A future for PET imaging in Alzheimer's disease.

Three well-established neuroimaging markers are now included in the revised criteria for amnestic (typical) forms of Alzheimer's disease [[5]]: hippocampal atrophy assessed by MRI, temporoparietal hypometabolism shown by FDG-PET, and increased brain amyloid deposition using fibrillar amyloid PET. Can molecular PET imaging help to evidence the phenotypic diversity of Alzheimer's disease and reveal if and how the regional distribution of the pathological -amyloid and tau proteins explain the clinical expression of Alzheimer's disease? So far, amyloid PET studies of typical or atypical early-onset of Alzheimer's disease patients have shown diffuse cortical -amyloid deposits, regardless of the clinical presentation, and have not demonstrated a correlation between the cognitive profile, metabolic changes, and the distribution of the pathological protein. Importantly, the work of Sala et al. emphasizes that, although it is less specific for Alzheimer's disease than "pathophysiological" tracers (i.e., those targeting tau and amyloid), the easily accessible FDG is a powerful and efficient diagnostic tool for the diagnosis of amnestic and atypical Alzheimer's disease, even in prodromal phases. [Extracted from the article]