title: Spike wave location and density disturb sleep slow waves in patients with CSWS (continuous spike waves during sleep).
abstract: OBJECTIVE
  In CSWS (continuous spike waves during sleep) activation of spike waves during slow wave sleep has been causally linked to neuropsychological deficits, but the pathophysiologic mechanisms are still unknown. In healthy subjects, the overnight decrease of the slope of slow waves in NREM (non-rapid eye movement) sleep has been linked to brain recovery to regain optimal cognitive performance. Here, we investigated whether the electrophysiologic hallmark of CSWS, the spike waves during sleep, is related to an alteration in the overnight decrease of the slope, and if this alteration is linked to location and density of spike waves.
  
  
  METHODS
  In a retrospective study, the slope of slow waves (0.5-2 Hz) in the first hour and last hour of sleep (19 electroencephalography [EEG] electrodes) of 14 patients with CSWS (3.1-13.5 years) was calculated. The spike wave "focus" was determined as the location of highest spike amplitude and the density of spike waves as spike wave index (SWI).
  
  
  RESULTS
  There was no overnight change of the slope of slow waves in the "focus." Instead, in "nonfocal" regions, the slope decreased significantly. This difference in the overnight course resulted in a steeper slope in the "focus" compared to "nonfocal" electrodes during the last hour of sleep. Spike wave density was correlated with the impairment of the overnight slope decrease: The higher the SWI, the more hampered the slope decrease.
  
  
  CONCLUSIONS
  Location and density of spike waves are related to an alteration of the physiologic overnight decrease of the slow wave slope. This overnight decrease of the slope was shown to be closely related to the recovery function of sleep. Such recovery is necessary for optimal cognitive performance during wakefulness. Therefore we propose the impairment of this process by spike waves as a potential mechanism leading to neuropsychological deficits in CSWS. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here.
authors.affiliation: Pediatric Sleep Disorders Center, University Children's Hospital Zurich, Zurich, Switzerland; Division of Clinical Neurophysiology, University Children's Hospital Zurich, Zurich, Switzerland; Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland.
authors.forename: Bigna K
authors.initials: BK
authors.lastname: Bölsterli Heinzle
authors.forename: Sara
authors.initials: S
authors.lastname: Fattinger
authors.forename: Salomé
authors.initials: S
authors.lastname: Kurth
authors.forename: Monique K
authors.initials: MK
authors.lastname: Lebourgeois
authors.forename: Maya
authors.initials: M
authors.lastname: Ringli
authors.forename: Thomas
authors.initials: T
authors.lastname: Bast
authors.forename: Hanne
authors.initials: H
authors.lastname: Critelli
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schmitt
authors.forename: Reto
authors.initials: R
authors.lastname: Huber
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D012890:Sleep / Q000502:physiology*
keywords: Cognition; Electrical status epilepticus during sleep (ESES); Epilepsy