Clinical Neurophysiology/Epilepsy Fellow University of Virginia, Virginia
This abstract is recognized by Partners Against Mortality in Epilepsy for its contribution to improving the understanding of epilepsy-related mortality
Rationale: Sleep and epilepsy have bilateral interactions ranging from differentiating among seizure types, seizure exacerbation with sleep disturbances, and hypothesis regarding the role of sleep in seizure-related morbidity and mortality [1-2]. The goal of this study is to test the hypothesis that time of day accurately predicts preictal sleep-wake state in the epilepsy monitoring unit (EMU). Methods: We prospectively enrolled a consecutive series of patients undergoing inpatient epilepsy monitoring to measure preictal sleep-wake states. For each epileptic seizure recorded, continuous EEG data preceding seizure onset were reviewed and scored as W, N1-3, or REM in ten 30-second epochs. Sleep-wake states for preictal epochs were compared to nocturnal (0000-0559) versus diurnal (0600-1159) time of day. Results: A total of 190 seizures from 95 patients were accrued. Out of these, 102 seizures from 42 patients (mean = 2.4 seizures/patient, max = 13 seizures/patient, min 1 seizure/patient) met enrollment criteria. Fifty-seven percent were men. Age was mean ± standard deviation of 41±15 years. Eighty-five (85%) seizures occurred during the diurnal period, and 17 (17%) occurred during nocturnal period. Thirty-six percent of all seizures (n = 37) were preceded by at least one epoch (30 seconds) of sleep (Figure A). The proportion of patients asleep before seizures varied significantly from the overall distribution only during nocturnal period. Seventy-six percent of nocturnal seizures and 28% of diurnal seizures were preceded by sleep (Figure B). Therefore, the nocturnal time window from 0000-0559 had a sensitivity for sleep-onset seizures of 0.65 (95% confidence interval 0.48-0.78), a specificity of 0.06 (0.02 – 0.15), a positive predictive value of 0.28 (0.20 – 0.39), and a negative predictive value of 0.24 (0.10 - 0.39). Conclusions: In summary, time of day is an inaccurate surrogate for preictal sleep-wake state in the EMU despite a correlation between nocturnal period and sleep. These findings suggest that the inpatient environment may not promote appropriate sleep hygiene, and that accuracy of epidemiological studies that use time of day of seizure as an implicit or surrogate marker for state is limited.
References 1. Bazil CW. Sleep and Epilepsy. Semin Neurol. 2017;37(4):407-412. doi:10.1055/s-0037-1604352 2. Quigg M. Circadian rhythms: interactions with seizures and epilepsy. Epilepsy Res. 2000;42(1):43-55. doi:10.1016/s0920-1211(00)00157-1 Funding: Please list any funding that was received in support of this abstract.: none
