Influence of the location and type of epileptogenic lesion on scalp interictal epileptiform discharges and high-frequency oscillations

Epilepsia ◽  
2017 ◽  
Vol 58 (12) ◽  
pp. 2153-2163 ◽  
Author(s):  
Carolina Cuello-Oderiz ◽  
Nicolas von Ellenrieder ◽  
François Dubeau ◽  
Jean Gotman
Keyword(s):  
High Frequency ◽  
High Frequency Oscillations ◽  
Epileptiform Discharges ◽  
Interictal Epileptiform Discharges ◽  
Epileptogenic Lesion

scholarly journals The Oscillatory Basis of Working Memory Function and Dysfunction in Epilepsy

2021 ◽  
Vol 14 ◽  
Author(s):  
Olivia N. Arski ◽  
Julia M. Young ◽  
Mary-Lou Smith ◽  
George M. Ibrahim
Keyword(s):  
Working Memory ◽  
High Frequency ◽  
Large Scale ◽  
Memory Function ◽  
Epileptic Activity ◽  
Functional Roles ◽  
High Frequency Oscillations ◽  
Epileptiform Discharges ◽  
Interictal Epileptiform Discharges

Working memory (WM) deficits are pervasive co-morbidities of epilepsy. Although the pathophysiological mechanisms underpinning these impairments remain elusive, it is thought that WM depends on oscillatory interactions within and between nodes of large-scale functional networks. These include the hippocampus and default mode network as well as the prefrontal cortex and frontoparietal central executive network. Here, we review the functional roles of neural oscillations in subserving WM and the putative mechanisms by which epilepsy disrupts normative activity, leading to aberrant oscillatory signatures. We highlight the particular role of interictal epileptic activity, including interictal epileptiform discharges and high frequency oscillations (HFOs) in WM deficits. We also discuss the translational opportunities presented by greater understanding of the oscillatory basis of WM function and dysfunction in epilepsy, including potential targets for neuromodulation.

scholarly journals Dual mechanisms of ictal high frequency oscillations in human rhythmic onset seizures

2020 ◽  
Author(s):  
Elliot H. Smith ◽  
Edward M. Merricks ◽  
Jyun-You Liou ◽  
Camilla Casadei ◽  
Lucia Melloni ◽  
...  
Keyword(s):  
High Frequency ◽  
Activity Patterns ◽  
Field Potential ◽  
Information Theoretic ◽  
High Frequency Oscillations ◽  
Epileptiform Discharges ◽  
Before And After ◽  
Spatial Domains ◽  
Intracranial Electrodes ◽  
Seizure Localization

ABSTRACTHigh frequency oscillations (HFOs) recorded from intracranial electrodes during epileptiform discharges are a proposed biomarker of epileptic brain tissue and may also be useful for seizure forecasting, with mixed results. Despite such potential for HFOs, there is limited investigation into the spatial context of HFOs and their relationship to simultaneously recorded neuronal activity. We sought to further understand the biophysical underpinnings of ictal HFOs using unit recordings in the human neocortex and mesial temporal lobe during rhythmic onset seizures. We compare features of ictal discharges in both the seizure core and penumbra (spatial seizure domains defined by multiunit activity patterns). We report differences in spectral features, unit-local field potential coupling, and information theoretic characteristics of HFOs before and after local seizure invasion. Furthermore, we tie these timing-related differences to spatial domains of seizures, showing that penumbral discharges are widely distributed and less useful for seizure localization.

scholarly journals High-Frequency Oscillations on Interictal Epileptiform Discharges in Routinely Acquired Scalp EEG: Can It Be Used as a Prognostic Marker?

2021 ◽  
Vol 15 ◽  
Author(s):  
Hanan El Shakankiry ◽  
Susan T. Arnold
Keyword(s):  
Prognostic Marker ◽  
High Frequency ◽  
Medical Center ◽  
Time Base ◽  
Unprovoked Seizure ◽  
Scalp Eeg ◽  
High Frequency Oscillations ◽  
Epileptiform Discharges ◽  
Significant Difference ◽  
Scalp Electroencephalogram

