Deterministic Tractography of the Nigrostriatal-Nigropallidal Pathway in Parkinson’s Disease

Abstract

We hypothesized that deterministic tractography is practical and sensitive to changes in the complex nigrostriatal and nigropallidal pathway (NSP) in Parkinson’s disease (PD). Using diffusion tensor imaging (DTI) tractography, we investigated the NSP to evaluate differences between PD patients and controls, and examined their clinico-radiologic correlation. Structural and DTI brain scans were obtained in 40 subjects (21 PD patients and 19 healthy controls). We isolated the NSP using a user-friendly DTI toolkit based on deterministic brute-force tractography. DTI parameters of fractional anisotropy (FA), mean, axial, and radial diffusivity, and streamline count of the NSP were measured. Average FA (p < 0.01) and streamline count (p < 0.001) were significantly lower in the PD compared to control group. Mean diffusivity and radial diffusivity were significantly higher in the PD group (p < 0.05). Average streamline count correlated with the United Parkinson’s Disease Rating Scale motor score (p < 0.05). Point-to-point FA profiles of the tract demonstrated peak divergence between PD and control towards the tract midpoint rather than the distal grey matter. Our findings demonstrated a clinically and radiologically practical application of DTI tractography to the NSP in PD, without requiring complex imaging sequences for anatomical localization or segmentation software.

Diffusion tensor tractography of brainstem fibers and its application in pain

“…The NST is a dopaminergic pathway that is involved in Parkinson's disease. Individual tractography-guided quantitative DTI measures of this tract have been suggested as a promising marker for identifying Parkinson's disease and such measurements may correlate with the severity of motor dysfunction [65][66][67]. NST is also suggested to control depressive fatigue states in Parkinson's Disease [68,69].…”

Neurite orientation dispersion and density imaging of the nigrostriatal pathway in Parkinson's disease: Retrograde degeneration observed by tract-profile analysis

“…Only the b ¼ 0 and 1000 s/mm 2 datasets of the diffusionweighted data were used to generate tractography. To achieve successful visualization of the small fibers, DWIs were subjected to up-sampling with trilinear interpolation to 1 mm 3 resolution in MATLAB (version 7.9.0; The Mathworks, Inc., Natick, MA, USA), based on a published protocol [16,17]. The nigrostriatal tract (as the tract of interest) and the corticospinal tract (CST) (as the control tract) were visualized and analyzed with TrackVis version 0.6.0.1 (http://www.trackvis.org/).…”

“…Earlier, the Diffusion Toolkit version 0.6.3 was used to reconstruct DWIs and generate fiber track data for visualization by TrackVis. The modified fiber assignment by a continuous tracking algorithm was used to obtain optimal visualization of the tract, with an FA threshold of 0.2, angle threshold of 60 for nigrostriatal and of 35 for corticospinal tractography, and default step length of 0.1 mm [16,18]. Then, to isolate the tracts, regions of interest (ROIs) were applied in the designated areas by two authors (C.A.…”

“…A nigrofugal tracing study demonstrated that nigrostriatal projections traverse the GP to synapse directly in the striatum. Moreover, striatomesencephalic fibers from the posterior putamen have been found to form a discrete bundle coursing through the GP to converge at the SN [16].…”

Diffusion Tensor Tractography of Brainstem Fibers and Its Application in Pain

“…The NST is a dopaminergic pathway that is involved in Parkinson’s disease. Individual tractography-guided quantitative DTI measures of this tract have been suggested as a promising marker for identifying Parkinson’s disease and such measurements may correlate with the severity of motor dysfunction [34–36]. NST is also suggested to control depressive fatigue states in Parkinson’s Disease [37,38].…”