Seizure clustering: risks and outcomes

Patients with epilepsy often experience seizures in clusters. In this preliminary study, we examined the prevalence of self-reported clustering and identified potential risk factors and outcomes associated with reported clustering for further analysis in an ongoing prospective diary study.

Detailed intake questionnaires were administered. Subjects reporting their typical seizure pattern to be three or more seizures within a 24-h period were classified as clusterers. Magnetic resonance imaging (MRI) and EEG data were obtained, and epilepsy was classified by International League Against Epilepsy (ILAE) criteria. All subjects completed Beck Anxiety and Depression Inventories, and Quality of Life in Epilepsy testing.

Overall, 29% of subjects reported typical seizure clustering. Extratemporal lobe epilepsy [p = 0.02; OR, 3.0 (1.1-7.8)] was significantly associated with reported seizure clustering. Remote symptomatic epilepsy was associated with clustering [p = 0.03; OR, 2.3 (1.1-4.3)], particularly in association with a history of head trauma with loss of consciousness before epilepsy onset [p = 0.003; OR, 4.2 (1.6-11.1)], although this analysis was limited. Reported clustering was significantly associated with a history of convulsive status epilepticus (SE) [p = 0.029; OR, 3.0 (1.1-8.3)], other seizure-related hospitalization [p = 0.006; OR, 5.3 (1.5-17.6)], and worse seizure control (p = 0.004). Quality-of-life measures were not significantly associated with reported clustering.

These preliminary results identify extratemporal epilepsy and possibly head trauma as potential risk factors for reported seizure clustering and indicate a significant association between reported clustering and convulsive SE. Additionally, seizure clustering appears to be a marker for more intractable epilepsy. The ongoing diary study will refine the definition of seizure clustering and further evaluate specific predictors of poor and favorable outcomes of clustering.