title: Characteristics of generalised epileptiform activity.
abstract: OBJECTIVE
  To study the age-related occurrence of specific features of generalised epileptiform activity (GEA), their correlation with EEG background activity (BA), and their internal correlation.
  
  
  METHODS
  17,723 consecutive routine EEGs from 12,511 patients were annotated and categorised into a database. The first EEG containing GEA from all 325 patients with such activity were selected and categorised for GEA features. The BA was studied in multivariable fractional polynomial regression models including intervening variables. The GEA features were studied in similar models for age-dependency and internal correlation.
  
  
  RESULTS
  High GEA-amplitude and low GEA-frequency correlated with BA slowing. The occurrence of 'irregular spike/sharp slow wave' pattern increased with age (p=0.003). Hyperventilation sensitivity was not age-related. There was no correlation between hyperventilation sensitivity and photoparoxysmal response. The age-related probability for specific GEA-types was established.
  
  
  CONCLUSIONS
  High GEA-amplitude and low GEA-frequency correlate with BA slowing, indicating cerebral cortical dysfunction. Hyperventilation sensitivity and photoparoxysmal response independently increase the yield of EEG. There is no age-dependency for hyperventilation sensitivity showing that an upper age threshold for hyperventilation provocation is inappropriate.
  
  
  CONCLUSIONS
  The results extend our understanding of GEA and help the electroencephalographer in weighing the various GEA components.
authors.affiliation: Section of Clinical Neurophysiology, Department of Neurology, Haukeland University Hospital, Jonas Liesvei 65, N-5021 Bergen, Norway. harald.aurlien@helse-bergen.no
authors.forename: H
authors.initials: H
authors.lastname: Aurlien
authors.forename: I O
authors.initials: IO
authors.lastname: Gjerde
authors.forename: G E
authors.initials: GE
authors.lastname: Eide
authors.forename: J C
authors.initials: JC
authors.lastname: Brøgger
authors.forename: N E
authors.initials: NE
authors.lastname: Gilhus
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D001921:Brain / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D016208:Databases, Factual / Q000706:statistics & numerical data; D004569:Electroencephalography / Q000145:classification / Q000379:methods* / Q000706:statistics & numerical data; D004829:Epilepsy, Generalized / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D008875:Middle Aged; D011336:Probability; D012189:Retrospective Studies; D055815:Young Adult