1998 Volume 35 Issue 11 Pages 738-743
We evaluated changes in the scalp-recorded electroencephalogram (EEG) and evoked responses induced by transcranial magnetic stimulation (TMS) in four stroke patients. The center of a circular coil was positioned at the vertex. Forty clockwise stimulations were administered every 3-5 sec with the maximum output of electric current. A circuit that blocked the input for 150 msec after stimulation was used to reduce stimulus artifact. EEGs were recorded from F3/4, C3/4, P3/4, and T3/4. Slowing of the EEG was observed immediately (150 msec) after each stimulation. The incidence of changes ranged from 10 to 80% and the duration of the change ranged from 250 to 600 msec. A densely hemiplegic patient with a large subcortical lesion who was taking anticonvulsant medication had an abnormal baseline EEG and showed a lower incidence of EEG changes compared to patients with mild to moderate hemiplegia or pontine lesions. In a patient with mild hemiplegia due to a lacunar infarction, averaged TMS-evoked electroencephalographic responses appeared as gentle positive waves, fused with 1 to 3 negative peaks. The methods used in this study may be useful in evaluating the sensitivity of stroke patients to TMS.
