IC-P1-009: Patterns of cerebral hypoperfusion in amnestic and dysexecutive MCI subgroups

Abstract

Background: Few studies on mild cognitive impairment (MCI) have examined non-amnestic MCI patients. The objective of this study was to compare MRI measurements of resting state cerebral perfusion in two subgroups of MCI patients. Specifically, patients with dysexecutive MCI (dMCI), operationally defined as individuals with report of recent onset of dysexecutive symptoms (e.g., attention, multi-tasking, behavior) and/or had impaired scores on executive, but not memory, measures (N 17), patients with amnestic MCI (aMCI), who had impaired memory, but not executive function (N 18), and cognitively normal elderly controls (N 25). Methods: All subjects underwent arterial spin-labeling and structural MR imaging. Perfusion images were analyzed on a voxel-by-voxel basis and thresholded at an uncorrected voxel-level p-value of 0.001 and a cluster size of 10 voxels with SPM2. Results: Relative to controls, dMCI patients showed hypoperfusion in the right middle frontal cortex, while aMCI patients showed hypoperfusion in the left middle frontal cortex and right precuneus. Compared to dMCI, aMCI patients showed hypoperfusion in the right precuneus and middle cingulum bilaterally. Compared to aMCI, dMCI patients showed hypoperfusion in the right frontal lobe, near the precentral gyrus when we used a more liberal voxel-level threshold of p 0.003. We also examined correlations between cognition, function, and resting state cerebral perfusion. Better Trail-making scores (a measure of executive function) correlated with greater resting state cerebral perfusion in the middle frontal cortex, bilaterally in controls, in the precentral gyrus in aMCI patients, and in the left cuneus and right parietal cortex in dMCI patients. Lower scores on the Functional Activities Questionnaire (indicating less functional dependence) correlated with greater resting state perfusion in the right postcentral gyrus, left inferior and superior frontal cortex in aMCI patients and in the right cuneus, left precuneus, and right superior temporal lobe in dMCI patients. Conclusions: The finding that aMCI and dMCI patients exhibited different spatial patterns of cerebral hypoperfusion supports the existence of two distinct subgroups of MCI. Furthermore, these results suggest that resting cerebral perfusion in the less affected brain regions (i.e., frontal cortex in aMCI, posterior cortex in dMCI) is related to cognition and function in MCI patients.