Abstracts

Rationale: Humans have individual differences in the timing of their daily activities falling between two ends of a spectrum: morning types and evening types. We recently reported that patients with idiopathic generalized epilepsy (IGE) with onset in adolescence have a strong tendency towards an evening chronotype when compared to patients with localization-related epilepsy (LRE). It is not clear if all IGE syndromes share this tendency or if it is limited to certain specific syndromes. We now demonstrate that this tendency is seen in IGE syndromes characterized by the occurrence of seizures on awakening, but not in those characterized by a random circadian distribution of seizures. Methods: We administered the English version of the Horne-Östberg self-assessment questionnaire to 52 patients with IGE with onset in adolescence and to a control group of 20 patients with localization-related epilepsy (LRE). IGE syndromes were divided in two groups based on the circadian distribution of the seizures. The IGE-Awakening group included IGE syndromes with seizures on awakening: JME, juvenile absence epilepsy (JAE) and IGE with GTC on awakening. The IGE-Random group included IGE syndromes with a random circadian distribution of seizures: IGE with GTC only, and photosensitive epilepsy (PE). Test scores were compared between the two groups and to the controls using t-test. Results: The IGE-Awakening group (n=37) included the following: JME 22 (59.5%), JAE 10 (27%), IGE-GTC on Awakening 5 (13.5%). The mean age of this group was 24.4 (r: 14-54) years. The IGE-Random group (n=15) included: IGE-GTC 8 (53.4%), PE 5 (33.3%), other 2 (13.3%). The mean age of this group was 23.1 (r: 13-50) years. The control group (n=20) had a mean age of 30.2 (r: 15-47) years. There was a significant difference between the two IGE groups: mean test score was 39.16 (r:21-62) for the IGE- Awakening group, and 48.6 (r: 33-64) for the IGE -Random group (p=0.0021). Mean score of LRE group was 54.6 (r: 32-73). The difference between the IGE-Awakening group and the controls was highly significant (p<0.00001). The difference between the IGE-Random group and the controls was not significant. Conclusions: This study demonstrates that the evening chronotype strongly predominates in patients IGE syndromes of adolescence with seizures on awakening. IGE syndromes with a random circadian distribution of seizures do not show this tendency. Results suggest that the pathophysiological mechanisms that determine the circadian chronotypes and the IGE syndromes with seizures on awakening may be related.