Magnetic brain source imaging of focal epileptic activity: a synopsis of 455 cases

Stefan, Hermann

doi:10.1093/brain/awg239

Cited by 287 publications

(194 citation statements)

References 37 publications

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“…No spike averaging was performed. The location, orientation, and strength of dipole sources that best fit the measured magnetic fields were calculated using the SECD model (Stefan et al, 2003;Pataraia et al, 2004). The following statistics criteria were used when reviewing the SECD results: goodness of fit 480%, confidence volume 51000 mm 3 , reduced 2 5 1.5, and dipole moment between 100-500 nAm.…”

Section: Megmentioning

confidence: 99%

Correlating magnetoencephalography to stereo-electroencephalography in patients undergoing epilepsy surgery

Murakami

Wang

Marashly

et al. 2016

Brain

134

103

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) for a scientific commentary on this article.Magnetoencephalography and stereo-electroencephalography are often necessary in the course of the non-invasive and invasive presurgical evaluation of challenging patients with medically intractable focal epilepsies. In this study, we aim to examine the significance of magnetoencephalography dipole clusters and their relationship to stereo-electroencephalography findings, area of surgical resection, and seizure outcome. We also aim to define the positive and negative predictors based on magnetoencephalography dipole cluster characteristics pertaining to seizure-freedom. Included in this retrospective study were a consecutive series of 50 patients who underwent magnetoencephalography and stereo-electroencephalography at the Cleveland Clinic Epilepsy Center. Interictal magnetoencephalography localization was performed using a single equivalent current dipole model. Magnetoencephalography dipole clusters were classified based on tightness and orientation criteria. Magnetoencephalography dipole clusters, stereo-electroencephalography findings and area of resection were reconstructed and examined in the same space using the patient's own magnetic resonance imaging scan. Seizure outcomes at 1 year postoperative were dichotomized into seizurefree or not seizure-free. We found that patients in whom the magnetoencephalography clusters were completely resected had a much higher chance of seizure-freedom compared to the partial and no resection groups (P = 0.007). Furthermore, patients had a significantly higher chance of being seizure-free when stereo-electroencephalography completely sampled the area identified by magnetoencephalography as compared to those with incomplete or no sampling of magnetoencephalography results (P = 0.012). Partial concordance between magnetoencephalography and interictal or ictal stereo-electroencephalography was associated with a much lower chance of seizure freedom as compared to the concordant group (P = 0.0075). Patients with one single tight cluster on magnetoencephalography were more likely to become seizure-free compared to patients with a tight cluster plus scatter (P = 0.0049) or patients with loose clusters (P = 0.018). Patients whose magnetoencephalography clusters had a stable orientation perpendicular to the nearest major sulcus had a better chance of seizure-freedom as compared to other orientations (P = 0.042). Our data demonstrate that stereo-electroencephalography exploration and subsequent resection are more likely to succeed, when guided by positive magnetoencephalography findings. As a corollary, magnetoencephalography clusters should not be ignored when planning the stereo-electroencephalography strategy. Magnetoencephalography tight cluster and stable orientation are positive predictors for a good seizure outcome after resective surgery, whereas the presence of scattered sources diminishes the probability of favourable outcomes. The concordance pattern between magnetoencephalography and stereo-electroencephalography is a strong...

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Section: Megmentioning

confidence: 99%

Correlating magnetoencephalography to stereo-electroencephalography in patients undergoing epilepsy surgery

Murakami

Wang

Marashly

et al. 2016

Brain

134

103

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“…The localization procedure has been previously documented. [12][13][14] Up to 128 channels of EEG recordings were performed simultaneously with all MEG studies. The magnetic source images, consisting of the dipoles coregistered with the preoperative MR images, were then fused with the postoperative MRI using BrainLAB software to assess the cluster location with regard to the resection cavity (Fig.…”

Section: Methodsmentioning

confidence: 99%

Correlation between magnetoencephalography-based “clusterectomy” and postoperative seizure freedom

