Brain Imaging Abnormalities in Mixed Alzheimer's and Subcortical Vascular Dementia
Hyunwoo Lee1, Vanessa Wiggermann2, Alexander Rauscher2
1Division of Neurology, Department of Medicine, University of British Columbia, Vancouver, BC, Canada.
Background:
A large proportion of Alzheimer's disease (AD) patients have coexisting subcortical vascular dementia (SVaD), a condition referred to as mixed dementia (MixD). Brain imaging features of MixD presumably include those of cerebrovascular disease and AD pathology, but are difficult to characterize due to their heterogeneity.
Objective:
To perform an exploratory analysis of conventional and non-conventional structural magnetic resonance imaging (MRI) abnormalities in MixD and to compare them to those observed in AD and SVaD.
Methods:
We conducted a cross-sectional, region-of-interest-based analysis of 1) hyperintense white-matter signal abnormalities (WMSA) on T2-FLAIR and hypointense WMSA on T1-weighted MRI; 2) diffusion tensor imaging; 3) quantitative susceptibility mapping; and 4) effective transverse relaxation rate (R2*) in N = 17 participants (AD:5, SVaD:5, MixD:7). General linear model was used to explore group differences in these brain imaging measures.
Results:
Model findings suggested imaging characteristics specific to our MixD group, including 1) higher burden of WMSAs on T1-weighted MRI (versus both AD and SVaD); 2) frontal lobar preponderance of WMSAs on both T2-FLAIR and T1-weighted MRI; 3) higher fractional anisotropy values within normal-appear white-matter tissues (versus SVaD, but not AD); and 4) lower R2* values within the T2-FLAIR WMSA areas (versus both AD and SVaD).
Conclusion:
These findings suggest a preliminary picture of the location and type of brain imaging characteristics associated with MixD. Future imaging studies may employ region-specific hypotheses to distinguish MixD more rigorously from AD or SVaD.
Insights
Mixed dementia (MixD) shows distinct brain imaging features, including a higher white-matter signal abnormality burden and frontal lobe prevalence. These findings help differentiate MixD from Alzheimer's disease and vascular dementia.
Area of Science:
- Neuroimaging
- Neurology
- Radiology
Background:
- Alzheimer's disease (AD) often co-occurs with subcortical vascular dementia (SVaD), forming mixed dementia (MixD).
- Brain imaging in MixD is complex due to the heterogeneity of AD and cerebrovascular pathologies.
- Characterizing MixD's unique imaging profile is crucial for accurate diagnosis.
Purpose of the Study:
- To explore conventional and non-conventional structural MRI abnormalities in MixD.
- To compare these imaging features against those in AD and SVaD.
- To identify potential imaging biomarkers for differentiating MixD.
Main Methods:
- Cross-sectional, region-of-interest analysis of 17 participants (AD:5, SVaD:5, MixD:7).
- Utilized T2-FLAIR and T1-weighted MRI for white-matter signal abnormalities (WMSA).
- Employed diffusion tensor imaging, quantitative susceptibility mapping, and R2* relaxometry.
Main Results:
- MixD exhibited a higher WMSA burden on T1-weighted MRI compared to AD and SVaD.
- WMSAs showed a frontal lobar preponderance in MixD on both T2-FLAIR and T1-weighted MRI.
- MixD had higher fractional anisotropy in normal-appearing white matter and lower R2* in WMSA areas compared to SVaD and AD.
Conclusions:
- Preliminary imaging characteristics for MixD have been identified.
- Findings suggest specific patterns of white-matter abnormalities and tissue properties in MixD.
- Future research should focus on region-specific hypotheses for rigorous MixD differentiation.
