Effects of Parkinson’s Disease on Mechanical and Microstructural Properties of the Brain

Abstract Magnetic Resonance Elastography (MRE) is a method capable of mapping the brain’s mechanical properties, however, the microstructural mechanisms responsible for these biomechanical properties remain largely unknown. For this reason, the present study utilized multidimensional diffusion-MRI (MD-dMRI), apart from MRE, to extract microstructural parameters for a cohort of Parkinson’s disease (PD) patients and healthy controls. Significant softening effects in the temporal and occipital lobes in PD were associated with an increase in mean diffusivity, whereas other microstructural properties, e.g. microscopic FA (µFA), largely remained unchanged. Across most regions, stiffness declined with age, which was correlated with a decrease in μFA and an increase in MD. We hypothesize that age softening effects mostly can be explained by neuronal atrophy, whereas PD effects involve additional mechanisms. Competing Interest Statement The authors have declared no competing interest. Funding Statement This research has been partially funded by Häsa, Medicin och Teknik (grant No. 2022-0688), MedTechLabs, Digital Futures, Vinnova through AIDA (project ID: 2319) and the Swedish Research Council (grant No. 2022-03389). Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: We obtained a written informed consent form prior to the participation from all subjects and obtained ethical approval from the Swedish Ethical Review Authority (Dnr. 2022-03209-02). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data availability The MR imaging data in this study are subject to ethical and legal restrictions and cannot be shared publicly, however anonymized data can be made available upon reasonable request to researchers who meet the legal requirements. Please contact the corresponding author for more information.