title: Defining abnormal slow EEG activity in acute ischaemic stroke: Delta/alpha ratio as an optimal QEEG index.
abstract: OBJECTIVE
  Quantitative electroencephalographic (QEEG) indices sensitive to abnormal slow (relative to faster) activity power seem uniquely informative for clinical management of ischaemic stroke (IS), including around acute reperfusion therapies. However these have not been compared between IS and control samples. The primary objective was to identify the QEEG slowing index and threshold value which can most accurately discriminate between IS patients and controls.
  
  
  METHODS
  The samples comprised 28 controls (mean age: 70.4; range: 56-84) and 18 patients (mean age: 69.3; range: 51-86). Seven indices were analysed: relative bandpower (delta, theta, alpha, beta), delta/alpha power ratio (DAR), (delta+theta)/(alpha+beta) ratio (DTABR) and QSLOWING. The accuracies of each index for classifying participants (IS or control) were analysed using receiver operating characteristic (ROC) techniques.
  
  
  RESULTS
  All indices differed significantly between the samples (p<.001). DAR alone exhibited optimal classifier accuracy, with a threshold of 3.7 demonstrating 100% sensitivity and 100% specificity for discriminating between radiologically-confirmed, acute IS or control. DTABR and relative delta were the next most accurate classifiers.
  
  
  CONCLUSIONS
  DAR of 3.7 demonstrated maximal accuracy for classifying all 46 participants as acute IS or control.
  
  
  CONCLUSIONS
  DAR assessment may inform clinical management of IS and perhaps other neurocritical patients.
authors.affiliation: UQ Centre for Clinical Research, University of Queensland, Brisbane, Australia; Centre for Allied Health Research, Royal Brisbane and Women's Hospital, Metro North Hospital and Health Service, Queensland, Australia. Electronic address: finnigan.simon@gmail.com.
authors.forename: Simon
authors.initials: S
authors.lastname: Finnigan
authors.affiliation: School of Medicine, University of Queensland, Brisbane, Australia; Acute Stroke Unit, Neurology Department, Royal Brisbane and Women's Hospital, Metro North Hospital and Health Service, Queensland, Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Wong
authors.affiliation: School of Medicine, University of Queensland, Brisbane, Australia; Acute Stroke Unit, Neurology Department, Royal Brisbane and Women's Hospital, Metro North Hospital and Health Service, Queensland, Australia.
authors.forename: Stephen
authors.initials: S
authors.lastname: Read
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000513:Alpha Rhythm / Q000502:physiology*; D002545:Brain Ischemia / Q000175:diagnosis* / Q000503:physiopathology; D003700:Delta Rhythm / Q000502:physiology*; D004569:Electroencephalography / Q000379:methods / Q000592:standards; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020521:Stroke / Q000175:diagnosis* / Q000503:physiopathology
keywords: Acute ischaemic stroke; Alpha activity; Delta activity; Quantitative electroencephalography