Localization of epileptic foci using a large-area magnetometer and functional brain anatomy.

We used a large-area, 7-channel, first-order superconducting quantum interference device (SQUID) gradiometer to preoperatively determine the sites of epileptic foci in 2 patients with intractable temporal lobe seizures. The equivalent dipoles for the epileptic spikes were located with respect to external landmarks of the skull and in relation to the generation sites of magnetic auditory evoked responses. It was also possible, for the first time, to determine the location of the equivalent source using simultaneously measured data from seven locations only. The sites of the equivalent dipoles, in the right temporal lobe, agreed with the electrocorticographic and depth electrode recordings made during the operation.