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Dynamic Electrical Source Imaging (DESI) of Seizures and Interictal Epileptic Discharges Without Ensemble Averaging

B. Erem, D. Hyde, J. Peters, F. Duffy, S. Warfield
IEEE Trans Med Imaging

The method presented in this paper, Dynamic Electrical Source Imaging (DESI), addresses the problem of non-invasively localizing the brain’s electrical activity during seizures and interictal epileptic discharges from electroencephalographic (EEG) measurements on the scalp surface. DESI works by first identifying a dynamical system that models the generation of measured scalp EEG over short time segments, and then solving an inverse problem to reconstruct time-varying amplitudes of distributed electrical sources in the cortex. A key point of this paper is that the method was used to localize data from before, during, and after seizures without individually marking, time-aligning, and averaging discharges, which can be a time-consuming process and a potential source of errors.
 
The video contains an example of the time-varying source amplitudes reconstructed by DESI during seizure activity. This patient had previously undergone epilepsy surgery to excise the left anterior temporal lobe, but continued to have seizures. Seizures recorded during subsequent EEG monitoring were localized using DESI. The video shows propagating source activity originating from the anterior tip of the remaining left temporal lobe. Cumulative activity maps show that this was a frequently occurring pattern during 4 separate seizures. The patient underwent a second surgery to further excise tissue, the margins of which are shown with dotted lines, which succeeded in stopping seizures. DESI successfully localized this frequent activity to within the margins of this surgery.