Relationship of temporal lobe seizures to sleep and arousal: A combined scalp-intracranial electrode study

Study Objectives: The role of arousal from sleep in promoting epileptic seizures is controversial. To examine the question of whether seizures precede or follow arousals from sleep, we defined the timing of temporal lobe seizures in relation to sleep and arousal using combined scalp-intracranial electrodes. Design: Retrospective review of 67 sleep-related mesial temporal lobe seizures in 14 subjects. Setting: Inpatient epilepsy monitoring laboratory. Patients: Subjects with medically refractory mesial temporal lobe seizures undergoing epilepsy surgery evaluations. Interventions: None. Measurements and Results: Electroencephalographic (EEG) and/or polygraphic recordings and videotapes were independently reviewed to determine intracranial electrode seizure onset times and time of initial arousal from sleep. In 60 seizures in 13 subjects, intracranial ictal onsets always preceded clinical arousals from sleep. Electrographic signs of arousal in the scalp EEG, defined by the presence of sustained alpha or theta activity, either coincided with or followed, but never preceded, intracranial ictal onsets. In seven seizures in one subject with known seizures upon awakening, intracranial ictal onsets always followed clinical arousals and electrographic signs of arousal from sleep. Seven of the 14 subjects had electrooculogram and chin electromyogram monitoring; in these subjects, no seizures occurred during REM sleep with the majority occurring during NREM stage 2 sleep. Conclusions: Most sleep-related temporal lobe seizures occurred during NREM sleep and preceded arousals, supporting the premise that processes involved in the initiation and maintenance of NREM sleep play a greater role in facilitating temporal seizures than those involved in promoting REM sleep and arousal. However, arousal from sleep may provoke seizures in exceptional cases.