Figure 5: A typical example of 10/20 display undetectable spike (case 5). (a) The icEEG (upper) shows a right mesial temporal spike. Interictal spike is shown at electrodes nos. 17–22 which are located over the mesial temporal region. The EEG (lower) simultaneously recorded 256-channel dEEG with 19-channel 10/20 display. (b) Placement of subdural electrodes and the location of the interictal spike. Solid circle indicates the electrodes which show the interictal spike. (c) 256-channel dEEG topographic plot of the corresponding spike. The view is looking down on top of the head with nose at the top. The distribution of spike discharge not seen in the 10/20 montage is over the right-face electrodes (right upper corner). The 256-channnel topographic plot was instructive in localizing the spike to the anterior basal surface of the temporal lobe. (d) The source estimation by dEEG is superimposed on a standard MRI. The interictal spike is localized to the right mesial temporal region.