Purpose:
The aim of this study was to investigate the differences in early (EOAD) and
late (LOAD) onset of Alzheimer ́s disease, as well as glucose uptake, regional cerebral blood flow
(R1), amyloid depositions, and functional brain connectivity between normal young (YC) and Old
Controls (OC).
Methodology:
The study included 22 YC (37 ± 5 y), 22 OC (73 ± 5.9 y), 18 patients with EOAD (63 ± 9.5 y), and 18 with LOAD (70.6 ± 7.1 y). Patients underwent FDG and PIB PET/CT. R1 im-
ages were obtained from the compartmental analysis of the dynamic PIB acquisitions. Images were
analyzed by a voxel-wise and a VOI-based approach. Functional connectivity was studied from the
R1 and glucose uptake images.
Results:
OC had a significant reduction of R1 and glucose uptake compared to YC, predominantly
at the dorsolateral and mesial frontal cortex. EOAD and LOAD vs. OC showed a decreased R1 and
glucose uptake at the posterior parietal cortex, precuneus, and posterior cingulum. EOAD vs.
LOAD showed a reduction in glucose uptake and R1 at the occipital and parietal cortex and an in-
creased at the mesial frontal and temporal cortex. There was a mild increase in an amyloid deposi-
tion at the frontal cortex in LOAD vs. EOAD. YC presented higher connectivity than OC in R1 but
lower connectivity considering glucose uptake. Moreover, EOAD and LOAD showed a decreased
connectivity compared to controls that were more pronounced in glucose uptake than R1.
Conclusion:
Our results demonstrated differences in amyloid deposition and functional imaging be-
tween groups and a differential pattern of functional connectivity in R1 and glucose uptake in each
clinical condition. These findings provide new insights into the pathophysiological processes of
AD and may have an impact on patient diagnostic evaluation.