title: Prediction of rhythmic and periodic EEG patterns and seizures on continuous EEG with early epileptiform discharges.
abstract: BACKGROUND
  Continuous EEG (cEEG) is necessary to document nonconvulsive seizures (NCS), nonconvulsive status epilepticus (NCSE), as well as rhythmic and periodic EEG patterns of 'ictal-interictal uncertainty' (RPPIIU) including periodic discharges, rhythmic delta activity, and spike-and-wave complexes in neurological intensive care patients. However, cEEG is associated with significant recording and analysis efforts. Therefore, predictors from short-term routine EEG with a reasonably high yield are urgently needed in order to select patients for evaluation with cEEG.
  
  
  OBJECTIVE
  The aim of this study was to assess the prognostic significance of early epileptiform discharges (i.e., within the first 30 min of EEG recording) on the following: (1) incidence of ictal EEG patterns and RPPIIU on subsequent cEEG, (2) occurrence of acute convulsive seizures during the ICU stay, and (3) functional outcome after 6 months of follow-up.
  
  
  METHODS
  We conducted a separate analysis of the first 30 min and the remaining segments of prospective cEEG recordings according to the ACNS Standardized Critical Care EEG Terminology as well as NCS criteria and review of clinical data of 32 neurological critical care patients.
  
  
  RESULTS
  In 17 patients with epileptiform discharges within the first 30 min of EEG (group 1), electrographic seizures were observed in 23.5% (n = 4), rhythmic or periodic EEG patterns of 'ictal-interictal uncertainty' in 64.7% (n = 11), and neither electrographic seizures nor RPPIIU in 11.8% (n = 2). In 15 patients with no epileptiform discharges in the first 30 min of EEG (group 2), no electrographic seizures were recorded on subsequent cEEG, RPPIIU were seen in 26.7% (n = 4), and neither electrographic seizures nor RPPIIU in 73.3% (n = 11). The incidence of EEG patterns on cEEG was significantly different between the two groups (p = 0.008). Patients with early epileptiform discharges developed acute seizures more frequently than patients without early epileptiform discharges (p = 0.009). Finally, functional outcome six months after discharge was significantly worse in patients with early epileptiform discharges (p=0.01).
  
  
  CONCLUSIONS
  Epileptiform discharges within the first 30 min of EEG recording are predictive for the occurrence of ictal EEG patterns and for RPPIIU on subsequent cEEG, for acute convulsive seizures during the ICU stay, and for a worse functional outcome after 6 months of follow-up. This article is part of a Special Issue entitled Status Epilepticus.
authors.affiliation: Karl Landsteiner Institute for Clinical Epilepsy Research and Cognitive Neurology, 2nd Neurological Department, General Hospital Hietzing with Neurological Center Rosenhuegel, Vienna, Austria. Electronic address: johannes-peter.koren@wienkav.at.
authors.forename: J
authors.initials: J
authors.lastname: Koren
authors.affiliation: Department of Neurosurgery, Medical University of Vienna, Vienna, Austria.
authors.forename: J
authors.initials: J
authors.lastname: Herta
authors.affiliation: 1st Neurological Department, General Hospital Hietzing with Neurological Center Rosenhuegel, Vienna, Austria.
authors.forename: S
authors.initials: S
authors.lastname: Draschtak
authors.affiliation: 1st Neurological Department, General Hospital Hietzing with Neurological Center Rosenhuegel, Vienna, Austria.
authors.forename: G
authors.initials: G
authors.lastname: Pötzl
authors.affiliation: Karl Landsteiner Institute for Clinical Epilepsy Research and Cognitive Neurology, 2nd Neurological Department, General Hospital Hietzing with Neurological Center Rosenhuegel, Vienna, Austria.
authors.forename: S
authors.initials: S
authors.lastname: Pirker
authors.affiliation: Austrian Institute of Technology GmbH (AIT), Safety & Security Department, Vienna, Austria.
authors.forename: F
authors.initials: F
authors.lastname: Fürbass
authors.affiliation: Austrian Institute of Technology GmbH (AIT), Safety & Security Department, Vienna, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Hartmann
authors.affiliation: Austrian Institute of Technology GmbH (AIT), Safety & Security Department, Vienna, Austria.
authors.forename: T
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 Rosenhuegel, Vienna, Austria.
authors.forename: C
authors.initials: C
authors.lastname: Baumgartner
mesh_terms: D003422:Critical Care; D003700:Delta Rhythm / Q000187:drug effects; D004569:Electroencephalography / Q000187:drug effects*; D004827:Epilepsy / Q000188:drug therapy* / Q000453:epidemiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D012640:Seizures / Q000188:drug therapy* / Q000453:epidemiology / Q000503:physiopathology; D013226:Status Epilepticus / Q000188:drug therapy* / Q000453:epidemiology / Q000503:physiopathology; D016896:Treatment Outcome; D035501:Uncertainty
keywords: ACNS Standardized Critical Care EEG Terminology; Continuous EEG; Early epileptiform discharges; Nonconvulsive seizures; Rhythmic and periodic EEG patterns of ‘ictal–interictal uncertainty’