Thalamic projection fiber integrity in de novo Parkinson’s disease
Background and Purpose: Post-mortem studies of advanced Parkinson’s disease (PD) have revealed disease-related pathology in the thalamus with an apparent predilection for specific thalamic nuclei. In the present study, we used diffusion tensor imaging (DTI) to investigate in vivo the microstructural integrity of six thalamic regions in de novo PD patients relative to healthy controls.
Materials and Methods: Forty subjects (20 with early-stage, untreated PD and 20 age- and sex-matched controls) were studied with a high-resolution DTI protocol at 3 Tesla to investigate the integrity of thalamic nuclei projection fibers. Two blinded, independent raters drew regions of interest (ROIs) in the following six thalamic regions: anterior nucleus (AN), ventral anterior nucleus (VA), ventral lateral nucleus (VL), dorsomedial nucleus (DM), ventral posterior lateral nucleus (VPL)/ventral posterior medial nucleus (VPM), and pulvinar (PU). Fractional anisotropy (FA) values were then calculated from the projection fibers in each region.
Results: FA values were reduced significantly in the fibers projecting from the AN, VA, and DM, but not the VPL/VPM and PU, in the PD group compared to the control group. In addition, there was a reduction in FA values that approached significance in the VL of PD patients. These findings were consistent across both raters.
Conclusion: The present study provides preliminary in vivo evidence of thalamic projection fiber degeneration in de novo PD and sheds light on the extent of disrupted thalamic circuitry as a result of the disease itself.