Abstracts

RATIONALE: We investigated the ictal patterns in electrocorticographic recordings and correlation with surgical outcomes in nonlesional neocortical epilepsy. METHODS: Seventeen patients were included in this study, who had intractable neocortical epilepsy documented by intracranial monitoring but no epileptogenic lesions on brain MRI. 157 ictal EEGs recorded by subdural grid were analyzed.We investigated number and location of ictal onset zone, thir morphology including frequency, consistency in repeated seizure, and persisting time as an active participant. Surgical outcome was determined by seizure reduction rate depending on seizure type. The duration of follow-up was 32-60 months. RESULTS: Stereotyped ictal onset zone actively involved throughtout each seizure was a significant prognostic factor (p < 0.05). Ictal onset area with shifting laterality or regionality in each ictus was correlated with poor prognosis. However, neither number of electrodes involved in initial changes nor frequencies of EEG rhythms at onset was a significant prognostic factor. CONCLUSIONS: Intracranial ictal EEG patterns can predict the surgical outcome in nonlesional neocortical epilepsy. Well established ictal circuit with consistent EEG onset zone having persistent ictal activity during individual seizure is an important prognostic factor.