Inadequacy of standard screen resolution for localization of seizures recorded from intracranial electrodes.

Seizures recorded during long-term monitoring with implanted intracranial electrodes are typically interpreted by visual inspection alone by using digital display systems. When high-frequency activity is digitized and displayed on a typical monitor, it is altered in ways that are not always appreciated and that may have an impact on the intracranial EEG (ICEEG) interpretation. We describe a case of a neocortical-onset seizure in which false localization occurred with a 12-s per screen display. Because frequencies in excess of 100 Hz are not uncommon in neocortical seizures, at most 4 to 5 s of EEG, depending on the screen resolution, data-sampling rate, and other factors, should be displayed at one time during visual interpretation to localize the seizure onset. Alternatively, spectral analysis should be performed on recordings of neocortical seizures to detect high-frequency activity that may be missed on visual inspection.