Variation of frontal P20 potential due to rotation of the N20-P20 dipole moment of SEPs.

We have applied the artificial neural network method to estimate the N20-P20 dipole from scalp SEP potentials, and have investigated the rotation of the dipole moment caused by the compression effect of a brain tumor (para-Rolandic tumor) adjacent to the central sulcus. The variation of the frontal P20 potential was demonstrated by the rotation of the N20-P20 dipole moment in 8 cases of para-Rolandic tumor. By estimation of the rotation of the dipole moment, it may be possible to obtain preoperative information regarding the relation between the central sulcus and the tumor.