Cerebral Hypoperfusion and Hypometabolism Detected by Arterial Spin Labeling MRI and FDG-PET in Early-Onset Alzheimer's Disease

Background and purpose: Early-onset Alzheimer's disease (EOAD) is frequently associated with atypical clinical presentations and its early detection remains a challenging issue. In this study, we used arterial spin labeling (ASL), a noninvasive perfusion MRI sequence, and [(18)F]-FDG-PET to detect the perfusion and metabolic features in patients with EOAD.

Methods: All patients were investigated in the French reference center for young-onset dementia and were assessed by MRI, including a pseudo-continuous ASL (pCASL) sequence, and [(18)F]-FDG-PET. Quantitative analyses and intermodality comparison with correlation analysis were made after data processing including correction of partial volume effects, cortical projection, and specific intensity normalization.

Results: We prospectively included 37 patients with EOAD with a mean age of 58.3 years. The areas of most severe hypoperfusion detected with ASL were located in the parietal lobes, the precuneus, the right posterior cingulate cortex, and the frontal lobes (P < .05). The areas of lowest glucose metabolism detected by [(18)F]-FDG-PET were identified in the temporoparietal cortex and the precuneus (P < .05). Hypometabolic regions were more extensive than hypoperfused regions on ASL maps whereas ASL highlighted alterations in the frontal lobes without apparent hypometabolism on [(18)F]-FDG-PET maps.

Conclusions: ASL and [(18)F]-FDG-PET detected pathological areas of similar distribution mainly located in the inferior parietal lobules and local zones in the temporal cortex in patients with EOAD. Our preliminary study showed that ASL and [(18)F]-FDG-PET may have a complementary role in combination with structural MRI for the assessment of suspected EOAD.