Background

Preserved integrity of the corticospinal tract (CST) is a marker of good upper-limb behavior and recovery following stroke. However, there is less understanding of neural mechanisms that might help facilitate upper-limb motor recovery in stroke survivors with extensive CST damage.

Objective

The purpose of this study was to investigate resting state functional connectivity in chronic stroke survivors with different levels of CST damage and to explore neural correlates of greater upper-limb motor performance in stroke survivors with compromised ipsilesional CST integrity.

Methods

Thirty chronic stroke survivors (24 males, aged 64.7 ± 10.8 years) participated in this study. Three experimental sessions were conducted to: 1) obtain anatomical (T1, T2) structural (diffusion) and functional (resting state) MRI sequences, 2) determine CST integrity with transcranial magnetic stimulation (TMS) and conduct assessments of upper-limb behavior, and 3) reconfirm CST integrity status. Participants were divided into groups according to the extent of CST damage. Those in the extensive CST damage group did not show TMS evoked responses and had significantly lower ipsilesional fractional anisotropy.

Results

Of the 30 chronic stroke survivors, 12 were categorized as having extensive CST damage. Stroke survivors with extensive CST damage had weaker functional connectivity in the ipsilesional sensorimotor network and greater functional connectivity in the ipsilesional fronto-parietal network compared to those with preserved CST integrity. For participants with extensive CST damage, improved motor performance was associated with greater functional connectivity of the ipsilesional fronto-parietal network and higher fractional anisotropy of the ipsilesional rostral superior longitudinal fasciculus.

Conclusions

Stroke survivors with extensive CST damage have greater resting state functional connectivity of an ipsilesional fronto-parietal network that appears to be a behaviorally relevant neural mechanism that improves upper-limb motor performance.

中文翻译：

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当皮质脊髓束完整性受损时，额叶顶叶参与慢性中风运动表现

背景

皮质脊髓束（CST）的完整性是良好的上肢行为和中风后恢复的标志。但是，对神经机制的了解较少，这可能有助于促进遭受广泛CST损害的中风幸存者的上肢运动恢复。

目的

这项研究的目的是调查具有不同水平的CST损伤的慢性卒中幸存者的静息状态功能连通性，并探索与受损的CST完整性受损的卒中幸存者更大的上肢运动表现的神经相关性。

方法

30名慢性中风幸存者（24名男性，年龄64.7±10.8岁）参加了这项研究。进行了三个实验阶段：1）获取解剖（T1，T2）结构（扩散）和功能（静止状态）MRI序列，2）通过经颅磁刺激（TMS）确定CST完整性并进行上肢行为评估， 3）重新确认CST完整性状态。根据CST损伤的程度将参与者分为几组。广泛的CST损伤组中的那些没有显示TMS诱发的反应，并且同病分数的各向异性明显降低。

结果

在30名慢性中风幸存者中，有12名被归类为具有广泛的CST损害。与保留CST完整性的患者相比，遭受CST损伤严重的卒中幸存者在同病感觉运动网络中的功能连通性较弱，而在同病额顶网络中的功能连通性更高。对于遭受广泛的CST损伤的参与者，运动性能的改善与同侧额顶壁网络的功能连接性增强和同侧喙上纵筋膜的更高的分数各向异性有关。

结论

CST损伤严重的卒中幸存者具有同侧额顶网络的更好的静止状态功能连通性，这似乎是行为上相关的神经机制，可改善上肢运动表现。