The localizing value of depth electroencephalography in 32 patients with refractory epilepsy

Clinical seizure manifestations, physical examination, radiological studies, neuropsychological tests, and scalp and depth electroencephalographic (EEG) studies were done to localize seizure foci in 32 patients, 23 of whom have undergone surgery with more than one year of follow-up. Of 16 patients with unlocalized scalp EEGs, depth EEG detected a consistent focal seizure onset in 3. Of 15 patients with localized scalp EEGS, depth EEG revealed multiple foci in 3 and inaccurate localization of the focus by scalp EEG in 4. Therefore, localization by scalp EEG was inaccurate in 10 of 31 patients. When depth EEG revealed a consistent focal seizure onset and this localization was used to determine to surgical resection site, good to excellent results were obtained in 12 of 13 patients. When depth EEG revealed additional foci of seizure origin, surgical results were fair or poor in all patients. No other localizing criteria predicted depth EEG results or surgical success with such accuracy. Furthermore, some criteria, including neuropsychological tests and radiological abnormalities, were falsely localizing at times. Therefore, of the presently available localizing criteria, depth EEG appears to be the most accurate.