93 It is likewise unclear if either measure is a better predictor of risk for selleck inhibitor subsequent decline.88,91 Structural MRI studies have begun to examine medial temporal lobe volumes as predictors of MCI. An earlier study of highly functioning cognitively normal subjects found baseline measurements of hippocampal size to predict subsequent changes in memory performance and the development of MCI.94 More Inhibitors,research,lifescience,medical contemporary studies have analyzed scans at two or more time points to calculate volumetric rates of change.95-98 These studies confirm that higher rates of atrophy affecting medial temporal

lobe structures can predict longitudinal cognitive decline and the emergence of MCI. Such results also highlight the potential for using structural MRI as outcome measures in pharmacological trials targeting MCI Inhibitors,research,lifescience,medical subjects. At

present, however, it is uncertain whether neuropsychological decline can be more robustly detected over a shorter time interval than structural radiographical change. Functional imaging Functional imaging research in MCI has included studies using positron emission tomography pgx), single Inhibitors,research,lifescience,medical photon emission computed tomography (SPECT), functional magnetic resonance imaging (fMRI), and magnetic resonance spectroscopy (MRS). Positron emission tomography PET studies using the radiotracer 2-deoxy-2[18F]fluoro-D-glucose (18FDG)

have been employed for Inhibitors,research,lifescience,medical over 20 years to study regional rates of glucose utilization in the brain. AD patients tend to exhibit characteristic metabolic reductions in the temporal and parietal association cortices99-101; a distribution that coincides with the neuropathological distribution of AD pathology FDG studies in patients with MCI have demonstrated similar topographic patterns, as well as metabolic reductions in the posterior cingulate gyrus.102-106 Subjects at high genetic risk for AD (due to apolipoprotein E4 [ApoE-4] homozygocity) also exhibit glucose utilization Inhibitors,research,lifescience,medical reductions in regions similar to those that become involved in AD.107 Evidence is conflicting concerning the presence of metabolic reductions within the medial temporal anatomy affected in early AD. Some groups have not found differences,108 while others have reported either decreased glucose utilization rates affecting the hippocampus and other limbic structures including the mammilary bodies, amygdala, and medial thalamus.109,110 One study found metabolic reductions within the entorhinal cortex to be associated with longitudinal decline to MCI and AD.111 These studies, however, draw their conclusions from small samples and purport to measure structures that challenge the spatial resolving power of the equipment.

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