Electromagnetic methods for presurgical evaluation of epilepsy

Electromagnetic methods are the most important diagnostic tools in the presurgical evaluation of medically intractable epilepsy. Localization of the source of the epileptic discharge is essential, in the presence or absence of structural lesions. Scalp electroencephalography (EEG), intracranial EEG and magnetoencephalography provide temporal resolutions of millisecond-order that are adequate to evaluate the physiology of the disease. The advantages and limitations of these electromagnetic methods are based on the following characteristics: 1) space-sampling and sensor position; 2) time-sampling and measurement time; 3) effect of ambient- and brain-noises and; 4) source localization methods. Combined and complementary use of these electromagnetic methods can provide the information essential for the surgical treatment of epilepsy.