On-scalp magnetoencephalography for childhood epilepsies

AbstractMagnetoencephalography (MEG) is an established method to investigate epilepsy. Current MEG systems house hundreds of cryogenic sensors in a rigid, one-size-fits-all helmet, which results in several limitations, particularly in children. On-scalp MEG based on optically-pumped magnetometers (OPMs) may alleviate these limitations.We report on five children (5–11 years old) with self-limited focal (n=3) or structural (n=2) epilepsy who underwent cryogenic (102 magnetometers) and on-scalp (32 OPMs) MEG. We compared the two modalities for the detection and localization of interictal epileptiform discharges (IEDs).We identified IEDs in all children with comparable sensor topographies for both MEG devices. IED amplitudes were 2.3-4.8 times higher with on-scalp MEG and signal-to-noise ratio (SNR) was also 27-60% higher with on-scalp MEG in all but one patient with large head movement artifacts. The neural source of averaged IEDs was located at about 5 mm (n=3) or higher (8.3 mm, n=1; 15.6 mm, n=1) between on-scalp and cryogenic MEG.Despite limited number of sensors and scalp coverage, on-scalp MEG detects IEDs in epileptic children with higher SNR than cryogenic MEG. This technology, which is in constant development, should become a reference in the diagnostic workup of epilepsy and replace cryogenic MEG in the near future.

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Source localization of interictal epileptiform discharges: Comparison of three different techniques to improve signal to noise ratio

Clinical Neurophysiology ◽

10.1016/j.clinph.2005.11.014 ◽

2006 ◽

Vol 117 (3) ◽

pp. 562-571 ◽

Cited By ~ 16

Author(s):

Dominik Zumsteg ◽

Alon Friedman ◽

Heinz Gregor Wieser ◽

Richard A. Wennberg

Keyword(s):

Source Localization ◽

Signal To Noise Ratio ◽

Signal To Noise ◽

Epileptiform Discharges ◽

Interictal Epileptiform Discharges ◽

Noise Ratio

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First experiences of whole-head OP-MEG recordings from a patient with Epilepsy

10.1101/2021.09.28.21264047 ◽

2021 ◽

Author(s):

Stephanie J Mellor ◽

Umesh Vivekananda ◽

George C O'Neill ◽

Tim M Tierney ◽

David Doig ◽

...

Keyword(s):

Focal Cortical Dysplasia ◽

New Technology ◽

Cryogenic Cooling ◽

Single Subject ◽

Optically Pumped ◽

Scalp Eeg ◽

Epileptiform Discharges ◽

Interictal Epileptiform Discharges ◽

The Right ◽

Video Eeg

Optically Pumped Magnetometer based Magnetoencephalography (OP-MEG) has significant potential for clinical use in pre-surgical planning in epilepsy. Unlike current clinical MEG, the sensors do not require cryogenic cooling and so can be placed directly on the patient's head. This allows the patient to move during the recording and means that the sensor positions can be chosen to suit the patient's head shape and suspected epileptogenic focus. However, OP-MEG is a new technology, and more work is needed to demonstrate this potential. We present OP-MEG recordings from a patient (male in their 30s) with a radiologically identifiable focal cortical dysplasia (FCD) in the right superior frontal sulcus approximately 1.9 cm3 in volume. Previous scalp EEG studies and prolonged video-EEG telemetry did not identify any interictal epileptiform abnormalities. We recorded 30 minutes of OP-MEG with 62-channel, whole-head sensor coverage. During the experiment, the patient's head was unconstrained. We localised interictal epileptiform discharges (IEDs) from this recording with a beamformer and by fitting a dipole to the averaged IED data. Both the beamformer peak and dipole fit locations were within 2.3 cm of the MRI lesion boundary. This single subject, proof-of-concept recording provides further evidence that OP-MEG can be a useful and minimally invasive tool in the clinical evaluation of epilepsy.

