Related Experiment Video
Updated: May 27, 2026
Diffusion Tensor Magnetic Resonance Imaging in the Analysis of Neurodegenerative Diseases
Published on: July 28, 2013
Gray Matter Microstructure Measured Using Diffusion Imaging as a Biomarker of Severity in Lewy Body Diseases
Angeliki Zarkali1,2,3,4, Ivelina Dobreva1, Naomi Hannaway1
1Dementia Research Centre, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom.
Background:
Despite widespread cortical involvement in Lewy body diseases, conventional gray matter magnetic resonance imaging (MRI) shows limited sensitivity. Diffusion-weighted MRI-derived microstructural measures have shown utility in Alzheimer's disease, but their application across the Lewy body disease spectrum remains limited.
Objectives:
The goal was to examine gray matter microstructure in 197 participants across the Lewy body disease spectrum (88 Lewy body dementia [LBD], 109 Parkinson's disease, and normal cognition [PD-NC]) and 46 controls.
Methods:
Tissue-weighted neurite density index, tissue-weighted orientation dispersion index, and free water fraction were examined across 200 cortical and 32 subcortical regions. We compared these cross-sectionally between LBD, PD-NC and controls, and longitudinally over 3 years in a subset of 100 patients with Parkinson's disease cognitively intact at baseline. We assess associations with disease severity and plasma p-tau217 levels.
Results:
LBD showed widespread cortical and subcortical increases in free water fraction and, to lesser extent, orientation dispersion compared to controls and PD-NC, despite minimal atrophy and no neurite density differences. In temporoparietal regions, increases in free water fraction and orientation dispersion correlated with cognitive, but not motor, severity, and with plasma p-tau217. Longitudinally, Parkinson's disease patients who developed cognitive impairment showed greater free water fraction increases within bilateral temporal regions, right thalamus, and right caudate.
Conclusions:
Diffusion-derived microstructural measures, particularly free water fraction are sensitive to early and progressive gray matter changes associated with cognitive decline in Lewy body diseases. Findings suggest microstructural disruption without overt neuronal loss and support free water fraction as a potential biomarker for disease staging and progression. © 2026 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.
Insights
Diffusion MRI measures, especially free water fraction, detect early gray matter changes in Lewy body diseases, correlating with cognitive decline. These findings suggest microstructural disruption and support free water fraction as a potential biomarker for disease progression.
Area of Science:
- Neuroimaging
- Neurology
- Biomarker Discovery
Background:
- Conventional MRI shows limited sensitivity to cortical changes in Lewy body diseases.
- Diffusion-weighted MRI measures offer potential for assessing brain microstructure.
Purpose of the Study:
- To investigate gray matter microstructure across the Lewy body disease spectrum using diffusion MRI.
- To compare microstructural changes in Lewy body dementia (LBD) and Parkinson's disease (PD) patients with controls.
- To assess longitudinal changes and associations with clinical severity and biomarkers.
Main Methods:
- Examined tissue-weighted neurite density index, orientation dispersion index, and free water fraction in cortical and subcortical regions.
- Cross-sectional comparisons between LBD, PD-NC (Parkinson's disease with normal cognition), and controls.
- Longitudinal analysis over 3 years in a subset of PD patients.
Main Results:
- Lewy body dementia (LBD) exhibited increased free water fraction and orientation dispersion compared to controls and PD-NC.
- Temporoparietal free water fraction increases correlated with cognitive severity and plasma p-tau217.
- Longitudinally, PD patients who developed cognitive impairment showed greater free water fraction increases in specific brain regions.
Conclusions:
- Diffusion-derived measures, particularly free water fraction, are sensitive to early gray matter changes in Lewy body diseases.
- Findings suggest microstructural disruption precedes overt neuronal loss.
- Free water fraction shows promise as a biomarker for staging and monitoring Lewy body disease progression.
