Amyloid involvement in subcortical regions predicts cognitive decline

Area of Science:

• Neuroscience
• Neurology
• Radiology

Background:

• Amyloid-beta (Aβ) deposition is a hallmark of Alzheimer's disease (AD).
• Subcortical amyloid involvement is increasingly recognized but its predictive value for cognitive impairment remains under investigation.
• Understanding the pattern of amyloid spread is crucial for developing accurate staging and prognostic tools.

Purpose of the Study:

• To determine if amyloid involvement in subcortical brain regions predicts cognitive impairment.
• To establish a novel amyloid staging scheme based on the extent of subcortical amyloid deposition.
• To investigate the relationship between amyloid staging and cognitive/neuroimaging markers of AD progression.

Main Methods:

• Utilized data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) including cognitively normal individuals, participants with mild cognitive impairment (MCI), and those with Alzheimer's disease (AD).
• Assessed amyloid deposition in key subcortical structures: amygdala, putamen, and caudate nucleus using PET imaging.
• Developed a 3-stage amyloid staging model (Stage 0, 1, 2) incorporating both cortical and subcortical amyloid involvement.

Main Results:

• Amyloid accumulation followed a downward pattern, initiating in cortical regions and subsequently spreading to subcortical structures.
• Longitudinal analyses revealed significantly steeper cognitive decline (MMSE, ADAS-cog 13), brain metabolism reduction (FDG PET SUVR), and hippocampal atrophy in higher amyloid stages (Stage 2 > Stage 1 > Stage 0).
• Stage 2 participants exhibited the most rapid progression in cognitive scores, brain metabolism, and hippocampal volume loss compared to Stage 1.

Conclusions:

• Amyloid deposition exhibits a characteristic downward spread from neocortex to subcortical regions.
• The proposed amyloid staging scheme, incorporating subcortical involvement, effectively predicts cognitive decline.
• This staging system offers insights into how regional amyloid accumulation influences cognitive impairment through brain structural and functional changes.