Magnetoencephalography in clinical epileptology and Epilepsy research

Baumgartner, Christoph; Deecke, Lüder

doi:10.1007/bf01140589

Cited by 15 publications

(5 citation statements)

References 78 publications

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“…3 Magnetoencephalography (MEG), a non-invasive tool for the assessment of focal epileptic activity, has been reported to accurately localise specific epileptic discharges in a variety of publications [4][5][6][7][8][9] and to be particularly useful in combination with MRI data-known as ''magnetic source imaging'' (MSI). [10][11][12][13][14][15][16][17] Although MEG has been successfully applied in presurgical evaluation of lesional epilepsies, [18][19][20][21][22][23] no systematic studies have as yet been conducted about the spatial relation between MEG localisation of spike activity, MRI localisation of lesions, histological examination, and surgical outcome in patients with cavernomas.…”

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confidence: 99%

Magnetoencephalography (MEG) predicts focal epileptogenicity in cavernomas

Stefan

2004

Journal of Neurology, Neurosurgery & Psychiatry

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Objective: The aim of this study was to identify the irritative epileptic zone in patients with cavernomas by means of magnetoencephalography (MEG). Method: Among 82 patients operated for epilepsy, whose presurgical evaluation had included MEG, histological assessment of the tissue removed had confirmed cavernomas in eight. These eight patients had epilepsy since 18.6 (SD 12.7) years on average. The monitoring lasted about 2.1 (SD 1.3) hours and a median 20.9 (SD 14.3) spikes per hour were recorded. Spontaneous brain activity was recorded by means of a 74 channel dual unit MEG system (Magnes II, 4-D Neuroimaging) with simultaneous EEG recording (31 scalp electrodes). Spike analysis was performed using different source (moving dipole, current density reconstruction) and head models (spherical shells, BEM). Co-registration of neurophysiological and imaging data (MRI) was based upon anatomical landmarks. Results: In 6/8 patients co-localisation from the cavernoma and epileptic zone was found. In two patients the focus was localised in the parieto-occipital lobe, in three patients in the frontal lobe and in three patients in the temporal lobe. In one case of temporal and one case of frontal lobe focus localisation there was no spatial relationship to the cavernoma. Conclusion: In cases of focal seizures due to a single cavernoma, MEG may precisely delineate the epileptogenic tissue bordering the lesion. In patients with multiple cavernomas or dual pathology, MSI may reveal the complexity of the case, and contribute to the decision about further invasive diagnostics and more sophisticated therapeutic measures. MEG is a promising method for prediction of the epileptic zone in cavernoma related epilepsies, and thus it can contribute to decision making about and planning of epilepsy surgery. C avernous angiomas represent about 5-20% of all vascular malformations in the central nervous system. Multiple cavernomas may occur in 20-40% of affected patients. Magnetic resonance imaging (MRI) is the most appropriate method to identify cavernomas. Microhaemorrhages within and around the lesions are an integral diagnostic feature that can usually only be inferred from irregular haemosiderin deposits detectable in T1 and T2 weighted MR images.Seizures are estimated to occur in 40-70% of patients with cavernomas. Most of the seizures are focal, without or with secondary generalisation.1 A number of different mechanisms have been proposed to cause epilepsy: mass effects on, gliosis of, or haemosiderin deposition in the surrounding brain tissue. Studies using neocortical seizure models indicated that the tissue adjacent to rather than within the lesion exhibits hyperexcitability and thus may be critical in seizure generation. Intracellular neuronal recordings showed that especially neocortical neurones in the vicinity of cavernous malformations had a greater propensity for large complex spontaneous synaptic events than neurones neighbouring tumours. These data also revealed that occurrence of these abnormalities was proportional to ...

