Abstracts

This is a Late Breaking abstract

Rationale: Ictal semiology provides a window into the regions of the brain affected by seizure activity in real-time. Distinct features of semiology, such as automatisms and head turns, can be recreated in theory using neurostimulation. Yet, few studies have quantified neural activity to confirm which regions are significantly activated when distinct behaviors are observed during actual seizures. Seizures recorded during intracranial EEG (ICEEG) monitoring can be visualized on reconstructed brains to provide clinically accurate localizations of seizure onset and spread using a recently published open-source data visualization approach called OPSCEA (omni-planar and surface casting of epileptiform activity). Here, we expand on OPSCEA by applying the timing of semiology features to localize “symptom-onset-zones” to confirm hypothetical neural underpinnings of semiology behaviors in a quantitative manner.

Methods: Using ICEEG recordings of patients with medically-refractory seizures who underwent intracranial implantation of grid, strip and depth electrodes (range, 96-156 electrodes per patient), we selected seven patients that had highly similar electrographic seizures (mesial temporal onset, spread to lateral temporal lobe, followed by rolandic cortex, and finally progression to bilateral tonic-clonic) based on OPSCEA visualization review. Blinded to the ICEEG data, we reviewed clinical-monitoring video recordings of those same seizures and comprehensively annotated head, face, neck, and limb behaviors throughout the peri-ictal period at 5 Hz time resolution. As an initial application we looked at the change of neural activity in the precentral gyrus (primary motor cortex) 15 seconds before and after the onset of each patient’s versive head turn.

Results: The OPSCEA visualization platform was successfully outfitted with timecourse plots of (1) peri-ictal linelength transform across all channels, and (2) a semiology index across all observable body regions (Figure 1). These composite videos enabled simultaneous viewing of dynamic seizure activity projected as a heatmap onto the patient’s reconstructed 3-D brain, electrode coordinates, and the timecourse of this activity across all channels along with semiology features (Figure 2). We found significantly increased ictal activity among electrodes within the precentral gyrus in the majority of patients (p < 0.05, Bonferroni-corrected; 4 of the 7 patients).