The importance of sleep deprivation as a mechanism for activating interictal epileptiform paroxysms

Although sleep deprivation has been used for years in electroencephalography (EEG) as a method for activating interictal epileptiform discharges (IED) in patients with a strong suspicion of epilepsy, its sensitivity and specificity are still under discussion. We conducted a descriptive retrospective study of paediatric patients who were referred to a neurophysiology clinic for epilepsy assessment. The results of the sleep-deprived EEG (SD-EEG) were compared with those of the wakefulness EEG (W-EEG) carried out in each patient in order to describe the performance of each method as a mechanism for activating IED. A total of 500 patients were analysed (830 SD-EEG and 1018 W-EEG). IED were detected in 44% of the W-EEG. SD-EEG increased the capacity of the test to detect IED by 35%. IED (not detected in the W-EEG) were detected in 25.1% of the SD-EEG in which spontaneous sleep was achieved. In the group of focal epilepsies, it was found that W-EEG detected IED in 60.1% versus the 79.12% displayed with SD-EEG. In generalised epilepsies this difference was more marked (27.2% and 77.2%, respectively). In patients in whom no IED were detected following an SD-EEG (23.7%) and the clinical suspicion of epilepsy was still high, nocturnal polysomnography was performed and interictal epileptiform activity was observed in 13.6%. SD-EEG increases the chances of recording IED by 35% with respect to W-EEG. Sleep deprivation is a method for activating epileptiform paroxysms, regardless of whether the EEG is performed while sleeping or not, although this effect is more pronounced in patients who do manage to sleep.