Generalized Q-sampling Imaging-based Fiber Tracking Measures in White Matter Pathways Associated with Speech Impairment in Parkinson's Disease: An Analysis of Sex Effects

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Co-authors:

Alpen Ortug - Massachusetts General Hospital, Harvard Medical School

Abstract Body : Parkinson’s disease (PD) is a progressive neurodegenerative disorder affecting multiple systems, with severity often linked to age of onset. Men, who are twice as likely as women to be affected, tend to experience more severe and faster-progressing symptoms. Speech disorders are prevalent in up to 89% of PD patients due to motor and nonmotor deficits. This study focuses on the frontal aslant tract (FAT) and Arcuate fasciculus (AF), critical white matter pathways related to verbal fluency. While prior studies have explored white matter microstructure alterations in PD using diffusion-weighted imaging, FAT and AF diffusion metrics have not been assessed. Our study, utilizing Generalized Q-sampling Imaging (GQI), aims to map these pathways, explore white matter diffusivity differences in PD, and compare sex effects and verbal fluency test measures. We have included publicly available diffusion-weighted images (DWI) of 27 PD patients (Age: 64 ± 8, 14 M, 13F) and 26 age (66± 8, 14 M, 12F), sex, and education-matched control subjects. Details about the protocol of MRI acquisition and demographics can be reviewed on the official webpage of Parkinson’s Disease Datasets (https://www.nitrc.org/projects/parktdi/). We used high-quality diffusion-weighted images (120 gradient directions, b = 2500 s/mm2) with a Generalized Q-sampling Imaging (GQI) model (DSI Studio software) for the reconstruction of the white matter pathways. We used the Automatic Fiber Tracking (AutoTrack) option for the virtual dissection of the AF and FAT in DSI Studio software. The anatomical accuracy of the tracts was quality-checked and decided not to interfere manually with any of the AutoTrack results. Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), quantitative anisotropy (QA), and track volume measures were obtained and analyzed. The mean verbal fluency test results were as follows: (Letters: F PD 37 ± 8, F Control 38± 10; M PD 34 ± 8, M Control 42 ± 8), (Categories: F PD 46 ± 10, F Control 51± 10; M PD 43 ± 8, M Control 46± 10). We observed a significant decrease in left FAT volume in male PD subjects compared to controls, along with significantly lower quantitative anisotropy (QA) in the bilateral FAT and left AF in the male PD group. QA, reflecting the degree of anisotropy in diffusion, is associated with axonal density and decreases with axonal loss. Our preliminary results suggest a more severe impact on the microstructure of the FAT in male PD subjects. However, there was no correlation between verbal fluency test measures and QA. Future studies could expand the subject group, incorporating structural and functional imaging data while exploring laterality findings.