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https://www.readbyqxmd.com/read/28194133/current-and-emerging-potential-of-magnetoencephalography-in-the-detection-and-localization-of-high-frequency-oscillations-in-epilepsy
#1
REVIEW
Eleonora Tamilia, Joseph R Madsen, Patricia Ellen Grant, Phillip L Pearl, Christos Papadelis
Up to one-third of patients with epilepsy are medically intractable and need resective surgery. To be successful, epilepsy surgery requires a comprehensive preoperative evaluation to define the epileptogenic zone (EZ), the brain area that should be resected to achieve seizure freedom. Due to lack of tools and methods that measure the EZ directly, this area is defined indirectly based on concordant data from a multitude of presurgical non-invasive tests and intracranial recordings. However, the results of these tests are often insufficiently concordant or inconclusive...
2017: Frontiers in Neurology
https://www.readbyqxmd.com/read/28160749/interrater-reliability-of-visually-evaluated-high-frequency-oscillations
#2
Aaron M Spring, Daniel J Pittman, Yahya Aghakhani, Jeffrey Jirsch, Neelan Pillay, Luis E Bello-Espinosa, Colin Josephson, Paolo Federico
OBJECTIVE: High frequency oscillations (HFOs) and interictal epileptiform discharges (IEDs) have been shown to be markers of epileptogenic regions. However, there is currently no 'gold standard' for identifying HFOs. Accordingly, we aimed to formally characterize the interrater reliability of HFO markings to validate the current practices. METHODS: A morphology detector was implemented to detect events (candidate HFOs, lower-threshold events, and distractors) from the intracranial EEG (iEEG) of ten patients...
December 30, 2016: Clinical Neurophysiology: Official Journal of the International Federation of Clinical Neurophysiology
https://www.readbyqxmd.com/read/28115239/high-frequency-oscillations-and-mesial-temporal-lobe-epilepsy
#3
REVIEW
Maxime Lévesque, Zahra Shiri, Li-Yuan Chen, Massimo Avoli
The interest of epileptologists has recently shifted from the macroscopic analysis of interictal spikes and seizures to the microscopic analysis of short events in the EEG that are not visible to the naked eye but are observed once the signal has been filtered in specific frequency bands. With the use of new technologies that allow multichannel recordings at high sampling rates and the development of computer algorithms that permit the automated analysis of extensive amounts of data, it is now possible to extract high-frequency oscillations (HFOs) between 80 and 500Hz from the EEG; HFOs have been further categorised as ripples (80-200Hz) and fast ripples (250-500Hz)...
January 20, 2017: Neuroscience Letters
https://www.readbyqxmd.com/read/28113472/a-spatially-focused-method-for-high-density-electrode-based-functional-brain-mapping-applications
#4
Chih-Wei Chang, Yue-Loong Hsin, Wentai Liu
Mapping the electric field of the brain with electrodes benefits from its superior temporal resolution but is prone to low spatial resolution property comparing with other modalities such as fMRI, which can directly impact the precision of clinical diagnosis. Simulations show that dense arrays with straightforwardly miniaturized electrodes in terms of size and pitch may not improve the spatial resolution but only strengthen the cross coupling between adjacent channels due to volume conduction. We present a new spatially focused method to improve the electrode spatial selectivity and consequently suppress the neural signal coupling from the sources in the vicinity...
March 7, 2016: IEEE Transactions on Neural Systems and Rehabilitation Engineering
https://www.readbyqxmd.com/read/28113293/automatic-detection-and-classification-of-high-frequency-oscillations-in-depth-eeg-signals
#5
Nisrine Jrad, Amar Kachenoura, Isabelle Merlet, Fabrice Bartolomei, Anca Nica, Arnaud Biraben, Fabrice Wendling
GOAL: Interictal High Frequency Oscillations (HFOs [30-600 Hz]) have proven to be relevant biomarkers in epilepsy. In this paper, four categories of HFOs are considered: Gamma ([30- 80 Hz]), High-Gamma ([80-120 Hz]), Ripples ([120-250 Hz]) and Fast-Ripples ([250-600 Hz]). A universal detector of the four types of HFOs is proposed. It has the advantages of i) classifying HFOs, and thus being robust to inter- and intra-subject variability; ii) rejecting artefacts, thus being specific. METHODS: Gabor atoms are tuned to cover the physiological bands...
