Idiopathic rapid eye movement sleep behaviour disorder (iRBD)—a Parkinson’s disease (PD) prodrome—might exhibit neural changes similar to those in PD. Substantia nigra pars compacta (SNc) degeneration underlies motor symptoms of PD. In iRBD and early PD (ePD), we measured diffusion MRI (dMRI) in the caudal motor SNc, which overlaps the nigrosome-1—the earliest-degenerating dopaminergic neurons in PD—and in the striatum. Nineteen iRBD, 26 ePD (1.7 ± 0.03 years), and 46 age-matched healthy controls (HCs) were scanned at Western University, and 47 iRBD, 115 ePD (0.9 ± 0.01 years), and 56 HCs were scanned through the Parkinson’s Progression Markers Initiative, using 3T MRI. We segmented the SNc and striatum into subregions using automated probabilistic tractography to the cortex. We measured mean diffusivity (MD) and fractional anisotropy (FA) along white-matter bundles and subregional surfaces. We performed group-level and classification analyses. Increased caudal motor SNc surface MD was the only iRBD-HCs and ePD-HCs difference replicating across datasets (p_adj < 0.05). No iRBD-ePD differences emerged. Caudal motor SNc surface MD classified patient groups from HCs at the single-subject level with good-to-excellent balanced accuracy in an independent sample (0.91 iRBD and 0.86 iRBD and ePD combined), compared to fair performance for total SNc surface MD (0.72 iRBD and ePD). Caudal motor SNc surface MD correlated significantly with MDS-UPDRS-III scores in ePD patients. Using dMRI and automated segmentation, we detected changes suggesting altered microstructural integrity in iRBD and ePD in the nigrostriatal subregion known to degenerate first in PD. Surface MD of the caudal motor SNc presents a potential measure for inclusion in neuroimaging biomarkers of iRBD and PD.

特发性快速动眼睡眠行为障碍 (iRBD)——帕金森病 (PD) 的一种前驱症状——可能会表现出与 PD 类似的神经变化。黑质致密部 (SNc) 变性是 PD 运动症状的基础。在 iRBD 和早期 PD (ePD) 中，我们测量了尾部运动 SNc 的扩散 MRI (dMRI)，该 SNc 与 nigrosome-1（PD 中最早退化的多巴胺能神经元）和纹状体重叠。在西部大学扫描了 19 名 iRBD、26 名 ePD（1.7 ± 0.03 岁）和 46 名年龄匹配的健康对照（HC），并通过帕金森病进展扫描了 47 名 iRBD、115 名 ePD（0.9 ± 0.01 岁）和 56 名 HC标记计划，使用 3T MRI。我们使用皮层自动概率纤维束成像将 SNc 和纹状体分割成子区域。我们测量了沿白质束和次区域表面的平均扩散率（MD）和分数各向异性（FA）。我们进行了组级和分类分析。尾部运动 SNc 表面 MD 的增加是跨数据集复制的唯一 iRBD-HC 和 ePD-HC 差异（ p _adj < 0.05）。没有出现 iRBD-ePD 差异。尾部运动 SNc 表面 MD 在单个受试者水平上对来自 HC 的患者组进行了分类，在独立样本中具有良好到优秀的平衡准确性（0.91 iRBD 和 0.86 iRBD 和 ePD 组合），而总SNc 表面 MD 的公平表现（0.72 iRBD 和 ePD）。 ePD 患者尾部运动 SNc 表面 MD 与 MDS-UPDRS-III 评分显着相关。使用 dMRI 和自动分割，我们检测到的变化表明已知在 PD 中首先退化的黑质纹状体亚区域中 iRBD 和 ePD 的微观结构完整性发生了改变。 尾部运动 SNc 的表面 MD 为纳入 iRBD 和 PD 的神经影像生物标志物提供了潜在的衡量标准。