Source analysis of ictal EEG patterns in focal epilepsy

Methods: 65 seizure patterns recorded by surface EEG (35–53 channels, 256Hz) in 16 patients (0.7–20 years) were included in the analysis. 8 patients had dysplastic lesions (33 seizures) and 8 non-dysplastic lesions (5 tumor, 3 gliosis, 32 seizures). 14 patients underwent epilepsy surgery (11 seizure free). The earliest seizure pattern in preoperative Video-EEG was identified visually, the dominant frequency was determined by FFT and identical sinus periods were averaged (r>0,85 for 3–5 channels). A 4-shell spherical head model was used in the BESA™ source analysis. At first, one regional source was modeled (RS1). A regional source provides information on localization of activities independent from current orientation. An application of a two-independent-regional source model (RS2) followed. Anatomical relations were analyzed by 3D-T1-MRI superposition (BrainVoyager®).