IntroductionDespite all the efforts for optimizing epilepsy management in children over the past decades, there is no clear consensus regarding whether to treat or not to treat epileptiform discharges (EDs) after a first unprovoked seizure or the optimal duration of therapy with anti-seizure medication (ASM). It is therefore highly needed to find markers on scalp electroencephalogram (EEG) that can help identify pathological EEG discharges that require treatment.Aim of the studyThis retrospective study aimed to identify whether the coexistence of ripples/high-frequency oscillations (HFOs) with interictal EDs (IEDs) in routinely acquired scalp EEG is associated with a higher risk of seizure recurrence and could be used as a prognostic marker.Methods100 children presenting with new onset seizure to Children’s Medical Center- Dallas during 2015–2016, who were not on ASM and had focal EDs on an awake and sleep EEG recorded with sample frequency of 500 HZ, were randomly identified by database review. EEGs were analyzed blinded to the data of the patients. HFOs were visually identified using review parameters including expanded time base and adjusted filter settings.ResultsThe average age of patients was 6.3 years (±4.35 SD). HFOs were visually identified in 19% of the studied patients with an inter-rater reliability of 99% for HFO negative discharges and 78% agreement for identification of HFOs. HFOs were identified more often in the younger age group; however, they were identified in 11% of patients >5 years old. They were more frequently associated with spikes than with sharp waves and more often with higher amplitude EDs. Patients with HFOs were more likely to have a recurrence of seizures in the year after the first seizure (P < 0.05) and to continue to have seizures after 2 years (P < 0.0001). There was no statistically significant difference between the two groups with regards to continuing ASM after 2 years.ConclusionIncluding analysis for HFOs in routine EEG interpretation may increase the yield of the study and help guide the decision to either start or discontinue ASM. In the future, this may also help to identify pathological discharges with deleterious effects on the growing brain and set a new target for the management of epilepsy.

scholarly journals Kurtosis-Based Detection of Intracranial High-Frequency Oscillations for the Identification of the Seizure Onset Zone

2018 ◽  
Vol 28 (07) ◽  
pp. 1850001 ◽  
Author(s):  
Lucia Rita Quitadamo ◽  
Roberto Mai ◽  
Francesca Gozzo ◽  
Veronica Pelliccia ◽  
Francesco Cardinale ◽  
...  
Keyword(s):  
High Frequency ◽  
Computational Time ◽  
Seizure Onset ◽  
Time Frequency ◽  
High Frequency Oscillations ◽  
Epileptiform Discharges ◽  
Seizure Onset Zone ◽  
Potential Biomarker ◽  
Eeg Data

Pathological High-Frequency Oscillations (HFOs) have been recently proposed as potential biomarker of the seizure onset zone (SOZ) and have shown superior accuracy to interictal epileptiform discharges in delineating its anatomical boundaries. Characterization of HFOs is still in its infancy and this is reflected in the heterogeneity of analysis and reporting methods across studies and in clinical practice. The clinical approach to HFOs identification and quantification usually still relies on visual inspection of EEG data. In this study, we developed a pipeline for the detection and analysis of HFOs. This includes preliminary selection of the most informative channels exploiting statistical properties of the pre-ictal and ictal intracranial EEG (iEEG) time series based on spectral kurtosis, followed by wavelet-based characterization of the time–frequency properties of the signal. We performed a preliminary validation analyzing EEG data in the ripple frequency band (80–250 Hz) from six patients with drug-resistant epilepsy who underwent pre-surgical evaluation with stereo-EEG (SEEG) followed by surgical resection of pathologic brain areas, who had at least two-year positive post-surgical outcome. In this series, kurtosis-driven selection and wavelet-based detection of HFOs had average sensitivity of 81.94% and average specificity of 96.03% in identifying the HFO area which overlapped with the SOZ as defined by clinical presurgical workup. Furthermore, the kurtosis-based channel selection resulted in an average reduction in computational time of 66.60%.

scholarly journals Dual mechanisms of ictal high frequency oscillations in human rhythmic onset seizures

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Elliot H. Smith ◽  
Edward M. Merricks ◽  
Jyun-You Liou ◽  
Camilla Casadei ◽  
Lucia Melloni ◽  
...  
Keyword(s):  
Local Field ◽  
Local Field Potential ◽  
High Frequency ◽  
Activity Patterns ◽  
Field Potential ◽  
Information Theoretic ◽  
High Frequency Oscillations ◽  
Epileptiform Discharges ◽  
Before And After ◽  
Spatial Domains

