Focus Lateralization in Mesial Temporal Lobe Epilepsy: A Comparison of Linear and Nonlinear Measures.
Abstract number :
B.05
Submission category :
Year :
2001
Submission ID :
1662
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
R.G. Andrzejak, Epileptology, University of Bonn, Bonn, Germany; K. Lehnertz, PhD, Epileptology, University of Bonn, Bonn, Germany; C. Rieke, Inst for Radiation and Nuclear Physics, University of Bonn, Bonn, Germany; F. Mormann, Epileptology, University o
RATIONALE: A number of studies indicate that the application of measures derived from the theory of nonlinear deterministic dynamical systems allows localization of epileptic foci from interictal intracranial EEG recordings. In order to determine whether these results are specifically caused by nonlinear deterministic components we now investigate if measures that were developed for the characterization of linear dynamical systems allow the extraction of similar information from the EEG.
METHODS: In our analysis we compared the performance of a number of nonlinear and linear measures regarding the discriminative power for the side of the focal hemisphere. As nonlinear measures we used the neuronal complexity loss and the fraction of nonlinear determinism. As linear measures we used spectral power in different frequency bands (d,J,a and b), statistical moments of higher order (skewness and kurtosis) and the decay time of the autocorrelation function. All measures were calculated from interictal intracranial EEG recordings from 25 patients with unilateral mesial temporal lobe epilepsy. Average duration of each recording was 84 min per patient.
RESULTS: The highest discriminative power was obtained for the fraction of nonlinear determinism and the neuronal complexity loss. All linear measures proved to be less specific for the focal hemisphere. Among the linear measures, the d-band power and the decay time of the autocorrelation function yet showed a high discriminative power, whereas the statistical moments turned out to be quite unspecific for the epileptogenic hemisphere.
CONCLUSIONS: The higher performance of nonlinear measures suggests that the epileptogenic process comprises nonlinear deterministic components. Nonetheless, both linear and nonlinear measures can contribute valuable information to the lateralization of the focal hemisphere without the necessity of observing actual seizure activity.