Comparative Study between Visusal Analysis and Low Resolution Electromagnetic Tomography (LORETA) Method in the Localization of Epileptiform Discharges

ABSTRACT

BACKGROUND: LORETA (Low Resolution Electromagnetic Tomography) produces a three-dimensional current density mapping from digitized EEG (electroencephalography) data. A comparison between visual waveform analysis of scalp EEG and LORETA method may be helpful for the exact localization of epileptiform discharges. METHODS: Digital EEG data from 20 subjects showing epileptiform discharges that were localized in the left or right frontotemporal regions (F7, F8) were studied. Those EEG waves were recorded using international 10~20 system. Phase reversals in bipolar montage were converted to referential montage and waveforms were analyzed visually. Those spike waves were converted into three-dimensional potential density mapping by LORETA method and maximum negative potential density region was determined. RESULTS: The same localization in the frontotemporal region (F7, F8) between two methods was noted in 16 subjects (80.0%). The discordant localization by LORETA method was noted in 4 subjects (20.0%). In different localiza-tion subjects, their locations were frontopolar region (Fp1, Fp 2) in 2 subjects, lateral temporal region (T7, T8) in 1 and posterior temporal region (P7, P8) in 1 subject, respectively. CONCLUSIONS: Even though the localization of epileptiform discharges by visual waveform analysis is a traditional method, electrical potential density mapping by LORETA can be a useful adjunctive localization method. If detailed localization is needed, LORETA method should increase accuracy.