Parietal epileptic mirror focus detected with a whole-head neuromagnetometer

WHOLE-head magnetoencephalographic recordings revealed two parietal epileptic foci in homotopic areas of the hemispheres. The discharges occurred 17–20 ms later on the left than on the right hemisphere, implying the existence of a left-sided mirror focus. The foci were about 1 cm posterior to the hand primary somatosensory area, identified by evoked response measurements, and thus suggested epileptic activity at the parietal association cortex, in agreement with the observed callosal conduction time.