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confidence: 99%

Magnetoencephalography (MEG) predicts focal epileptogenicity in cavernomas

Stefan

2004

Journal of Neurology, Neurosurgery & Psychiatry

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“…On invasive EEG, epileptic discharges can be recorded from widespread areas of the temporal lobe including mesial, basal, and even lateral temporal lobe structures [73]. Dipoles represent the center of gravity of this activity but do not provide information on its spatial extent [13,20,74]. Source localizations projected to the mediobasal aspects of the temporal lobe or even to the hippocampus therefore should not be considered evidence that MEG can record epileptic activity selectively from these structures.…”

Section: Temporal Lobe Epilepsymentioning

confidence: 98%

“…All these systems, however, exhibited serious disadvantages for the measurement of spontaneous brain activity, because coverage of the entire brain in a single recording session was impossible [13]. Thus, the recent introduction of whole-head systems with more than 100 channels ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Magnetoencephalography in presurgical epilepsy evaluation

et al. 2002

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The introduction of whole-head magnetoencephalography (MEG) systems facilitating simultaneous recording from the entire brain surface has led to a major breakthrough of MEG in presurgical epilepsy evaluation. Localizations of the interictal spike zone with MEG showed excellent agreement with invasive electrical recordings, were useful to clarify the spatial relationship of the irritative spike zone to structural lesions, and could attribute epileptic activity to lobar subcompartments both in temporal lobe and extratemporal epilepsy. MEG was especially useful for the study of patients with non-lesional neocortical epilepsy and of patients with large lesions, where it provided unique information on the epileptogenic zone. It could reliably localize sensorimotor cortex prior to surgical procedures adjacent to central fissure. MEG language mapping yielded concordant results with the Wada test and cortical stimulation studies. MEG localizations of epileptic activity and essential brain regions were successfully integrated into frameless stereotaxy systems providing accurate functional information intraoperatively. Because MEG and EEG yield both complementary and confirmatory information, combined MEG-EEG recordings in conjunction with advanced source modeling techniques will further improve the noninvasive evaluation of epilepsy patients and constantly reduce the need for invasive procedures.

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“…Extracranial recording of brain activity by means of multi-channel SQUID magnetometers has become an important research tool in recent years (for a representative selection of topics see recent conference proceedings, e.g. Sato (1989), Williamson et al (1989), Hoke et al (1992), Baumgartner et al (1995)) and is also of great potential interest to the neurologist for the localization of epileptogenic tissue (e.g. Sutherling et al (1991), Stefan et al (1992), Smith et al (1994)).…”

Section: Introductionmentioning

confidence: 99%

RF-SQUID to DC-SQUID upgrade of a 28-channel magnetoencephalography (MEG) system

Diekmann

Jürgens

Becker

et al. 1996

Meas. Sci. Technol.

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A Dornier 28-channel magnetoencephalography (MEG) system equipped with RF-SQUIDs and control electronics made by CTF (Port Coquitlam, BC, Canada) was upgraded by replacing the RF-SQUIDs with DC-SQUIDs developed at the University of Jena, Germany. New preamplifiers were designed that emulate the function of the system's original RF amplifiers. This allowed the continuing use of the system's control electronics without any modification. Retaining these control devices was instrumental for preserving the system's unique ability to derive software-defined gradiometer measurements from its magnetometer signals, and also saved a considerable investment of control software tailored to the characteristics of these devices. The performance of the upgraded system compares favourably to that of other multichannel instruments; its software gradiometer channels typically attain an overall sensitivity of 9 fT Hz −1/2 (an improvement by a factor of three over the original RF system) and suppress residual noise inside the shielded room by 40 to 60 dB. Also described are the procedures used to calibrate the system, to eliminate crosstalk between neighbouring channels, and to determine the coefficients for optimum suppression of ambient noise by the software gradiometer.

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Magnetoencephalography in clinical epileptology and Epilepsy research

Cited by 15 publications

References 78 publications

Magnetoencephalography (MEG) predicts focal epileptogenicity in cavernomas

Magnetoencephalography (MEG) predicts focal epileptogenicity in cavernomas

Magnetoencephalography in presurgical epilepsy evaluation

RF-SQUID to DC-SQUID upgrade of a 28-channel magnetoencephalography (MEG) system

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