The mechanisms which lead to recovery of motor function after a stroke are poorly understood. Change of amplitude of motor evoked potential (MEP) is thought to be one of the factors which may contribute to recovery. We have investigated the change of MEPs in stroke patients during conventional and intensive training. The subjects were 27 patients with hemiplegia due to stroke (55.1±13.4 years old, 15.1±12.7 weeks after onset). They received intensive training of the hemiplegic upper limbs for 2 to 6 weeks in addition to the basic conventional training for 2 weeks. After training, Ueda's grade and Brunnstrom stage were improved. Focal transcranial magnetic stimulation (TMS) to the abductor pollicis brevis was followed up by evaluating amplitude of MEPs in 12 patients. The affected hemisphere was marked out over the central area in a 1cm or 2cm grid. TMS were given to 10 to 20 points using a figure-of-eight coil to elicit MEPs in contralateral abductor pollicis brevis muscle. The amplitudes of MEPs were measured peak-to-peak on each hemisphere at rest or under weak voluntary contraction. Based on the change of amplitude of MEP, 12 patients were devided into 3 groups; 1) decreased MEP amplitude group (1 case), 2) increased MEP amplitude group (4 cases), 3) no changed MEP amplitude group (7 cases). In decreased MEP group, the patient recovered to the level of Brunnstrom stage VI. In increased MEP group, the patients recovered to the level of Brunnstrom stage IV or V. In no changed MEP group, the patients recovered to the level of Brunnstrom stage V or VI. Functional outcome of decreased and no changed MEP group was better than that of increased MEP group. These results suggest any relationship between the cortical excitability and the functional recovery after stroke.
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