Diffusion tensor imaging of cingulum fibers in mild cognitive impairment and Alzheimer disease

TLDR

Neuroimaging in mild cognitive impairment and Alzheimer disease typically shows medial temporal lobe atrophy and reduced glucose metabolism and cerebral blood flow in the posterior cingulate gyrus. The study seeks to determine whether MCI and AD are associated with diffusion tensor imaging abnormalities in the cingulum fibers, whether white matter changes extend to the corpus callosum, and whether adding DTI improves accuracy in distinguishing AD and MCI from healthy aging. DTI and structural MRI were performed on 17 AD patients, 17 MCI patients, and 18 cognitively normal controls. Fractional anisotropy was significantly reduced in the cingulum fibers of MCI and more so in AD, was also reduced in the splenium of the corpus callosum only in AD, and adding DTI to hippocampal volume improved discrimination of MCI and AD from cognitively normal subjects.

Abstract

<b>Background: </b> Neuroimaging in mild cognitive impairment (MCI) and Alzheimer disease (AD) generally shows medial temporal lobe atrophy and diminished glucose metabolism and cerebral blood flow in the posterior cingulate gyrus. However, it is unclear whether these abnormalities also impact the cingulum fibers, which connect the medial temporal lobe and the posterior cingulate regions. <b>Objective: </b> To use diffusion tensor imaging (DTI), by measuring fractional anisotropy (FA), to test 1) if MCI and AD are associated with DTI abnormalities in the parahippocampal and posterior cingulate regions of the cingulum fibers; 2) if white matter abnormalities extend to the neocortical fiber connections in the corpus callosum (CC); 3) if DTI improves accuracy to separate AD and MCI from healthy aging vs structural MRI. <b>Methods: </b> DTI and structural MRI were preformed on 17 patients with AD, 17 with MCI, and 18 cognitively normal (CN) subjects. <b>Results: </b> FA of the cingulum fibers was significantly reduced in MCI, and even more in AD. FA was also significantly reduced in the splenium of the CC in AD, but not in MCI. Adding DTI to hippocampal volume significantly improved the accuracy to separate MCI and AD from CN. <b>Conclusion: </b> Assessment of the cingulum fibers using diffusion tensor imaging may aid early diagnosis of Alzheimer disease.