Asymmetric Amyloid Deposition as an Early Sign of Progression in Mild Cognitive Impairment Due to Alzheimer Disease.

PURPOSE In typical Alzheimer disease with dementia (ADD), amyloid pathologies affect both cerebral hemispheres symmetrically. However, the spatial distribution of amyloid-β (Aβ) in the early stage of ADD or over the course of disease has not been investigated. Therefore, we explored asymmetric pattern of Aβ deposition in both hemispheres according to the ADD continuum using 18F-florbetaben PET. METHODS Sixty-eight subjects, including 15 Aβ-negative normal controls, 28 Aβ-positive mild cognitive impairment (Aβ+ MCI), and 25 Aβ-positive ADD (Aβ+ ADD) subjects, were enrolled. Differences in the asymmetry index and SUV ratio in each of the 6 target regions (4 cortical lobes, cingulate, precuneus) plus composite region between groups were explored. RESULTS The composite and target regional asymmetry indices were significantly different between groups and was highest in Aβ+ MCI (composite, occipital, and temporal, P < 0.001; frontal, P = 0.004). The composite and target regional SUV ratios were significantly different according to 3 groups with gradual increase and were highest in Aβ+ ADD (composite and all target regions, P < 0.001). CONCLUSIONS The asymmetric pattern of amyloid deposition was distinct between Aβ-negative normal controls and Aβ+ MCI. This pattern disappeared as the disease progressed. These data indicate that asymmetric amyloid deposition may be an early sign of MCI over the course of ADD.