Leveraging electrophysiologic correlates of word encoding to map seizure onset zone in focal epilepsy: Task‐dependent changes in epileptiform activity, spectral features, and functional connectivity

Magnetoencephalography (MEG) is increasingly used for presurgical planning in people with medically refractory focal epilepsy. Localization of interictal epileptiform activity, a surrogate for the seizure onset zone whose removal may prevent seizures, is challenging and depends on the use of multiple complementary techniques. Accurate and reliable localization of epileptiform activity from spontaneous MEG data has been an elusive goal. One approach toward this goal is to use a novel Bayesian inference algorithm—the Champagne algorithm with noise learning—which has shown tremendous success in source reconstruction, especially for focal brain sources. In this study, we localized sources of manually identified MEG spikes using the Champagne algorithm in a cohort of 16 patients with medically refractory epilepsy collected in two consecutive series. To evaluate the reliability of this approach, we compared the performance to equivalent current dipole (ECD) modeling, a conventional source localization technique that is commonly used in clinical practice. Results suggest that Champagne may be a robust, automated, alternative to manual parametric dipole fitting methods for localization of interictal MEG spikes, in addition to its previously described clinical and research applications.

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Interictal epileptiform activity outside the seizure onset zone impacts cognition

Brain ◽

10.1093/brain/awx143 ◽

2017 ◽

Vol 140 (8) ◽

pp. 2157-2168 ◽

Cited By ~ 31

Author(s):

Hoameng Ung ◽

Christian Cazares ◽

Ameya Nanivadekar ◽

Lohith Kini ◽

Joost Wagenaar ◽

...

Keyword(s):

Epileptiform Activity ◽

Seizure Onset ◽

Seizure Onset Zone

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Seizure Onset Zone Localization from Ictal High-Density EEG in Refractory Focal Epilepsy

Brain Topography ◽

10.1007/s10548-016-0537-8 ◽

2016 ◽

Vol 30 (2) ◽

pp. 257-271 ◽

Cited By ~ 29

Author(s):

Willeke Staljanssens ◽

Gregor Strobbe ◽

Roel Van Holen ◽

Gwénaël Birot ◽

Markus Gschwind ◽

...

Keyword(s):

Focal Epilepsy ◽

High Density ◽

Seizure Onset ◽

Seizure Onset Zone

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The seizure onset zone drives state-dependent epileptiform activity in susceptible brain regions

Clinical Neurophysiology ◽

10.1016/j.clinph.2019.05.032 ◽

2019 ◽

Vol 130 (9) ◽

pp. 1628-1641 ◽

Cited By ~ 2

Author(s):

Joshua M. Diamond ◽

Julio I. Chapeton ◽

William H. Theodore ◽

Sara K. Inati ◽

Kareem A. Zaghloul

Keyword(s):

Epileptiform Activity ◽

Brain Regions ◽

Seizure Onset ◽

State Dependent ◽

Seizure Onset Zone

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Prolonged postictal hemianopsia after a focal extraoccipital onset seizure

BMJ Case Reports ◽

10.1136/bcr-2020-239021 ◽

2021 ◽

Vol 14 (1) ◽

pp. e239021

Author(s):

Vibhangini S Wasade ◽

Jennifer L Logan

Keyword(s):

Epileptiform Activity ◽

Diagnostic Evaluation ◽

Onset Seizure ◽

Seizure Onset ◽

Seizure Termination ◽

Seizure Onset Zone ◽

History Of ◽

Epilepsy Monitoring

We report a case of a prolonged postictal hemianopsia occurring after a focal extraoccipital seizure. A 55-year-old man with a history of neurosyphilis, treated with penicillin, presented to our epilepsy monitoring unit (EMU) for diagnostic evaluation of his spells occurring for 2 years. The spell semiology was stereotypical, described as oral and manual automatisms, speech difficulty and unresponsiveness. During the EMU stay, after his typical seizure was recorded, he experienced right hemianopsia lasting for 2 hours. Electrographically, the ictal pattern was prominent over the left temporal derivation and propagated to the left occipital derivation as the seizure progressed. Interictal epileptiform activity was over the left temporal derivations. We support the view that postictal phenomenon may represent merely a seizure termination zone and not be necessarily localising to the seizure onset zone. Furthermore, prolonged isolated postictal symptom of hemianopsia could also be noted in rare situations.

