Lateralizing Value of Interictal Spikes on Overnight Sleep‐EEG Studies in Temporal Lobe Epilepsy

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Abstract
Summary: Purpose: To determine the lateralizing value of interictal epileptiform discharges (IEDs) recorded during overnight sleep‐EEG studies in temporal lobe epilepsy. Because IEDs are more prevalent in non‐rapid eye movement (NREM) sleep than in wakefulness, overnight sleep‐EEG recordings may contribute additional lateralizing information to the epilepsy surgery evaluation beyond daytime EEGs. Methods: Twenty‐four subjects with medically refractory temporal lobe epilepsy underwent continuous overnight sleep‐EEG recordings. Subjects were seizure free ≤24 h before study and receiving stable doses of medication. The IED foci recorded on overnight studies were compared with daytime EEGs, interictal samples, and ictal recordings during long‐term monitoring, brain magnetic resonance images (MRIs), and surgical outcome. Results: (a) In all 24 subjects, including 13 without IEDs on daytime EEGs, temporal IEDs were present during NREM sleep and were exclusively or predominantly (Conclusions: When combined with other investigations, IEDs recorded on overnight studies add prognostic data to the epilepsy surgery evaluation not provided by daytime EEGs.