A Quantitatively Measure of Complexity for Interictal Epileptic Spikes Focus
Abstract number :
3.022
Submission category :
1. Basic Mechanisms / 1C. Electrophysiology/High frequency oscillations
Year :
2022
Submission ID :
2204999
Source :
www.aesnet.org
Presentation date :
12/5/2022 12:00:00 PM
Published date :
Nov 22, 2022, 05:27 AM
Authors :
Rosario Ciliento, MD – University of Wisconsin; simone russo, MD – University of Milan; Zhixin Wang, Mrs – University College London; Andrea Pigorini, PhD – University of Milan; Cynthia Papantonatos, Research Specialist – University of Wisconsin; Graham Findlay, PhD student – University of Wisconsin; elsa juan, researcher – University of Amsterdam; Benjamin Jones, Researcher – University of Wisconsin; Brinda Sevak, Research Specialist – University of Wisconsin; Dillon Scott, Research Specialist – University of Wisconsin; Armand Mensen, PostDoc – Netherlands Institute for Neuroscience; ruben verhagen, Researcher – Vrije Universiteit Amsterdam; Rama Maganti, Neurologist – University of Wisconsin; Brady Riedner, senior Scientist – University of Wisconsin; aaron Struck, Neurologist – University of Wisconsin; Marcello Massimini, Professor – University of Milan; Giulio Tononi, Professor – University of Wisconsin; Melanie Boly, Neurologist – University of Wisconsin
Rationale: At the neuronal level, interictal spikes (IS) manifest as sudden and large (20-40 mV) membrane potential positive shifts, accompanied by bursts of action potentials, followed by long-lasting (400-600 msec) 5-10 mv hyperpolarization periods, accompanied by a local suppression of high frequencies. Here we hypothesized that at the scalp level, a Perturbational Complexity Index (PCI) measuring the complexity of the spike-wave response could accurately capture the local disruption of neuronal activity by interictal spikes and could constitute a new reliable objective marker of spike lateralization which could have clinical utility_x000D_
Methods: A total of 18 patients with focal epilepsy underwent overnight high-density EEG recordings (HDEEG, 256 electrodes) in the Epilepsy Monitoring Unit of the University of Wisconsin, Madison. After sleep scoring using standard AASM criteria, HD-EEG data were down-sampled to 200 Hz, and filtered between 0, 5, and 40 Hz. Artifact rejection was performed using custom Matlab scripts to reject bad channels and bad epochs, and epochs containing only N2-N3 stages were selected. IS were manually marked and verified by a certified epileptologist (MB). The IS overnight range is 24 to 1473 per focus. After selecting the time point with maximum amplitude peak of the IS, 2 s of data around the event were selected and averaged. We identified the channels with maximum amplitude in each patient and for each spike type and we selected 7 channels in the IS foci, 7 in the homologous contralateral zone and 7 channels in the midline. In 3 subjects with bilateral epilepsy, we used both foci (resulting in 21 foci in total). Finally, we computed PCI based on state transitions (PCIst) on the 3 regions of interests, and computed the average PCISt across the 7 channels. Wilcoxon signed-rank test (focal vs contralateral, focal vs. midline, midline vs. contralateral), 1-way ANOVA and Kruskal Wallis tests (focal vs. midline vs. contralateral) were used to estimate the statistical significance of the differences. Individual results for lateralization were computed_x000D_
Results: At the group level, the IS focus shows reduced PCIst values (mean = 4.9 ± 1.2) compared to the midline (mean = 7.2 ± 3.3) and homologous contralateral regions (mean = 6.9 ± 3.7). The differences between IS focus and control regions are statistically significant: focal vs contralateral p=0.019, focal vs. midline p=0.046; no difference between midline and contralateral p=0.64; 1-way ANOVA p=0.019; Kruskal Wallis test p=0.016. At the individual level, 16/21 IS foci had lower PCIst value compared to midline, and 15/21 compared to the analogous contralateral region; 10/21 midline regions also had lower PCIst value compared to contralateral side_x000D_
Conclusions: PCIst quantitatively measures the reduced complexity in the IS focus compared to contralateral and midline regions and seems to be a promising objective marker for the lateralization of IS in patients with focal epilepsy. Future steps will involve the measurement of complexity in different behavioral states (Wake and REM sleep) and the quantitative assessment of the high frequency (20-40 Hz) suppression during the downstate._x000D_
Funding: Tiny Blue Dot Foundation, NIH K23NS112473 (Dr. Boly)
Basic Mechanisms