Magnetoencephalography in the presurgical evaluation of epilepsy

Kharkar, Siddharth; Knowlton, Robert C.

doi:10.1016/j.yebeh.2014.11.029

Cited by 45 publications

(29 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Information on a lower spatial resolution level, like determination of the correct hemisphere or of the temporal versus extratemporal areas, is important for preoperative evaluation. 47 We showed that MEG hubs may contribute to identification of the epileptogenic zone at a reasonable spatial resolution (i.e., at the resolution of ROIs in the AAL atlas). In addition, we found that a high average betweenness centrality in the resection cavity discriminated seizure-free from not seizure-free patients.…”

Section: Discussionmentioning

confidence: 82%

“…Preoperative identification of the ROIs that fall within the epileptogenic zone and the lobe that contains the epileptogenic zone is a prerequisite for neurosurgery in refractory epilepsy. Information on a lower spatial resolution level, like determination of the correct hemisphere or of the temporal versus extratemporal areas, is important for preoperative evaluation . We showed that MEG hubs may contribute to identification of the epileptogenic zone at a reasonable spatial resolution (i.e., at the resolution of ROIs in the AAL atlas).…”

Section: Discussionmentioning

confidence: 91%

See 1 more Smart Citation

Identifying the epileptogenic zone in interictal resting‐state MEG source‐space networks

et al. 2016

View full text Add to dashboard Cite

Objective: In one third of patients, seizures remain after epilepsy surgery, meaning that improved preoperative evaluation methods are needed to identify the epilepto-genic zone. A potential framework for such a method is network theory, as it can be applied to noninvasive recordings, even in the absence of epileptiform activity. Our aim was to identify the epileptogenic zone on the basis of hub status of local brain areas in interictal magnetoencephalography (MEG) networks. Methods: Preoperative eyes-closed resting-state MEG recordings were retrospectively analyzed in 22 patients with refractory epilepsy, of whom 14 were seizure-free 1 year after surgery. Beamformer-based time series were reconstructed for 90 corti-cal and subcortical automated anatomic labeling (AAL) regions of interest (ROIs). Broadband functional connectivity was estimated using the phase lag index in artifact-free epochs without interictal epileptiform abnormalities. A minimum spanning tree was generated to represent the network, and the hub status of each ROI was calculated using betweenness centrality, which indicates the centrality of a node in a network. The correspondence of resection cavity to hub values was evaluated on four levels: resection cavity, lobar, hemisphere, and temporal versus extratemporal areas. Results: Hubs were localized within the resection cavity in 8 of 14 seizure-free patients and in zero of 8 patients who were not seizure-free (57% sensitivity, 100% specificity, 73% accuracy). Hubs were localized in the lobe of resection in 9 of 14 seizure-free patients and in zero of 8 patients who were not seizure-free (64% sensitivity, 100% specificity, 77% accuracy). For the other two levels, the true negatives are unknown; hence, only sensitivity could be determined: hubs coincided with both the resection hemisphere and the resection location (temporal versus extratemporal) in 11 of 14 seizure free patients (79% sensitivity). Significance: Identifying hubs noninvasively before surgery is a valuable approach with the potential of indicating the epileptogenic zone in patients without interictal abnormalities.

show abstract

Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 91%

Identifying the epileptogenic zone in interictal resting‐state MEG source‐space networks

et al. 2016

View full text Add to dashboard Cite

show abstract

“…Noninvasive source localization of interictal spikes is the most common clinical application of magnetoencephalography (MEG), and MEG source imaging (MSI) is now of accepted benefit in the presurgical investigation of patients with medically intractable epilepsy. 1 In recent decades, many patients with intractable epilepsy have been treated with various forms of neurostimulation, including thalamic deep brain stimulation (DBS). 2,3 Patients with suboptimal seizure control after thalamic DBS might in some cases benefit from further investigations for resective epilepsy surgery, including MSI.…”

mentioning

confidence: 99%

Feasibility of magnetoencephalographic source imaging in patients with thalamic deep brain stimulation for epilepsy

