Circadian and ultradian patterns of epileptiform discharges differ by seizure‐onset location during long‐term ambulatory intracranial monitoring. (11th July 2016)

• Record Type: Journal Article
• Authors: Spencer, David C.; Sun, Felice T.; Brown, Sarah N.; Jobst, Barbara C.; Fountain, Nathan B.; Wong, Victoria S. S.; Mirro, Emily A.; Quigg, Mark
• Is Part Of: Epilepsia. Volume 57:issue 9(2016)
• Page Start: 1495
• Page End: 1502
• Publication Date: 2016-07-11
• Subjects: Circadian rhythms -- Responsive neurostimulation -- Epileptiform -- Epilepsy; Epilepsy -- Periodicals; 616.853
• DOI: 10.1111/epi.13455
• Languages: English
• ISSNs: 0013-9580

Abstract

Summary: Objective: Previous studies reporting circadian patterns of epileptiform activity and seizures are limited by (1) short‐term recording in an epilepsy monitoring unit (EMU) with altered antiepileptic drugs (AEDs) and sleep, or (2) subjective seizure diary reports. We studied circadian patterns using long‐term ambulatory intracranial recordings captured by the NeuroPace RNS System. Methods: Retrospective study of RNS System trial participants with stable detection parameters over a continuous 84‐day period. We analyzed all detections and long device–detected epileptiform events (long episodes) and defined a subset of subjects in whom long episodes represented electrographic seizures (LE‐SZ). Spectrum resampling determined the dominant frequency periodicity and cosinor analysis identified significant circadian peaks in detected activity. Chi‐square analysis was used to compare subjects grouped by region of seizure onset. Results: In the 134 subjects, detections showed a strongly circadian and uniform pattern irrespective of region of onset that peaked during normal sleep hours. In contrast, long episodes and LE‐SZ patterns varied by region. Neocortical regions had a monophasic, nocturnally dominant rhythm, whereas limbic regions showed a more complex pattern and diurnal peak. Rhythms in some individual limbic subjects were best fit by a dual oscillator (circadian + ultradian) model. Significance: Epileptiform activity has a strong 24 h periodicity with peak nocturnal occurrence. Limbic and neocortical epilepsy show divergent circadian influences. These findings confirm that circadian patterns of epileptiform activity vary by seizure‐onset zone, with implications for treatment and safety, including SUDEP.