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

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.

Can the retina be used to diagnose and plot the progression of Alzheimer's disease?

“…In patients with AD, diffuse tensor imaging shows increase in total diffusivity, radial diffusivity and decreased fractional isotropy in the optic nerves (Nishioka et al 2015). This technique is sensitive and specific and has been used to demonstrate beta-amyloid plaques ex vivo in mouse and human retina and in vitro screening of chemical compounds for amyloidogenesis.…”

Ocular and Visual Manifestation of Alzheimer’s Disease: A Literature Review II Part: Clinical Studies

“…On the other side, Alichniewicz et al (17) found decreased activation in frontal eyes fields, and Jacobs et al (18) found increased activation in the visual pathways of MCI and early AD patients. By using diffusion tension imaging, Nishioka et al (19) demonstrated that the visual pathway from the eyes to the brain is affected both in the MCI and, to a greater extend, in the AD; pathological changes were found mainly in the optic nerves. In a heterogenous series of patients with tau pathology, Rahimi et al (20) found tau deposition both in the optic nerve and in the lateral geniculate nucleus.…”

Glutamine + glutamate level predicts the magnitude of microstructural organization in the gray matter in the healthy elderly

“…doi:10.1017/S1041610219001418 extracellular space enlargement in GM (Elman et al, 2017;Neil et al, 2002). Many previous DTI studies have revealed altered FA and MD even in normal aging (Abe et al, 2008;Benedetti et al, 2006;Garcia-Lazaro et al, 2016), age-related neurodegenerative diseases, such as mild cognitive impairment and Alzheimer's disease (Nesteruk et al, 2016;Nishioka et al, 2015), demyelinating diseases, such as multiple sclerosis (de Kouchkovsky et al, 2016), and neuropsychiatric diseases, such as depression and schizophrenia (Jiang et al, 2017;Singh et al, 2016). Most of these studies have focused on WM or deep GM such as the hippocampus, because these brain regions have high directionality in water diffusion (Manna et al, 2015;Ziyan and Westin, 2008), whereas water diffusion in the cerebral cortex has an isotropic direction at the level of conventional DTI resolution (Elman et al, 2017).…”