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Prognostic Significance of Interictal Epileptiform Discharges in Newly Diagnosed Seizure Disorders

Yearbook of Neurology and Neurosurgery ◽

10.1016/j.yneu.2011.04.009 ◽

2011 ◽

Vol 2011 ◽

pp. 195

Author(s):

G.N. Breningstall

Keyword(s):

Prognostic Significance ◽

Newly Diagnosed ◽

Seizure Disorders ◽

Epileptiform Discharges ◽

Interictal Epileptiform Discharges

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Prevalence of Interictal Epileptiform Discharges in Children Less Than One Year of Age Referred for Polysomnography

The Neurodiagnostic Journal ◽

10.1080/21646821.2015.1043224 ◽

2015 ◽

Vol 55 (2) ◽

pp. 122-132

Author(s):

Adetayo Adeleye ◽

Alice W. Ho ◽

Alberto Nettel-Aguirre ◽

Valerie Kirk ◽

Jeffrey Buchhalter

Keyword(s):

Epileptiform Discharges ◽

Interictal Epileptiform Discharges ◽

One Year

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Zero-crossing patterns reveal subtle epileptiform discharges in the scalp EEG

Scientific Reports ◽

10.1038/s41598-021-83337-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jan Pyrzowski ◽

Jean- Eudes Le Douget ◽

Amal Fouad ◽

Mariusz Siemiński ◽

Joanna Jędrzejczak ◽

...

Keyword(s):

Normal Subjects ◽

Intracranial Eeg ◽

Zero Crossing ◽

Temporal Precision ◽

Scalp Eeg ◽

Epileptiform Discharges ◽

Interictal Epileptiform Discharges ◽

Eeg Recordings ◽

Patients With Epilepsy ◽

Low Amplitude

AbstractClinical diagnosis of epilepsy depends heavily on the detection of interictal epileptiform discharges (IEDs) from scalp electroencephalographic (EEG) signals, which by purely visual means is far from straightforward. Here, we introduce a simple signal analysis procedure based on scalp EEG zero-crossing patterns which can extract the spatiotemporal structure of scalp voltage fluctuations. We analyzed simultaneous scalp and intracranial EEG recordings from patients with pharmacoresistant temporal lobe epilepsy. Our data show that a large proportion of intracranial IEDs manifest only as subtle, low-amplitude waveforms below scalp EEG background and could, therefore, not be detected visually. We found that scalp zero-crossing patterns allow detection of these intracranial IEDs on a single-trial level with millisecond temporal precision and including some mesial temporal discharges that do not propagate to the neocortex. Applied to an independent dataset, our method discriminated accurately between patients with epilepsy and normal subjects, confirming its practical applicability.

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Detection of Intracranial Signatures of Interictal Epileptiform Discharges from Concurrent Scalp EEG

International Journal of Neural Systems ◽

10.1142/s0129065716500167 ◽

2016 ◽

Vol 26 (04) ◽

pp. 1650016 ◽

Cited By ~ 11

Author(s):

Loukianos Spyrou ◽

David Martín-Lopez ◽

Antonio Valentín ◽

Gonzalo Alarcón ◽

Saeid Sanei

Keyword(s):

Detection Algorithm ◽

The Other ◽

Intracranial Eeg ◽

Scalp Eeg ◽

Epileptiform Discharges ◽

Interictal Epileptiform Discharges ◽

Scalp Electroencephalogram ◽

Patients With Epilepsy ◽

Electrical Activities ◽

The Brain

Interictal epileptiform discharges (IEDs) are transient neural electrical activities that occur in the brain of patients with epilepsy. A problem with the inspection of IEDs from the scalp electroencephalogram (sEEG) is that for a subset of epileptic patients, there are no visually discernible IEDs on the scalp, rendering the above procedures ineffective, both for detection purposes and algorithm evaluation. On the other hand, intracranially placed electrodes yield a much higher incidence of visible IEDs as compared to concurrent scalp electrodes. In this work, we utilize concurrent scalp and intracranial EEG (iEEG) from a group of temporal lobe epilepsy (TLE) patients with low number of scalp-visible IEDs. The aim is to determine whether by considering the timing information of the IEDs from iEEG, the resulting concurrent sEEG contains enough information for the IEDs to be reliably distinguished from non-IED segments. We develop an automatic detection algorithm which is tested in a leave-subject-out fashion, where each test subject’s detection algorithm is based on the other patients’ data. The algorithm obtained a [Formula: see text] accuracy in recognizing scalp IED from non-IED segments with [Formula: see text] accuracy when trained and tested on the same subject. Also, it was able to identify nonscalp-visible IED events for most patients with a low number of false positive detections. Our results represent a proof of concept that IED information for TLE patients is contained in scalp EEG even if they are not visually identifiable and also that between subject differences in the IED topology and shape are small enough such that a generic algorithm can be used.

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