EEG spike source localization before and after surgery for temporal lobe epilepsy: a BOLD EEG-fMRI and independent component analysis study

Abstract

Simultaneous measurements of EEG-functional magnetic resonance imaging (fMRI) combine the high temporal resolution of EEG with the distinctive spatial resolution of fMRI. The purpose of this EEG-fMRI study was to search for hemodynamic responses (blood oxygen level-dependent -BOLD responses) associated with interictal activity in a case of right mesial temporal lobe epilepsy before and after a successful selective amygdalohippocampectomy. Therefore, the study found the epileptogenic source by this noninvasive imaging technique and compared the results after removing the atrophied hippocampus. Additionally, the present study investigated the effectiveness of two different ways of localizing epileptiform spike sources, i.e., BOLD contrast and independent component analysis dipole model, by comparing their respective outcomes to the resected epileptogenic region. Our findings suggested a right hippocampus induction of the large interictal activity in the left hemisphere. Although almost a quarter of the dipoles were found near the right hippocampus region, dipole modeling resulted in a widespread distribution, making EEG analysis too weak to precisely determine by itself the source localization even by a sophisticated method of analysis such as independent component analysis. On the other hand, the combined EEG-fMRI technique made it possible to highlight the epileptogenic foci quite efficiently.

Neurorestorative Effects of Constraint-Induced Movement Therapy after Stroke: An Integrative Review

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“…the state of lowest energy; however, when this occurs, the excess energy is emitted in the form of electromagnetic radiation. This energy is detected by the fMRI device and allows the formation of anatomical images [39].…”

“…It allows the studying of neural networks dynamically by tracking specific responses in several spatial scales; however, fMRI can measure only hemodynamic changes such as variations in blood volume, or intravascular magnetic susceptibility [41]. Moreover, regardless of whether it is an incipient technique, fMRI has been applied to a variety of functional studies, ranging from simple to complex experiments such as neuropsychological investigations [39]. Thus, it stands out by allowing the exploration of various brain functions, due to its high ability to differentiate tissues.…”

EEG-fMRI Co-Registration: From Research to a Potential Pre- Surgical Tool

“…A new tool, simultaneous recording of EEG and functional MRI (fMRI) is being used mainly as a research modality that exploits the complementary advantages of both the techniques, EEG and functional MRI [2][3][4][5][6][7][8][9][10][11][12][13] . EEG detects the electrical activity from the surface of the scalp originating from the cortical pyramidal cells.…”

Selection of independent components based on cortical mapping of electromagnetic activity

“…The source information of an IC can be calculated by estimating the associated brain activity from the scalp topography of the IC. Dipole fitting (Scherg and Von Cramon 1985) is a widely used method for source localization (Cao et al 2002, Debener et al 2005, Onton et al 2005, Sercheli et al 2009. However, this method requires a fixed number of dipoles and initial guesses of dipole parameters to be made in advance (Michel et al 2004).…”