Narcoleptic Patients Show Fragmented EEG-Microstructure During Early NREM Sleep

ALENA KUHN; VERENA BRODBECK; ENZO TAGLIAZUCCHI; ASTRID MORZELEWSKI; FREDERIC VON WEGNER; HELMUT LAUFS

BRAIN TOPOGRAPHY

SPRINGER

Lugar: Berlin; Año: 2014

0896-0267

Narcolepsy is a chronic disorder of the sleepwakecycle with pathological shifts between sleep stages.These abrupt shifts are induced by a sleep-regulating flip-flop mechanism which is destabilized in narcolepsy withoutobvious alterations in EEG oscillations. Here, we focuson the question whether the pathology of narcolepsy isreflected in EEG microstate patterns. 30 channel awake andNREM sleep EEGs of 12 narcoleptic patients and 32healthy subjects were analyzed. Fitting back the dominantamplitude topography maps into the EEG led to a temporalsequence of maps. Mean microstate duration, ratio totaltime (RTT), global explained variance (GEV) and transitionprobability of each map were compared between bothgroups. Nine patients reached N1, 5 N2 and only 4 N3. Allhealthy subjects reached at least N2, 19 also N3. Fourdominant maps could be found during wakefulness and allNREM- sleep stages in healthy subjects. During N3, narcolepsypatients showed an additional fifth map. The meanmicrostate duration was significantly shorter in narcolepticpatients than controls, most prominent in deep sleep. Singlemaps? GEV and RTT were also altered in narcolepsy.Being aware of the limitation of our low sample size,narcolepsy patients showed wake-like features during sleepas reflected in shorter microstate durations. These microstructuralEEG alterations might reflect the intrusion ofbrain states characteristic of wakefulness into sleep and aninstability of the sleep-regulating flip-flop mechanismresulting not only in pathological switches between REMandNREM-sleep but also within NREM sleep itself, whichmay lead to a microstructural fragmentation of the EEG.