Abstracts

RATIONALE: Emergence from true sleep is a feature that has been considered to reliably distinguish epileptic seizures from non-epileptic seizures (NES). However, there is a scarcity of systematic studies examining NES to explicitly determine if such events occur in true sleep.
METHODS: All cases of NES verified by long term video-electroencephalographic (VEEG) monitoring at our center for the period 1998-2000 were collected for analysis. All seizure events in these patients were reviewed. Events were included if characterized by sudden time-limited observable alterations of behavior and movement that had no corresponding EEG correlate. Events were rejected if (1) semiologically consistent with recognized frontal lobe seizure types and (2) they behaviorally resembled parasomnias, movement disorders, cardiac syncope, or other syndromes. 806 events that fulfilled these criteria were reviewed, and their relationship to the patient[scquote]s sleep-wake cycle was determined.
RESULTS: Based on observation of the patients[scquote] behavior alone, 118/806 total NES events seemingly emerged out of sleep. 111/118 of these events clinically emerged during an EEG background featuring a well-defined posterior dominant alpha rhythm, consistent with wakefulness or pre-ictal [dsquote]pseudosleep[dsquote]. However, 4/118 events, in three different patients, emerged during well characterized stage II or III non-REM sleep. The remaining 3/118 events, in three different patients, occurred within seconds of arousal from EEG-verified sleep (non-REM in two, REM in the third), well before the patients would be capable of performing any complex cognitive tasks. In all cases, patients were fully awakened by the nurse responding to the event. All patients with sleep-onset NES also had recorded waking events during the same monitoring experience that were semiologically indistinguishable.
CONCLUSIONS: NES is a common disorder, but often presents many challenges in its differentiation from epilepsy. This is the largest VEEG study to date of the relationship between NES and the sleep-wake cycle, and the first demonstration of occurrence out of EEG-verified sleep. We posit that such sleep-dependent events could not be the product of the awake, conscious mind. This study suggests that NES, in some patients, is a demonstrably non-conscious behavior, and that emergence from sleep cannot be considered an absolute violation obviating the diagnosis of NES.