ESI and fMRI of interictal and ictal epileptic discharges

A major challenge in planning and performing resective surgery in drug-resistant epilepsy is the accurate identification of the epileptogenic zone. Currently, intracranial EEG is considered to be the most reliable preresective functional localisation method. Our objective is to non-invasively localise the epileptogenic zone using simultaneous high-density EEG source imaging (ESI) and fMRI of interictal and ictal discharges. We performed two 128-channel EEG recordings, in a shielded room and simultaneous EEG-fMRI, of a focal epilepsy patient in a single session and captured interictal discharges and one seizure exhibiting oscillatory activity of 14 Hz. The locations described by fMRI and ESI of interictal events in the MR scanner and shielded room show good anatomical agreement with each other; the ictal ESI; and with video EEG monitoring, PET and ictal SPECT. Averaging of ictal oscillatory periods strengthens the localisation, while the quantity of concordant interictal events supports reliability of interictal localisations. Simultaneous high-density EEG and fMRI acquisition non-invasively provides added localising information in a multimodal context. Concordant simultaneous ESI and fMRI localisation of interictal and ictal events shows promise in improving noninvasive presurgical evaluation of epilepsy.