Diffusion Tensor Imaging Reveals Visual Pathway Damage in Patients with Mild Cognitive Impairment and Alzheimer's Disease

Article type: Research Article

Authors: Nishioka, Christopher^a | Poh, Christina^b | Sun, Shu-Wei^{a; c; d; e; *} | for the Alzheimer's Disease Neuroimaging Initiative¹

Affiliations: [a] Neuroscience Graduate Program, University of California, Riverside, CA, USA | [b] Loma Linda University School of Medicine, Loma Linda, CA, USA | [c] Departments of Basic Sciences and Radiation Medicine, School of Medicine, Loma Linda University, Loma Linda, CA, USA | [d] Department of Pharmaceutical Science, School of Pharmacy, Loma Linda University, Loma Linda, CA, USA | [e] Department of Bioengineering, University of California, Riverside, CA, USA

Correspondence: [*] Correspondence to: Shu-Wei (Richard) Sun, PhD, Basic Science, School of Medicine, Loma Linda University, Loma Linda, CA 92354, USA. Tel.: +1 909 558 7115; Cell: +1 314 409 4670; E-mail: rsun@llu.edu.

Note: [1] Data used in preparation of this article were obtained from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database (adni.loni.usc.edu). As such, the investigators within the ADNI contributed to the design and implementation of ADNI and/or provided data but did not participate in analysis or writing of this report. A complete listing of ADNI investigators can be found at: http://adni.loni.usc.edu/wp-content/uploads/how_to_apply/ADNI_Acknowledgement_List.pdf

Abstract: Visual deficits are commonly seen in patients with Alzheimer's disease (AD), but postmortem histology has not found substantial damage in visual cortex regions, leading to the hypothesis that the visual pathway, from eye to the brain, may be damaged in AD. Diffusion tensor imaging (DTI) has been used to characterize white matter abnormalities. However, there is a lack of data examining the optic nerves and tracts in patients with AD. In this study, we used DTI to analyze the visual pathway in healthy controls, patients with mild cognitive impairment (MCI) and AD using scans provided by the Alzheimer's Disease Neuroimaging Initiative (ADNI). We found significant increases in the total diffusivity and radial diffusivity and reductions in fractional anisotropy in optic nerves among AD patients. Similar but less extensive changes in these metrics were seen in MCI patients as compared to controls. The differences in DTI metrics between groups mirrored changes in the splenium of the corpus callosum, which has commonly been shown to exhibit white matter damage during AD and MCI. Our findings indicate that white matter damage extends to the visual system, and may help explain the visual deficits experienced by AD patients.

Keywords: Alzheimer's disease, Alzheimer's Disease Neuroimaging Initiative, diffusion tensor imaging, human, mild cognitive impairment, optic nerve, optic tract, visual pathway

DOI: 10.3233/JAD-141239

Journal: Journal of Alzheimer's Disease, vol. 45, no. 1, pp. 97-107, 2015