November 29, 2016: IEEE Transactions on Bio-medical Engineering
https://www.readbyqxmd.com/read/28107659/high-frequency-oscillations-and-seizure-like-discharges-in-the-entorhinal-cortex-of-the-in-vitro-isolated-guinea-pig-brain
#6
Laura Uva, Davide Boido, Massimo Avoli, Marco de Curtis, Maxime Lévesque
We analyzed the patterns of seizure-like activity and associated high-frequency oscillations (HFOs) induced by the K(+) channel blocker 4-aminopyridine (4AP, 50μM) or the GABAA receptor antagonist bicuculline methiodide (BMI, 50μM) in the in vitro isolated guinea pig brain preparation. Extracellular field recordings were obtained from the medial entorhinal cortex (EC) using glass pipettes or silicon probes; 4AP or BMI were applied through the basilar artery. Ripples (80-200Hz) or fast ripples (250-500Hz) occurred at higher rates shortly before ictal events induced by 4AP or BMI, respectively...
January 6, 2017: Epilepsy Research
https://www.readbyqxmd.com/read/28063789/co-occurrence-of-high-frequency-oscillations-and-delayed-responses-evoked-by-intracranial-electrical-stimulation-in-stereo-eeg-studies
#7
Cristian Donos, Ioana Mîndruţă, Mihai Dragoş Malîia, Alin Raşină, Jean Ciurea, Andrei Barborica
OBJECTIVE: To perform a side-by-side comparison of two epileptogenicity biomarkers, high frequency oscillations (HFOs) and delayed responses (DRs), as a result of single-pulse electrical stimulation. METHODS: We have recorded stimulation-evoked HFOs and DRs in 16 epileptic patients undergoing presurgical evaluation using the stereoelectroencephalographic method. To evaluate converging and complementary information provided by the biomarkers, we analyzed them individually and for logical "and"/"or" combinations between them...
December 18, 2016: Clinical Neurophysiology: Official Journal of the International Federation of Clinical Neurophysiology
https://www.readbyqxmd.com/read/28060325/interictal-high-frequency-oscillations-detected-with-simultaneous-magnetoencephalography-and-electroencephalography-as-biomarker-of-pediatric-epilepsy
#8
Christos Papadelis, Eleonora Tamilia, Steven Stufflebeam, Patricia E Grant, Joseph R Madsen, Phillip L Pearl, Naoaki Tanaka
Crucial to the success of epilepsy surgery is the availability of a robust biomarker that identifies the Epileptogenic Zone (EZ). High Frequency Oscillations (HFOs) have emerged as potential presurgical biomarkers for the identification of the EZ in addition to Interictal Epileptiform Discharges (IEDs) and ictal activity. Although they are promising to localize the EZ, they are not yet suited for the diagnosis or monitoring of epilepsy in clinical practice. Primary barriers remain: the lack of a formal and global definition for HFOs; the consequent heterogeneity of methodological approaches used for their study; and the practical difficulties to detect and localize them noninvasively from scalp recordings...
December 6, 2016: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/28043201/physiological-ripples-associated-with-sleep-spindles-differ-in-waveform-morphology-from-epileptic-ripples
#9
Jonas C Bruder, Matthias Dümpelmann, Daniel Lachner Piza, Malenka Mader, Andreas Schulze-Bonhage, Julia Jacobs-Le Van
High frequency oscillations (HFOs, 80-500[Formula: see text]Hz) serve as novel electroencephalography (EEG) markers of epileptic tissue. The differentiation of physiological and epileptic HFO is an important challenge and is complicated by the fact that both types are generated in mesiotemporal structures. This study aimed to identify oscillation features that serve to distinguish physiological ripples associated with sleep spindles and epileptic ripples. We studied 19 patients with chronic intracranial EEG(iEEG) with mesiotemporal implantation and simultaneous scalp EEG...
November 2, 2016: International Journal of Neural Systems
https://www.readbyqxmd.com/read/27965619/dynamic-changes-in-spectral-and-spatial-signatures-of-high-frequency-oscillations-in-rat-hippocampi-during-epileptogenesis-in-acute-and-chronic-stages
#10
Pan-Pan Song, Jing Xiang, Li Jiang, Heng-Sheng Chen, Ben-Ke Liu, Yue Hu
OBJECTIVE: To analyze spectral and spatial signatures of high frequency oscillations (HFOs), which include ripples and fast ripples (FRs, >200 Hz) by quantitatively assessing average and peak spectral power in a rat model of different stages of epileptogenesis. METHODS: The lithium-pilocarpine model of temporal lobe epilepsy was used. The acute phase of epilepsy was assessed by recording intracranial electroencephalography (EEG) activity for 1 day after status epilepticus (SE)...
