title: Rhythmic and periodic EEG patterns of 'ictal-interictal uncertainty' in critically ill neurological patients.
abstract: OBJECTIVE
  To study periodic and rhythmic EEG patterns classified according to Standardized Critical Care EEG Terminology (SCCET) of the American Clinical Neurophysiology Society and their relationship to electrographic seizures.
  
  
  METHODS
  We classified 655 routine EEGs in 371 consecutive critically ill neurological patients into (1) normal EEGs or EEGs with non-specific abnormalities or interictal epileptiform discharges, (2) EEGs containing unequivocal ictal EEG patterns, and (3) EEGs showing rhythmic and periodic EEG patterns of 'ictal-interictal uncertainty' (RPPIIIU) according to SCCET.
  
  
  RESULTS
  313 patients (84.4%) showed normal EEGs, non-specific or interictal abnormalities, 14 patients (3.8%) had EEGs with at least one electrographic seizure, and 44 patients (11.8%) at least one EEG containing RPPIIIU, but no EEG with electrographic seizures. Electrographic seizures occurred in 11 of 55 patients (20%) with RPPIIIU, but only in 3 of 316 patients (0.9%) without RPPIIIU (p⩽0.001). Conversely, we observed RPPIIIU in 11 of 14 patients (78.6%) with electrographic seizures, but only in 44 of 357 patients (12.3%) without electrographic seizures (p⩽0.001).
  
  
  CONCLUSIONS
  On routine-EEG in critically ill neurological patients RPPIIIU occur 3 times more frequently than electrographic seizures and are highly predictive for electrographic seizures.
  
  
  CONCLUSIONS
  RPPIIIU can serve as an indication for continuous EEG recordings.
authors.affiliation: Karl Landsteiner Institute for Clinical Epilepsy Research and Cognitive Neurology, 2nd Neurological Department, General Hospital Hietzing with Neurological Center Rosenhügel, Vienna, Austria.
authors.forename: Johannes P
authors.initials: JP
authors.lastname: Koren
authors.affiliation: Department of Neurosurgery, Medical University of Vienna, Vienna, Austria.
authors.forename: Johannes
authors.initials: J
authors.lastname: Herta
authors.affiliation: Karl Landsteiner Institute for Clinical Epilepsy Research and Cognitive Neurology, 2nd Neurological Department, General Hospital Hietzing with Neurological Center Rosenhügel, Vienna, Austria.
authors.forename: Susanne
authors.initials: S
authors.lastname: Pirker
authors.affiliation: Austrian Institute of Technology GmbH (AIT), Safety & Security Department, Vienna, Austria.
authors.forename: Franz
authors.initials: F
authors.lastname: Fürbass
authors.affiliation: Austrian Institute of Technology GmbH (AIT), Safety & Security Department, Vienna, Austria.
authors.forename: Manfred
authors.initials: M
authors.lastname: Hartmann
authors.affiliation: Austrian Institute of Technology GmbH (AIT), Safety & Security Department, Vienna, Austria.
authors.forename: Tilmann
authors.initials: T
authors.lastname: Kluge
authors.affiliation: Karl Landsteiner Institute for Clinical Epilepsy Research and Cognitive Neurology, 2nd Neurological Department, General Hospital Hietzing with Neurological Center Rosenhügel, Vienna, Austria. Electronic address: christoph.baumgartner@wienkav.at.
authors.forename: Christoph
authors.initials: C
authors.lastname: Baumgartner
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D016638:Critical Illness / Q000453:epidemiology; D004569:Electroencephalography / Q000379:methods / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009422:Nervous System Diseases / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D010507:Periodicity; D035501:Uncertainty
keywords: EEG in coma; EEG patterns; Electrographic seizures; Periodic EEG patterns; Rhythmic EEG patterns; Standardized Critical Care EEG Terminology