REPETITIVE MAGNETIC NERVE-STIMULATION - TECHNICAL CONSIDERATIONS AND CLINICAL USE IN THE ASSESSMENT OF NEUROMUSCULAR-TRANSMISSION

We assessed to what extent repetitive magnetic stimulation can replace the electrical method. Fifteen healthy subjects and 3 patients with m yasthenia gravis were investigated using stimulation of the median, ul nar, axillary and accessory nerves. Single, as well as 3/sec repetitiv e magnetic and electrical stimuli were applied. When comparing the res ults of magnetic vs. electrical stimulation, amplitudes, areas and sha pes of compound muscle action potentials were not significantly differ ent. Although single magnetic stimuli were much less uncomfortable tha n the electrical stimuli, differences in comfort were much smaller in the repetitive protocol, because muscular contractions under the magne tic stimulation coil caused unpleasant movements of, for example, the neck. Additional problems arose from technical limitations of the prot otype magnetic stimulator used: stimulation intensity was significantl y limited, resulting in an inability to elicit supramaximal responses in 11 of the 154 investigations. Overheating of the stimulator coil fo rced us to give the coil extra time to cool down. These problems might be solved in the future by more focused stimulus geometry and introdu ction of cooling devices. It is concluded that magnetic stimulation ca n elicit responses which are equivalent to the electrical method in re petitive nerve stimulation. Al present due to some shortcomings it can not replace electrical stimulation in routine repetitive nerve stimula tion.