Principles of magnetoencephalography.

Magnetoencephalography (MEG) is a new, noninvasive functional test equivalent to EEG. It has been used to localize the sources of evoked responses and interictal and ictal epileptiform discharges and to study patients with psychiatric illnesses, cerebrovascular accidents, and migraine. In epilepsy research, it is hoped that MEG will provide information similar to that yielded by depth or subdural electrode recording, or that the combination of these methods will provide more information than either one alone. The application of MEG appears to be widening, although it is not yet a routine clinical diagnostic tool. The utility of MEG is limited by technological problems, but new and more efficient systems are becoming available. Within several years, advances in the technology and understanding of MEG may modify the course of its application.