Background and Objectives: The corpus callosum is a site of pathological involvement in the neurodegenerative disorder amyotrophic lateral sclerosis (ALS). The corpus callosum shows widespread cortical connectivity topographically distributed along its length. Initial limb weakness in ALS is typically unilateral, becoming bilateral with disease progression. The precise anatomical substrate for this spread is uncertain. The present study investigated sub-regional variations in corpus callosum integrity in ALS, and whether these reflect a relationship with the development of unilateral or bilateral limb weakness. Methods: Sporadic ALS patients were categorized into unilateral (n = 14) or bilateral (n = 25) limb weakness at the time of assessment and underwent diffusion tensor imaging. Probabilistic bundle-specific tracking was carried out using MRtrix and TractSeg to parcellate the corpus callosum into seven anatomical segments (rostrum; genu; rostral body; anterior midbody; posterior midbody; isthmus; splenium). White matter tract integrity was assessed in all segments and compared with MRI data acquired from 25 healthy controls. Results: In the combined patient group, the most prominent differences in diffusivity metrics were in the rostral body, posterior midbody and isthmus of the corpus callosum (p < 0.04). Loss of corpus callosum integrity was most prominent in the sub-group with unilateral limb weakness at the time of scanning (p < 0.05). Conclusions: Corpus callosum involvement in ALS is detectable across multiple segments, in keeping with a widespread cortical distribution of pathology. The association of unilateral limb weakness with greater loss of corpus callosum integrity informs connectivity-based hypotheses of symptom propagation in ALS.

背景和目的：胼胝体是神经退行性疾病肌萎缩侧索硬化（ALS）的病理学参与部位。胼胝体显示出沿其长度在地形上分布的广泛的皮质连接。ALS 最初的肢体无力通常是单侧的，随着疾病进展变为双侧。这种扩散的精确解剖底物是不确定的。本研究调查了 ALS 胼胝体完整性的亚区域变化，以及这些变化是否反映了与单侧或双侧肢体无力发展的关系。方法：散发性 ALS 患者分为单侧（n  = 14）或双侧（n = 25) 评估时肢体无力并接受弥散张量成像。使用 MRtrix 和 TractSeg 进行概率束特定跟踪，将胼胝体分成七个解剖部分（讲台；膝；延髓；前中体；后中体；峡部；脾）。评估所有节段的白质束完整性，并与从 25 名健康对照获得的 MRI 数据进行比较。结果：在合并患者组中，扩散性指标的最显着差异在胼胝体的喙体、后中部和峡部（p  < 0.04）。胼胝体完整性的丧失在扫描时单侧肢体无力的亚组中最为突出（p  < 0.05）。结论：胼胝体在 ALS 中的参与可在多个节段中检测到，与病理的广泛皮质分布保持一致。单侧肢体无力与胼胝体完整性损失更大的关联为基于连通性的 ALS 症状传播假设提供信息。