Comparisons of MEG, EEG, and ECoG source localization in neocortical partial epilepsy in humans

Nakasatp, Nobukazu; Lévesque, Michel; Barth, Daniel S.; Baumgartner, Christoph; Rogers, Robert L.; Sutherling, William W.

doi:10.1016/0013-4694(94)90067-1

Cited by 186 publications

(81 citation statements)

References 13 publications

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“…This is compared to a localization accuracy of 17 mm for MEG measurements of artificial dipoles generated from implanted subdural strips [Balish et al, 1991]. Other studies have estimated accuracy by comparing lesion data (e.g., tumor, epileptogenic focus) in epileptic patients with the non-invasive location estimates from EEG [Diekmann et al, 1998;Herrendorf et al, 2000;Ko et al, 1998;Krings et al, 1998;Nakasato et al, 1994] or MEG [Diekmann et al, 1998;Ko et al, 1998;Mikuni et al, 1997;Nakasato et al, 1994;Sutherling et al, 1987Sutherling et al, , 1988aStefan et al, 1994;Tiihonen et al, 1990]. Similar to the results of the artificial current dipoles, the EEG and MEG accuracy were comparable (ranging from 10 -20 mm).…”

Section: Introductionmentioning

confidence: 75%

Monte Carlo simulation studies of EEG and MEG localization accuracy

Liu¹,

Dale²,

Belliveau³

2002

Human Brain Mapping

330

256

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Both electroencephalography (EEG) and magnetoencephalography (MEG) are currently used to localize brain activity. The accuracy of source localization depends on numerous factors, including the specific inverse approach and source model, fundamental differences in EEG and MEG data, and the accuracy of the volume conductor model of the head (i.e., the forward model). Using Monte Carlo simulations, this study removes the effect of forward model errors and theoretically compares the use of EEG alone, MEG alone, and combined EEG/MEG data sets for source localization. Here, we use a linear estimation inverse approach with a distributed source model and a realistic forward head model. We evaluated its accuracy using the crosstalk and point spread metrics. The crosstalk metric for a specified location on the cortex describes the amount of activity incorrectly localized onto that location from other locations. The point spread metric provides the complementary measure: for that same location, the point spread describes the mis-localization of activity from that specified location to other locations in the brain. We also propose and examine the utility of a "noise sensitivity normalized" inverse operator. Given our particular forward and inverse models, our results show that 1) surprisingly, EEG localization is more accurate than MEG localization for the same number of sensors averaged over many source locations and orientations; 2) as expected, combining EEG with MEG produces the best accuracy for the same total number of sensors; 3) the noise sensitivity normalized inverse operator improves the spatial resolution relative to the standard linear estimation operator; and 4) use of an a priori fMRI constraint universally reduces both crosstalk and point spread. Hum. Brain Mapping 16:47-62, 2002.

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Section: Introductionmentioning

confidence: 75%

Monte Carlo simulation studies of EEG and MEG localization accuracy

Liu¹,

Dale²,

Belliveau³

2002

Human Brain Mapping

330

256

View full text Add to dashboard Cite

show abstract

“…Previous studies suggested that the localization accuracy of MEG was higher than that of conventional scalp EEG (10,14) because of the absence of disturbance by the inhomogeneous conductivity of cranial tissues. However, only a few studies have correlated the MEG spike localization with the postoperative seizure outcome (13,14,16,17).…”

mentioning

confidence: 96%

“…Spike localization by magnetoencephalography (MEG) has been compared with localization by intracranial EEG (2,(9)(10)(11)(12)(13)(14), positron emission tomography (PET) (15) and single-photon emission computed tomography (SPECT) (9). Previous studies suggested that the localization accuracy of MEG was higher than that of conventional scalp EEG (10,14) because of the absence of disturbance by the inhomogeneous conductivity of cranial tissues.…”

