Bilateral repetitive transcranial magnetic stimulation to motor impairment in stroke patients.

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Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive method that can change the excitability of the human cortex. We have reported that low-frequency rTMS over the contralesional primary motor cortex (M1) improved motor performance of the affected hand in stroke patients. Moreover, we investigated whether bilateral rTMS adding high frequency rTMS over the ipsilesional M1 might improve the motor function of the affected hand in stroke patients. The stronger excitability of ipsilesional M1 might be induced by low frequency rTMS that facilitate the excitability of the ipsilesional M1 by reducing the transcallosal inhibition and high frequency rTMS that directly stimulate the ipsilesional Ml. In recent we analyze the data from these results, we will establish new neurorehabilitative strategies for stroke.It has been considered that the surviving structures and networks would contribute the motor recovery in stroke patients, however, the mechanism of reorganization after stroke remains uncertain. We have conducted the virtual lesion study using TMS to investigate the mechanism of motor recovery. It appears that patients with poor motor function used the ipsilesional premotor cortex (PMC) to move the paretic side. We found that, compared with the reaction time delays and silent period, the inhibition function decreased in the PMC. This reorganization of the PMC showed a negative correlation with relatively good function of the upper arm when compared with that of the hand. Regarding reorganization, it has been reported that hand and upper arm regions compete of areas within the cortex. The excitability that is unevenly distributed in the upper arm due to weak inhibitory function of the PMC might cause poor reorganization of the cortex that controls the hand. This large-scale reorganization outside the ipsilesional M1 is a lengthy process that never results in complete recovery.