Difference of the hippocampal and white matter microalterations in MCI patients according to the severity of subcortical vascular changes: neuropsychological correlates of diffusion tensor imaging

OBJECTIVES: Most imaging studies of mild cognitive impairment (MCI) have focused on gray matter alterations, although many MCI patients demonstrate subcortical vascular changes. We investigated the changes of the hippocampal area and various white matter areas in MCI patients with using diffusion tensor imaging (DTI), according to the severity of subcortical vascular changes, and we then correlated the DTI findings with the neuropsychological results. PATIENTS AND METHODS: Among the 40 MCI patients, the 21 non-vascular MCI (nvMCI) and 19 vascular MCI (vMCI) patients were subdivided according to Erkinjuntti's imaging criteria. The mean diffusivity (MD) and fractional anisotropy (FA) were compared in the bilateral temporal, frontal, parietal and occipital white matter regions, as well as in the bilateral hippocampi, centrum semiovale, and the midline genu and splenum of the corpus callosum among the nvMCI and vMCI patients and the 17 controls. The neuropsychological findings were also compared between the subgroups. RESULTS: All the MCI patients showed decreased FA and increased MD in all the regions except the occipital areas. In the parietal regions and centrum semiovale, the vMCI patients had a greater FA decrease than the nvMCI patients and controls. In the hippocampi, the FA was lowest in the nvMCI patients. The memory function in the nvMCI patients was more impaired than that in the vMCI patients. The vMCI patients showed impairment of the visuospatial and frontal executive functions. CONCLUSION: We were able to correlate the microstructural alterations with the neuropsychological findings in the MCI subgroups.