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White matter damage in Alzheimer's disease assessed in vivo using diffusion tensor magnetic resonance imaging
M Bozzali1, A Falini, M Franceschi
1Neuroimaging Research Unit, Department of Neuroscience, Scientific Institute and University Ospedale San Raffaele, Milan, Italy.
Objective:
To investigate the extent and the nature of white matter tissue damage of patients with Alzheimer's disease using diffusion tensor magnetic resonance imaging (DT-MRI).
Background:
Although Alzheimer's disease pathology mainly affects cortical grey matter, previous pathological and MRI studies showed that also the brain white matter of patients is damaged. However, the nature of Alzheimer's disease associated white matter damage is still unclear.
Methods:
Conventional and DT-MRI scans were obtained from 16 patients with Alzheimer's disease and 10 sex and age matched healthy volunteers. The mean diffusivity (D), fractional anisotropy (FA), and inter-voxel coherence (C) of several white matter regions were measured.
Results:
D was higher and FA lower in the corpus callosum, as well as in the white matter of the frontal, temporal, and parietal lobes from patients with Alzheimer's disease than in the corresponding regions from healthy controls. D and FA of the white matter of the occipital lobe and internal capsule were not different between patients and controls. C values were also not different between patients and controls for any of the regions studied. Strong correlations were found between the mini mental state examination score and the average overall white matter D (r=0.92, p<0.001) and FA (r=0.78; p<0.001).
Conclusions:
White matter changes in patients with Alzheimer's disease are likely to be secondary to wallerian degeneration of fibre tracts due to neuronal loss in cortical associative areas.
Insights
Alzheimer's disease patients show significant white matter damage, particularly in the corpus callosum and frontal, temporal, and parietal lobes, correlating with cognitive decline.
Area of Science:
- Neuroimaging
- Neuropathology
- Diffusion Tensor Magnetic Resonance Imaging (DT-MRI)
Background:
- Alzheimer's disease (AD) primarily impacts cortical grey matter.
- Evidence suggests white matter integrity is also compromised in AD patients.
- The precise nature of AD-associated white matter damage remains incompletely understood.
Purpose of the Study:
- To quantify and characterize white matter tissue alterations in Alzheimer's disease.
- Utilize diffusion tensor magnetic resonance imaging (DT-MRI) to assess white matter integrity.
- Investigate the relationship between white matter changes and cognitive function in AD.
Main Methods:
- Acquired conventional and DT-MRI scans from 16 AD patients and 10 healthy controls.
- Measured mean diffusivity (D), fractional anisotropy (FA), and inter-voxel coherence (C) in key white matter regions.
- Correlated white matter diffusion metrics with Mini-Mental State Examination (MMSE) scores.
Main Results:
- Elevated mean diffusivity (D) and reduced fractional anisotropy (FA) were observed in the corpus callosum and frontal, temporal, and parietal white matter of AD patients compared to controls.
- No significant differences in D, FA, or coherence (C) were found in the occipital lobe white matter or internal capsule.
- Strong positive correlations were identified between MMSE scores and overall white matter D (r=0.92) and FA (r=0.78).
Conclusions:
- White matter abnormalities in Alzheimer's disease are likely secondary to Wallerian degeneration.
- This degeneration results from axonal loss in fibre tracts connected to affected cortical associative areas.
- DT-MRI reveals widespread white matter damage in AD, linked to cognitive impairment.