1-A-D-6. High-rate REM sleep high frequency oscillations (HFOs) are specific to epileptogenicity

It is difficult to distinguish epileptic high-frequency oscillations (HFOs) from physiological ones. We hypothesized that sleep stages affect the occurrence of epileptic and physiological HFOs differently and that rapid eye movement (REM) sleep HFOs are more specific to epileptogenicity. Thirteen patients with drug-resistant epilepsy underwent extraoperative intracranial EEG monitoring. Interictal HFOs were detected semi-automatically on EEGs taken during different sleep stages. The z-score of the HFO occurrence rate was calculated from the baseline rate obtained from non-epileptogenic areas. Electrodes showing HFOs at a higher z-score during REM than non-REM sleep were labeled “REM-dominant HFO” electrodes. The correlation between areas of surgical resection and REM-dominant HFO electrodes was associated with postoperative seizure freedom. The rate of HFO occurrence was significantly lower during REM sleep than during non-REM sleep. Of 1071 electrodes, 107 were defined as REM-dominant HFO electrodes. Inclusion of these electrodes in surgical resection was associated with postoperative freedom from seizures. Sleep stage influenced the occurrence of HFOs. The rate of HFO occurrence was lower during REM sleep than during non-REM sleep. Cortical areas exhibiting a less suppressive effect of REM sleep on HFOs are a specific marker of the epileptogenic zone.