Abstracts

Establishing Feasibility for Measuring Multi-Unit Activity Within Ictal Period of Seizures with Preserved vs Impaired Consciousness

Abstract number : 2.035
Submission category : 3. Neurophysiology / 3C. Other Clinical EEG
Year : 2023
Submission ID : 826
Source : www.aesnet.org
Presentation date : 12/3/2023 12:00:00 AM
Published date :

Authors :
Presenting Author: Urszula Gorska-Klimowska, PhD. – UW Madison

Beril Mat, MD. – UW-Madison; Colin Denis, MS. – UW Madison; Brinda Sevak, MS. – UW Madison; Dillon Scott, BS. – UW Madison; Csaba Kozma, MS. – New Castle University, UK; Mariel Kalkach Aparicio, MD., MBE. – UW Madison; Maximilian Grobbelaar, BS. – UW Madison; Aaron Suminski, PhD. – UW Madison; Aaron Struck, MD. – UW Madison; Giulio Tononi, MD., PhD. – UW Madison; Melanie Boly, MD., PhD. – UW Madison; Wendell Lake, MD. – UW Madison

Rationale:
Loss of consciousness is a hallmark of many epileptic seizures. We recently showed that generalization during focal to bilateral tonic-clonic (FBTC) seizures was accompanied by increased cortical high-gamma power, and in two patients with Utah arrays, by an increase in cortical firing outside the seizure onset zone (SOZ). Here we examine the feasibility of using Behnke-Fried recordings to investigate multi-unit activity (MUA) changes not only during FBTC, but also during focal impaired awareness (FIA) and focal aware (FA) seizures.  

Methods:
We analyzed Behnke-Fried recordings from 22 seizures in six epileptic patients, implanted at the University of Wisconsin-Madison. Video assessments quantified behavioral responsiveness, amnesia, and tonic-clonic activities. Four patients had electrodes in the SOZ (1 FBTC and 4 FIA). MUA was extracted by filtering signal from 300-3000 Hz; waveforms crossing 4.5 standard deviations from the mean were extracted from 10 minutes pre-ictally to seizure end. Spikes were sorted by combining visual inspection with k-means clustering using UltraMegaSort2000. Clusters corresponding to line-noise artifacts were excluded from the analysis. We quantified overall firing rate for the remaining MUA (data from 10 electrodes during six FBTC, 15 electrodes during eight FIA, and 13 electrodes during eight FA seizures), averaging it across all contacts for each micro-electrode then across the first/second halves of the seizures (or across pre/post-generalization for FBTC); all data were baseline-normalized. Differences across time periods were quantified using Wilcoxon signed-rank test, with statistics corrected for multiple comparisons using a false discovery rate (FDR).

Results:
During FBTC seizures, areas remote from SOZ displayed a 1.8-fold increase in firing rate at seizure onset then a further increase to 4.6-fold after generalization (both p< 0.05)
Neurophysiology