Fokas Emily, Taga Myriam, Hayes Leticia, Charalambous Charalambos C, Raju Sharmila, Wang Ziyue, Shao Yongzhao, Mazzoni Pietro, Stepanov Valentin, Fieremans Els, Schambra Heidi
Department of Neurology, New York University Grossman School of Medicine, NY, USA.
Department of Neurology, Duke University School of Medicine, Durham, NC, USA.
Brain. 2025 Mar 11. doi: 10.1093/brain/awaf095.
After stroke, upper extremity (UE) motor recovery may be mediated in part by transcallosal projections between hemispheres. The interhemispheric competition model posits that transcallosal inhibition (TI) from the contralesional hemisphere is abnormally strengthened following stroke and interferes with motor recovery. This model has recently been questioned. In this longitudinal study, we aimed to definitively confirm or refute a maladaptive role of contralesional TI in subacute motor recovery. We assessed 30 mild-to-moderately impaired subjects over the six months following ischemic stroke. We tracked contralesional TI and motor functions in the proximal and distal segments of the paretic UE. We used transcranial magnetic stimulation to examine the ipsilateral silent period (iSP) in an arm and hand muscle. We used quantitative and clinical testing to examine deficits in muscle strength, motor control, and individuation; UE segmental impairment; and UE activity limitation. We assessed the relationships of contralesional TI to motor functions in the subacute period. Despite recovery of most motor functions in the proximal and distal UE, contralesional TI was largely static and unrelated to recovery of any motor function. There were inconsistent associations between stronger TI, less hand impairment, and less activity limitation in the subacute period overall. We found no compelling evidence to suggest a maladaptive role of contralesional TI in UE motor recovery in mild-to-moderately impaired stroke subjects. The scattered associations between stronger TI and better levels of paretic UE function suggest a potential supportive role rather than a limiting one. These findings challenge the validity of the interhemispheric competition model in the subacute recovery period, and prompt reconsideration of neuromodulatory strategies that subacutely target contralesional TI.
中风后，上肢（UE）运动功能的恢复可能部分由半球间的胼胝体投射介导。半球间竞争模型认为，中风后对侧半球的胼胝体抑制（TI）异常增强，干扰了运动功能的恢复。该模型最近受到了质疑。在这项纵向研究中，我们旨在明确证实或反驳对侧TI在亚急性运动恢复中的不良适应作用。我们评估了30名缺血性中风后6个月内轻度至中度受损的受试者。我们追踪了患侧UE近端和远端节段的对侧TI和运动功能。我们使用经颅磁刺激来检测手臂和手部肌肉的同侧静息期（iSP）。我们使用定量和临床测试来检测肌肉力量、运动控制和个体化方面的缺陷；UE节段性损伤；以及UE活动受限情况。我们评估了亚急性期对侧TI与运动功能之间的关系。尽管患侧UE近端和远端的大多数运动功能有所恢复，但对侧TI在很大程度上保持稳定，且与任何运动功能的恢复均无关联。总体而言，在亚急性期，较强的TI、较轻的手部损伤和较少的活动受限之间的关联并不一致。我们没有找到令人信服的证据表明对侧TI在轻度至中度受损的中风患者的UE运动恢复中起不良适应作用。较强的TI与患侧UE较好的功能水平之间的分散关联表明其可能起支持作用而非限制作用。这些发现挑战了半球间竞争模型在亚急性恢复期的有效性，并促使重新考虑在亚急性期针对对侧TI的神经调节策略。
