Magnetoencephalographic localization of epileptic foci using a 37-channel biomagnetometer]

The magnetoencephalography (MEG) and electroencephalography (EEG) were recorded simultaneously from 10 normal subjects using a 37-channel biomagnetometer. No paroxysmal spikelike waveform was observed in MEG at rest with eyes closed. The MEG and EEG were recorded also from 16 patients with primary epilepsy and 24 patients with secondary epilepsy. The examination proved to be safe for both normal subjects and patients with epilepsy. Interictal spikes were observed in 27 cases during the examination. The percentage of spikes identified in MEG but not in EEG was found to be 2. 3% of all spikes. The foci of the spikes identified in MEG were localized and determined in 20 cases. In 10 patients with secondary epilepsy, the localization of the foci were compared with the lesion demonstrated by magnetic resonance imaging (MRI) or computerized tomography (CT) and with the findings of EEG. In 6 cases, the foci by MEG were consistent. In the 4 cases where the MEG foci did not correspond to the MRI or CT findings, MEG foci were supported by the findings of EEG. MEG allows three-dimensional localization and enables us to elucidate the propagation of paroxysms. MEG was very useful in diagnosing epilepsy.     

脑磁图累积源成像在药物难治性颞叶癫痫术前评估中的应用

目的 探讨脑磁图累积源成像（MEG）在难治性颞叶癫痫术前评估中的应用价值。方法 回归分析法2006年1月至2018年1月手术治疗的11例难治性颞叶癫痫临床资料。使用MRI、长程视频脑电图、MEG以及颅内电极脑电图（IEEG）帮助定位致痫灶并制定手术方案,术后随访1年,按Engel分级评估疗效。结果 MRI无明显异常5例;异常6例,其中2例与手术侧一致。11例IEEG均有异常,其中9例与手术侧一致。11例MEG均有异常,9例与手术侧一致,主要集中在4~30 Hz;MEG与IEEG一致7例。11例中,9例有效,2例无效;其中Engel分级Ⅰ级6例,Ⅱ级1例,Ⅲ级2例,Ⅳ级2例。结论 MEG分析能为难治性颞叶癫痫术前评估提供重要信息,帮助识别致痫灶和潜在癫痫网络。     

Magnetoencephalography in partial epilepsy: Clinical yield and localization accuracy

The goals of this study were to determine (1) the yield of magnetoencephalography (MEG) according to epilepsy type, (2) if MEG spike sources colocalize with focal epileptogenic pathology, and (3) if MEG can identify the epileptogenic zone when scalp ictal electroencephalogram (EEG) or magnetic resonance imaging (MRI) fail to localize it. Twenty-two patients with mesial temporal (10 patients), neocortical temporal (3 patients), and extratemporal lobe epilepsy (9 patients) were studied. A 37-channel biomagnetometer was used for simultaneously recording MEG with EEG. During the typical 2–3–hour MEG recording session, interictal epileptiform activity was observed in 16 of 22 patients. MEG localization yield was greater in patients with neocortical epilepsy (92%) than in those with mesial temporal lobe epilepsy (50%). In 5 of 6 patients with focal epileptogenic pathology, MEG spike sources were colocalized with the lesions. In 11 of 12 patients with nonlocalizing (ambiguous abnormalities or normal) MRI, MEG spike sources were localized in the region of the epileptogenic zone as ultimately defined by all clinical and EEG information (including intracranial EEG). In conclusion, MEG can reliably localize sources of spike discharges in patients with temporal and extratemporal lobe epilepsy. MEG sometimes provides noninvasive localization data that are not otherwise available with MRI or conventional scalp ictal EEG.     

脑磁图在癫外科灶定位中的作用(附47例分析)

目的探讨脑磁图(MEG)在癫外科灶定位中的临床价值。方法回顾性分析47例行MEG及头皮视频脑电图(V-EEG)检查的难治性癫病人的病例资料。其中39例接受手术治疗;10例开颅行皮质脑电(ECoG)监测。将MEG的结果与发作期及发作间期V-EEG及ECoG结果进行对比分析。结果MEG显示灶位置与发作间期和发作期V-EEG结果吻合率分别达76.6%和80.9%,与发作间期和发作期ECoG的吻合率均为80.0%。39例手术病人中,术后EngelⅠ级21例,Ⅱ级10例,Ⅲ级8例;其中29例拟切除的区域涉及到解剖学意义上的功能区,术中根据MEG显示的功能区位置进行了适当的处理,术后神经系统功能障碍未加重。结论MEG为无创性检查,对高频放电检出率较高,弥补了脑电在介质衰减方面的不足;同时也有利于癫外科治疗中对功能区的保护。     

