genu and splenium of the midline corpus callosum. Analysis was performed using Functool. Statistics for anterior and posterior white matter, as well as the genu and splenium were compared between the groups. The study was approved by the Ethics Committee of IPUB-UFRJ and informed consent obtained.ResultsDTI-FA showed lower anisotropy values in the anterior region (subcortical white matter and genu), but not in the posterior region (subcortical white matter and splenium), in elderly normal subjects compared to young subjects.ConclusionThe results may represent loss of integrity of anterior (frontal) white matter fibers in the elderly subjects. These fibers constitute important intra- and inter-hemispheric tracts, components of neural networks that provide cognitive, behavioral, motor and sensory integration. The loss of integrity of the anterior segments of the studied fiber systems with ageing, represents a disconnection process that may underlie clinical manifestations found in elderly subjects such as executive dysfunction.
Highlights
To study the integrity of hemispheric subcortical white matter by comparing normal young and elderly subjects using quantitative fractional anisotropy (DTI-FA)
The diffusion tensor imaging (DTI)-FA values for the genu, but not the splenium, were significantly lower in the elderly in comparison to the young group
The inter-sample measures of the anterior subcortical white matter, showed significantly lower anisotropy in the elderly compared to the young group
Summary
Abstract – To study the integrity of hemispheric subcortical white matter by comparing normal young and elderly subjects using quantitative fractional anisotropy (DTI-FA). Conclusion: The results may represent loss of integrity of anterior (frontal) white matter fibers in the elderly subjects These fibers constitute important intra- and inter-hemispheric tracts, components of neural networks that provide cognitive, behavioral, motor and sensory integration. The most widely used measure of anisotropy is DTIFA that allows quantification, where the values obtained represent an average of the sampled fibers in a given region of interest (ROI) It is a highly sensitive but fairly nonspecific biomarker of neuropathology and microstructural architecture of white matter and is generally considered a marker of its integrity.[8,9] Several studies demonstrated that the organization of white matter fiber bundles is the basis for DTI-FA. Analysis of lesions identified by neuroimaging and verified neuropathologically has shown that low DTI-FA values are indicative of axonal damage and demyelination.[8,9] analysis of regions visually identified as unaffected, may show similar derangement of the microarchitecture of the white matter.[11,12] Changes may be seen upon comparing brains of younger with older subjects, showing the effect of age on white matter.[5,6]
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