Computational protocol: Relationship between high-frequency oscillations and spikes in a case of temporal lobe epilepsy

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Protocol publication

[…] Our patient underwent intracranial video-EEG for 71 h. The electrodes were three bilateral temporal epicortical electrodes, six left frontal epicortical electrodes, and an intracranial depth electrode with five electrical contacts in the left temporal lobe. The most medial depth electrode contact (denoted LH1) was in the anterior left hippocampus and the most lateral in the lateral temporal cortex. An epicortical reference electrode was placed near the right vertex. A Natus XLTEK system (Oakville, Ontario, Canada) was used. The A/D conversion rate was 512 Hz. For standard EEG, a low-pass filter of 70 Hz and a high-pass filter of 1 Hz was used (XLTEK filter type not specified). Examples (A) were converted to European Data Format, filtered (8-pole Bessel filters) using EDFbrowser (www.teuniz.net/edfbrowser/) and plotted using SigmaPlot 11 (Systat Software, Inc., San Jose, CA).There were frequent interictal epileptiform discharges localized exclusively to LH1. Electrode LH1 also showed frequent ripples. Fast ripples were not investigated. Ripples and interictal spikes were visually counted by a single observer (VS) on a reduced data set consisting of 5 min per hour of EEG. Electrode LH1 was selected for visual analysis of both interictal spikes and ripple frequency oscillations, which were displayed in the same montage on the same screen. For ripples, the time scale was set to maximum resolution, amplification was set to 2 μV/mm, low-pass filter was set at 250 Hz, and high-pass filter was set at 70 Hz. Interictal spikes were analyzed with an amplification of 30 μV/mm, low-pass filter at 70 Hz, and high-pass filter at 1 Hz. The operational definition of “ripple” for the purpose of this analysis included any oscillation that clearly stood out of the background, with at least six phases in the oscillation and a peak-to-peak amplitude of more than 25 μV (A).The patient was given 1500 mg of levetiracetam twice a day and 150 mg of lacosamide twice a day on admission. Her medications were discontinued on day one of recording. Three seizures occurred on day 3 of recording, each one with onset clearly localized to LH1. This provided an opportunity to compare the time course of ripple and spike occurrences in the SOZ. […]

Pipeline specifications

Software tools EDFbrowser, SigmaPlot
Applications Miscellaneous, Clinical electrophysiology
Organisms Homo sapiens
Diseases Epilepsy, Temporal Lobe