Abstract:

Objective  To observe and explore the activation pattern and functional reorganization mechanism of motor cortex in acute ischemic stroke patients.  Methods  A total of 22 patients with first-ever acute ischemic stroke were included in this study. Functional magnetic resonance imaging (fMRI) was used to observe the changing of activation pattern and functional reorganization of motor cortex in finger-tapping task. National Institutes of Health Stroke Scale (NIHSS) and Fugl-Meyer Assessment Scale for Upper Extremity (FMA-UE) were used to evaluate motor function, and neuroelectrophysiology monitored resting motor threshold (RMT). Spearman rank correlation analysis was used to analyze the correlation between activation of region of interest (ROI) and neurological function, motor function and neuroelectrophysiology. Moreover, dynamic causal model (DCM) was used to analyze the intrahemispheric and interhemispheric effective connectivity between brain regions in finger-tapping task.  Results  Movements of the affected hand showed significant signal activation in the ipsilesional primary motor cortex (M1), premotor cortex (PMC) and bilateral supplementary motor area (SMA), while the contralesional PMC, posterior parietal cortex (PPC) and bilateral cerebellar hemisphere also showed slight activation. Movements of the unaffected hand showed significant activation in the contralesional M1, PMC and SMA, while the ipsilesional SMA and inferior parietal lobule also showed slight activation. The activation value of ipsilesional M1 was negatively correlated with neurological function (NIHSS score; r_s = -0.452, P = 0.035) and positively correlated with motor function of upper extremity (FMA-UE score; r_s = 0.543, P = 0.009). The activation value of ipsilesional sensorimotor cortex (SMC) was positively correlated with RMT (r_s = 0.718, P = 0.001). The advantage model of DCM showed bidirectional suppressive influence of connectivity between bilateral M1, negative effective connectivity from contralesional SMA to M1, positive effective connectivity from contralesional SMA to ipsilesional M1 and from ipsilesional SMA to contralesional SMA. The intensity of effective connectivity from contralesional to ipsilesional M1 was negatively correlated with motor function (FMA-UE score; r_s = -0.461, P = 0.047). The intensity of effective connectivity from contralesional SMA to contralesional M1 was positively correlated with motor function (FMA-UE score; r_s = 0.533, P = 0.041).  Conclusions  fMRI combined with neurological function, motor function and electrophysiology can be used to observe activation pattern and functional reorganization mechanism of motor cortex in acute ischemic stroke patients, and provide new insights into understanding the motor impairment and functional reorganization after stroke and rehabilitation therapy.

Key words: Stroke, Brain ischemia, Motor cortex, Magnetic resonance imaging

摘要：

目的 探讨急性缺血性卒中患者运动皮质激活模式和功能重组改变。方法 采用fMRI观察22 例急性缺血性卒中患者进行对指运动任务时的运动皮质激活模式和功能重组改变，采用美国国立卫生研究院卒中量表（NIHSS）评价神经功能、Fugl-Meyer上肢评价量表（FMA-UE）评价上肢运动功能，神经电生理学监测静息运动阈值。采用Spearman 秩相关分析探讨兴趣区激活强度与神经功能、运动功能和神经电生理学的相关性，动态因果模型分析对指运动时双侧大脑半球间和大脑半球内有效连接。结果 急性缺血性卒中患者患侧对指运动主要表现为患侧初级运动皮质、运动前区皮质和双侧辅助运动区激活，同时伴健侧运动前区皮质、后顶叶皮质和双侧小脑半球少量激活；健侧对指运动主要表现为健侧初级运动皮质、运动前区皮质和辅助运动区激活，同时伴患侧辅助运动区、顶下小叶少量激活。患侧初级运动皮质激活强度值与神经功能（NIHSS 评分）呈负相关（r_s = -0.452，P = 0.035）、与上肢运动功能（FMA-UE 评分）呈正相关（r_s = 0.543，P = 0.009），患侧感觉运动皮质激活强度值与患侧静息运动阈值呈正相关（r_s  = 0.718，P = 0.001）。在动态因果模型所示优势模型中，双侧初级运动皮质间存在双向负性有效连接；健侧辅助运动区对健侧初级运动皮质存在负性有效连接，对患侧初级运动皮质存在正性有效连接；患侧辅助运动区对健侧辅助运动区存在正性有效连接。健侧初级运动皮质对患侧初级运动皮质的有效连接强度值与上肢运动功能（FMA-UE 评分）呈负相关（r_s = -0.461，P = 0.047），健侧辅助运动区对健侧初级运动皮质的有效连接强度值与上肢运动功能（FMA-UE 评分）呈正相关（r_s = 0.533，P = 0.041）。结论 fMRI 结合神经功能和运动功能评价及神经电生理学监测可以有效观察急性缺血性卒中患者运动皮质激活模式和功能重组改变，为理解脑卒中运动障碍和功能重组以及进行康复治疗提供指导。

关键词: 卒中, 脑缺血, 运动皮质, 磁共振成像