Vadera¹,

Jehi

Burgess

et al. 2013

FOC

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Object During the presurgical evaluation of patients with medically intractable focal epilepsy, a variety of noninvasive studies are performed to localize the hypothetical epileptogenic zone and guide the resection. Magnetoencephalography (MEG) is becoming increasingly used in the clinical realm for this purpose. No investigators have previously reported on coregisteration of MEG clusters with postoperative resection cavities to evaluate whether complete “clusterectomy” (resection of the area associated with MEG clusters) was performed or to compare these findings with postoperative seizure-free outcomes. Methods The authors retrospectively reviewed the charts and imaging studies of 65 patients undergoing MEG followed by resective epilepsy surgery from 2009 until 2012 at the Cleveland Clinic. Preoperative MEG studies were fused with postoperative MRI studies to evaluate whether clusters were within the resected area. These data were then correlated with postoperative seizure freedom. Results Sixty-five patients were included in this study. The average duration of follow-up was 13.9 months, the mean age at surgery was 23.1 years, and the mean duration of epilepsy was 13.7 years. In 30 patients, the main cluster was located completely within the resection cavity, in 28 it was completely outside the resection cavity, and in 7 it was partially within the resection cavity. Seventy-four percent of patients were seizure free at 12 months after surgery, and this rate decreased to 60% at 24 months. Improved likelihood of seizure freedom was seen with complete clusterectomy in patients with localization outside the temporal lobe (extra–temporal lobe epilepsy) (p = 0.04). Conclusions In patients with preoperative MEG studies that show clusters in surgically accessible areas outside the temporal lobe, we suggest aggressive resection to improve the chances for seizure freedom. When the cluster is found within the temporal lobe, further diagnostic testing may be required to better localize the epileptogenic zone.

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“…The localization of the origin of interictal epileptiform discharges (IEDs) plays a major role in the presurgical work-up of patients with focal refractory epilepsy, especially, using MEG (Englot et al, 2015;Knowlton, 2008;Ossenblok et al, 2007;Pataraia et al, 2004;Stefan et al, 2003) and more recently simultaneous EEG and fMRI (Thornton et al, 2010;Zijlmans et al, 2002). Nowadays the identification of the network underlying the IEDs is an auxiliary tool for the question where to place an intracortical grid or stereotactic depth electrodes for presurgical evaluation in refractory candidates (Pataraia et al, 2004;Schulz et al, 2000;van Houdt et al, 2013van Houdt et al, , 2012Walczak et al, 1990).…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal mapping of interictal epileptiform discharges in human absence epilepsy: A MEG study

2016

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a b s t r a c tPurpose: Although absence epilepsy is considered to be a prototypic type of generalized epilepsy, it is still under debate whether generalized 3 Hz spike-and-wave discharges (SWDs) might have a cortical focal origin. Here it is investigated whether focal interictal epileptiform discharges (IEDs), which typically occur in the electro-(EEG) and magnetoencephalogram (MEG) in case of focal epilepsy, are present in the MEG of children with absence epilepsy. Next, the location of the sources of the IEDs is established, and it is investigated whether the location is concordant to the earlier established focal cortical regions involved in the generalized SWDs of these children. Methods: Whole head MEG recordings of seven children with absence epilepsy were reviewed with respect to the presence of IEDs (spikes and sharp waves). These IEDs were grouped into distinct clusters, in which each contribution to a cluster yields a comparable magnetic field distribution. Source localization was then performed onto the average signal of each cluster using an equivalent current dipole model and a realistic head model of the cortical surface. Results: IEDs were detected in 6 out of 7 patients. Source reconstruction indicated most often frontal, central or parietal origins of the IED in either the left and or right hemisphere. Spatiotemporal assessment of the IEDs indicated a stable location of the averages of these discharges, indicating a single underlying cortical source. Discussion: The outcome of this pilot study shows that MEG is well suited for the detection of IEDs and suggests that their estimated sources coincide rather well with the cortical regions involved during the spikes of the SWDs. It is discussed whether the presence of IEDs, classically seen as a marker of focal epilepsies, indicate that absence epilepsy should be considered as a focal type of epilepsy, in which changes in the network are evolving rapidly.

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Magnetic brain source imaging of focal epileptic activity: a synopsis of 455 cases

Cited by 287 publications

References 37 publications

Correlating magnetoencephalography to stereo-electroencephalography in patients undergoing epilepsy surgery

Correlating magnetoencephalography to stereo-electroencephalography in patients undergoing epilepsy surgery

Correlation between magnetoencephalography-based “clusterectomy” and postoperative seizure freedom

Spatiotemporal mapping of interictal epileptiform discharges in human absence epilepsy: A MEG study

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