Toward a definition of MEG spike: Parametric description of spikes recorded simultaneously by MEG and depth electrodes

Nowak, Rafał; Santiuste, Marta; Russi, Antonio

doi:10.1016/j.seizure.2009.07.002

Cited by 25 publications

(17 citation statements)

References 17 publications

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“…MEG/EEG recordings were manually inspected by experienced evaluators for the occurrence of epileptic spikes according to the criteria of the International Federation of Clinical Neurophysiology, taking special characteristics of MEG spikes into account. 12,13 All recorded epileptic MEG spikes and their EEG correlates were averaged in each patient. Moving equivalent current dipoles (moving ECD) were calculated from averaged MEG spikes using a single sphere head model.…”

Section: Magnetoencephalgraphy/electroencephalgraphy (Meg/eeg) Data Acquisition and Source Localisationmentioning

confidence: 99%

MEG-based identification of the epileptogenic zone in occult peri-insular epilepsy

Heers

Rampp

Stefan

et al. 2012

Seizure

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Section: Magnetoencephalgraphy/electroencephalgraphy (Meg/eeg) Data Acquisition and Source Localisationmentioning

confidence: 99%

MEG-based identification of the epileptogenic zone in occult peri-insular epilepsy

Heers

Rampp

Stefan

et al. 2012

Seizure

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“…Epileptic MEG spikes were chosen according to the characteristics used for EEG. 20,21 For this study, clinical reports of MEG findings were used to avoid interpretational bias.…”

Section: M/eeg Proceduresmentioning

confidence: 99%

Detection of epileptic spikes by magnetoencephalography and electroencephalography after sleep deprivation

Heers

Rampp

Kaltenhäuser

et al. 2010

Seizure

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Introduction:In diagnosis of epilepsies electrophysiological findings play a key role. While spontaneous electroencephalography (EEG) and EEG with sleep deprivation (EEGsd) are widely evaluated and used, application of magnetoencephalography (MEG) in this field is primarily limited to presurgical assessment of focal epilepsies. Methods: In this study we retrospectively compared MEG (M/EEG) and EEGsd in 63 (55) patients with focal and generalized epilepsy with regard to occurrence of epileptic spikes. Results: MEG could record epileptic spikes in 38 patients (60%), while EEGsd recorded spikes in only 32 patients (51%). In a group of 55 patients simultaneous MEG/EEG (M/EEG) was able to record spikes in 38 patients (71%) compared to epileptic spikes in 28 patients (51%) recorded by EEGsd. In a subgroup of 17 MR-negative patients simultaneous M/EEG could record epileptic spikes in all patients, while EEGsd was successful in only 11 (64%) of them. Conclusion: In this study, MEG showed a tendency to record epileptic spikes in more patients than EEGsd. Furthermore, simultaneous M/EEG has been shown to be especially successful in detection of epileptic spikes in patients with MR-negative epilepsy. This might at least in parts be explained by neocortical predominance of MR-negative epilepsy. Thus, this study motivates prospective studies to evaluate the substitutability of EEGsd by MEG more extensively.

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“…The spike shape, in particular its late slow wave part, has been proposed to have an impact on the sign of the hemodynamic response . Generally, the spike shapes recorded in different sessions can show considerable variations (Nowak et al 2009;Fernandez et al 2005) which may affect the corresponding BOLD responses. For example, Salek-Haddadi et al (2006) showed that including additional information about the duration of interictal discharges led to increased sensitivity in analyzing combined EEG-fMRI recordings.…”

Section: Introductionmentioning

confidence: 99%

Modeling of the Neurovascular Coupling in Epileptic Discharges

et al. 2011

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Despite the interest in simultaneous EEG-fMRI studies of epileptic spikes, the link between epileptic discharges and their corresponding hemodynamic responses is poorly understood. In this context, biophysical models are promising tools for investigating the mechanisms underlying observed signals. Here, we apply a metabolic-hemodynamic model to simulated epileptic discharges, in part generated by a neural mass model. We analyze the effect of features specific to epileptic neuronal activity on the blood oxygen level dependent (BOLD) response, focusing on the issues of linearity in neurovascular coupling and on the origin of negative BOLD signals. We found both sub- and supra-linearity in simulated BOLD signals, depending on whether one observes the early or the late part of the BOLD response. The size of these non-linear effects is determined by the spike frequency, as well as by the amplitude of the excitatory activity. Our results additionally indicate a minor deviation from linearity at the neuronal level. According to a phase space analysis, the possibility to obtain a negative BOLD response to an epileptic spike depends on the existence of a long and strong excitatory undershoot. Moreover, we strongly suggest that a combined EEG-fMRI modeling approach should include spatial assumptions. The present study is a step towards an increased understanding of the link between epileptic spikes and their BOLD responses, aiming to improve the interpretation of simultaneous EEG-fMRI recordings in epilepsy.

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Toward a definition of MEG spike: Parametric description of spikes recorded simultaneously by MEG and depth electrodes

Cited by 25 publications

References 17 publications

MEG-based identification of the epileptogenic zone in occult peri-insular epilepsy

MEG-based identification of the epileptogenic zone in occult peri-insular epilepsy

Detection of epileptic spikes by magnetoencephalography and electroencephalography after sleep deprivation

Modeling of the Neurovascular Coupling in Epileptic Discharges

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