Abstract High frequency oscillations (HFOs) are bursts of neural activity in the range of 80 Hz or higher, recorded from intracranial electrodes during epileptiform discharges. HFOs are a proposed biomarker of epileptic brain tissue and may also be useful for seizure forecasting. Despite such clinical utility of HFOs, the spatial context and neuronal activity underlying these local field potential (LFP) events remains unclear. We sought to further understand the neuronal correlates of ictal high frequency LFPs using multielectrode array recordings in the human neocortex and mesial temporal lobe during rhythmic onset seizures. These multiscale recordings capture single cell, multiunit, and LFP activity from the human brain. We compare features of multiunit firing and high frequency LFP from microelectrodes and macroelectrodes during ictal discharges in both the seizure core and penumbra (spatial seizure domains defined by multiunit activity patterns). We report differences in spectral features, unit-local field potential coupling, and information theoretic characteristics of high frequency LFP before and after local seizure invasion. Furthermore, we tie these time-domain differences to spatial domains of seizures, showing that penumbral discharges are more broadly distributed and less useful for seizure localization. These results describe the neuronal and synaptic correlates of two types of pathological HFOs in humans and have important implications for clinical interpretation of rhythmic onset seizures.

scholarly journals Dual mechanisms of ictal high frequency oscillations in rhythmic onset seizures

2020 ◽  
Author(s):  
Elliot H. Smith ◽  
Edward M. Merricks ◽  
Jyun-You Liou ◽  
Camilla Casadei ◽  
Lucia Melloni ◽  
...  
Keyword(s):  
High Frequency ◽  
Activity Patterns ◽  
Information Theoretic ◽  
High Frequency Oscillations ◽  
Epileptiform Discharges ◽  
Electrophysiological Recordings ◽  
Before And After ◽  
Spatial Domains ◽  
Intracranial Electrodes ◽  
Seizure Localization

ABSTRACTObjectiveHigh frequency oscillations (HFOs) recorded from intracranial electrodes during epileptiform discharges have been proposed as a biomarker of epileptic brain sites and may also be a useful feature for seizure forecasting, with mixed results. Currently, pathological subclasses of HFOs have been defined primarily by frequency characteristics. Despite this, there has been limited investigation into the spatial context of HFOs with recruitment of local cortex into seizure discharging. We sought to further understand the biophysical underpinnings of ictal HFOs.MethodsHere we examine ictal HFOs from multi-scale electrophysiological recordings during spontaneous human rhythmic onset seizures. We compare features of ictal discharges in both the seizure core and penumbra, as defined by multiunit activity patterns.ResultsWe show marked differences in spectral features, unit coupling, and information theoretic characteristics of HFOs during ictal discharges before and after local seizure invasion. Furthermore, we tie these timing-related differences to different spatial domains of seizures, showing that eccentric, penumbral discharges are widely distributed and less useful for seizure localization, which may explain the variable utility of HFOs in seizure localization and forecasting.InterpretationWe thus identify two distinct classes of ictal HFOs, implying two different mechanisms underlying pathological HFOs with contrasting significance for seizure localization.

scholarly journals Interictal Epileptiform Discharges are Task Dependent and are Associated with Lasting Electrocorticographic Changes

2021 ◽  
Vol 2 (2) ◽  
Author(s):  
Stephen Meisenhelter ◽  
Robert J Quon ◽  
Sarah A Steimel ◽  
Markus E Testorf ◽  
Edward J Camp ◽  
...  
Keyword(s):  
Epileptiform Activity ◽  
Memory Task ◽  
Low Frequency ◽  
Brain Regions ◽  
Blank Screen ◽  
High Frequency Oscillations ◽  
Epileptiform Discharges ◽  
Interictal Epileptiform Discharges ◽  
Task Dependence ◽  
Low Frequency Power

Abstract The factors that control the occurrence of interictal epileptiform discharges (IEDs) are not well understood. We suspected that this phenomenon reflects an attention-dependent suppression of interictal epileptiform activity. We hypothesized that IEDs would occur less frequently when a subject viewed a task-relevant stimulus compared with viewing a blank screen. Furthermore, IEDs have been shown to impair memory when they occur in certain regions during the encoding or recall phases of a memory task. Although these discharges have a short duration, their impact on memory suggests that they have longer lasting electrophysiological effects. We found that IEDs were associated with an increase in low-frequency power and a change in the balance between low- and high-frequency oscillations for several seconds. We found that the occurrence of IEDs is modified by whether a subject is attending to a word displayed on screen or is observing a blank screen. In addition, we found that discharges in brain regions in every lobe impair memory. These findings elucidate the relationship between IEDs and memory impairment and reveal the task dependence of the occurrence of IEDs.

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