Background. Upper-limb impairment in patients with chronic stroke appears to be partly attributable to an upregulated reticulospinal tract (RST). Here, we assessed whether the impact of corticospinal (CST) and RST connectivity on motor impairment and skill-acquisition differs in sub-acute stroke, using transcranial magnetic stimulation (TMS)–based proxy measures. Methods. Thirty-eight stroke survivors were randomized to either reach training 3-6 weeks post-stroke (plus usual care) or usual care only. At 3, 6 and 12 weeks post-stroke, we measured ipsilesional and contralesional cortical connectivity (surrogates for CST and RST connectivity, respectively) to weak pre-activated triceps and deltoid muscles with single pulse TMS, accuracy of planar reaching movements, muscle strength (Motricity Index) and synergies (Fugl-Meyer upper-limb score). Results. Strength and presence of synergies were associated with ipsilesional (CST) connectivity to the paretic upper-limb at 3 and 12 weeks. Training led to planar reaching skill beyond that expected from spontaneous recovery and occurred for both weak and strong ipsilesional tract integrity. Reaching ability, presence of synergies, skill-acquisition and strength were not affected by either the presence or absence of contralesional (RST) connectivity. Conclusion. The degree of ipsilesional CST connectivity is the main determinant of proximal dexterity, upper-limb strength and synergy expression in sub-acute stroke. In contrast, there is no evidence for enhanced contralesional RST connectivity contributing to any of these components of impairment. In the sub-acute post-stroke period, the balance of activity between CST and RST may matter more for the paretic phenotype than RST upregulation per se.

背景。慢性中风患者的上肢损伤似乎部分归因于上调的网状脊髓束 (RST)。在这里，我们使用基于经颅磁刺激 (TMS) 的代理措施评估了皮质脊髓 (CST) 和 RST 连接对运动障碍和技能获得的影响在亚急性中风中是否不同。方法. 38 名中风幸存者被随机分配接受中风后 3-6 周的培训（加上常规护理）或仅接受常规护理。在中风后 3、6 和 12 周，我们用单脉冲 TMS 测量了同侧和对侧皮质连接（分别代表 CST 和 RST 连接）与预激活的三头肌和三角肌的弱的单脉冲 TMS、平面伸展运动的准确性、肌肉力量（运动指数）和协同作用（Fugl-Meyer 上肢评分）。结果. 协同作用的强度和存在与 3 周和 12 周时与麻痹上肢的同侧 (CST) 连接相关。训练导致平面伸展技能超出自发恢复的预期，并且发生在弱和强的同侧道完整性。到达能力、协同作用的存在、技能习得和力量不受对侧（RST）连接存在或不存在的影响。结论. 同侧 CST 连接程度是亚急性卒中近端灵活性、上肢力量和协同表达的主要决定因素。相比之下，没有证据表明增强的对侧 RST 连接会导致任何这些损伤成分。在中风后的亚急性期，CST 和 RST 之间的活动平衡对于麻痹表型可能比 RST 上调本身更重要。