Multimodal estimation of epileptic foci with dipole localization method and other technique

To clarify the diagnostic value of the dipole localization method in estimating the epileptic focus in various types of localization-related epilepsy, dipole analysis of interictal spikes in epileptic patients was performed. Three-layered realistically-shaped models (Scalp-Skull-Brain model, SSB model) were used to compare the results with regional abnormalities revealed by various neuroimaging techniques and clinical manifestations. Subjects were 22 patients with localization-related epilepsy, including 11 cases with localized MRI abnormalities and 9 cases with abnormal SPECT findings. The results of spike dipole location coincided with the clinical findings in 20 of 22 cases. In the two cases with frontal lobe epilepsy, the results did not coincide. In 10 of 11 cases with MRI abnormality dipoles were located within the area of organic lesions. In all 10 cases with SPECT abnormal findings, regional hypoperfusion was found at the area corresponding to the location of the dipole, although SPECT findings showed a wider area as the epileptic focus. In conclusion, dipole estimation using the SSB model can be considered to be a useful technique for noninvasive investigation of epileptic focus.