Objective: Using diffusion tensor imaging (DTI) data of healthy volunteers and patients with Parkinson’s disease (PD) with and without mild cognitive impairment (MCI),  we search the change of the medial structure in PD patients.

Background: The main pathological target of Parkinson’s disease (PD) is the dopaminergic projection to the basal ganglia. Up-regulation of the midline structure (e.g. medial prefrontal cortex, cingulate cortex and precuneus (aPrC)) is repeatedly reported [1, 2].  There may also exists up-regulation of microstructure, measured by DTI, in the area.

Method: Participants: PD without mild cognitive impairment (PD-nonMCI, n = 20, age 59.4 ± 5.0). PD with mild cognitive impairment (PD-MCI, n = 19, age 63.0 ± 5.1). Healthy volunteers (HV, n = 16, age; 61.8 ± 5.5).  Methods:  All the participants underwent DTI, and fractional anisotropy (FA), mean diffusivity (MD) and radial diffusivity (RD) images, as well as tractography were created [3, 4]. With four regions of interests located in the anterior cingulate area, posterior cingulate area, and anterior and posterior parts of precuneus (aPrC and pPrC), individual FA, MD and RD were measured and compared among the groups.  Correlation analysis between FA and cognitive scores (measured by Brixton representing executive function, and RAVLT representing memory function), were calculated, in PD and HV, respectively.  Further, the numbers of tract passing the PrC toward to the dorsal and ventral cingulum bundles, and toward to the paracentral area directly, were counted [5], and correlation rates were calculated with the FA, in PD and HV, respectively.

Results: The FA in the aPrC was increased in the PD-nonMCI, compared to the HV.  The MD and RD in the region were increased in the PD-MCI compared to PD-nonMCI.  The FA in the region was correlated with the RAVLT scores in HV, whereas the FA was correlated with the Brixton in PD patients. The FA in aPrC was correlated with the number of the dorsal cingulum bundle in PD, but not in HV.

Conclusion: The increased connection in the in the aPrC may support cognition, especially in executive function, in PD patients.  The increased FA is associated with connection to the cingulum bundle, plausibly supporting information transfer from the posterior area to the anterior area compensating the dysfunction of the basal ganglia.

References: [1] Nagano-Saito et al, 2004. Cognitive- and motor-related regions in Parkinson’s disease: FDOPA and FDG PET studies. [2] Nagano-Saito et al, 2016. Patterns of longitudinal neural activity linked to different cognitive profiles in Parkinson’s disease. [3] Grayfallidis et al, 2015. Dipy, a library for the analysis of diffusion MRI data. [4] Côté et al, 2013. Tractometer: Toward validation of tractography pipelines. [5] Wassermann et al, 2016. The white matter query language: a novel approach for describing human white matter anatomy.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/increased-fractional-anisotropy-in-precuneus-in-parkinsons-disease-without-mild-cognitive-impairment-a-diffusion-tensor-imaging-study/