Aberrant Fiber Coherence of Amygdala−Accumbens−Pallidum Pathway Is Associated With Disorganized Nigrostriatal−Nigropallidal Pathway in Parkinson's Disease

Abstract

Background: Motor disturbances in Parkinson's disease (PD) mainly result from the degeneration of classic motor pathways. Given that the specific limbic pathway participates in movements, it is reasonable to consider that limbic pathway have the pathologic potential of motor disturbance in PD. Purpose: To explore the white matter changes of limbic and motor pathways and their relations in PD patients. Study Type: Prospective. Population: 39 PD patients and 55 normal controls. Sequence: Sagittal 3D T 1-weighted fast spoiled gradient recalled sequence, diffusion-weighted spin echo-echo planar imaging sequence on a 3T scanner. Assessment: Probabilistic tractography was used to reconstruct the motor pathways (nigrostriatal−nigropallidal and basal ganglia−motor cortex pathways) and limbic pathway (amygdala−accumbens−pallidum pathway). White matter alterations of these pathways were evaluated by fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), neurite density (NDI), and orientation dispersion (ODI). Clinical assessment was conducted by a neurologist. Statistical Tests: Group comparisons were performed using unpaired t-tests. Pearson or Spearman correlation was used to explore the relationships between variables. Results: Compared with normal controls, PD patients showed decreased ODI as well as increased MD and AD in the bilateral nigrostriatal−nigropallidal pathway (P < 0.05), decreased FA in left basal ganglia−motor cortex pathway (P < 0.05), and decreased ODI in left limbic pathway (P < 0.05

Diffusion Magnetic Resonance Imaging-Based Biomarkers for Neurodegenerative Diseases

“…The loss of dopaminergic neurons in SN is considered to reduce the dopaminergic function of connections from the SN pars compacta to the corpus striatum, known as the nigrostriatal pathway, leading to the characteristic motor signs of PD [ 124 ]. Andica et al [ 125 ] and Guo et al [ 126 ] used NODDI to report decreased ICVF and ODI, respectively, in the nigrostriatal pathways of patients with PD compared to the controls. Interestingly, the changes in ICVF were only observed in the contralateral distal part of the nigrostriatal pathway, suggesting retrograde degeneration [ 125 ].…”

“…Interestingly, the changes in ICVF were only observed in the contralateral distal part of the nigrostriatal pathway, suggesting retrograde degeneration [ 125 ]. Furthermore, Guo et al [ 126 ] reported decreased ODI, together with a trend of increasing FA in the contralateral amygdala-accumbens-pallidum pathway, which suggested hyperconnectivity related to pathological progression.…”

Editorial for “Aberrant Hyperconnectivity of Amygdala‐Accumbens‐Pallidum Pathway Is Associated With Disorganized Nigrostriatal Pathway in Parkinson's Disease”

“…4 In the current issue of the Journal of Magnetic Resonance Imaging, the article by Guo et al attempts to investigate the microstructural changes of limbic and motor pathways and their relations to reveal the potential pathological foundation regarding motor disruption in Parkinson's disease (PD) by using single-and two-shell diffusion MRI. 5 Probabilistic tractography was used to reconstruct the nigrostriatal, basal ganglia-motor cortex and amygdala-accumbens-pallidum pathways in a total of 94 participants (55 healthy controls [HC] and 39 PD patients). Diffusion tensor imaging (DTI) 6 metrics-fractional anisotropy (FA) and mean diffusivity (MD)-were calculated from single-shell diffusion images.…”

“…Aberrant enhanced coherence of the limbic pathway (ODI) was also significantly positively correlated with the degeneration of the nigrostriatal pathway (MD), thus suggesting a relevant role of the limbic-motor interface in the pathophysiology of PD. 5 Although diffusion MRI and tractography have raised interest in the last decades, some limitations need to be considered. Indeed, these tools present strengths but also weaknesses and intrinsic technical shortcomings.…”

“…In addition, PD patients exhibited significantly decreased ODI in the amygdala‐accumbens‐pallidum pathway, along with a trend of increased FA, likely indicating enhanced coherence in such white matter tracts. Aberrant enhanced coherence of the limbic pathway (ODI) was also significantly positively correlated with the degeneration of the nigrostriatal pathway (MD), thus suggesting a relevant role of the limbic‐motor interface in the pathophysiology of PD 5 …”