T he intraoperative use of neurophysiological techniques allows reliable identification of the sensorimotor region, and constitutes a prerequisite for its anatomical and functional preservation. The clinical impact of IOM has been demonstrated in various publications. 6,7,21,22,[25][26][27][28][29]31,33, 64, [76] [77] [78] 89, [98] [99] [100] Although the basic principle of cortical stimulation is the application of an electrical impulse on the cortex, two different methods have been

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... ave been established, the BCS and the MCS techniques. Recent literature shows a wide spectrum of application for both techniques, and a discussion is ongoing in which either method is favored. Therefore, controversy exists regarding the superiority of each method. However, cortical electrical stimulation, especially in patients in whom general anesthesia has been induced, is a complex neurophysiological phenomenon. Both techniques are suitable to perform cortical stimulation; however, they differ in their electrophysiological parameters. The purpose of this manuscript was to present the basic mechanisms for both methods and to explain the differences in their effect on the motor cortical system.