Dataset Information

Increased gamma and decreased fast ripple connections of epileptic tissue: A high-frequency directed network approach.

ABSTRACT:

Objective

New insights into high-frequency electroencephalographic activity and network analysis provide potential tools to improve delineation of epileptic tissue and increase the chance of postoperative seizure freedom. Based on our observation of high-frequency oscillations "spreading outward" from the epileptic source, we hypothesize that measures of directed connectivity in the high-frequency range distinguish epileptic from healthy brain tissue.

Methods

We retrospectively selected refractory epilepsy patients with a malformation of cortical development or tumor World Health Organization grade I/II who underwent epilepsy surgery with intraoperative electrocorticography for tailoring the resection based on spikes. We assessed directed functional connectivity in the theta (4-8 Hz), gamma (30-80 Hz), ripple (80-250 Hz), and fast ripple (FR; 250-500 Hz) bands using the short-time direct directed transfer function, and calculated the total, incoming, and outgoing propagation strength for each electrode. We compared network measures of electrodes covering the resected and nonresected areas separately for patients with good and poor outcome, and of electrodes with and without spikes, ripples, and FRs (group level: paired t test; patient level: Mann-Whitney U test). We selected the measure that could best identify the resected area and channels with epileptic events using the area under the receiver operating characteristic curve, and calculated the positive and negative predictive value, sensitivity, and specificity.

Results

We found higher total and outstrength in the ripple and gamma bands in resected tissue in patients with good outcome (ripple_total : P = .01; ripple_out : P = .04; gamma_total : P = .01; gamma_out : P = .01). Channels with events showed lower total and instrength, and higher outstrength in the FR band, and higher total and outstrength in the ripple, gamma, and theta bands (FR_total : P = .05; FR_in : P < .01; FR_out : P = .02; gamma_total : P < .01; gamma_in : P = .01; gamma_out : P < .01; theta_total : P = .01; theta_out : P = .01). The total strength in the gamma band was most distinctive at the channel level (positive predictive value [PPV]_good = 74%, PPV_poor = 43%).

Significance

Interictally, epileptic tissue is isolated in the FR band and acts as a driver up to the (fast) ripple frequency range. The gamma band total strength seems promising to delineate epileptic tissue intraoperatively.

SUBMITTER: Zweiphenning WJEM

PROVIDER: S-EPMC6852371 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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Publications

Increased gamma and decreased fast ripple connections of epileptic tissue: A high-frequency directed network approach.

Zweiphenning Willemiek J E M WJEM Keijzer Hanneke M HM van Diessen Eric E van 't Klooster Maryse A MA van Klink Nicole E C NEC Leijten Frans S S FSS van Rijen Peter C PC van Putten Michel J A M MJAM Braun Kees P J KPJ Zijlmans Maeike M

Epilepsia 20190722 9

<h4>Objective</h4>New insights into high-frequency electroencephalographic activity and network analysis provide potential tools to improve delineation of epileptic tissue and increase the chance of postoperative seizure freedom. Based on our observation of high-frequency oscillations "spreading outward" from the epileptic source, we hypothesize that measures of directed connectivity in the high-frequency range distinguish epileptic from healthy brain tissue.<h4>Methods</h4>We retrospectively se ...[more]

PMID: 31329277

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Project description:Objective: We examined the interrater reliability and generalizability of high-frequency oscillation (HFO) visual evaluations in the ripple (80-250 Hz) band, and established a framework for the transition of HFO analysis to routine clinical care. We were interested in the interrater reliability or epoch generalizability to describe how similar the evaluations were between reviewers, and in the reviewer generalizability to represent the consistency of the internal threshold each individual reviewer. Methods: We studied 41 adult epilepsy patients (mean age: 35.6 years) who underwent intracranial electroencephalography. A morphology detector was designed and used to detect candidate HFO events, lower-threshold events, and distractor events. These events were subsequently presented to six expert reviewers, who visually evaluated events for the presence of HFOs. Generalizability theory was used to characterize the epoch generalizability (interrater reliability) and reviewer generalizability (internal threshold consistency) of visual evaluations, as well as to project the numbers of epochs, reviewers, and datasets required to achieve strong generalizability (threshold of 0.8). Results: The reviewer generalizability was almost perfect (0.983), indicating there were sufficient evaluations to determine the internal threshold of each reviewer. However, the interrater reliability for 6 reviewers (0.588) and pairwise interrater reliability (0.322) were both poor, indicating that the agreement of 6 reviewers is insufficient to reliably establish the presence or absence of individual HFOs. Strong interrater reliability (≥0.8) was projected as requiring a minimum of 17 reviewers, while strong reviewer generalizability could be achieved with <30 epoch evaluations per reviewer. Significance: This study reaffirms the poor reliability of using small numbers of reviewers to identify HFOs, and projects the number of reviewers required to overcome this limitation. It also provides a set of tools which may be used for training reviewers, tracking changes to interrater reliability, and for constructing a benchmark set of epochs that can serve as a generalizable gold standard, against which other HFO detection algorithms may be compared. This study represents an important step toward the reconciliation of important but discordant findings from HFO studies undertaken with different sets of HFOs, and ultimately toward transitioning HFO analysis into a meaningful part of the clinical epilepsy workup.

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Dataset Information

Increased gamma and decreased fast ripple connections of epileptic tissue: A high-frequency directed network approach.

Objective

Methods

Results

Significance

Publications

Increased gamma and decreased fast ripple connections of epileptic tissue: A high-frequency directed network approach.

Similar Datasets

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