ABSTRACT of the Platform Presentation at the Fifth International Cleveland Clinic-Bethel Epilepsy Symposium, May 22-25, 1994
We have implemented a system for the on-line detection and localization of focal interictal spikes from intraoperative electrocorticographic recordings obtained previous to the surgical resection of the epileptic focus. The system is based on the Spatio-Temporal Laplacian (STL) transformation, which maps the time-varying, two dimensional potential field sampled by a planar array of electrodes placed on the exposed cerebral cortex into a new three-dimensional space (x, y, time) where the focal interictal events will appear selectively magnified. These will be distinguished on the basis of their characteristic "sharpness" in space and in time, measured by the SL ("Spatial Laplacian") and TL ("Temporal Laplacian") components of the STL, respectively.
The system has been implemented for on-line operation in a NeXT computer equipped with a 16 channel, A/D board. The STL algorithm runs in the DSP of the architecture , while the main CPU manages the user interaction and on-line display of results for focus localization.
The system has been used in 15 seizure surgery cases, in conjunction with the traditional methods of ECoG interpretation. Six of those cases have been evaluated off-line by a panel of 4 experts. Using their opinions as the gold standard, the system was found to have average sensitivity of 78%, average specificity of 78% and an accuracy of 90% in the distribution of interictal activity detected.