A Quantitative Measure of Complexity in Interictal Epileptiform Discharges Across Spatial Topography
Abstract number :
3.115
Submission category :
2. Translational Research / 2C. Biomarkers
Year :
2022
Submission ID :
2204938
Source :
www.aesnet.org
Presentation date :
12/5/2022 12:00:00 PM
Published date :
Nov 22, 2022, 05:27 AM
Authors :
Dillon Scott, BS – University of Wisconsin Madison; Brinda Sevak, MS – University of Wisconsin Madison; Colin Denis, MS – University of Wisconsin Madison; Lisa Bateman, MD, PhD – University of Columbia; Giulio Tononi, MD, PhD – University of Wisconsin Madison; aaron Struck, MD, PhD – University of Wisconsin Madison; Vaclav Kremen, PhD – University of Wisconsin Madison; Catherine Schevon, MD, PhD – University of Columbia; Sameer Sheth, MD, PhD – Baylor University; Melanie Boly, MD, PhD – University of Wisconsin Madison
Rationale: The complexity of cortical activations evoked during transcranial magnetic stimulation and single-pulse electrical stimulation is typically quantified with the perturbational complexity index (PCI). The same principles employed by PCI can be used to examine the complexity of interictal spike waves, a hallmark feature of focal epilepsy, in intracranial electroencephalography (IEEG) data across patterns of sleep and wakefulness as well as in the seizure focus and the healthy brain. The analysis of intracranial data also provides a unique opportunity to examine the complexity of spike waves without contamination by muscle artifacts.
Methods: One night of seizure-free sleep was selected for 6 patients implanted with intracranial electrodes. Three patients were implanted with depth electrodes and three patients were implanted with a combination of strip and grid subdural electrodes. Nights were manually sleep scored by identifying non-rapid eye movement sleep with increases in the delta/beta ratio as well as the presence of slow waves and spindles. Interictal spikes were manually marked and aligned at the peak amplitude for the first and last hours of sleep and wakefulness before running PCI calculations. PCI was calculated for one electrode each in the seizure focus, near the seizure focus, and in the healthy brain. We then assessed whether there was a consistent change in spike complexity during sleep and wake and in the seizure focus and healthy brain.
Results: When comparing the spike complexity during sleep versus wake, we found that 4/6 patients displayed a higher complexity during wake and 2/6 patients had complexity which did not change significantly between the two conditions. The seizure focus had consistently lower complexity in each of the four wake and sleep states examined. During the wake before sleep and the first hour of sleep, 4/6 patients had the lowest complexity in the seizure focus, while the same was true during the last hour of sleep and the wake after sleep for 5/6 and 3/6 patients respectively. When comparing spike complexity between the seizure focus and healthy brain areas, seizure focus areas displayed consistently lower complexity with 5/6 patients having reduced complexity in the seizure focus and seizure focus-adjacent areas. Visual analysis confirms that this lower complexity coincides with a suppression of low frequency activity in seizure focus areas immediately following interictal spikes.
Conclusions: We observed that complexity of interictal spikes is notably lower in the seizure focus with 5/6 patients showing a decline as well as suppressed low frequency activity. In addition, state-dependent changes in spike complexity were observed in 4/6 patients with complexity decreasing during sleep. The results of this analysis serve to provide a clearer picture of the spatiotemporal signaling properties of epileptic brain matter.
Funding: Tiny Blue Dot Foundation
Translational Research