Abstracts

Rationale: Dense array EEG (dEEG) has been a powerful tool for electrical source localization noninvasively. However validation studies measuring the accuracy of dEEG source imaging are still needed. The purpose of this study is to evaluate the accuracy of dEEG for the source localization of interictal spikes by comparing dEEG and intracranial EEG (icEEG).Methods: We performed simultaneous recording of interictal spikes by both scalp 256-channels dEEG and icEEG with four patients with medically refractory neocortical epilepsy. All of them were surgical candidates and underwent subdural electrode implantation to determine ictal onset and define functional areas. One patient showed a lesion on the MRI in the right parietal lobe. The dEEG was used to noninvasively estimate the source of the interictal spikes detected by the 256-channel dEEG array, which was then compared to the activity measured directly at the source by the icEEG.Results: We captured 287 interictal spikes were measured with the icEEG from the four patients. 155 spikes (54%) were visually detected by the dEEG upon examination of the 256-channel head surface array. The spike amplitudes detected by the 256-channel dEEG correlated with icEEG spike amplitudes (p < 0.01). All spikes detected in dEEG were localized to the same lobe correctly and closed to the position confirmed by subdural electrodes. Surgical resections were based on the ic EEG findings.Conclusions: The results demonstrate that 256-channel dEEG can reliably detect interictal spikes and localize them with reasonable accuracy. 256-channel dEEG may be clinically useful in the presurgical work-up for epilepsy and have potential to reduce the need for invasive EEG evaluation.