Abstracts

Rationale: Scalp ictal patterns have been routinely used for localizing mesial and neocortical seizure onset in patients with temporal lobe epilepsy (TLE). Scalp theta ictal onset correlates with mesial TLE, whereas scalp delta ictal onset correlates with neocortical TLE. However, these observations were limited by the lack of hippocampal EEG recording in the previous studies. The objective of this study is to determine the localizing value of scalp ictal EEG patterns in patients with TLE with hippocampal recording. Methods: Simultaneous scalp and intracranial EEG recordings were performed in patients with TLE during pre-surgical evaluation. Intracranial EEG was recorded from both hippocampus and temporal neocortex. Scalp ictal EEG patterns were correlated with corresponding intracranial ictal EEG discharges. Results: A total of 63 seizures were recorded from scalp EEG in 23 patients with TLE. Of which, 49 seizures in 19 patients were recorded as theta ictal onset; whereas 14 seizures in 5 patients were recorded as delta ictal onset. One patient had both delta and theta ictal onset on scalp EEG. Both scalp theta and delta ictal onsets were all correlated with hippocampal ictal onset in this study. Of the patients with scalp delta ictal onset, two had mesial temporal sclerosis and three had normal MRI. Conclusions: Both theta and delta ictal onset patterns on scalp EEG are correlated with mesial temporal seizures. Therefore scalp delta ictal onset is not a reliable EEG marker for temporal neocortical ictal onset as commonly believed. Funding: None