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Contribution of ictal source imaging for localizing seizure onset zone in patients with focal epilepsy patients

Neurology ◽

10.1212/wnl.0000000000011109 ◽

2020 ◽

pp. 10.1212/WNL.0000000000011109

Author(s):

Shuai Ye ◽

Lin Yang ◽

Yunfeng Lu ◽

Michal T. Kucewicz ◽

Benjamin Brinkmann ◽

...

Keyword(s):

Surgical Resection ◽

Focal Epilepsy ◽

High Density ◽

Concordance Rate ◽

Added Value ◽

Seizure Onset ◽

Source Imaging ◽

Intracranial Eeg ◽

Seizure Onset Zone ◽

Eeg Recordings

ObjectiveTo determine whether seizure onset zone can be accurately localized prior to surgical planning in focal epilepsy patients, we performed non-invasive EEG recordings and source localization analyses on 39 patients.MethodsIn a total of 39 focal epilepsy patients, we recorded and extracted 138 seizures and 1,325 interictal epileptic discharges using high-density EEG. We have investigated a novel approach for directly imaging sources of seizures and interictal spikes from high density EEG recordings, and rigorously validated it for noninvasive localization of seizure onset zone (SOZ) determined from intracranial EEG findings and surgical resection volume. Conventional source imaging analyses were also performed for comparison.ResultsIctal source imaging showed a concordance rate of 95% when compared to intracranial EEG or resection results. The average distance from estimation to seizure onset (intracranial) electrodes is 1.35 cm in patients with concordant results, and 0.74 cm to surgical resection boundary in patients with successful surgery. About 41% of the patients were found to have multiple types of interictal activities; coincidentally, a lower concordance rate and a significantly worse performance in localizing SOZ were observed in these patients.ConclusionNoninvasive ictal source imaging with high-density EEG recording can provide highly concordant results with clinical decisions obtained by invasive monitoring or confirmed by resective surgery. By means of direct seizure imaging using high-density scalp EEG recordings, the added value of ictal source imaging is particularly high in patients with complex interictal activity patterns, who may represent the most challenging cases with poor prognosis.

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Statistical Features in High-Frequency Bands of Interictal iEEG Work Efficiently in Identifying the Seizure Onset Zone in Patients with Focal Epilepsy

Entropy ◽

10.3390/e22121415 ◽

2020 ◽

Vol 22 (12) ◽

pp. 1415

Author(s):

Most. Sheuli Akter ◽

Md. Rabiul Islam ◽

Toshihisa Tanaka ◽

Yasushi Iimura ◽

Takumi Mitsuhashi ◽

...

Keyword(s):

High Frequency ◽

State Of The Art ◽

Focal Epilepsy ◽

Epileptic Seizures ◽

Gradient Boosting ◽

Statistical Features ◽

Seizure Onset ◽

Seizure Onset Zone ◽

Frequency Components ◽

Final Score

The design of a computer-aided system for identifying the seizure onset zone (SOZ) from interictal and ictal electroencephalograms (EEGs) is desired by epileptologists. This study aims to introduce the statistical features of high-frequency components (HFCs) in interictal intracranial electroencephalograms (iEEGs) to identify the possible seizure onset zone (SOZ) channels. It is known that the activity of HFCs in interictal iEEGs, including ripple and fast ripple bands, is associated with epileptic seizures. This paper proposes to decompose multi-channel interictal iEEG signals into a number of subbands. For every 20 s segment, twelve features are computed from each subband. A mutual information (MI)-based method with grid search was applied to select the most prominent bands and features. A gradient-boosting decision tree-based algorithm called LightGBM was used to score each segment of the channels and these were averaged together to achieve a final score for each channel. The possible SOZ channels were localized based on the higher value channels. The experimental results with eleven epilepsy patients were tested to observe the efficiency of the proposed design compared to the state-of-the-art methods.

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Temporal Lobe Epilepsy Semiology

Epilepsy Research and Treatment ◽

10.1155/2012/751510 ◽

2012 ◽

Vol 2012 ◽

pp. 1-10 ◽

Cited By ~ 19

Author(s):

Robert D. G. Blair

Keyword(s):

Temporal Lobe Epilepsy ◽

Temporal Lobe ◽

Focal Epilepsy ◽

Intractable Epilepsy ◽

Febrile Seizures ◽

Mesial Temporal Sclerosis ◽

Careful Study ◽

Seizure Onset ◽

Seizure Semiology ◽

Seizure Onset Zone

Epilepsy represents a multifaceted group of disorders divided into two broad categories, partial and generalized, based on the seizure onset zone. The identification of the neuroanatomic site of seizure onset depends on delineation of seizure semiology by a careful history together with video-EEG, and a variety of neuroimaging technologies such as MRI, fMRI, FDG-PET, MEG, or invasive intracranial EEG recording. Temporal lobe epilepsy (TLE) is the commonest form of focal epilepsy and represents almost 2/3 of cases of intractable epilepsy managed surgically. A history of febrile seizures (especially complex febrile seizures) is common in TLE and is frequently associated with mesial temporal sclerosis (the commonest form of TLE). Seizure auras occur in many TLE patients and often exhibit features that are relatively specific for TLE but few are of lateralizing value. Automatisms, however, often have lateralizing significance. Careful study of seizure semiology remains invaluable in addressing the search for the seizure onset zone.

