Diurnal and sleep/wake patterns of epileptic spasms in different age groups

Epileptic spasms are seizures that occur predominantly in children and are characterized by clusters of brief axial movements. Epileptic spasms may occur in the context of a variety of syndromes. Previous research has found that epileptic spasms occur in a sleep/wake and diurnal rhythm. The purpose of this study was to identify these patterns in different age groups.

Charts of 2,021 patients with epilepsy undergoing video-electroencephalography (EEG) monitoring over a 10-year period were reviewed for presence of epileptic spasms and analyzed for their occurrence during the day (6 a.m. to 6 p.m.) or night, out of wake or sleep, and in 3-h time-blocks throughout the day. Exact epileptic spasm time, EEG localization, and the presence or absence of magnetic resonance imaging lesion were also recorded. Patients were separated into two age groups: A ages 3 and under, and over age 3. Statistical analysis of seizure occurrence in time bins was carried out using binomial calculations. p-Values <0.05 were taken as significant. Using exact seizure times, a generalized linear mixed model of the Poisson-family with a square root link function was used to calculate mean seizure times. Age, as a binary variable, and time, as a categorical variable, was treated as fixed effect predictors, and individual effects were modeled as random effects. For comparison between the two age groups, over age 3 and under age 3, seizure times were transformed into circular variables. A circular analysis of variance test was used to assess for the difference in mean seizure time, assuming a von Mises distribution of the circle.

We analyzed 219 clusters of epileptic spasms in 51 patients (15 girls; mean age 2.15 ± 2.22 years). Forty-two patients younger than 3 years of age had 163 seizures and nine patients older than 3 years had 56 seizures. Epileptic spasms occurred predominantly during wakefulness (p < 0.001) and during daytime (p < 0.001). Epileptic spasms occurred most frequently between 9 a.m. and noon (p < 0.05) and between 3 p.m. and 6 p.m. (p < 0.001). Patients without magnetic resonance imaging lesions had most seizures between 9 a.m. and noon (p < 0.01) and 3 p.m. and 6 p.m. (p < 0.001). Thirty-seven patients had 157 epileptic spasms (71.2%) with generalized EEG patterns and 14 patients had 62 epileptic spasms (28.8%) with focal EEG patterns. Generalized EEG seizures occurred more frequently than focal EEG seizures (p < 0.001). Following age stratification, patients younger than 3 years had most epileptic spasms between 9 a.m. and noon (p < 0.05) and 3 p.m. and -6 p.m. (p < 0.01) and patients older than 3 years had most epileptic spasms between 6 a.m. and -9 a.m. (p < 0.05) and a second peak between 3 p.m. and 6 p.m., although the difference was not statistically significant due to insufficient numbers. Using continuous time analysis, the mean seizure time in the under age 3 and the over age 3 groups was 2:24 p.m. and 11:40 a.m. Using a circular analysis of variance test, the difference between mean seizure times in these groups was found to be statistically significant (p = 0.038).

Epileptic spasms occur more frequently in the waking state and daytime. Younger patients have epileptic spasms mostly between 9 a.m. and noon and 3 p.m. and -6 p.m., and older patients have epileptic spasms mostly between 6 a.m. and 9 a.m. These findings emphasize age-related changes in epileptic spasm pathophysiology or potentially evolution of disease with age.