Abstracts

Rationale: Electrical source imaging (ESI) has been established as a promising tool for epilepsy evaluation. Although spike localization has often provided useful information for seizure onset zone (SOZ), it may not be sufficient to guide neurosurgical resection in many patients. As a result, it usually needs dense array EEG (dEEG) to capture a number of representative seizures and localize the ictal oscillations. The goal of this study is source localization of interictal spikes and seizure onset using 256 dEEG recordings and high-resolution individual head models constructed from the patient’s magnetic resonance image (MRI).Methods: (1) Localizing interictal spikes: Long term monitoring (LTM) EEG is run through a semi-automated spike detection algorithm. The appropriate number of spike topographies has been detected and suggest the number of unique epileptiform foci for each individual. Interictal spikes are averaged and localized at 50% of spike peak using standardized Low Resolution Electromagnetic Tomography (sLORETA) method with individual head model. (2) Localizing ictal onset: a physician visually identifies seizure onset. Ictal oscillatory features are characterized by joint time-frequency analysis and ictal oscillations associated with seizure onset are localized using sLORETA. (3) A validation using intracranial EEG and surgical outcomes.Results: In this preliminary study, five patients with epilepsy were examined and validated. Interictal spikes and multiple seizures from each patient were identified and consistently aligned with intracranial EEG and surgical outcomes localizations. The result supports the ability of the noninvasive dEEG recording to localize the seizure onset zone precisely.Conclusions: Precise localization requires high dense array EEG, advanced source localization algorithms and high-resolution individual electrical head models. To optimize noninvasive identification of the seizure onset zone for pre-surgical planning, it is necessary to use several complementary techniques such as interictal spikes and seizure onset to more accurately localize the epileptogenic foci.