Differences in cortical perfusion detected by arterial spin labeling in nonamnestic and amnestic subtypes of early-onset Alzheimer's disease.

Objectives: Early-onset Alzheimer's disease (EOAD) begins before the age of 65 and is characterized by a faster clinical course and the frequency of nonamnestic symptoms compared to late onset Alzheimer disease (LOAD). However, the pathophysiological process of EOAD remains unclear. We expected that ASL may show widespread cortical hypoperfusion in EOAD compared to LOAD and in nonamnestic EOAD compared to amnestic EOAD.

Methods: In this study, 26 EOAD patients (16 amnestic and 10 nonamnestic patients), 29 LOAD patients and 12 healthy controls underwent pseudo-continuous ASL and 3D FFE T1 sequences. Statistical comparisons between EOAD, LOAD and control groups were made after surface-based analysis of CBF maps in regressing out the cortical thickness.

Results: ASL showed a more severe hypoperfusion in nonamnestic EOAD patients compared to amnestic EOAD ones, with mean CBF values (± std) of 26.9 (± 3.8) and 46.6 (± 24.1) mL/100 g/min respectively (P = 0.014), located in the bilateral temporo-parietal neocortex, the precuneus, the posterior cingulate cortices (PCC) and frontal lobes. Comparison between EOAD and LOAD patients showed a trend to hypoperfusion in the left parietal lobe, PCC and precuneus in EOAD (P < 0.001 uncorrected).

Conclusions: Different patterns of hypoperfusion between nonamnestic and amnestic EOAD subtypes were identified, with a more severe and extensive hypoperfusion in nonamnestic patients. A trend towards more severe hypoperfusion was detected in EOAD compared to LOAD. Further studies are needed to validate ASL as a potential tool for the distinction of EOAD subtypes and the prediction of the time course of the disease.