title: How long shall we record electroencephalography?
abstract: BACKGROUND
  The duration of electroencephalography (EEG) recordings varies widely among laboratories. Although several recommendations had been published, there are no previous studies directly addressing this.
  
  
  OBJECTIVE
  To assess the effect of the recording duration on detection of EEG abnormalities in a tertiary referral centre for epilepsy.
  
  
  METHODS
  We have reviewed 1005 EEG recordings and determined the shortest recording duration necessary to identify interictal EEG abnormalities.
  
  
  RESULTS
  Standard, awake recordings shorter than 20 min yielded a significantly lower incidence of abnormal findings as compared to longer recordings. Although there was an increase in the diagnostic yield from 30 to 180 min recording duration, this failed to reach the level of significance. For sleep recordings, there was no significant increase in the diagnostic yield beyond 30 min.
  
  
  CONCLUSIONS
  Our results provide evidence for recommending at least 20 min recording duration for standard awake EEGs and 30 min for sleep EEG recordings. As data were derived from patients referred to our epilepsy centre, the results are only valid for epilepsy-related indications.
authors.affiliation: Department of Clinical Neurophysiology, Danish Epilepsy Centre, Dianalund, Denmark; Department of Neurology, Emergency University Hospital of Bucharest, Bucharest, Romania.
authors.forename: L
authors.initials: L
authors.lastname: Craciun
authors.forename: E
authors.initials: E
authors.lastname: Gardella
authors.forename: J
authors.initials: J
authors.lastname: Alving
authors.forename: D
authors.initials: D
authors.lastname: Terney
authors.forename: I
authors.initials: I
authors.lastname: Mindruta
authors.forename: J
authors.initials: J
authors.lastname: Zarubova
authors.forename: S
authors.initials: S
authors.lastname: Beniczky
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography / Q000379:methods*; D004827:Epilepsy / Q000175:diagnosis / Q000503:physiopathology; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D017286:Polysomnography / Q000379:methods; D012189:Retrospective Studies; D012890:Sleep / Q000502:physiology; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology; D055815:Young Adult
keywords: duration; epilepsy; interictal; sleep; standard