Mild cognitive impairment and Alzheimer disease: Regional diffusivity of water

PURPOSE: To compare the regional diffusivity of water in the brains of norm ally aging elderly people and patients with mild cognitive impairment (MCI) or Alzheimer disease. MATERIALS AND METHODS: Magnetic resonance images were obtained in 21 patien ts with Alzheimer disease, 19 patients with MCI, and 55 normally aging elde rly control subjects without evidence of cognitive impairment. Regions of i nterest were drawn to compare the apparent diffusion coefficient (ADC) and the anisotropy index (Al) in frontal, parietal, temporal, occipital, anteri or, and posterior cingulate white matter (WM), and the thalami and hippocam pi. RESULTS: Hippocampal ADC was higher in MCI and Alzheimer disease patients t han in control subjects. ADC of the temporal stem and posterior cingulate, occipital, and parietal WM was higher in Alzheimer disease patients than in control subjects. Except for occipital Al, which was lower in MCI patients than in control subjects, there were no differences in Al among the three groups for any of the regions. CONCLUSION: Hippocampal ADC was significantly different between control sub jects and MCI patients, many of whom likely have preclinical Alzheimer dise ase. Elevation in hippocampal ADC may reflect early ultrastructural changes in the progression of Alzheimer disease.