P2-178: Hippocampal and white matter changes in MCI patients according to the presence or the absence of subcortical vascular changes

Abstract

Mild cognitive impairment(MCI) refers to a transitional state between normal aging and dementia, and it is clinically heterogeneous. Although most imaging studies of MCI have focused on gray matter alterations, many MCI patients have subcortical vascular disease on magnetic resonance imaging(MRI) scan. However it is not known whether these findings are associated with the cognitive dysfunction. Diffusion tensor imaging(DTI) detects the microstructural alterations in white matter by measuring the directionality of molecular diffusion. We investigated the alterations of white matter as well as hippocampus in MCI patients according to the presence or the absence of subcortical vascular disease by using DTI, and compared the differences between two groups. Forty consecutive patients with memory complaints, at least one neuropsychological memory test below 1.5 standard deviation of the normal for age and education, and maintained activities of daily living, were included. 21 patients with MCI had no ischemic lesions and 19 patients were found to have subcortical vascular changes, by the Erkinjuntti's imaging criteria. For 21 non–vascular MCI(nvMVI), 19 vascular MCI(vMCI) and 17 controls, mean diffusivity(MD) and fractional anisotropy(FA) were measured in the bilateral temporal, frontal, parietal and occipital white matter regions as well as in the bilateral hippocampi, sentrum semiovale and the corpus callosum (genu and splenum), and the differences were compared by analysis of variance and multiple comparison. All patients with MCI, both vascular and non–vascular, showed decreased FA and increased MD values in the other regions except occipital white matter, compared to the controls. For the FA, both types of MCI patients had decreased FA values in the corpus callosum, frontal and temporal regions, compared to the controls. In the parietal areas and centrum semiovale, vMCI patients had more decreased FA values than nvMCI patients and the controls. In the hippocampus, FA values were lowest in the nvMCI patients. FA values of vMCI patients were also significantly lower than the controls. The findings of region–specific MD increases were similar to those of FA. The DTI can be a useful tool to quantify MCI pathology in vivo, and to evaluate the alterations of intracerebral microstructure.