Open Access

L. Elshoff, Muthuraman Muthuraman, G. Wiegand, J. Raethjen, U. Stephani, M. Siniatchkin

• Purpose: In the presurgical evaluation of children with refractory focalepilepsy the main difficulty is to locate the exact point of seizure onset.The aim of this study was to characterize the areas of seizure onset as wellas the epileptic network involved in seizure propagation usingDynamicimaging of coherent sources (DICS)of ictal EEGs. Method: DICS is an inverse solution in the frequency domain whichdescribes neuronal networks and coherence of oscillatory brain activityby applying a spatial filter (Gross et al. PNAS 2001; 98:694–699). In 15children with refractory focal epilepsy, typical seizures were selectedfrom the EEGs recorded during the presurgical evaluation. For every sei-zure, two data sets of 10 s duration were extracted: one EEG segmentcontained the seizure onset and the other segment included the middlepart of the seizure. For both segments, the frequency range was definedand analyzed with DICS. The brain area with the strongest power in thecorresponding frequencyPurpose: In the presurgical evaluation of children with refractory focalepilepsy the main difficulty is to locate the exact point of seizure onset.The aim of this study was to characterize the areas of seizure onset as wellas the epileptic network involved in seizure propagation usingDynamicimaging of coherent sources (DICS)of ictal EEGs. Method: DICS is an inverse solution in the frequency domain whichdescribes neuronal networks and coherence of oscillatory brain activityby applying a spatial filter (Gross et al. PNAS 2001; 98:694–699). In 15children with refractory focal epilepsy, typical seizures were selectedfrom the EEGs recorded during the presurgical evaluation. For every sei-zure, two data sets of 10 s duration were extracted: one EEG segmentcontained the seizure onset and the other segment included the middlepart of the seizure. For both segments, the frequency range was definedand analyzed with DICS. The brain area with the strongest power in thecorresponding frequency range was defined as a reference region and itscoherence with the entire brain was computed using DICS. The result ofthe reference region was compared with the electroclinical localizationof seizure onset as well as with the postoperative resection site to deter-mine concordance. Results: For the beginning of the seizure, a good concordance betweenresults of the DICS localization and postoperative outcome was achievedin all 15 patients. The analysis of seizure propagation revealed an epilep-tic network which resembled reverberation of epileptic activity betweendifferent brain areas. Conclusion: DICS may be a useful tool to define the seizure onset zoneand study epileptic networks.…