Newton Jennifer M, Ward Nick S, Parker Geoffrey J M, Deichmann Ralf, Alexander Daniel C, Friston Karl J, Frackowiak Richard S J
Wellcome Department of Imaging Neuroscience, University College London London, UK.
Brain. 2006 Jul;129(Pt 7):1844-58. doi: 10.1093/brain/awl106. Epub 2006 May 15.
Recovery of motor function after subcortical stroke appears to be related to the integrity of descending connections from the ipsilesional cortical motor system, a view supported by the observation of greater than normal movement-related activation in ipsilesional motor regions in chronic subcortical stroke patients. This suggests that damage to the descending output fibres from one region of the cortical motor system may be compensated by activity in areas that retain corticofugal outputs. Though the trajectories of corticofugal fibres from each major component of the motor system through the corona radiata and internal capsule are well described in non-human primates, they have not been described fully in humans. Our study set out to map the trajectories of these connections in a group of healthy volunteers (8 male, 4 female; age range = 31-68 years, median = 48.5 years) and establish whether this knowledge can be used to assess stroke-induced disconnection of the cortical motor system and better interpret functional reorganization of the cortical motor system. We describe the trajectories of the connections from each major component of the motor system to the cerebral peduncle using diffusion-weighted imaging and probabilistic tractography in normal subjects. We observed good reproducibility of these connections over subjects. The comparative topography of these connections revealed many similarities between humans and other primates. We then inferred damage to corticofugal pathways in stroke patients (n = 3) by comparing the overlap between regions of subcortical white matter damage with the trajectories of the connections to each motor area. In a small series of case studies, we found that inferred disconnections could explain enhanced hand-grip-related responses, as assessed with functional MRI, in the ipsilesional motor system. These results confirm that selective disruption of motor corticofugal fibres influences functional reorganization and outcome in individual patients.
皮质下卒中后运动功能的恢复似乎与同侧皮质运动系统下行连接的完整性有关，这一观点得到了以下观察结果的支持：在慢性皮质下卒中患者的同侧运动区域，与运动相关的激活大于正常水平。这表明，皮质运动系统一个区域的下行输出纤维受损，可能会由保留皮质传出纤维的区域的活动来补偿。虽然在非人类灵长类动物中，已经很好地描述了运动系统各主要组成部分的皮质传出纤维通过放射冠和内囊的走行轨迹，但在人类中尚未得到充分描述。我们的研究旨在绘制一组健康志愿者（8名男性，4名女性；年龄范围=31-68岁，中位数=48.5岁）中这些连接的轨迹，并确定这些知识是否可用于评估卒中引起的皮质运动系统断开连接情况，以及更好地解释皮质运动系统的功能重组。我们使用正常受试者的扩散加权成像和概率性纤维束成像，描述了运动系统各主要组成部分到大脑脚的连接轨迹。我们观察到这些连接在受试者之间具有良好的可重复性。这些连接的比较性拓扑结构揭示了人类与其他灵长类动物之间的许多相似之处。然后，我们通过比较皮质下白质损伤区域与每个运动区域连接轨迹之间的重叠，推断卒中患者（n=3）的皮质传出通路损伤情况。在一系列小型病例研究中，我们发现，如通过功能磁共振成像评估，推断出的连接中断可以解释同侧运动系统中与握力相关的反应增强。这些结果证实，运动皮质传出纤维的选择性中断会影响个体患者的功能重组和预后。
