title: Consistent topography and amplitude symmetry are more typical than morphology of epileptiform discharges in genetic generalized epilepsy.
abstract: OBJECTIVE
  To provide a quantitative evaluation of typical electroencephalographic (EEG) abnormalities in genetic generalized epilepsy (GGE).
  
  
  METHODS
  We prospectively performed 24-h ambulatory EEG recordings in a cohort of patients with GGE. The diagnosis was established according to the International League Against Epilepsy criteria. Details of all epileptiform discharges across the 24-h time scale were entered into an electronic database. We carried out descriptive statistics to provide a quantitative breakdown of typical EEG abnormalities.
  
  
  RESULTS
  A total of 6923 epileptiform discharges from 105 abnormal 24-h ambulatory EEGs were analyzed. 96% of discharges were symmetric in amplitude with fronto-central maximum topographically. Only 24% of the paroxysms had typical morphology while 43% were regular. Photoparoxysmal response, eye-closure sensitivity and hyperventilation-induced generalized paroxysms were less common in around 10%, whereas occipital intermittent rhythmic delta activity was very rare (2%).
  
  
  CONCLUSIONS
  Our results indicate that generalized discharges with symmetric amplitude and fronto-central maxima are the most consistent findings in GGE, and other features are observed less frequently.
  
  
  CONCLUSIONS
  Epileptiform discharges displaying highly consistent amplitude symmetry coupled with fronto-central topography should provoke consideration of GGE. Recognition of variations from typical abnormalities is important to avoid the risk of misdiagnosis and delayed diagnosis.
authors.affiliation: Department of Medicine, St. Vincent's Hospital, The University of Melbourne, Melbourne, Australia; Department of Neuroscience, Monash Medical Centre, Melbourne, Australia. Electronic address: Udaya.Seneviratne@svhm.org.au.
authors.forename: Udaya
authors.initials: U
authors.lastname: Seneviratne
authors.affiliation: Department of Medicine, St. Vincent's Hospital, The University of Melbourne, Melbourne, Australia. Electronic address: markcook@unimelb.edu.au.
authors.forename: Mark
authors.initials: M
authors.lastname: Cook
authors.affiliation: Department of Medicine, St. Vincent's Hospital, The University of Melbourne, Melbourne, Australia. Electronic address: wendyl@unimelb.edu.au.
authors.forename: Wendyl
authors.initials: W
authors.lastname: D'Souza
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000293:Adolescent; D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D015331:Cohort Studies; D004569:Electroencephalography / Q000379:methods*; D004829:Epilepsy, Generalized / Q000175:diagnosis* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D055815:Young Adult
keywords: EEG; Generalized epilepsy; Morphology; Seizure; Spike–wave; Topography