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Amyloid PET imaging in patients with mild cognitive impairment: a 2-year follow-up study
J Koivunen1, N Scheinin, J R Virta
1Turku PET Centre, University of Turku, Turku, Finland.
Background:
Patients with amnestic mild cognitive impairment (MCI) have greater risk of conversion to Alzheimer disease (AD). Increased brain amyloid burden in AD and MCI has been demonstrated with PET using [(11)C] Pittsburgh compound B (PiB) as a tracer.
Objective:
To evaluate change in β-amyloid deposition in with MCI during 2-year follow-up.
Methods:
Patients with MCI and controls were studied with [(11)C] PiB PET, MRI, and neuropsychometry at baseline and these investigations were repeated in patients with MCI after follow-up.
Results:
Those patients with MCI converting to AD during follow-up had greater [(11)C] 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 nonconverters. In converters, there was no significant change in [(11)C] PiB uptake, whereas an increase was seen as compared to baseline in nonconverters in the anterior and posterior cingulate, temporal and parietal cortices, and putamen. Hippocampal atrophy was greater in converters at baseline than in nonconverters, 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 [(11)C] PiB retention changing modestly when conversion to AD occurs. Longer follow-up is needed to determine whether nonconverters would convert to AD later, which would suggest accelerated [(11)C] PiB retention preceding clinical conversion.
Insights
Patients with mild cognitive impairment (MCI) converting to Alzheimer's disease (AD) show increased amyloid deposition. Brain atrophy progresses in both converters and non-converters, but amyloid changes modestly during MCI progression.
Area of Science:
- Neuroimaging
- Neurology
- Alzheimer's Disease Research
Background:
- Mild cognitive impairment (MCI) increases the risk of progression to Alzheimer's disease (AD).
- Amyloid-beta plaque accumulation, a hallmark of AD, can be visualized using PET imaging with tracers like Carbon-11 Pittsburgh compound B ([(11)C] PiB).
Purpose of the Study:
- To assess changes in beta-amyloid deposition in individuals with MCI over a two-year period.
- To investigate the relationship between amyloid burden, brain atrophy, and conversion to AD.
Main Methods:
- [(11)C] PiB PET scans, MRI, and neuropsychological tests were administered at baseline and follow-up in MCI patients.
- Control groups were included for comparison at baseline.
- Analysis focused on [(11)C] PiB retention and hippocampal volume changes.
Main Results:
- MCI patients who converted to AD exhibited higher baseline [(11)C] PiB retention in several brain regions compared to non-converters.
- While converters showed no significant change in [(11)C] PiB uptake, non-converters demonstrated an increase in specific cortical and subcortical areas.
- Hippocampal atrophy was greater at baseline in converters and increased significantly in both groups over time.
Conclusions:
- Amyloid deposition and hippocampal atrophy appear to follow distinct trajectories during MCI evolution towards AD.
- Modest changes in [(11)C] PiB retention accompany significant hippocampal atrophy preceding or during conversion to AD.
- Further longitudinal studies are necessary to determine if non-converters eventually convert, indicating potential preclinical amyloid changes.
