title: Factors influencing clinical features of absence seizures.
abstract: OBJECTIVE
  The clinical features of absence seizures in idiopathic generalized epilepsy have been held to be syndrome-specific. This hypothesis is central to many aspects of epilepsy research yet has not been critically assessed. We examined whether specific factors such as epilepsy syndrome, age, and state determine the features of absence seizures.
  
  
  METHODS
  Children with newly presenting absence seizures were studied using video electroencephalography (EEG) recording. We analyzed whether a child's epilepsy syndrome, age, state of arousal, and provocation influenced specific clinical features of their absence seizures: duration, eyelid movements, eye opening, and level of awareness during the seizure.
  
  
  RESULTS
  Seizures (509) were evaluated in 70 children with the following syndromes: Childhood absence epilepsy (CAE), 37; CAE plus photoparoxysmal response (PPR), 10; juvenile absence epilepsy (JAE), 8; juvenile myoclonic epilepsy (JME), 6; unclassified, 9. Seizure duration was associated with epilepsy syndrome as children with JME had shorter seizures than in other syndromes, independent of age. Age independently influences level of awareness and eye opening. Arousal or provocation affected all features except level of awareness. Specific factors unique to the child independently influenced all features; the nature of these factors has not been identified.
  
  
  CONCLUSIONS
  The view that the clinical features of absence seizures have syndrome-specific patterns is not supported by critical analysis. We show that confounding variables profoundly affect clinical features and that syndromes also show marked variation. Variation in clinical features of absence seizures results from a complex interaction of many factors that are likely to be genetically and environmentally determined.
authors.affiliation: Department of Pediatrics, Wellington School of Medicine, University of Otago, Wellington, New Zealand. lynette.sadleir@otago.ac.nz
authors.forename: Lynette G
authors.initials: LG
authors.lastname: Sadleir
authors.forename: Ingrid E
authors.initials: IE
authors.lastname: Scheffer
authors.forename: Sherry
authors.initials: S
authors.lastname: Smith
authors.forename: Bendix
authors.initials: B
authors.lastname: Carstensen
authors.forename: John
authors.initials: J
authors.lastname: Carlin
authors.forename: Mary B
authors.initials: MB
authors.lastname: Connolly
authors.forename: Kevin
authors.initials: K
authors.lastname: Farrell
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D001364:Awareness / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography; D004832:Epilepsy, Absence / Q000175:diagnosis* / Q000503:physiopathology*; D005133:Eye Movements / Q000502:physiology; D005143:Eyelids / Q000503:physiopathology; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D011939:Mental Recall / Q000502:physiology; D013997:Time Factors