Utilization of magnetoencephalography results to obtain favourable outcomes in epilepsy surgery

Fischer, Martin J.

doi:10.1093/brain/awh333

Cited by 154 publications

(100 citation statements)

References 14 publications

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“…Some used anatomical measures such as SECDs located contiguously within neighbouring gyri (Oishi et al, 2006). Others used an ellipsoid model to display results from hierarchical cluster analysis (Fischer et al, 2005). The lack of a consistent and clinically relevant definition of cluster characteristics may also account for discrepancies in the literature that reviews the effect of resection in the presence of MEG clusters: some authors report better results when a single cluster was removed in its entirety (Fischer et al, 2005;Oishi et al, 2006;Vadera et al, 2013), whereas others did not find a clear correlation between the proportion of dipoles within the resection volume with the probability of subsequent seizure-freedom (Kim et al, 2013).…”

Section: Meg Cluster Characteristicsmentioning

confidence: 99%

“…Others used an ellipsoid model to display results from hierarchical cluster analysis (Fischer et al, 2005). The lack of a consistent and clinically relevant definition of cluster characteristics may also account for discrepancies in the literature that reviews the effect of resection in the presence of MEG clusters: some authors report better results when a single cluster was removed in its entirety (Fischer et al, 2005;Oishi et al, 2006;Vadera et al, 2013), whereas others did not find a clear correlation between the proportion of dipoles within the resection volume with the probability of subsequent seizure-freedom (Kim et al, 2013). In addition to the lack of consensus regarding definition of cluster, one needs to be reminded that the density, distribution, and extent of MEG dipoles do not just reflect the size of the epileptogenic generator, but are also determined by the type of spikegenerating pathology as well as the signal to noise ratio of the recording (Bagic et al, 2011).…”

Section: Meg Cluster Characteristicsmentioning

confidence: 99%

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Correlating magnetoencephalography to stereo-electroencephalography in patients undergoing epilepsy surgery

Murakami

Wang

Marashly

et al. 2016

Brain

135

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: Meg Cluster Characteristicsmentioning

confidence: 99%

Section: Meg Cluster Characteristicsmentioning

confidence: 99%

Correlating magnetoencephalography to stereo-electroencephalography in patients undergoing epilepsy surgery

Murakami

Wang

Marashly

et al. 2016

Brain

135

103

View full text Add to dashboard Cite

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“…For each subject, the center of mass of the fitted ECDs was first calculated as the mean of all ECD coordinates across all sEMG channels, for each HD-sEMG derivation separately. Then, to characterize the spread of the ECDs, their coordinates relative to their center of mass were subjected to a principal component analysis to construct an ellipsoid centered on their center of mass, with the lengths of the axes along principal components equal to one standard deviation as derived from singular values (Fischer et al 2005). The volume and major axis of this ellipsoid provided a measure of the degree of the ECD spread around the center of mass.…”

Section: Data Processingmentioning

confidence: 99%

Spatial variability in cortex-muscle coherence investigated with magnetoencephalography and high-density surface electromyography

Piitulainen

Botter

Bourguignon

et al. 2015

Journal of Neurophysiology

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muscle coherence (CMC) reflects coupling between magnetoencephalography (MEG) and surface electromyography (sEMG), being strongest during isometric contraction but absent, for unknown reasons, in some individuals. We used a novel nonmagnetic high-density sEMG (HD-sEMG) electrode grid (36 mm ϫ 12 mm; 60 electrodes separated by 3 mm) to study effects of sEMG recording site, electrode derivation, and rectification on the strength of CMC. Monopolar sEMG from right thenar and 306-channel whole-scalp MEG were recorded from 14 subjects during 4-min isometric thumb abduction. CMC was computed for 60 monopolar, 55 bipolar, and 32 Laplacian HD-sEMG derivations, and two derivations were computed to mimic "macroscopic" monopolar and bipolar sEMG (electrode diameter 9 mm; interelectrode distance 21 mm). With unrectified sEMG, 12 subjects showed statistically significant CMC in 91-95% of the HD-sEMG channels, with maximum coherence at ϳ25 Hz. CMC was about a fifth stronger for monopolar than bipolar and Laplacian derivations. Monopolar derivations resulted in most uniform CMC distributions across the thenar and in tightest cortical source clusters in the left rolandic hand area. CMC was 19 -27% stronger for HD-sEMG than for "macroscopic" monopolar or bipolar derivations. EMG rectification reduced the CMC peak by a quarter, resulted in a more uniformly distributed CMC across the thenar, and provided more tightly clustered cortical sources than unrectifed sEMGs. Moreover, it revealed CMC at ϳ12 Hz. We conclude that HD-sEMG, especially with monopolar derivation, can facilitate detection of CMC and that individual muscle anatomy cannot explain the high interindividual CMC variability.

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“…24 In addition, previous reports have demonstrated more favorable seizure outcomes when the resection area includes the MEG spike cluster. 4,21 A recent study from another institution demonstrated similar results for patients with extratemporal epilepsy. That series included 31 patients who did not undergo invasive monitoring, including several with temporal lobe epilepsy.…”

Section: Discussionmentioning

confidence: 67%

Magnetoencephalography-guided resection of epileptogenic foci in children

Albert

Ibrahim²,

Otsubo

et al. 2014

PED

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Object Resective surgery is increasingly used in the management of pediatric epilepsy. Frequently, invasive monitoring with subdural electrodes is required to adequately map the epileptogenic focus. The risks of invasive monitoring include the need for 2 operations, infection, and CSF leak. The aim of this study was to evaluate the feasibility and outcomes of resective epilepsy surgery guided by magnetoencephalography (MEG) in children who would have otherwise been candidates for electrode implantation. Methods The authors reviewed the records of patients undergoing resective epilepsy surgery at the Hospital for Sick Children between 2001 and 2010. They identified cases in which resections were based on MEG data and no intracranial recordings were performed. Each patient's chart was reviewed for presentation, MRI findings, MEG findings, surgical procedure, pathology, and surgical outcome. Results Sixteen patients qualified for the study. All patients had localized spike clusters on MEG and most had abnormal findings on MRI. Resection was carried out in each case based on the MEG data linked to neuronavigation and supplemented with intraoperative neuromonitoring. Overall, 62.5% of patients were seizure free following surgery, and 20% of patients experienced an improvement in seizures without attaining seizure freedom. In 2 cases, additional surgery was performed subsequently with intracranial monitoring in attempts to obtain seizure control. Conclusions MEG is a viable alternative to invasive monitoring with intracranial electrodes for planning of resective surgery in carefully selected pediatric patients with localization-related epilepsy. Good candidates for this approach include patients who have a well-delineated, localized spike cluster on MEG that is concordant with findings of other preoperative evaluations and patients with prior brain pathologies that make the implantation of subdural and depth electrodes somewhat problematic.

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Utilization of magnetoencephalography results to obtain favourable outcomes in epilepsy surgery

Cited by 154 publications

References 14 publications

Correlating magnetoencephalography to stereo-electroencephalography in patients undergoing epilepsy surgery

Correlating magnetoencephalography to stereo-electroencephalography in patients undergoing epilepsy surgery

Spatial variability in cortex-muscle coherence investigated with magnetoencephalography and high-density surface electromyography

Magnetoencephalography-guided resection of epileptogenic foci in children

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