Abstracts

Rationale: EEG data during temporal lobe seizures have been reported to show lateralized buildup of theta (4-7Hz) activity following a period of generalized attenuation near the seizure focus with loss of awareness. However the exact dynamics of the theta activity, and clinical significance of such a buildup is not known. Methods: Ictal and baseline EEG data from 9 patients with temporal lobe epilepsy were analyzed using wavelet based algorithm to study the frequency flow dynamics. Results: We found that prior to onset of seizure; the frequency flow gradually builds up to 5-12Hz range at the focus and at distant channels unlike during baseline conditions of the same patients. Using wavelet based method we could analyze frequency flow dynamics instantaneously from rapidly changing EEG signals. Conclusions: Although the exact significance of frequency buildup is not clear, it is interesting to note that the buildup is seen not only at the focus but also at distant channels and is clearly different from the baseline conditions. This might suggest that during temporal lobe seizure the neuronal interactions propagate over large regions of the brain even at the very initial stages. Number of subjects in our analysis is small and also this study included only patients with temporal lobe epilepsy. We plan to study more patients with temporal lobe as well as other types of epilepsy including non-temporal and generalized epilepsy to explore whether the same kind of frequency flow dynamics are observed.