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Quantitative susceptibility mapping reveals differences between subtypes of Lewy body dementia
Rohan Bhome1,2, George E C Thomas1, Naomi Hannaway1
1Dementia Research Centre, University College London, London WC1N 3AR, UK.
Brain : a Journal of Neurology
|September 4, 2025
Summary
Quantitative susceptibility mapping (QSM) reveals iron differences between Dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD). These findings suggest DLB and PDD are distinct conditions, potentially benefiting from targeted treatments and QSM as a biomarker.
Area of Science:
- Neuroimaging
- Neurology
- Biomarker Discovery
Background:
- Dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD) are subtypes of Lewy body dementia, often viewed on a disease spectrum.
- Conventional MRI lacks sensitivity to differentiate underlying neurobiological processes between DLB and PDD.
- Identifying subtype-specific differences is crucial for developing targeted treatments for Lewy body dementia.
Purpose of the Study:
- To investigate neurobiological differences between DLB and PDD using quantitative susceptibility mapping (QSM).
- To assess the potential of QSM as an imaging biomarker for Lewy body dementia subtypes and disease severity.
- To explore relationships between QSM values, cognitive performance, and overall disease severity.
Main Methods:
- Quantitative susceptibility mapping (QSM) was applied to 66 individuals with Lewy body dementia (45 DLB, 21 PDD), 86 with Parkinson's disease and normal cognition (PD-NC), and 37 healthy controls.
- Voxel-wise and region of interest (ROI) analyses were conducted to compare QSM values across brain regions.
- Relationships between QSM values and clinical measures (cognitive performance, Movement Disorders Society Unified Parkinson's disease Rating Scale) were assessed.
Main Results:
- Individuals with Lewy body dementia exhibited higher QSM values in widespread brain regions compared to PD-NC.
- PDD showed significantly higher QSM values than DLB across numerous brain regions, particularly the substantia nigra pars reticulata.
- Increased QSM values correlated positively with overall disease severity in DLB and PDD patients across several brain areas.
Conclusions:
- QSM detects distinct neurobiological differences, specifically iron deposition patterns, between DLB and PDD.
- DLB and PDD may represent distinct clinical entities, warranting subtype-specific therapeutic strategies and clinical trial designs.
- QSM shows promise as a sensitive imaging biomarker for assessing disease severity and progression in Lewy body dementia clinical trials.
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