2016: Frontiers in Neurology
https://www.readbyqxmd.com/read/27913322/automatic-detection-and-classification-of-high-frequency-oscillations-in-depth-eeg-signals
#11
Nisrine Jrad, Amar Kachenoura, Isabelle Merlet, Fabrice Bartolomei, Anca Nica, Arnaud Biraben, Fabrice Wendling
GOAL: Interictal High Frequency Oscillations (HFOs [30-600 Hz]) have proven to be relevant biomarkers in epilepsy. In this paper, four categories of HFOs are considered: Gamma ([30- 80 Hz]), High-Gamma ([80-120 Hz]), Ripples ([120-250 Hz]) and Fast-Ripples ([250-600 Hz]). A universal detector of the four types of HFOs is proposed. It has the advantages of i) classifying HFOs, and thus being robust to inter- and intra-subject variability; ii) rejecting artefacts, thus being specific. METHODS: Gabor atoms are tuned to cover the physiological bands...
November 29, 2016: IEEE Transactions on Bio-medical Engineering
https://www.readbyqxmd.com/read/27912169/non-harmonicity-in-high-frequency-components-of-the-intra-operative-corticogram-to-delineate-epileptogenic-tissue-during-surgery
#12
Evelien E Geertsema, Maryse A van 't Klooster, Nicole E C van Klink, Frans S S Leijten, Peter C van Rijen, Gerhard H Visser, Stiliyan N Kalitzin, Maeike Zijlmans
OBJECTIVE: We aimed to test the potential of auto-regressive model residual modulation (ARRm), an artefact-insensitive method based on non-harmonicity of the high-frequency signal, to identify epileptogenic tissue during surgery. METHODS: Intra-operative electrocorticography (ECoG) of 54 patients with refractory focal epilepsy were recorded pre- and post-resection at 2048Hz. The ARRm was calculated in one-minute epochs in which high-frequency oscillations (HFOs; fast ripples, 250-500Hz; ripples, 80-250Hz) and spikes were marked...
January 2017: Clinical Neurophysiology: Official Journal of the International Federation of Clinical Neurophysiology
https://www.readbyqxmd.com/read/27896067/relationship-between-high-frequency-oscillations-and-spikes-in-a-case-of-temporal-lobe-epilepsy
#13
Vishwanath Sagi, M Steven Evans
OBJECTIVE: The aim of this case report was to study the relationship between high-frequency oscillations (HFOs), spikes, and seizures in a patient with temporal lobe epilepsy. INTRODUCTION: During intracranial electroencephalography (EEG), HFOs are thought to be a marker for the seizure onset zone (SOZ). High-frequency oscillations are classified into ripples with frequencies of 70-200 Hz and fast ripples with frequencies of 200-500 Hz. Although HFOs are thought to be a marker for the SOZ, their relationship to spikes has not been studied in detail, especially within the SOZ...
2016: Epilepsy & Behavior Case Reports
https://www.readbyqxmd.com/read/27882298/high-frequency-oscillations-and-high-frequency-functional-network-characteristics-in-the-intraoperative-electrocorticogram-in-epilepsy
#14
W J E M Zweiphenning, M A van 't Klooster, E van Diessen, N E C van Klink, G J M Huiskamp, T A Gebbink, F S S Leijten, P H Gosselaar, W M Otte, C J Stam, K P J Braun, G J M Zijlmans
OBJECTIVE: High frequency oscillations (HFOs; > 80 Hz), especially fast ripples (FRs, 250-500 Hz), are novel biomarkers for epileptogenic tissue. The pathophysiology suggests enhanced functional connectivity within FR generating tissue. Our aim was to determine the relation between brain areas showing FRs and 'baseline' functional connectivity within EEG networks, especially in the high frequency bands. METHODS: We marked FRs, ripples (80-250 Hz) and spikes in the electrocorticogram of 14 patients with refractory temporal lobe epilepsy...
2016: NeuroImage: Clinical
https://www.readbyqxmd.com/read/27875125/time-frequency-strategies-for-increasing-high-frequency-oscillation-detectability-in-intracerebral-eeg
#15
Nicolas Roehri, Jean-Marc Lina, John C Mosher, Fabrice Bartolomei, Christian-George Benar
BACKGROUND: High-frequency oscillations (HFOs) are considered to be highly representative of brain tissues capable of producing epileptic seizures. The visual review of HFOs on intracerebral electroencephalography is time consuming and tedious, and it can be improved by time-frequency (TF) analysis. The main issue is that the signal is dominated by lower frequencies that mask the HFOs. Our aim was to flatten (i.e., whiten) the frequency spectrum to enhance the fast oscillations while preserving an optimal signal to noise ratio (SNR)...
