Clinical application of spike averaging to dipole tracing method.

As part of our studies on localization of epileptic foci, dipole analysis using averaged spikes were compared with that using individual spikes for 25 patients with localization related epilepsy. Our results are as follows. 1) In the group which showed stable dipoles from individual spikes, dipole localization from averaged and individual spikes were similar, although the former showed a higher dipolarity and more stable location, for the entire spike discharge including the peak, trough and wave. The high dipolarity was due to improved signal to noise ratio obtained from averaging. 2) The cases with centrotemporal spike focus including benign childhood epilepsy with centrotemporal spikes showed more reliable dipoles. In the cases with frontal lobe epilepsy, reliable dipoles were rarely obtained even with averaged spikes. Each method provided independent information, so they are of complementary value.