SAFETY OF RAPID-RATE TRANSCRANIAL MAGNETIC STIMULATION - HEART-RATE AND BLOOD-PRESSURE CHANGES

We examined the influence of rapid-rate transcranial magnetic stimulat ion on heart rate and blood pressure in 13 healthy volunteers. In a fi rst series three different cortical magnetic stimuli were applied: ove r C3, C4 and Fz (10/20 system), in a second series additionally over P z. We also used a stimulus over the brachial plexus and a sham stimulu s. Five stimuli of each location were applied with a Cadwell high spee d magnetic stimulator using a focal point circular coil. Stimulus trai n duration was 500 ms, stimulus frequency 20 Hz. Stimulus strength was 70-90% of maximum stimulator output, 20% of maximum stimulator output above subjects' individual motor threshold. The subjects assessed sti mulus inconvenience immediately after stimulation. ECG and blood press ure (Finapres) were recorded continuously during the 1 h test. In all subjects there was a clearly marked autonomic response with heart rate acceleration and decrease in blood pressure after all stimuli. There was no difference in responses between cortical stimuli. Blood pressur e decrease after sham stimulation was significantly smaller than after cortical stimulation, it was more marked after brachial plexus stimul ation. Autonomic reaction correlates well with subjective estimation o f stimulus inconvenience. We conclude the observed effect of rapid-rat e transcranial magnetic stimulation to be associated to rather an unsp ecific arousal reaction than to a direct stimulation of autonomic cort ex areas. We did not observe any clinically relevant side-effects. (C) 1997 Elsevier Science Ireland Ltd.