Wavelet analysis of generalized tonic-clonic epileptic seizures

摘要

The analysis of generalized tonic-clonic seizures is usually difficult with quantitative EEG techniques due to muscle artifact. We applied two quantifiers based on the Wavelet Transform to evaluate 20 seizures from eight consecutive patients admitted for video-EEG monitoring. We studied the relative wavelet energy and the wavelet entropy over time. In 16/20 events we found significant decremental activity in the relative wavelet energy associated with frequency band 0.8-3.2 Hz (delta activity) at the seizure onset, indicating that the seizure is dominated by medium frequency bands 3.2-12.8 Hz (theta and alpha bands). In 19/20 events the mean wavelet entropy presents lower values during the ictal period compared to the pre-ictal period, indicating that the associated dynamic is more ordered and simple. Thus the employed tools show good accuracy for detecting changes in the system dynamic. We conclude that this behavior could be induced by frequency tuning in the neuronal activity triggered by an hypothetic epileptic focus.