Localization value of magnetoencephalography interictal spikes in adult nonlesional neocortical epilepsy (original) (raw)
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Seizure, 2011
Epilepsy surgery is an option for patients with medically refractory epilepsy. To achieve a better outcome post surgery, it is very important to take various presurgical evaluations into account for determining an appropriate surgical plan. Over the past two decades, more comprehensive presurgical assessments and advanced techniques have become available. High-resolution magnetic resonance imaging (MRI) has been known as the best preoperative diagnosis for patients with lesional refractory neocortical epilepsy (NE). 1-3 Digital video electroencephalography (VEEG) provides us with a definitive diagnosis of seizure-like events, while intracranial VEEG (iVEEG) is commonly used to define the ictal onset zone (IOZ). However, surgical resection of the IOZ alone does not always yield a favorable operative outcome because iVEEG electrodes only record signals in their direct vicinity and are blind for other areas, making it difficult to judge whether the IOZ really represents the ictal generator or is the result of propagation from elsewhere. 4 However, in a number of reports, 5 it was pointed out that it is also difficult to judge whether spike foci represent the epileptogenic zone. Furthermore, Holmes et al. 6 reported that only unifocal interictal epileptiform discharges (IEDs) restricted to the seizure onset zone could be used as a marker for epileptogenicity, while others showed that (rapid) spike Seizure 20 (2011) 692-700
Does magnetoencephalography add to scalp video-EEG as a diagnostic tool in epilepsy surgery?
Neurology, 2004
Objective:The authors evaluated the sensitivity and selectivity of interictal magnetoencephalography (MEG) versus prolonged ictal and interictal scalp video-electroencephalography (V-EEG) in order to identify patient groups that would benefit from preoperative MEG testing.Methods:The authors evaluated 113 consecutive patients with medically refractory epilepsy who underwent surgery. The epileptogenic region predicted by interictal and ictal V-EEG and MEG was defined in relation to the resected area as perfectly overlapping with the resected area, partially overlapping, or nonoverlapping.Results:The sensitivity of a 30-minute interictal MEG study for detecting clinically significant epileptiform activity was 79.2%. Using MEG, we were able to localize the resected region in a greater proportion of patients (72.3%) than with noninvasive V-EEG (40%). MEG contributed to the localization of the resected region in 58.8% of the patients with a nonlocalizing V-EEG study and 72.8% of the pati...
Utilization of magnetoencephalography results to obtain favourable outcomes in epilepsy surgery
Brain, 2004
Magnetoencephalography (MEG) is a well-known technique in the presurgical evaluation of epilepsy patients. Like EEG, it can detect and localize epileptic activity. Epilepsy surgery can be used to evaluate MEG source localizations. Resection volumes were determined in 33 epilepsy surgery patients. The resection volume, taken together with the post-operative outcome, was used to evaluate MEG results. The scattering MEG localizations of interictal epileptic activity were represented by an ellipsoidal volume. Using this MEG results ellipsoid, it was demonstrated that a high coverage by the resection volume and a small distance to the resection volume are both correlated to a favourable outcome; in addition, a homogeneous distribution of MEG localizations is correlated to a favourable outcome. This study shows that MEG source localization can help to delineate epileptic activity and, along with other techniques, should be taken into account for epilepsy surgery.
Utility of Magnetoencephalography in the Evaluation of Recurrent Seizures after Epilepsy Surgery
Epilepsia, 2007
Purpose: To study the role of magnetoencephalography (MEG) in the surgical evaluation of children with recurrent seizures after epilepsy surgery. Methods: We studied 17 children with recurrent seizures after epilepsy surgery using interictal and ictal scalp EEG, intracranial video EEG (IVEEG), MRI, and MEG. We analyzed the location and distribution of MEG spike sources (MEGSSs) and the relationship of MEGSSs to the margins of previous resections and surgical outcome. Results: Clustered MEGSSs occurred at the margins of previous resections within two contiguous gyri in 10 patients (group A), extended spatially from a margin by ≤3 cm in three patients (group B), and were remote from a resection margin by >3 cm in six patients (group C). Two patients had concomitant group A and C clusters. Thirteen patients underwent second surgeries. IVEEG was used in four patients. Six of seven patients with group A MEGSS clusters did not require IVEEG for second surgeries. Follow-up periods ranged from 0.6 to 4.3 years (mean: 2.6 years). Eleven children, including eight who became seizure-free, achieved Engel class I or II. Conclusion: Our data demonstrate the utility of MEG for evaluating patients with recurrent seizures after epilepsy surgery. Specific MEGSS cluster patterns delineate epileptogenic zones. Removing cluster regions adjacent to the margins of previous resections, in addition to removing recurrent lesions, achieves favorable surgical outcome. Cluster location and extent identify which patients require IVEEG, potentially eliminating IVEEG for some. Patients with remotely located clusters require IVEEG for accurate assessment and localization of the entire epileptogenic zone.
