Characterization of focal seizures in scalp electroencephalograms based on energy of signal and time-frequency analysis

Abstract

This work presents a method for characterization of focal seizures from scalp digital electroencephalograms (EEG) obtained in the Central League Against Epilepsy in Bogotá, which were acquired from patients between 13 and 53 years old. This characterization was performed in segments of 500 ms with presence of focal seizures that had been initially identified and labeled by a specialist during their visual examination. After selection of the segments and channels for analysis, the energy of the signals were calculated with the idea that the energy of focal seizures could be larger than the one of their side waves in the segments. This procedure produced peaks of energy corresponding to the seizures and, some times, to noise and artifacts. In order to identify the peaks of energy of the seizures an analysis with continuous wavelet transform was performed. It was found that the mother wavelet 'bior2.2' allowed more easily the identification of such seizures from the seventh scale of the analysis. The method allowed the identification of the 65% of the seizures labeled by the specialist. © 2011 Springer-Verlag Berlin Heidelberg.