Spatiotemporal analysis of interictal epileptic spikes. A stereoelectroencephalographic study

Interictal epileptic spikes (IES) were recorded and averaged in 4-15 channels, in seven adult epileptics with intracerebral electrodes. IES relations were revealed by comparing the onset of the averaged IES in each channel, with one being used alternatively as the triggering channel. The records were analysed and sorted by comparing the morphology of individual IES and the final average morphology. There was a dominant group of IES on each recording site channel representing about 65-80% and decidedly influencing the average morphology of all IES. The major limitation of IES averaging is the loss of information due to the IES relative heterogeneity. Nevertheless, it reveals the main basic relationships in the large numbers of IES. On the other hand, IES averaging helps to minimize fortuitous spatiotemporal relations between recording sites. The relationship between IES in two channels was considered as significant only when these channels were observed both before and after the mutual switching of the role of triggered and triggering channel. The relations were then considered significant in only about 18% of all possible relations.