Epilepsia, 2013
Purpose: To investigate the utility of magnetic source imaging (MSI) and ictal single photon emission computed tomography (SPECT), each compared with intracranial electroencephalography (EEG) (ICEEG), to localize the epileptogenic zone (EZ) and predict epilepsy surgery outcome in patients with nonlesional neocortical focal epilepsy. Methods: Studied were 14 consecutive patients with nonlesional neocortical epilepsy who underwent presurgical evaluation including ICEEG, positive MSI, and localizing subtraction Ictal SPECT coregistered to MRI (SISCOM) analysis. Follow-up after epilepsy surgery was ‡24 months. ICEEG, MSI, and SPECT results were classified using a sublobar classification. Key Findings: Of 14 patients, 6 (42.9%) became seizurefree after surgery. Sublobar ICEEG focus was completely resected in 11 patients; 5 (45.5%) of them became seizurefree. Concordance of ICEEG and MSI and complete focus resection was found in 5 (35.7%) patients; 80% of them became seizure-free. Sublobar ICEEG-MSI concordance and complete focus resection significantly increased the chance of seizure freedom after epilepsy surgery (p = 0.038). In contrast, of the 6 patients (42.9%) with concordant ICEEG and SISCOM and complete focus resection, only 66.7% became seizure-free (p = 0.138). Assuming concordant results, the additive value to ICEEG alone for localizing the EZ is higher with ICEEG-MSI (odds ratio 14) compared to ICEEG-SISCOM (odds ratio 6). Significance: This study shows that combination of MSI and/or SISCOM with ICEEG is useful in the presurgical evaluation of patients with nonlesional neocortical epilepsy. Concordant test results of either MSI or SISCOM with ICEEG provide useful additive information for that provided by ICEEG alone to localize the EZ in this most challenging group of patients. When sublobar concordance with ICEEG is observed, MSI is more advantageous compared to SISCOM in predicting seizure-free epilepsy surgery outcome.
Journal of Clinical Neurophysiology, 2009
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Epilepsia, 2007
Purpose: The diagnosis of frontal lobe epilepsy may be compounded by poor electroclinical localization, due to distributed or rapidly propagating epileptiform activity. This study aimed at developing optimal procedures for localizing interictal epileptiform discharges (IEDs) of patients with localization related epilepsy in the frontal lobe. To this end the localization results obtained for magnetoencephalography (MEG) and electroencephalography (EEG) were compared systematically using automated analysis procedures. Methods: Simultaneous recording of interictal EEG and MEG was successful for 18 out of the 24 patients studied. Visual inspection of these recordings revealed IEDs with varying morphology and topography. Cluster analysis was used to classify these discharges on the basis of their spatial distribution followed by equivalent dipole analysis of the cluster averages. The locations of the equivalent dipoles were compared with the location of the epileptogenic lesions of the patient or, if these were not visible at MRI with the location of the interictal onset zones identified by subdural electroencephalography. Results: Generally IEDs were more abundantly in MEG than in the EEG recordings. Furthermore, the duration of the MEG spikes, measured from the onset till the spike maximum, was in most patients shorter than the EEG spikes. In most patients, distinct spike subpopulations were found with clearly different topographical field maps. Cluster analysis of MEG spikes followed by dipole localization was successful (n = 14) for twice as many patients as for EEG source analysis (n = 7), indicating that the localizability of interictal MEG is much better than of interictal EEG. Conclusions: The automated procedures developed in this study provide a fast screening method for identifying the distinct categories of spikes and the brain areas responsible for these spikes. The results show that MEG spike yield and localization is superior compared with EEG. This finding is of importance for the diagnosis and preoperative evaluation of patients with frontal lobe epilepsy. KEY WORDS: Frontal lobe epilepsy-Interictal epileptiform discharges-Cluster analysis-Equivalent dipole localization. Patients with frontal lobe epilepsy (FLE) comprise about 20% of the group of patients with localization related epilepsy. For mesiotemporal lobe epilepsy, it has been reported (e.g., by Boon and D'Havé, 1995; Gilliam et al.,