These authors contributed equally.
Full-Length Original Research
Spike wave location and density disturb sleep slow waves in patients with CSWS (continuous spike waves during sleep)
Version of Record online: 20 MAR 2014
Wiley Periodicals, Inc. © 2014 International League Against Epilepsy
Volume 55, Issue 4, pages 584–591, April 2014
How to Cite
Epilepsia, 55(4):584–591, 2014
- Issue online: 22 APR 2014
- Version of Record online: 20 MAR 2014
- Manuscript Accepted: 27 JAN 2014
- Children's Research Center Zurich
- Swiss League against Epilepsy
- Anna Müller Grocholski-Foundation
- Swiss National Science Foundation. Grant Number: PP00A3-114923
- University of Zurich
- Electrical status epilepticus during sleep (ESES);
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.
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).
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.
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.
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