Background: Because of the ongoing development of disease modifying therapies, it is potentially of great
clinical value to identify subjects at a high risk of developing Alzheimer’s disease (AD). Patients with amnestic mild
cognitive impairment (MCI) represent a group of individuals with greater risk of conversion to AD. Increased brain
amyloid burden in AD and MCI has been demonstrated with PET using [11C]PIB.
Objective: To compare levels of beta-amyloid deposition during an approximately 24-month (range 16-39) followup
period in 29 MCI patients, 12 of whom remained MCI and 17 of whom converted to AD, and in 13 healthy
elderly control individuals.
Method: Patients with MCI and controls were studied with [11C]PIB PET, MRI and neuropsychometry at baseline.
These investigations were repeated in MCI patients after follow-up for 24 months.
Results: At group level, patients with MCI had increased [11C]PIB uptake in several cortical regions. Those MCI
patients converting to AD had greater [11C]PIB retention in the posterior cingulate (p=0.020), in the lateral frontal
cortex (p=0.006), in the temporal cortex (p=0.022), in the putamen (p=0.041) and in the caudate nucleus (p=0.025)
as compared to non-converters. In the MCI converters, there was no significant change in [11C]PIB uptake during
the follow-up, whereas [11C]PIB uptake increased as compared to baseline in the MCI non-converters in the
anterior and posterior cingulates, temporal and parietal cortices and in the putamen. Hippocampal atrophy was
greater in MCI converters at baseline than in non-converters, but increased significantly in both groups during
follow-up.
Conclusions: Hippocampal atrophy and amyloid deposition seem to dissociate during the evolution of MCI, the
atrophy increasing clearly and [11C]PIB retention changing modestly when conversion to AD occurs. Future studies
will determine whether the increased [11C]PIB uptake and hippocampal atrophy in MCI non-converts will predict
conversion to AD during longer follow-up.
