Objective: To quantify biomarkers for recently-diagnosed PD patients in the midbrain and their dopaminergic connections to the striatum.

Background: The development of improved PD treatments or even cures is dependent on reliable and sensitive biomarkers. Our lab found that in MRI, the caudal-motor sub-region of the striatum, the most DA-depleted region in PD, was significantly smaller in a random sample of PD patients compared to healthy controls. We aimed to validate this finding in the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) in a sample of recently-diagnosed PD patients. Investigating early-PD patients could develop a sensitive biomarker for PD diagnosis

Method: 21 recently-diagnosed PD patients and 20 age-matched healthy controls were scanned in both 3T and 7T. Diffusion-weighted imaging (DWI) scans were acquired. In 3T and 7T, following preprocessing, the cortex, striatum, SNc, and VTA were segmented according to the CIT168 atlas. The cortex, SNc, and VTA were each parcellated into functionally-derived sub-regions, comprising the limbic, executive, rostral-motor, caudal-motor, parietal, temporal, and occipital sub-regions. To assess SNc and VTA connectivity, probabilistic tractography was performed with seeds in SNc and VTA sub-regions to sub-region targets in the striatum and cortex.

Results: In 3T, no significant volumetric differences were found. However, in the striatum, PD participants had significantly greater left volume lateralization in the caudal motor region compared to controls (CT=0.97, PD=1.29, p=0.023). PDs also had significantly less right mean diffusivity compared to controls (CT=0.915, PD=0.982, p=0.004). A binary logistic regression of these measures and follow-up ROC analysis demonstrated their capacity to distinguish PD from control (AOC=0.76, p=0.0004). In the midbrian, fractional anisotropy (a measurement for connectivity) of the caudal motor region was significantly lower in PDs compared to controls (CT=0.372, PD=0.309, p=0.046). This difference was able to distinguish PD patient from control (AOC=0.728, p=0.011). 7T and other analyses and discussed in terms of their ability to act as biomarkers in PD

Conclusion: Diffusion MRI measures of the striatum and midbrain may have the ability to differentiate early PD from control. This may be able to accurately diagnose PD patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-use-of-diffusion-weighted-imaging-to-detect-structural-biomarkers-in-recently-diagnosed-parkinsons-disease-patients/