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confidence: 99%

Surgical Implications of Neuromagnetic Spike Localization in Temporal Lobe Epilepsy

et al. 2002

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Summary:Purpose: To investigate the clinical usefulness of magnetoencephalography (MEG) as a guide to the surgical treatment of temporal lobe epilepsy (TLE).Methods: Preoperative spike localization by MEG was compared with seizure outcome and postoperative spike localization at 12 months after resective surgery in 16 patients with TLE. Spike localization was classified into anterior temporal (AT) and non-AT localization in 11 patients without neocortical lesion treated with anterior temporal lobectomy (ATL); and lesion and lobar localization in five patients with neocortical lesion treated with lesionectomy (n ‫ס‬ 3) or lesionectomy with medial temporal resection (n ‫ס‬ 2).Results: All five patients with AT localization became seizure free and spike free after surgery. Among the six patients with non-AT localization, two became seizure free and spike free, two became seizure free with residual spikes, one had residual seizures but no spikes, and one had both residual seizures and spikes. All three patients with lesion localization and two with lobar localization had favorable seizure outcome and became spike free after surgery.Conclusions: MEG spike localization can identify neocortical sources remote from the presumed epileptogenic area. Favorable seizure outcome can be expected in patients with AT localization after ATL and patients with lesion localization after lesionectomy. In contrast, non-AT localization indicates either nonmedial TLE or spike propagation to the posterior and extratemporal neocortex. Similarly, lobar localization indicates spike propagation from an epileptogenic lesion or extensive epileptogenicity. Patients with non-AT localization or lobar localization should undergo intensive evaluations, such as intracranial EEG, for improved seizure outcome.

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“…Magnetoencephalography (MEG) is a noninvasive neurophysiologic technique to detect the magnetic fields generated by electric currents in the brain, and has been frequently used to localize the epileptic discharges in patients with focal epilepsy (Stefan et al 1992;Nakasato et al 1994;Knowlton et al 1997;Jin et al 2007), but not in patients with insular epilepsy.…”

mentioning

confidence: 99%

Localization of Abnormal Discharges Causing Insular Epilepsy by Magnetoencephalography

Park

Nakasato

Tominaga

2012

Tohoku J. Exp. Med.

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The insula, one of the five cerebral lobes of the brain, is located deep within the brain and lies mainly beneath the temporal lobe. Insular epilepsy can be easily confused and misdiagnosed as temporal lobe epilepsy (TLE) because of the similar clinical symptoms and scalp electroencephalography (EEG) findings due to the insula location and neuronal connections with the temporal lobe. Magnetoencephalography (MEG) has higher sensitivity and spatial resolution than scalp EEG, and thus can often identify epileptic discharges not revealed by scalp EEG. Simultaneous scalp EEG and MEG were performed to detect and localize epileptic discharges in two patients known to have insular epilepsy associated with cavernous angioma in the insula. Epileptic discharges were detected as abnormal spikes in the EEG and MEG findings. In Patient 1, the sources of all MEG spikes detected simultaneously by EEG and MEG (E/ M-spikes) were localized in the anterior temporal lobe, similar to TLE. In contrast, the sources of all MEG spikes detected only by MEG (M-spikes) were adjacent to the insular lesion. In Patient 2, the sources of all MEG spikes detected simultaneously by EEG and MEG (E/M-spikes) were localized in the anterior temporal lobe. These findings indicate that MEG allows us to detect insular activity that is undetectable by scalp EEG. In conclusion, simultaneous EEG and MEG are helpful for detecting spikes and obtaining additional information about the epileptic origin and propagation in patients with insular epilepsy.

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Comparisons of MEG, EEG, and ECoG source localization in neocortical partial epilepsy in humans

Cited by 186 publications

References 13 publications

Monte Carlo simulation studies of EEG and MEG localization accuracy

Monte Carlo simulation studies of EEG and MEG localization accuracy

Surgical Implications of Neuromagnetic Spike Localization in Temporal Lobe Epilepsy

Localization of Abnormal Discharges Causing Insular Epilepsy by Magnetoencephalography

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