[Neuroimaging in mild cognitive impairment]

Abstract

I summarized the present status of Neuroimaging studies in mild cognitive impairment (MCI). Nation wide multi-center study with regard to single photon emission study had been started 3 year before and it is now going on in a good cooperation of many institute, covering 319 cases. This study was name as J-COSMIC (Japan Cooperative SPECT Study on Assessment of Mild Impairment of Cognitive Function). After one-year follow-up, 30 out of 120 cases were converted to Alzheimer's disease from MCI. Since last year, ADNI (Alzheimer' disease Neuroimaging Initiative) had started in US, very similar to J-COSMIC, but they adopted PET and MRI as the examination tool. The findings based on J-COSMIC is still unclear, but, we can say that the general cognitive evaluation methods such as MMSE is better than WMS-R, which measures the memory function itself with wide variation in each case. Similar to small size previous works, converter from MCI to Alzheimer's disease tended to show hypoperfusion in the parietal and frontal regions. Recent advance in the molecular imaging enabled us to visualize the deposition of amyloid protein in the brain parenchyma. It is still controversial as to application of the early diagnosis of Alzheimer's disease or MCI. S. Minoshima reported the hypometabolism in the early stage of Alzheimer's disease in the posterior cingulate gyrus or precuneus, but it has been still unknown why these areas showed hypoperfusion or hypometabolism in early phase of Alzheimer's disease. We examined the fiber connection of posterior cingulate region with other brain structures using diffusion weighted images. It was very surprising that such kind of small structures had a lot of connections, not only contralateral side, but also, parietal and temporal lobes, as well as anterior cigulate cortex. The function has been still been unclear, but we will be able to disclose their functions in the human brain in the future, which will be helpful for understanding the pathophysiological changes in MCI.