A preliminary fMRI study on activiation pattern and functional reorganization of motor cortex in acute ischemic stroke patients

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. DOI: 10.3969/j.issn.1672-6731.2017.12.005