Alzheimer's Imaging Consortium

Area of Science:

• Neuroimaging
• Neuropathology
• Vascular Neurology

Background:

• Atherosclerosis of the Circle of Willis (ACW) frequently co-occurs with Alzheimer's disease (AD).
• Understanding ACW's influence on AD-related neurodegeneration is crucial for developing effective disease-modifying treatments.
• Investigating ACW's impact on cortical microstructural changes can refine diagnostic precision for combined pathologies.

Purpose of the Study:

• To assess the impact of Atherosclerosis of the Circle of Willis (ACW) severity on cortical microstructural changes in Alzheimer's disease (AD).
• To identify potential cortical patterns indicative of combined vascular and neurodegenerative pathologies.
• To explore the utility of diffusion MRI metrics for patient stratification in AD clinical trials.

Main Methods:

• Structural and diffusion MRI data from 58 participants with intermediate/severe Alzheimer's disease neuropathologic change (ADNC) were analyzed.
• Participants were grouped based on ACW severity (none/mild vs. moderate/severe).
• Cortical diffusivity metrics (ParlPD, PerpPD+) were extracted and compared between groups, adjusted for relevant covariates and corrected for multiple comparisons.

Main Results:

• Higher ACW severity was associated with significantly lower ParlPD values in bilateral temporal and occipital regions.
• Lower PerpPD+ values were observed in the left occipital regions in participants with moderate/severe ACW.
• No significant differences were found in demographic, clinical, vascular risk factors, or whole-brain macrostructural MRI data between groups.

Conclusions:

• Cortical diffusivity metrics can detect distinct microstructural changes related to ACW severity in AD.
• These findings support the use of cortical diffusivity for patient stratification in clinical practice and trials.
• This research enhances understanding of combined vascular and neurodegenerative disease impacts on the brain.