Abstracts

RATIONALE: A clearer understanding of the relationship between extracranial and intracranial ictal EEG with extrahippocampal epilepsy could help in clinical decision-making. METHODS: We retrospectively analyzed surface EEG ictal recordings from 36 subjects with extra-hippocampal localization-related epilepsy who subsequently were studied with intracranial electrodes. We identified four categories of surface EEG ictal patterns and examined the yield of well-defined focal intracranial ictal patterns in each category. RESULTS: Eleven subjects had focal fast frequency surface patterns or minimal alteration in surface ictal EEG: All had well-defined focal intracranial ictal patterns. Nine subjects had surface patterns which resembled the temporal theta patterns described in patients with hippocampal epilepsy: Four of these subjects had well-defined focal intracranial patterns and five had regional patterns that were sufficient for surgical decision-making. Six subjects had other types of focal or lateralized surface EEG ictal patterns: Only one had a localizing intracranial pattern. Ten subjects had diffuse surfce ictal patterns: Two of these subjects had focal intracranial ictal patterns. CONCLUSIONS: In subjects with extra-hippocampal localization-related epilepsy, different categories of surface EEG ictal finidings are associated with different expectations for focal intracranial ictal patterns.