To analyze brain metabolism by regions measured by Positron Emission Tomography with 18F-fluorodeoxyglucose (PET-FDG) in patients with Mild Cognitive Impairment due to Alzheimer's Disease (MCI-AD) and AD Dementia (ADD), and correlate the regional metabolic values with the severity of neuropsychological clinical variables.

Patients with symptomatic AD usually present alterations in their cerebral metabolism measured by PET-FDG. In the amnesic EA phenotype, the regional differences reported between patients with MCI-AD and ADD have not been consistent. There are no published studies that correlated the metabolic value of each cortical region and the quantification of cognitive performance.

In this cross-sectional study, 24 patients with MCI-AD and 22 ADD were included, all right-handed and PET–PIB positive, matched by sex, age, and education, with differences in different cognitive variables (p<0.01). All were studied with PET-FDG with automated parcellation using the Klein and Tourville atlas. Differences between groups (Anova) were analyzed, and Principal Component (PC) analysis was performed to summarize vectors of higher variability. Vectors were compared through diagnoses and correlated with neuropsychological evaluation.

Patients with ADD showed lower metabolism than patients with MCI-AD(p<0.05) in different regions of interest. Four PCs were identified that summarized 84.77% of the metabolism variability of the cortices analyzed. No significant differences were found in the magnitude of the CP between MCI-AD and ADD patients(p>0.05). The first CP represented the magnitude of global metabolism and correlated with the age of the patients(p=0.04), the second CP weighted negatively frontal and positively occipital metabolism, and correlated negatively with semantic fluency(p=0.02), phonological fluency(p=0.04) and TMT-A(p:0.003). The third CP considered parahippocampal regions and correlated with recognition in verbal episodic memory(p=0.01).

Dimension reduction analysis represents a novel approach to summarize neuroimaging data. In this sample of patients with PET-PIB positive and symptomatic AD, CP extraction demonstrates correlation between regional metabolism and performance in neuropsychological tests.