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The comparative study of invasive electroencephalography modalities in temporal lobe epilepsy

Russian journal of neurosurgery ◽

10.17650/1683-3295-2021-23-3-14-22 ◽

2021 ◽

Vol 23 (3) ◽

pp. 14-22

Author(s):

V. M. Dzhafarov ◽

A. B. Dmitriev ◽

N. P. Denisova ◽

D. A. Rzaev

Keyword(s):

Temporal Lobe Epilepsy ◽

Temporal Lobe ◽

Focal Epilepsy ◽

Epileptogenic Zone ◽

Foramen Ovale ◽

Seizure Onset ◽

Depth Electrodes ◽

Seizure Onset Zone ◽

Temporal Lobe Seizures ◽

Mesial Temporal Lobe

Introduction. Invasive video-EEG monitoring (invasive EEG) is indicated in patients with refractory focal epilepsy while localization of the epileptogenic zone is unclear. Methods of invasive EEG in different groups of patients demonstrate variable results.Objective: to analyse the results of invasive EEG via subdural and depth electrodes in patients with refractory temporal lobe epilepsy with mesial temporal lobe seizures.Materials and methods. The series of 37 patients who underwent invasive EEG from 2013 to 2020 was retrospectively analysed. The study includes primary adult patients with structural refractory focal epilepsy with mesial temporal lobe seizures without tumor and vascular pathology. Patients were divided onto 3 groups: 1) with foramen ovale electrodes 2) subdural strip electrodes and 3) combination of subdural strips and depths electrodes. The results of anteromedial temporal lobectomy after 6 months were classified according to Engel scale.Results. A group with foramen ovale electrodes included 7 patients, subdural strips – 23, combination – 7. The seizure onset zone was detected in 36 (97 %) cases. Serious complications were observed in 2 (29 %) cases in the group with foramen ovale electrodes. The mean follow-up in 23 (76 %) patients after resective surgery was 28.3 months. Favourable results (Engel I, II) were observed in 4 (80 %) patients with foramen ovale electrodes, in 8 (67 %) patients with subdural electrodes, in 6 (100 %) with combination. Unfavourable results (Engel III, IV) were noted in 1 (20 %) patient with foramen ovale electrode, in 4 (33 %) patients with subdural strips.Conclusion. All the presented modalities of invasive EEG are effective for localizing of seizure onset zone in this category of patients. Foramen ovale electrode using may be limited due to increased risk of complications.

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Mapping of Seizure Networks

Invasive Studies of the Human Epileptic Brain ◽

10.1093/med/9780198714668.003.0038 ◽

2018 ◽

pp. 511-519

Author(s):

Olivier David

Keyword(s):

Data Analysis ◽

Focal Epilepsy ◽

Seizure Onset ◽

High Frequency Oscillations ◽

Signal Features ◽

Seizure Onset Zone ◽

Presurgical Assessment ◽

Computer Based ◽

Intracranial Electroencephalography ◽

Quantitative Neuroimaging

Intracranial electroencephalography (iEEG) is used to localize the seizure onset zone (SOZ) and connected neuronal networks in surgical candidates suffering from intractable focal epilepsy. Identification of the SOZ is usually based on visual inspection of iEEG signals, but new computer-based quantitative iEEG analyses are being developed to improve and expedite SOZ detection. Two main questions arise. First, which signal features are the best proxys to identify the SOZ and the propagation pathways constituting epileptic networks? Second, how can the results of data analysis be represented in a clinically useful and meaningful manner? This chapter adopts an epileptogenicity mapping approach based on maps of ictal high-frequency oscillations superimposed on neuroanatomy and illustrates the main concepts underlying mapping of seizure networks. Future quantitative iEEG approaches should complete and operationalize understanding of seizure networks. Quantitative neuroimaging of iEEG features of seizures should help provide better presurgical assessment of patients undergoing resective surgery.

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