Intracranial EEG Substrates of Scalp EEG Interictal Spikes

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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The Irritative Zone and Seizure Onset Zone in Acute ECOG: The Quest for Relevant Epileptogenic Tissue

Invasive Studies of the Human Epileptic Brain ◽

10.1093/med/9780198714668.003.0010 ◽

2018 ◽

pp. 120-130

Author(s):

André Palmini ◽

Eliseu Paglioli

Keyword(s):

Epilepsy Surgery ◽

Cost Effective ◽

Careful Analysis ◽

Cortical Surface ◽

Interictal Spikes ◽

Intracranial Eeg ◽

Seizure Onset Zone ◽

Cost Effective Approach ◽

Lesion Type ◽

Refractory Seizures

Acute intraoperative electrocorticography (ECoG) is a time-honoured technique to identify the relevant epileptogenic tissue (RET) and hence guide cortical resection to control medically refractory seizures. ECoG identifies the RET through careful analysis of pattern, morphology, frequency, and localization of interictal spikes recorded directly from the exposed cortical surface. Because the development and dissemination of chronic intracranial EEG recording techniques has put emphasis on ictal recordings (thus defining an ictal onset zone), acute ECoG is often considered unnecessary in surgical planning. The chapter describes limitations and advantages of acute ECoG to define the RET in comparison with more costly and risky procedures, particularly subdural grid and SEEG recording. Specifically, it shows how the integration of lesion type and sequentially recorded ECoG spikes during operation may provide a highly cost-effective approach to successful epilepsy surgery.

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Physiological Activity and Artefacts in Epileptic Brain in Subdural EEG

Invasive Studies of the Human Epileptic Brain ◽

10.1093/med/9780198714668.003.0007 ◽

2018 ◽

pp. 84-97

Author(s):

Beate Diehl ◽

Catherine A. Scott

Keyword(s):

Motor Cortex ◽

Brain Region ◽

Physiological Activity ◽

Brain Oscillations ◽

Intracranial Eeg ◽

Scalp Eeg ◽

Focal Pattern ◽

Mu Rhythms ◽

Eeg Recordings ◽

Central Pacemaker

‘Physiological activity and artefacts in epileptic brain in subdural EEG’ reviews intracranial appearances of physiological brain rhythms in each brain region, many of which are also seen on scalp EEG. The alpha rhythm has been described as originating from multiple occipital and extra-occipital cortical generators variously overlapping and influencing each other, probably under the relative control of a central pacemaker. Another more focal pattern has been described in intracranial EEG recordings in the calcarine region, with a third rhythm arising in midtemporal regions, not detectable in scalp EEG, with a frequency in the alpha or theta range. Lambda waves, sleep structures, and mu rhythms over motor cortex can also be detected on subdural electrodes. On a region-by-region basis, intracranial EEG appearances are summarized, including brain oscillations in hippocampus and motor cortex and their modifiers, as well as ongoing rhythms in cingulum. Common sources of physiological and non-physiological artefacts are reviewed.

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Electromagnetic source imaging using simultaneous scalp EEG and intracranial EEG: An emerging tool for interacting with pathological brain networks

Clinical Neurophysiology ◽

10.1016/j.clinph.2017.10.027 ◽

2018 ◽

Vol 129 (1) ◽

pp. 168-187 ◽

Cited By ~ 9

Author(s):

Seyed Amir Hossein Hosseini ◽

Abbas Sohrabpour ◽

Bin He

Keyword(s):

Brain Networks ◽

Source Imaging ◽

Intracranial Eeg ◽

Scalp Eeg ◽

Electromagnetic Source

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Electric Source Imaging on Intracranial EEG Localizes Spatiotemporal Propagation of Interictal Spikes in Children with Epilepsy

10.1109/embc46164.2021.9630246 ◽

2021 ◽

Author(s):

Margherita A.G. Matarrese ◽

Alessandro Loppini ◽

Saeed Jahromi ◽

Eleonora Tamilia ◽

Lorenzo Fabbri ◽

...

Keyword(s):

Interictal Spikes ◽

Source Imaging ◽

Intracranial Eeg ◽

Electric Source

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Scalp and Intracranial EEG in Medically Intractable Extratemporal Epilepsy with Normal MRI

ISRN Neurology ◽

10.5402/2012/942849 ◽

2012 ◽

Vol 2012 ◽

pp. 1-9 ◽

Cited By ~ 14

Author(s):

Tarek Zakaria ◽

Katherine Noe ◽

Elson So ◽

Gregory D. Cascino ◽

Nicholas Wetjen ◽

...

Keyword(s):

Epilepsy Surgery ◽

Surgical Outcome ◽

Favorable Outcome ◽

Rank Test ◽

Seizure Freedom ◽

Intracranial Eeg ◽

Scalp Eeg ◽

Kaplan Meier ◽

Postoperative Seizure ◽

Beta Frequency

Purpose. To investigate EEG and SPECT in the surgical outcome of patients with normal MRI (nonlesional) and extratemporal lobe epilepsy. Methods. We retrospectively identified 41 consecutive patients with nonlesional extratemporal epilepsy who underwent epilepsy surgery between 1997 and 2007. The history, noninvasive diagnostic studies (scalp EEG, MRI, and SPECT) and intracranial EEG (iEEG) monitoring was reviewed. Scalp and iEEG ictal onset patterns were defined. The association of preoperative studies and postoperative seizure freedom was analyzed using Kaplan-Meier analysis, log-rank test, and Cox proportional hazard. Results. Thirty-six of 41 patients had adequate information with a minimum of 1-year followup. Favorable surgical outcome was identified in 49% of patients at 1 year, and 35% at 4-year. On scalp EEG, an ictal onset pattern consisting of focal beta-frequency discharge (>13–125 Hz) was associated with favorable surgical outcome (P=0.02). Similarly, a focal fast-frequency oscillation (>13–125 Hz) on iEEG at ictal onset was associated with favorable outcome (P=0.03). Discussion. A focal fast-frequency discharge at ictal onset identifies nonlesional MRI, extratemporal epilepsy patients likely to have a favorable outcome after resective epilepsy surgery.

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