Orientational changes of white matter fibers in Alzheimer's disease and amnestic mild cognitive impairment

• Published in: Human brain mapping Vol. 42; no. 16; pp. 5397 - 5408
• Main Authors: Zhao, Haichao, Cheng, Jian, Liu, Tao, Jiang, Jiyang, Koch, Forrest, Sachdev, Perminder S., Basser, Peter J., Wen, Wei
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.11.2021
• Subjects: Abnormalities; Aged; Aged, 80 and over; Alzheimer Disease - diagnostic imaging; Alzheimer Disease - pathology; Alzheimer's disease; Amnesia - diagnostic imaging; Amnesia - pathology; amnestic mild cognitive impairment; Anisotropy; Atrophy; Bend properties; Cognitive ability; Cognitive Dysfunction - diagnostic imaging; Cognitive Dysfunction - pathology; Dementia; Diffusion Tensor Imaging; Disease prevention; Female; Fibers; geometric microstructure; Humans; Impairment; Investigations; Male; Medical imaging; Memory; Morphology; Nerve Fibers, Myelinated - pathology; Neurodegenerative diseases; Neuroimaging; orientation change; Pyramidal tracts; Radiation; Substantia alba; Substantia grisea; Thalamus; Ventricle; Ventricles (cerebral); white matter; White Matter - diagnostic imaging; White Matter - pathology; white matter; orientation change; amnestic mild cognitive impairment; Alzheimer's disease; geometric microstructure
• ISSN: 1065-9471; 1097-0193
• DOI: 10.1002/hbm.25628

White matter abnormalities represent early neuropathological events in neurodegenerative diseases such as Alzheimer's disease (AD), investigating these white matter alterations would likely provide valuable insights into pathological changes over the course of AD. Using a novel mathematical framework called “Director Field Analysis” (DFA), we investigated the geometric microstructural properties (i.e., splay, bend, twist, and total distortion) in the orientation of white matter fibers in AD, amnestic mild cognitive impairment (aMCI), and cognitively normal (CN) individuals from the Alzheimer's Disease Neuroimaging Initiative 2 database. Results revealed that AD patients had extensive orientational changes in the bilateral anterior thalamic radiation, corticospinal tract, inferior and superior longitudinal fasciculus, inferior fronto‐occipital fasciculus, and uncinate fasciculus in comparison with CN. We postulate that these orientational changes of white matter fibers may be partially caused by the expansion of lateral ventricle, white matter atrophy, and gray matter atrophy in AD. In contrast, aMCI individuals showed subtle orientational changes in the left inferior longitudinal fasciculus and right uncinate fasciculus, which showed a significant association with the cognitive performance, suggesting that these regions may be preferential vulnerable to breakdown by neurodegenerative brain disorders, thereby resulting in the patients' cognitive impairment. To our knowledge, this article is the first to examine geometric microstructural changes in the orientation of white matter fibers in AD and aMCI. Our findings demonstrate that the orientational information of white matter fibers could provide novel insight into the underlying biological and pathological changes in AD and aMCI. Orientational changes may be partially caused by the expansion of lateral ventricle, white matter atrophy and gray matter atrophy in Alzheimer's disease. The inferior longitudinal fasciculus and uncinate fasciculus may be more vulnerable to breakdown by neurodegenerative brain disorders, thereby resulting in the patients' cognitive impairment in amnestic mild cognitive impairment.