Magnetoencephalography in patients with tuberous sclerosis and localization-related epilepsy

PURPOSE: To clarify the usefulness of magnetoencephalography (MEG) for diagnosis of the spatial relations between spike foci and suspicious epileptogenic tubers on MRI in patients with tuberous sclerosis (TS) and to compare MEG spike foci with single-photon emission computed tomography (SPECT) findings. METHODS: We analyzed magnetic fields of epileptic spike discharges in 15 patients with TS and localization-related epilepsy (LRE) by using MEG (a whole-head 204-channel magnetometer system). We investigated the spatial relation between the equivalent current dipoles (ECDs) of interictal spike discharges and visible cortical tubers on MRI. We also compared results of MEG and MRI with SPECT findings. RESULTS: MEG detected a cluster of ECDs around one cortical tuber in six of 15 patients and clusters of ECDs around two cortical tubers in five patients. Interictal SPECT was disappointing in detection of epileptic foci in TS. However, MEG spike foci showed spatial consistency with ictal hyperperfusion areas in two patients. Three patients with single ECD clusters underwent surgical treatment: two have been seizure free, and one has obtained seizure reduction of >90%. CONCLUSIONS: ECDs were located around visible tuber nodules. MEG enabled precise localization of the epileptic foci and provided crucial information for surgical treatment in patients with TS and partial epilepsy. TS patients showing a single ECD cluster on MEG may be appropriate candidates for surgical treatment.     

脑磁图和视频脑电图在癫痫诊治中的应用(附337例报告)

目的探讨脑磁图(MEG)和视频脑电图(V-EEG)在癫痫诊治中的应用价值。方法本组应用MEG结合MRI、V-EEG对337例癫痫(其中174例为原发性癫痫,163例为继发性癫痫)患者行诊断及致痫灶定位检查;对本组251例(其中129例为原发性癫痫,122例为继发性癫痫)患者仅行抗癫痫药物治疗,86例(其中45例为原发性癫痫,41例为继发性癫痫)患者行手术治疗,治疗后6个月和1年均行MEG、V-EEG随访。结果 MEG检出癫痫患者319例,阳性检出率94.66%;V-EEG检出233例,阳性检出率69.14%。结合术中脑皮层电图监测,86例手术治疗的患者癫痫灶MEG精确定位率91.86%,V-EEG为61.63%,而对海马硬化检出率后者高于前者。药物治疗的251例癫痫患者6个月后复查MEG、V-EEG,治愈率31.87%,有效率达86.06%。手术治疗的86例患者术后6个月复查MEG、V-EEG,治愈率53.49%(46/86),有效率达90.70%(78/86)。结论脑磁图和视频脑电图的临床应用是癫痫诊治最为可靠的检测手段之一,也是判别癫痫发作类型,抗癫痫药物选择、评价药物疗效及选择停药时机的重要依据,对癫痫外科术前评估更是不可或缺的重要手段。     

MEG in frontal lobe epilepsies: localization and postoperative outcome

Purpose: This study aimed to analyze magnetoencephalography (MEG) localizations of epileptic clusters in different cortical regions of the frontal lobe and relate these findings to postoperative outcomes associated with frontal lobe epilepsy (FLE). Methods: Thirty‐nine patients from the Epilepsy Center of Erlangen‐Nuremberg University with or without lesions on their magnetic resonance imaging (MRI) scans underwent MEG measurements and operation and were then analyzed retrospectively. MEG data were obtained using systems with either 74 or 248 channels. Single dipole analysis assuming a spherical head model was performed for localization. Key Findings: Epileptic clusters were detected by MEG in 30 patients, corresponding to a sensitivity of 76.9%; there was a sensitivity of 66.7% (20 of 30) in patients with monofocal activity (70% had an Engel class 1 outcome) and 33.3% (10 of 30) in patients with multifocal activity (20% had an Engel class 1 outcome). Of the patients who had isolated clusters, the distance between the MEG localizations and the respective lesions was equal to or <3 cm in 90% (18 of 20) of patients (13 of them had an Engel class 1 outcome) and >3 cm in 10% (2 of 20) of patients (one of them had an Engel class 1 outcome). A statistical difference was found between the outcomes of patients with a single focus and with multiple foci (p < 0.05). Significance: Patients with a single focus had better postoperative outcomes compared with patients with multiple foci. MEG localizations close to the lesion marked the lesion or its surrounding network as epileptogenic. Therefore, source localization can provide important information for the presurgical evaluation of patients with FLE.     

