Statistical mapping of ictal high-frequency oscillations in epileptic spasms

Abstract

SUMMARYPurpose: We assessed 636 epileptic spasms seen in 11 children (median 44 spasms per child) and determined the spatial and temporal characteristics of ictal highfrequency oscillations (HFOs) in relation to the onset of spasms. Methods: Electrocorticography (ECoG) signals were sampled from 104-148 cortical sites per child, and the dynamic changes of ictal HFOs were animated on each individual's three-dimensional (3D) magnetic resonance (MR) image surface.

Electrophysiological Biomarkers of Epilepsy

“…Changes in HFO power were chiefly detected in the primary SOZ and rarely in sites of secondarily generalization of patients with focal epilepsy [90]. Similar changes in HFOs have been observed during epileptic spasms that, in some cases, occurred before the clinical onset, and were observed spreading across cortex and encompassing large cortical territories [91][92][93][94][95]. None of the aforementioned patient studies examined different types of HFO in relation to ictal EEG onset pattern, which is an area of research that could yield electrophysiological biomarkers [2].…”

“…One study using single pulse electrical stimulation found, in 2 patients, that complete or near complete removal of tissue that contained evoked fast ripple-frequency HFOs was associated with a seizure-free outcome, whereas in 7 patients who had removal of <50 % of sites that contained evoked fast ripplefrequency HFOs, only 2 were seizure-free, while the remaining 5 patients continued to have seizures [122]. Additionally, studies of ictal or peri-ictal HFOs found, in most cases, a larger proportion of patients who had ictal HFOs had better postsurgical outcome than patients who did not have ictal HFOs [91,95,123,124], but some did not find an association between fast ripple-frequency HFOs and outcome [125]. With respect to ictal HFO studies, if the area of seizure onset was completely removed in all patients, then the surgery outcome results suggest that in those patients who continued to have seizures, recording sites without ictal HFO could be distant from where seizures actually began.…”

Multivariate regression methods for estimating velocity of ictal discharges from human microelectrode recordings

“…High gamma band signal has been established as a useful index of population firing [27, 34–37]. However, because of its fast oscillations, it is difficult to specify a consistent single time point for each discharge.…”

Hochfrequenzoszillationen (80–500 Hz)

“…Dies erlaubt eine Mittelung über die iktalen HFO und so eine präzisere sowie automatisierte Auswertung. Es konnte zum einen gezeigt werden, dass zu Beginn der Anfälle eine fokale Erhöhung der Hochfrequenzaktivität im Anfallsursprung v. a. im Bereich zwischen 80 und 200 Hz auftrat [31,34]. Gleichzeitig konnte direkt vor dem Auftreten der iktalen motorischen Symptome eine Erhöhung der HFO-Zahl zwischen 200 und 300 Hz über den Motorarealen festgestellt werden, deren Ausmaß mit dem der motorischen Symptome korrelierte.…”

“…Gleichzeitig konnte direkt vor dem Auftreten der iktalen motorischen Symptome eine Erhöhung der HFO-Zahl zwischen 200 und 300 Hz über den Motorarealen festgestellt werden, deren Ausmaß mit dem der motorischen Symptome korrelierte. Diese direkte Korrelation lässt vermuten, dass die Entstehung von infantilen Spasmen tatsächlich im Neokortex und nicht, wie manchmal vorgeschlagen, in den subkortikalen Arealen stattfindet [2,31,34]. Zusätzlich konnte auch für die Entfernung von iktalen HFO eine Korrelation mit der postoperativen Anfallsfreiheit festgestellt werden [31].…”