Abstracts

Rationale: Memory deficit is one of the leading concerns of people with epilepsy. Previous work has shown that interictal epileptiform activity can cause acute impairment of memory (Horak et al., Epilepsia 2017). However, the relationship between epileptic discharges and chronic cognitive dysfunction in epilepsy is not fully understood. Methods: We conducted a free recall task in seven subjects with the NeuroPace RNS System. We correlated session-level task performance with the number of detections by the subjects’ RNS neurostimulators during the hours and days preceding the task sessions. RNS detection counts were normalized to the subject’s mean therapy rate. Results: We found that subjects that experienced an elevated rate of epileptic discharges (as indicated by RNS detection counts) in the four hours before starting the free recall task had worse performance on the task (n=14, r=-0.77, p=0.001). We found that this relationship becomes stronger when examining epochs of epileptic discharges that are temporally closer to the start of the cognitive task, and weaker when using broader epochs. Conclusions: Our results indicate that epileptic discharges are associated with poor memory performance over a long time course. However, it is unclear whether the epileptic discharges themselves are the cause of poor memory performance or a symptom of another pathological process. Subjects receive electrical stimulation when the RNS System detects epileptic discharges, which may also influence cognitive performance. These results indicate that study into the relationship between epileptic discharges and cognition is necessary to understand the pathological processes behind cognitive impairment in epilepsy. Funding: NSF EPSCoR 1632738Diamond Foundation Research Development Award