December 2016: IEEE Transactions on Bio-medical Engineering
https://www.readbyqxmd.com/read/27861778/correlation-of-fdg-pet-hypometabolism-and-seeg-epileptogenicity-mapping-in-patients-with-drug-resistant-focal-epilepsy
#16
Florence Lamarche, Anne-Sophie Job, Pierre Deman, Manik Bhattacharjee, Dominique Hoffmann, Céline Gallazzini-Crépin, Sandrine Bouvard, Lorella Minotti, Philippe Kahane, Olivier David
OBJECTIVE: Interictal [18F]fluorodeoxyglucose-positron emission tomography (FDG-PET) is used in the presurgical evaluation of patients with drug-resistant focal epilepsy. We aimed at clarifying its relationships with ictal high-frequency oscillations (iHFOs) shown to be a relevant marker of the seizure-onset zone. METHODS: We studied the correlation between FDG-PET and epileptogenicity maps in an unselected series of 37 successive patients having been explored with stereo-electroencephalography (SEEG)...
December 2016: Epilepsia
https://www.readbyqxmd.com/read/27764594/fast-accurate-localization-of-epileptic-seizure-onset-zones-based-on-detection-of-high-frequency-oscillations-using-improved-wavelet-transform-and-matching-pursuit-methods
#17
Min Wu, Ting Wan, Xiongbo Wan, Yuxiao Du, Jinhua She
This letter describes the improvement of two methods of detecting high-frequency oscillations (HFOs) and their use to localize epileptic seizure onset zones (SOZs). The wavelet transform (WT) method was improved by combining the complex Morlet WT with Shannon entropy to enhance the temporal-frequency resolution during HFO detection. And the matching pursuit (MP) method was improved by combining it with an adaptive genetic algorithm to improve the speed and accuracy of the calculations for HFO detection. The HFOs detected by these two methods were used to localize SOZs in five patients...
January 2017: Neural Computation
https://www.readbyqxmd.com/read/27733815/gpi-oscillatory-activity-differentiates-tics-from-the-resting-state-voluntary-movements-and-the-unmedicated-parkinsonian-state
#18
Joohi Jimenez-Shahed, Ilknur Telkes, Ashwin Viswanathan, Nuri F Ince
Background: Deep brain stimulation (DBS) is an emerging treatment strategy for severe, medication-refractory Tourette syndrome (TS). Thalamic (Cm-Pf) and pallidal (including globus pallidus interna, GPi) targets have been the most investigated. While the neurophysiological correlates of Parkinson's disease (PD) in the GPi and subthalamic nucleus (STN) are increasingly recognized, these patterns are not well characterized in other disease states. Recent findings indicate that the cross-frequency coupling (CFC) between beta band and high frequency oscillations (HFOs) within the STN in PD patients is pathologic...
2016: Frontiers in Neuroscience
https://www.readbyqxmd.com/read/27639348/high-frequency-oscillations-for-lateralizing-suspected-bitemporal-epilepsy
#19
Chunyan Liu, Ruihua Zhang, Guojun Zhang, Tao Yu, Junli Tai, Wei Du, Liping Li, Yuping Wang
OBJECTIVE: In some cases of single focus epilepsy, conventional video electroencephalography (EEG) cannot reveal the epileptogenic focus even when intracranial electrodes are used. Here, we tested whether analyzing high frequency oscillations (HFOs) can be used to determine the ictal onset zone in suspected bitemporal epilepsy and improve seizure outcome. METHODS: We prospectively studied 13 patients with refractory temporal seizures who were treated over a 4-year period and underwent bilateral placement of intracranial electrodes...
September 5, 2016: Epilepsy Research
https://www.readbyqxmd.com/read/27635628/intracranial-eeg-seizure-onset-patterns-correlate-with-high-frequency-oscillations-in-patients-with-drug-resistant-epilepsy
#20
Taissa Ferrari-Marinho, Piero Perucca, Francois Dubeau, Jean Gotman
OBJECTIVE: High-frequency oscillations (80-500Hz; HFOs) have been shown to be a specific biomarker of the seizure-onset zone. The relationship of HFOs with seizures having different intracranial electroencephalography (iEEG) morphological onsets, however, has shown significant relationships in experimental animals but has not been studied in humans. We investigated how interictal and ictal HFOs relate to different seizure-onset morphological patterns. METHODS: We analyzed the most representative seizure type of 37 patients with drug-resistant focal epilepsy who underwent iEEG for diagnostic evaluation...
September 6, 2016: Epilepsy Research
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