Uncinate fasciculus-correlated cognition in Alzheimer's disease: a diffusion tensor imaging study by tractography

Abstract

Background: Neuroimaging studies show increased diffusivity and decreased anisotropy in Alzheimer's disease (AD) patients by diffusion tensor imaging (DTI). Previous reports have analyzed a correlation with cognitive function and DTI parameters, but their results are inconsistent. A reason for this might be a region of interest (ROI) method, used to calculate parameters for DTI, because this method has various usages of how to place a ROI and includes summations of values for various neuronal fiber tracts, resulting in contamination of unintended fibers. To improve the instability with ROI placement, a tractography-based method might be useful. Our coworker reported decreased fractional anisotropy (FA) and increased apparent diffusion coefficient (ADC) of uncinate fasciculus (UF) in patients with AD by tractography. To confirm whether DTI parameter values are related to severity of cognitive function in patients with AD, we measured mean diffusion anisotropy and diffusivity of coregistered voxels along the tracking lines (i.e. tract of interest) of UF. Methods: The subjects were 30 patients with probable AD (NINCDS-ADRDA criteria). Assessment of cognitive function was carried out according to the Mini-Mental State Examination (MMSE) and the Alzheimer's Disease Assessment Scale-cognitive component-Japanese version (ADAS-Jcog). A 1.5-T clinical magnetic resonance unit was used to obtain diffusion tensor images. Diffusion tensors were computed and fiber-tract maps were created using 'dTV II' DTI software developed by Masutani et al. We measured mean FA and ADC values along the bilateral UF. Results: FA values were positively correlated with MMSE score (r = 0.67) and were negatively correlated with ADAS-Jcog score (r = -0.62), while ADC values were negatively correlated with MMSE score (r = -0.58) and were positively correlated with ADAS-Jcog score (r = 0.59). Conclusion: FA and ADC values might reflect the severity of cognitive dysfunction. The tract-of-interest method might be a useful tool for objectively evaluating DTI parameters in AD.

The SORL1 gene and convergent neural risk for Alzheimer’s disease across the human lifespan

“…59 It is important to note, however, that SORL1 is considered an Alzheimer's risk gene, based both on genome-wide analysis and meta-analysis. 14 Furthermore our findings align with previous investigations of regions/tracts that are first affected in early AD and MCI, such as the cingulum bundle, 50, 60 uncinate fasciculus, 61, 62 and corpus callosum. 63 …”

Correlates of virtual navigation performance in older adults

“…Although the function of the uncinate fasciculus is not well understood, it is thought to play a role in episodic memory formation and retrieval (Diehl et al, 2008; Levine et al, 1998). Differences in microstructural integrity of the uncinate fasciculus have been observed in Alzheimer’s disease (Kiuchi et al, 2009; Yasmin et al, 2008; Larroza et al, 2014; Serra et al, 2012), with FA in the bilateral uncinate fasciculus negatively associated with severity of cognitive impairment (Morikawa et al, 2010). While the findings in the present study did not survive correction for family-wise error, they provide suggestive evidence that microstructural differences in the uncinate fasciculus may contribute to age-related spatial navigation impairment.…”

Visualizing Non-Gaussian Diffusion: Clinical Application of q-Space Imaging and Diffusional Kurtosis Imaging of the Brain and Spine

“…Using the full tensor data, fractional anisotropy (FA) can be calculated for the index of the white matter anisotropic properties. These 2 metrics, ADC and FA, are now widely used to diagnose or evaluate disorders of the central nervous system, including stroke, 3 multiple sclerosis, 4 neoplasms, [5][6][7] neuropsychiatric disease, [8][9][10] and degenerative disease [11][12][13][14] in clinical situations. Despite their usefulness, however, FA and ADC have limitations.…”