Abstracts

RATIONALE: The objective was to determine the frequency content of the seizure onset and earliest spread of an epileptic seizure in hippocampal (HC) and neocortical (NC) seizures. METHODS: EEGs of 1 recorded seizures of 6 patients with temporal lobe epilepsy who underwent intracranial recording by subdural strip/ grid and/or depth electrodes were analyzed. The seizure onset frequency in recordings from the intracranial contact were determined using a Moving Fast Fourier Transform (FFT) analysis. The seizure onset in each electrode recording was established as the time when the amplitude of the most dominant ictal frequency increased. The frequency response characteristics of the seizure onset and the earliest seizure spread location were calculated. RESULTS: In five out of 6 seizures the onset frequencies contained related components. Of these, the most dominant frequency was in the 5-8 Hz range regardless of the NC or HC onset. The onset frequency of the sixth seizure (patient), of NC origin, consisted of a single high frequency component, 26Hz. Two of the six seizures spread with a lower frequency whereas the frequency of spread for the other four remained the same, regardless of seizure origin. CONCLUSIONS: There was no significant difference between the HC and NC seizure onset and spread frequencies. Time of seizure spread from the onset to the next location did not differ between the HC and the NC seizures. In view of the small sample, further analysis in more patients will be performed.