et al. 2016

View full text Add to dashboard Cite

SummarySource localization of interictal spikes in patients with medically refractory epilepsy is the most common clinical application of magnetoencephalography (MEG). In recent decades, many patients with intractable epilepsy have been treated with various forms of neurostimulation, including thalamic deep brain stimulation (DBS). Patients with suboptimal seizure control after DBS might in some cases benefit from further investigations for resective epilepsy surgery, including MEG source imaging (MSI). We sought to determine the feasibility and accuracy of MSI in the setting of active thalamic DBS. Simultaneous EEG/MEG was obtained in a patient using an Elekta 306‐channel MEG system, with high‐frequency (100 Hz) DBS of the thalamic anterior nuclei cycling between on and off states. Magnetic artifacts associated with the DBS apparatus were successfully suppressed using the spatiotemporal signal space separation (tSSS) method. Electrical stimulation artifact was removed by standard digital low‐pass filtering. Dipole source modeling results for spike foci in frontal and posterior temporal regions were comparable between stimulation on and stimulation off states, and the source solutions corresponded well to the localization of spikes documented by intracranial EEG. MSI is thus feasible and source solutions can be accurate when performed in patients with active thalamic DBS for epilepsy.

show abstract

“…Compared to scalp EEG, MEG possesses higher spatio-temporal resolution without signal distortions from the skull and scalp (Kirsch et al, 2007; Zumer et al, 2007), and is a valuable noninvasive diagnostic modality in the presurgical evaluation of epilepsy patients (Kharkar and Knowlton, 2014). In focal epilepsy patients, we recently examined the role of MEG-based studies in EZ localization and prediction of post-operative seizure outcome, by analyzing interictal spike localization (Englot et al, 2015b) and regional functional connectivity alterations (Englot et al, 2015a).…”

Section: Introductionmentioning

confidence: 99%

The sensitivity and significance of lateralized interictal slow activity on magnetoencephalography in focal epilepsy

et al. 2016

View full text Add to dashboard Cite

Objective Asymmetric large-amplitude slow activity is sometimes observed on interictal electroencephalography (EEG) in epilepsy. However, few studies have examined slowing during magnetoencephalography (MEG) recordings, which are performed primarily to localize interictal spikes. Also, no prior investigations have compared the sensitivity of MEG to scalp EEG in detecting slow rhythms. Methods We performed a retrospective cohort study of focal epilepsy patients who received MEG followed by surgical resection at our institution. We examined MEG, simultaneous EEG, and long-term EEG recordings for prominent asymmetric slow activity (delta-range, 1–4 Hz), and evaluated post-operative seizure outcomes. Results We studied 132 patients with ≥ 1 year post-operative follow-up (mean, 3.6 years). Mean age was 27 (range, 3–68) years, and 55% of patients were male. Asymmetric large-amplitude slow wave activity was observed on interictal MEG in 21 of 132 (16%) patients. Interictal slowing lateralized to the hemisphere of resection in all but one (95%) patient. Among the 21 patients with interictal MEG slowing, 11 (52%) individuals had similarly lateralized EEG slowing, 7 patients had no EEG slowing, and 3 had bilateral symmetric EEG slowing. Meanwhile, none of the 111 patients without lateralized MEG slowing had asymmetric EEG slowing, suggesting significantly higher sensitivity of MEG versus EEG in detecting asymmetric slowing (χ2 = 63.4, p < 0.001). MEG slowing was associated with shorter epilepsy duration with an odds ratio of 5.4 (1.7–17.0, 95% confidence interval). At last follow-up, 92 (70%) patients were seizure free (Engel I outcome), with no difference in seizure freedom rates between patients with (71%) or without (69%) asymmetric MEG slowing (χ2 = 0.4, p = 0.99). Significance MEG has higher sensitivity than scalp EEG in detecting asymmetric slow activity in focal epilepsy, which reliably lateralizes to the epileptogenic hemisphere. Other uses of MEG beyond spike localization may further improve presurgical evaluations in epilepsy.

show abstract

Magnetoencephalography in the presurgical evaluation of epilepsy

Cited by 45 publications

References 61 publications

Identifying the epileptogenic zone in interictal resting‐state MEG source‐space networks

Identifying the epileptogenic zone in interictal resting‐state MEG source‐space networks

Feasibility of magnetoencephalographic source imaging in patients with thalamic deep brain stimulation for epilepsy

The sensitivity and significance of lateralized interictal slow activity on magnetoencephalography in focal epilepsy

Contact Info

Product

Resources

About