Surface SSEP acquisition using a monopolar recording: effect of electrode configuration

Theoretical analysis suggests that the surface-recorded spinal somatosensory evoked potential (SSEP) is a triphasic waveform whose form is determined by naturally occurring low-pass filters such as tissue depth and conduction velocity dispersion. Typical clinical SSEP waveforms, however, do not always meet theoretical expectations. A plausible explanation for some of the waveform variation is the placement of recording electrodes on the skin surface, and the orientation of these electrodes with respect to the conducted action potential. A simple summation of waveforms is used in this paper to demonstrate the effect and importance of precise electrode placement on monopolar SSEP waveforms.