1 University of British Columbia, Vancouver, BC, Canada.
Neurorehabil Neural Repair. 2018 Aug;32(8):671-681. doi: 10.1177/1545968318785043. Epub 2018 Jul 4.
In the chronic phase after stroke, cortical excitability differs between the cerebral hemispheres; the magnitude of this asymmetry depends on degree of motor impairment. It is unclear whether these asymmetries also affect capacity for plasticity in corticospinal tract excitability or whether hemispheric differences in plasticity are related to chronic sensorimotor impairment.
Response to paired associative stimulation (PAS) was assessed bilaterally in 22 individuals with chronic hemiparesis. Corticospinal excitability was measured as the area under the motor-evoked potential (MEP) recruitment curve (AUC) at baseline, 5 minutes, and 30 minutes post-PAS. Percentage change in contralesional AUC was calculated and correlated with paretic motor and somatosensory impairment scores.
PAS induced a significant increase in AUC in the contralesional hemisphere ( P = .041); in the ipsilesional hemisphere, there was no significant effect of PAS ( P = .073). Contralesional AUC showed significantly greater change in individuals without an ipsilesional MEP ( P = .029). Percentage change in contralesional AUC between baseline and 5 m post-PAS correlated significantly with FM score ( r = -0.443; P = .039) and monofilament thresholds ( r = 0.444, P = .044).
There are differential responses to PAS within each cerebral hemisphere. Contralesional plasticity was increased in individuals with more severe hemiparesis, indicated by both the absence of an ipsilesional MEP and a greater degree of motor and somatosensory impairment. These data support a body of research showing compensatory changes in the contralesional hemisphere after stroke; new therapies for individuals with chronic stroke could exploit contralesional plasticity to help restore function.
在中风后的慢性期，大脑半球之间的皮质兴奋性存在差异；这种不对称的程度取决于运动障碍的严重程度。目前尚不清楚这些不对称性是否也会影响皮质脊髓束兴奋性的可塑性，或者半球间可塑性的差异是否与慢性感觉运动障碍有关。
在 22 名慢性偏瘫患者中双侧评估了成对关联刺激（PAS）的反应。在基线、PAS 后 5 分钟和 30 分钟测量运动诱发电位（MEP）募集曲线下面积（AUC）作为皮质兴奋性的指标。计算对侧 AUC 的百分比变化，并与患侧运动和感觉障碍评分相关。
PAS 在对侧半球引起 AUC 的显著增加（P=0.041）；在同侧半球，PAS 没有显著影响（P=0.073）。在没有同侧 MEP 的个体中，对侧 AUC 的变化明显更大（P=0.029）。在基线和 5 m 时，对侧 AUC 的百分比变化与 FM 评分（r=-0.443；P=0.039）和单丝阈值（r=0.444，P=0.044）显著相关。
在每个大脑半球内都存在 PAS 的不同反应。在偏瘫更严重的个体中，对侧可塑性增加，这表现为同侧 MEP 缺失和运动及感觉障碍程度更大。这些数据支持了大量研究表明中风后对侧半球会发生代偿性变化的观点；对于慢性中风患者，新的治疗方法可以利用对侧可塑性来帮助恢复功能。
