Relationship of Nonlinear Analysis, MRI and SPECT in the Lateralization of Temporal Lobe Epilepsy

Abstract

Objectives: The purpose of this study was to investigate the correlation of lateralization by nonlinear analysis, magnetic resonance imaging (MRI) and interictal single-photon emission computed tomography (SPECT) in patients with temporal lobe epilepsy. Methods: Twenty-three patients (7 males, 16 females) were examined by MRI, interictal SPECT and EEG. Nonlinear dynamic properties of neuronal networks were estimated by calculating correlation dimensions on interictal EEG signals and corresponding surrogate data. Lateralization was detected based on the criteria introduced in this study. Concordance rates of the results among the three methods were compared. Results: Epileptogenic foci were shown in the temporal areas in 21 patients using the nonlinear method (8 left, 2 right, 11 both), while 20 patients showed abnormalities in temporal lobes on MR images (13 left, 5 right, 2 both). Low cerebral blood flows of the temporal lobes were detected in all patients (11 left, 8 right, 4 both). Completely concordant lateralization was observed in 8 patients (35%) for the nonlinear method and MRI, in 9 patients (39%) for the nonlinear method and SPECT, and in 10 patients (43%) for MRI and SPECT. There were no significant differences among the concordance rates for these different methods. Conclusions: Our results revealed that correlation dimension is useful for differentiating dynamic properties of neuronal networks in the interictal state, and can provide informative data for localizing epileptogenic foci in epileptic patients. Therefore, the present nonlinear method is recommended for use with patients during presurgical evaluation.

EEG preprocessing for synchronization estimation and epilepsy lateralization

“…This lateralization is commonly made by visual inspection of interictal EEG [1], [2], ictal [3], [4] or using semiautomatic or automatic lateralization [5], [6]. In the framework of quantification methods for seizure lateralization two types of methods are presented in the literature: methods based on the temporal dynamics of EEG [7], [5] and those based on frequency domain [8], [9]. The main drawback in automatic lateralization using scalp EEG recordings is the presence of artifacts (eye blinking, muscular artifact, movement, chewing, etc.)…”