Multimodal assessment of nigrosomal degeneration in Parkinson's disease

• Published in: Parkinsonism & related disorders Vol. 80; pp. 102 - 107
• Main Authors: Langley, Jason, Huddleston, Daniel E., Crosson, Bruce, Song, David D., Factor, Stewart A., Hu, Xiaoping
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.11.2020
• Subjects: Iron; Neuromelanin; Nigrosome-1; Parkinson's disease; Substantia nigra; Iron; Parkinson's disease; Neuromelanin; Nigrosome-1; Substantia nigra
• ISSN: 1353-8020; 1873-5126
• DOI: 10.1016/j.parkreldis.2020.09.021

Approximately forty percent of all dopaminergic neurons in SNpc are located in five dense neuronal clusters, named nigrosomes. T2- or T2*-weighted images are used to delineate the largest nigrosome, named nigrosome-1. In these images, nigrosome-1 is a hyperintense region in the caudal and dorsal portion of the T2- or T2*-weighted substantia nigra. In PD, nigrosome-1 experiences iron accumulation, which leads to a reduction in T2-weighted hyperintensity. Here, we examine neuromelanin-depletion and iron deposition in regions of interest (ROIs) derived from quantitative-voxel based morphometry (qVBM) on neuromelanin-sensitive images and compare the ROIs with nigrosome-1 identified in T2*-weighted images. Neuromelanin-sensitive and multi-echo gradient echo imaging data were obtained. R2* was calculated from multi-echo gradient echo imaging data. qVBM analysis was performed on neuromelanin-sensitive images and restricted to SNpc. Mean neuromelanin-sensitive contrast and R2* was measured from the resulting qVBM clusters. Nigrosome-1 was segmented in T2*-weighted images of control subjects and its location was compared to the spatial location of the qVBM clusters. Two bilateral clusters emerged from the qVBM analysis. These clusters showed reduced neuromelanin-sensitive contrast and increased mean R2* in PD as compared to controls. Cluster-1 from the qVBM analysis was in a similar spatial location as nigrosome-1, as seen in T2*-weighted images. qVBM cluster-1 shows reduced neuromelanin-sensitive contrast and is in a similar spatial position as nigrosome-1. This region likely corresponds to nigrosome-1 while the second cluster may correspond to nigrosome-2. •Voxel-based analysis was used to determine regions of substantia nigra undergoing Parkinsonian neuronal loss.•Two bilateral clusters with reduced neuromelanin-sensitive contrast emerged from the voxel-based analysis.•Nigrosome-1 was segmented in T2*-weighted images.•One cluster from the voxel-based analysis shared significant overlap with nigrosome-1.•These results suggest that reductions in neuromelanin-sensitive contrast largely occur in the nigrosomes.