Epileptic seizure characterization by Lyapunov exponent of EEG signal

Purpose - The purpose of this paper is to develop the new method of estimation of the short-term largest Lyapunov exponent of electroencephalogram (EEG) waveforms for the detection and prediction of the epileptic seizure. Design/methodology/approach - The paper proposed the modifications concerned with the way of selection of the segments of EEG waveforms taking part in estimation of Lyapunov exponent, as well as determination of the distances between two time series. The proposed method is based on Kolmogorov-Smimov test of similarity of two vectors. Through the application of this test more accurate and less parameterized approach to the estimation of the short-term largest Lyapunov exponent of EEG waveforms has been obtained. Findings - The results of performed experiments have shown that in most cases our modified method has outperformed the classical procedure, leading to more stable results, closer to the neurologist indications. The analysis of the data has proved that the change of the largest Lyapunov exponent provides a lot of information regarding the epileptic seizure. The minimum value of Lyapunov exponent indicates fairly well the seizure moment. The Tindex applied for few different electrode sites can provide good advanced prediction of the incoming epileptic seizure. Practical implications - After additional experiments this method may find practical application for supporting the medical diagnosis of the epilepsy. Originality/value - The proposed modification of the estimation of the short-tenn largest Lyapunov exponent of the EEG waveforms eliminates some arbitrarily chosen parameters tuned by the user and leads to more accurate estimate. Such estimation results are better suited for the characterization of the epileptic activity.