Motor Imagery promotes brain functional recovery after stroke revealed by regional homogeneity

Zhang Ye1, Qiu Ming-guo1, Wang Li1, Zhang Jing-na1, Sang Lin-qiong1, Yang Jun2, Yan Ru-bing3,Wang Jian2

1Department of medical informatics and medical image, Third Military Medical University,

2Department of Radiology, Southwest Hospital,

3Department of Rehabilitation, Southwest Hospital.

Introduction：Motor imagery(MI) therapy has been applied to promote the moter recovery after stroke. However, the neural mechanism of the MI therapy remains unknown. In this study, regional homogeneity (ReHo) method was used to study the brain function changes of the stroke patients before and after the MI therapy.

Methods: Sixteen subcortical stroke patients and sixteen normal control were recruited. All resting state fMRI data were collected by a 3.0T Siemens MRI scanner using the following parameters: TR/TE/FA=2000ms/50ms/90°, slices number=35, thickness=3.0mm, FOV=220mm. Each session lasted for 260 seconds. 3D T1-weighted images in the sagittal plane were acquired using a MPRAGE sequence with TR/TE/FA=1900ms/2.34ms/7°, FOV=240mm, and slice thickness=1mm.

The motor imagery treatment lasted 30 days. Patients were requested to accept the training two times per day respectively at 1pm and 8pm. During each training, patients listened to an instruction along with soft music background which guided them to imagine the actual motions of their limbs for 20 minutes. At each time, there was a physician by their side to supervise.

Individual ReHo map was obtained by calculating the Kendall's coefficient of concordance in a voxel-by-voxel way using the Data Processing Assistant for rs-fMRI (DPARSF). Two-sample t-test was used to compare the ReHo values between stroke patients and NC groups (P<0.001, uncorrected, cluster size>50), also to evaluate the ReHo changes of the patients’ brain before and after the MI treatment (P<0.05, uncorrected, cluster size>50) in SPM8.

Results: The FMA score of the stroke patients was significantly increased after the MI treatment(P<0.05) which indicated the motor recovery. For the ReHo value, compared to the control subjects, the stroke patients exhibited the increased ReHo value mainly in the right occipital cortex, right superior parietal gyrus, right superior frontal gyrus, right insula, right putamen, left inferior parietal gyrus, left middle frontal gyrus, left medial superior frontal cortex and left precuneus(Fig.1). After the MI treatment, the stroke patients exhibited significant ReHo decrease in the right superior occipital gyrus, right parietal cortex, right medial superior frontal gyrus, left middle frontal gyrus and left inferior orbitofrontal cortex. ReHo value increased mainly in bilateral precuneus, right middle cingulum, left SMA, right postcentral gyrus, right middle temporal gyrus and left superior parietal gyrus (Fig.2).

Conclusion: Stroke patients showed significantly increased ReHo value mainly in frontal, parietal and occipital cortex during the resting-state, which suggested the disorder of the patients’ brain function. Also, our results showed right superior occipital gyrus, right superior parietal gyrus and left middle frontal gyrus of the patients, which showed incerased ReHo value compared to the NC group, exhibited decreased ReHo value after the MI treatment. And the motor-related regions such as SMA and postcentral gyrus showed incerased ReHo, which may suggest the improvement of the motor function in the patients’ brain. Thus our results may demonstrate that MI treatment could promote the brain functional recovery after stroke on some level.

References

Faralli, A. (2013), ‘Noninvasive strategies to promote functional recovery after stroke’, Neural Plast, 2013:854597.

Zimmermann, S.A. (2008), ‘Efficacy of motor imagery in post-stroke rehabilitation: a systematic review’, J Neuroeng Rehabil, 5:8.

Zang, Y. (2004), ‘ Regional homogeneity approach to fMRI data analysis’, NeuroImage, Vol. 22, pp. 394-400.