Patterns of cerebral hypoperfusion in amnestic and dysexecutive MCI.

Although early studies on mild cognitive impairment (MCI) focused on memory dysfunction; more recent studies suggest that MCI is clinically heterogeneous. The objective of this study is to examine patterns of cerebral perfusion in anmestic (N=12) and nonamnestic (N=12) single-domain MCI patients from 4 a priori regions of interest: middle and superior frontal cortex, posterior cingulate, and precuneus, to compare them relative to healthy controls (N=12), and to correlate perfusion with neuropsychologic measures. Relative to controls, all MCI patients had hypoperfusion in the posterior cingulate, bilaterally. MCI patients with executive dysfunctions also showed hypoperfusion in bilateral middle frontal cortex and the left precuneus relative to controls and in the left middle frontal cortex, left posterior cingulate, and left precuneus relative to amnestic MCI patients. Perfusion in the posterior cingulate correlated positively with memory performance whereas perfusion in all 4 a priori regions of interest, predominantly on the left side, correlated with executive function performance. The finding that single-domain MCI patients with prominent deficits in different cognitive domains exhibited different patterns of hypoperfusion relative to controls supports the existence of distinct subgroups of MCI. These data further suggest that cognitive impairment in MCI is related to cerebral hypoperfusion.