Abstracts

Rationale: Sudden unexpected death in epilepsy (SUDEP) is the most common cause of death in epilepsy patients. SUDEP involves a cascade of symptoms including apnea, cardiac arrythmia and asystole, with peri-ictal apnea always occurring first. Converging evidence suggests that the amygdala may be involved in SUDEP (Dlouhy et al., 2015; Lacuey et al., 2017), as both electrical stimulation of (Nobis et al., 2018) and seizure spread to (Nobis et al., 2020) the amygdala lead to cessation of breathing in epilepsy patients. Mortality after a seizure often occurs during sleep, which warrants further investigation of the relationship between epileptic activity in the amygdala and breathing during sleep.

Methods: Here, we analyzed interictal epileptiform activity in relation to ongoing respiratory activity during sleep in 5 patients undergoing intracranial monitoring for medically intractable epilepsy. Scalp EEG recordings were used to score sleep stages following traditional methods, and one hour of N2 sleep segments for each patient was obtained. Intracranial electrode recordings from the amygdala, piriform cortex, and hippocampus were analyzed for each patient. Interictal epileptiform activity was detected using a semi-automated approach. Specifically, when amplitude at 25–50 Hz increased to 3.5 standard deviations relative to background activity for each channel, timepoints of interictal epileptiform activity that exceeded this amplitude threshold and included less than 3 cycles were collected for further analysis following manual validation of each event.

Results: Preliminary findings indicate that interictal epileptiform activity in the amygdala tends to occur at a preferred phase of breathing for all patients, with most occurring near the end of exhalation and the start of inhalation (p < 0.05, Rayleigh’s test). Respiratory coupling of interictal spiking was also found in piriform cortex and hippocampus.