Electroclinical and magnetoencephalographic analysis of epilepsy in patients with congenital bilateral perisylvian syndrome

PURPOSE: Epilepsies in four patients with congenital bilateral perisylvian syndrome (CBPS) were studied electroclinically and by magnetoencephalography (MEG) to determine whether cortical dysplasia associated with this syndrome is epileptogenic. METHODS: We studied three women and one man (mean +/- SD age 30.8 +/- 3.4 years) with a diagnosis of CBPS based on magnetic resonance imaging (MRI). All had drug-resistant epilepsy. In addition to electroclinical analysis, the distribution of equivalent-current dipoles (ECDs) analyzed from MEG signals was examined. RESULTS: Patient 1 had left-sided parietal lobe epilepsy and ECDs clustered in the left temporoparietal lobe. Patient 2 had bilateral, independent temporoparietal lobe epilepsy, and ECDs were found in both hemispheres, with clustering in the right temporoparietal lobe but not in the left hemisphere. Patient 3 presumably had parietal lobe epilepsy with unidentified focus side and ECDs clustered in the left parietal and right temporal lobes. Patient 4 had symptomatic generalized epilepsy, and ECDs were observed in both hemispheres without clustering. In the three patients who had partial epilepsy (patients 1-3), clusters of ECDs overlaid the perisylvian dysplasia and were not found elsewhere. CONCLUSIONS: Patients with CBPS may have either symptomatic partial epilepsy or symptomatic generalized epilepsy, and those with partial epilepsy are likely to have temporoparietal foci. In addition, cortical dysplasia is closely related to the generation of partial seizures and may be epileptogenic per se. However, this study did not elucidate the relationship between cortical dysplasia and CBPS-generated generalized epilepsy.     

Increased spike frequency during general anesthesia with etomidate for magnetoencephalography in patients with focal epilepsies

ObjectiveMagnetoencephalography (MEG) is used for focus localization in presurgical evaluation of patients with focal epilepsies. In this proof-of-concept study, general anesthesia with etomidate was used to improve effectiveness of MEG-recordings.MethodsMEG-recordings of six patients with focal epilepsy were performed before and after application of etomidate. Spike frequency and localization accuracy of MEG with general anesthesia were compared with spontaneous MEG.ResultsAfter application of etomidate, an increase in spike frequency occurred in all patients, and movement artifacts were prevented. In one patient, spikes could only be detected by invasive EEG but not by MEG. The results were in accordance with spontaneous MEG or presurgical hypotheses about localizations of neocortical foci in three patients. Dipole localizations were distributed over fronto-temporal areas in three patients with ipsilateral temporo-mesial focus hypotheses.ConclusionsEtomidate ameliorated spike yield and stopped movement artifacts during MEG recordings in patients with focal epilepsy. Localization results were especially accurate in patients with neocortical epilepsy.SignificanceThese results could facilitate larger studies on the usefulness and safety of general anesthesia with etomidate that record and localize epileptic activity in patients with focal epilepsy by MEG.     

Automated localization of magnetoencephalographic interictal spikes by adaptive spatial filtering.

OBJECTIVE: Automated adaptive spatial filtering techniques can be applied to magnetoencephalographic (MEG) data collected from people with epilepsy. Source waveforms estimated by these methods have higher signal-to-noise ratio (SNR) than spontaneous MEG data, allowing identification and location of interictal spikes. The software tool SAM(g(2)) provides an adaptive spatial filtering algorithm for MEG data that yields source images of excess kurtosis and provides source time-courses in voxels exhibiting high excess kurtosis. The sensitivity and specificity of SAM(g(2)) in epilepsy is unknown. METHODS: Interictal MEG data from 36 patients with intractable epilepsy were analyzed using SAM(g(2)), and results compared with equivalent current dipole (ECD) fit procedures. RESULTS: When SNR of interictal spikes was high (compared to background) with a clear single focus, in most cases there was good agreement between ECD and SAM(g(2)). With multiple foci, there was typically overlap but imperfect concordance between results of ECD and SAM(g(2)). CONCLUSIONS: SAM(g(2)) may in some cases be equivalent to manual ECD fit for localizing interictal spikes with single locus and good SNR. Further studies are required to validate SAM(g(2)) with multiple foci or poor SNR. SIGNIFICANCE: In some cases, SAM(g(2)) might eventually assist or replace manual ECD analysis of MEG data.