Spatially filtered magnetoencephalography compared with electrocorticography to identify intrinsically epileptogenic focal cortical dysplasia

Ishii, Ryouhei; Canuet, Leonides; Ochi, Ayako; Xiang, Jing; Imai, Katsunori; Chan, Derrick; Iwase, Masao; Takeda, Masatoshi; Snead, O. Carter; Otsubo, Hiroshi

doi:10.1016/j.eplepsyres.2008.06.006

Cited by 35 publications

(36 citation statements)

References 13 publications

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“…These maps were aligned with each patient’s structural MRI scan on the basis of overlapping common fiducials. The source signal series were reconstructed within the frequency band of 3–70 Hz at all local maxima with an inter-peak spacing >10 mm in each map for g2 ≥ 3 (27–31, 33, 35, 40). Spike times were automatically marked in the source signal series and compared to the activity visible in the simultaneous EEG (32).…”

Section: Methodsmentioning

confidence: 99%

Localization of Interictal Epileptiform Activity Using Magnetoencephalography with Synthetic Aperture Magnetometry in Patients with a Vagus Nerve Stimulator

et al. 2014

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Magnetoencephalography (MEG) provides useful and non-redundant information in the evaluation of patients with epilepsy, and in particular, during the pre-surgical evaluation of pharmaco-resistant epilepsy. Vagus nerve stimulation (VNS) is a common treatment for pharmaco-resistant epilepsy. However, interpretation of MEG recordings from patients with a VNS is challenging due to the severe magnetic artifacts produced by the VNS. We used synthetic aperture magnetometry (g2) [SAM(g2)], an adaptive beamformer that maps the excessive kurtosis, to map interictal spikes to the coregistered MRI image, despite the presence of contaminating VNS artifact. We present a series of eight patients with a VNS who underwent MEG recording. Localization of interictal epileptiform activity by SAM(g2) is compared to invasive electrophysiologic monitoring and other localizing approaches. While the raw MEG recordings were uninterpretable, analysis of the recordings with SAM(g2) identified foci of peak kurtosis and source signal activity that was unaffected by the VNS artifact. SAM(g2) analysis of MEG recordings in patients with a VNS produces interpretable results and expands the use of MEG for the pre-surgical evaluation of epilepsy.

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Section: Methodsmentioning

confidence: 99%

Localization of Interictal Epileptiform Activity Using Magnetoencephalography with Synthetic Aperture Magnetometry in Patients with a Vagus Nerve Stimulator

et al. 2014

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“…The frequency ranging from 20 Hz to 70 Hz was used in several studies and is outside the range of alpha-band activity that would tend to drive the excess kurtosis negative [11–13]. To eliminate the background activity and contrast the interictal spike activity, we performed SAM(g2) analysis localized the epileptic zone in clinical [12, 14, 15].…”

Section: Methodsmentioning

confidence: 99%

Alteration of Interictal Brain Activity in Patients with Temporal Lobe Epilepsy in the Left Dominant Hemisphere: A Resting-State MEG Study

Zhu

Zhao

et al. 2014

BioMed Research International

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Resting MEG activities were compared between patients with left temporal lobe epilepsy (LTLE) and normal controls. Using SAMg2, the activities of MEG data were reconstructed and normalized. Significantly elevated SAMg2 signals were found in LTLE patients in the left temporal lobe and medial structures. Marked decreases of SAMg2 signals were found in the wide extratemporal lobe regions, such as the bilateral visual cortex. The study also demonstrated a positive correlation between the seizure frequency and brain activities of the abnormal regions after the multiple linear regression analysis. These results suggested that the aberrant brain activities not only were related to the epileptogenic zones, but also existed in other extratemporal regions in patients with LTLE. The activities of the aberrant regions could be further damaged with the increase of the seizure frequency. Our findings indicated that LTLE could be a multifocal disease, including complex epileptic networks and brain dysfunction networks.

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“…are reliably eliminated. One variant of this technique, SAM(g2), has been used successfully in the clinical setting to map the kurtotic (sharp) signature of epileptiform signals arising from interictal foci and to reconstruct the virtual electrodes associated with these generators [21,24,51,53,54,112,113,114]. Importantly, the virtual electrodes can be inspected for the presence of epileptiform activity, and exhibit a strong agreement with the activity recorded by ICEEG [21,26].…”

Section: Meg At Wake Forest Baptist Healthmentioning

confidence: 99%

“…In ~13% of all individuals, MEG-only spikes are detected, while in ~3% of all individuals EEG-only spikes occur, suggesting that in one-third of all EEG-negative individuals, MEG is expected to detect epileptiform signals [45]. Numerous clinical studies have demonstrated an excellent agreement between foci delineated by MEG/MSI and ICEEG [26,47,48,49,50,51,52], and MEG foci have been found to align with lesions such as tuberous sclerosis [53,54,55,56,57,58] and cortical dysplasia [50,51]. Similarly, retrospective studies have found that dipole maps of interictal spikes had clustered over subsequent resection volumes [46,59,60], even when video EEG results were nonlocalizing.…”

Section: Introductionmentioning

confidence: 99%

Magnetoencephalography: Clinical and Research Practices

et al. 2018

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Magnetoencephalography (MEG) is a neurophysiological technique that detects the magnetic fields associated with brain activity. Synthetic aperture magnetometry (SAM), a MEG magnetic source imaging technique, can be used to construct both detailed maps of global brain activity as well as virtual electrode signals, which provide information that is similar to invasive electrode recordings. This innovative approach has demonstrated utility in both clinical and research settings. For individuals with epilepsy, MEG provides valuable, nonredundant information. MEG accurately localizes the irritative zone associated with interictal spikes, often detecting epileptiform activity other methods cannot, and may give localizing information when other methods fail. These capabilities potentially greatly increase the population eligible for epilepsy surgery and improve planning for those undergoing surgery. MEG methods can be readily adapted to research settings, allowing noninvasive assessment of whole brain neurophysiological activity, with a theoretical spatial range down to submillimeter voxels, and in both humans and nonhuman primates. The combination of clinical and research activities with MEG offers a unique opportunity to advance translational research from bench to bedside and back.

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Spatially filtered magnetoencephalography compared with electrocorticography to identify intrinsically epileptogenic focal cortical dysplasia

Cited by 35 publications

References 13 publications

Localization of Interictal Epileptiform Activity Using Magnetoencephalography with Synthetic Aperture Magnetometry in Patients with a Vagus Nerve Stimulator

Localization of Interictal Epileptiform Activity Using Magnetoencephalography with Synthetic Aperture Magnetometry in Patients with a Vagus Nerve Stimulator

Alteration of Interictal Brain Activity in Patients with Temporal Lobe Epilepsy in the Left Dominant Hemisphere: A Resting-State MEG Study

Magnetoencephalography: Clinical and Research Practices

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