This study investigates the patho-physiological implications of the uncinate fasciculus (UF) in the two most
common forms of dementia, namely Alzheimer’s disease (AD) and dementia with Lewy bodies (DLB). Forty-five consecutive
patients diagnosed with either probable AD or DLB, and 16 individuals with amnesic mild cognitive impairment
(a-MCI) were investigated using diffusion tensor MRI. Thirteen healthy subjects (HS) were also studied as controls. In
each subject, the UF was bilaterally reconstructed by probabilistic tractography. From each UF, macroscopic volume and
correspondent fractional anisotropy (FA) (an index of microscopic white matter integrity) were derived for the whole
tract, and for the frontal and temporal portion of the UF. No significant between-group volumetric differences were found.
In contrast, FA values from the UF were reduced bilaterally in patients with dementia (either AD or DLB) compared to
HS. In addition, patients with AD showed reduced FA values compared to those with a-MCI. No significant FA difference
was found between AD and DLB patients, nor between a-MCI and HS. Finally, in all patients, UF FA values were associated
with neuropsychological scores at tests exploring memory and executive functions. This study indicates that the UF is
remarkably damaged in patients at the stage of dementia, independently from the diagnostic form. Moreover, this UF
damage seems to be driven by temporal involvement in AD, for which a prodromal stage (a-MCI) is defined.
Keywords: Uncinate fasciculus, Alzheimer’s disease, Mild cognitive impairment, Dementia with Lewy bodies, Diffusion tensor
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