Abstracts

Rationale: Arousal is one of the most primitive, powerful instincts critical for survival in all vertebrates. Arousal regulates consciousness, attention and information processing. The conventional teaching for arousal is that it is a brainstem driven phenomenon with information flow ascending rostrally to cortical structures. This classical view has been challenged with emerging evidence suggesting “descending” cortical feedback systems are equally important to maintain consciousness and structures like basal orbitofrontal can sustain arousal without brainstem in preclinical models. Seizures are susceptible to altered states of vigilance and can be present immediately after awakening. Conversely, arousal lasting for few seconds as the only clinical manifestation following the onset of a seizure is uncommon, and this phenomenon is termed as a "hypnopompic seizure”. Previous studies with scalp EEG or grid investigation have localized these seizures in mesial temporal lobe epilepsy. However, an ictal SPECT study has localized seizures manifesting as arousal in the anterior cingulate gyrus. We, therefore, explored the localization of hypnopompic seizures in our cohort who underwent stereo EEG investigation sampling temporal and frontal regions including anterior cingulum. Methods: A single-center retrospective study where all subjects undergoing stereo EEG investigation between 2014-2018 were included. Video EEG was reviewed to identify seizure induced arousal. Demographics, sleep stage before arousal, semiology, MRI, EEG, surgical outcome, and histopathology was reviewed. IRB approved the retrospective study. Results: Of 55 subjects who had undergone SEEG investigation, 14 (male=8) had hypnopompic seizures. All seizures arose from NREM sleep. Seizures were localized to amygdala-hippocampus (N=9), anterior cingulate (N=2), insula-perisylvian (N=3). The EKG was associated with increased heart rate suggesting autonomic arousal. Regardless of the origin of seizure, the spread pattern included anterior cingulate, orbitofrontal, amygdala hippocampus before arousal. Focal cortical dysplasia was the predominant histopathology among the subjects who underwent resection. Conclusions: Ictal arousal can be present in seizures localized to mesial temporal, orbitofrontal and anterior cingulate. Ictal arousal is associated with autonomic arousal. The network for ictal arousal includes mesial limbic structure, orbitofrontal and anterior cingulum. Funding: None