Biomarkers.

Area of Science:

• Neuroimaging
• Neurology
• Biomarkers

Background:

• Diffusion tensor imaging (DTI) is a valuable biomarker for assessing white matter integrity in neurodegenerative diseases.
• Previous studies have explored DTI in Alzheimer's disease/mild cognitive impairment (ADMCI), Parkinson's disease (PD), and cerebrovascular disease (CVD), but direct comparisons of white matter microstructure across these etiologies are limited.

Purpose of the Study:

• To characterize and compare white matter tract microstructure among patients with ADMCI, PD, and CVD.
• To investigate the utility of DTI metrics as biomarkers differentiating these neurodegenerative conditions.

Main Methods:

• Utilized DTI and T1 MRI data from the Ontario Neurodegenerative Disease Research Initiative (ONDRI) cohort.
• Reconstructed 39 white matter pathways using FreeSurfer's TRACULA and calculated DTI metrics (FA, MD, AxD, RD).
• Employed multivariate general linear models to assess the impact of diagnosis on DTI metrics across all reconstructed tracts.

Main Results:

• Diagnosis significantly affected all four DTI metrics (FA, MD, AxD, RD) across the white matter tracts.
• Parkinson's disease (PD) patients exhibited higher fractional anisotropy (FA) and lower mean diffusivity (MD), axial diffusivity (AxD), and radial diffusivity (RD) compared to ADMCI and CVD patients.
• Minimal significant differences were observed between ADMCI and CVD participants in white matter microstructure.

Conclusions:

• Parkinson's disease patients demonstrated more preserved white matter microstructural integrity compared to ADMCI and CVD patients.
• Lower FA and higher RD and MD values indicate compromised white matter integrity in ADMCI and CVD.
• Advanced diffusion imaging techniques may be required to detect subtle white matter microstructural alterations in PD.