Video electroencephalography (EEG) plays an important role in judging whether a clinical spell is an epileptic seizure or paroxysmal event, but its interpretation is not always straightforward. If clinical events without EEG correlates are strongly suggestive of seizures, we usually regard these spells as epileptic seizures. However, the electric/magnetic physiological profile of EEG-negative epileptic seizures remains unknown. We describe a 19-year-old man known to have epileptic seizures, in which both magnetoencephalography (MEG)-unique and EEG/MEG spikes were seen. Both types of spikes originated from the same source, but the EEG/MEG spikes were of significantly higher magnitude than the MEG-unique spikes. Therefore, some epileptic seizures, even though generated identically to the MEG-positive seizures, could be EEG-negative because of their smaller magnitude.
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