title: Atypical EEG abnormalities in genetic generalized epilepsies.
abstract: OBJECTIVE
  Bilateral, symmetric and synchronous generalized epileptiform activity is considered to be the typical electroencephalographic (EEG) abnormality in genetic generalized epilepsy (GGE). We sought to study atypical EEG abnormalities in a systematic way based on 24-h ambulatory EEG recordings.
  
  
  METHODS
  The diagnosis of GGE was validated and classified into syndromes according to the International League against Epilepsy criteria. All participants underwent 24-h ambulatory EEG recording. Epileptiform discharges were counted and detailed information was entered into an electronic database. Amplitude asymmetry, focal onset/offset of paroxysms, focal discharges, atypical morphology and generalized paroxysmal fast rhythm were defined as atypical abnormalities.
  
  
  RESULTS
  Of the total of 120 patients, 107 had abnormal EEGs, of which 66.4% had at least one atypical epileptiform abnormality on EEG. Atypical morphology was the most frequent abnormality in 93.4% of patients, followed by amplitude asymmetry (28.0%), focal discharges (21.5%), focal onset of paroxysms (13.1%), focal offset of paroxysms (8.2%) and generalized paroxysmal fast rhythm (1.9%). The analysis of individual discharges revealed that 76% of paroxysms were of atypical morphology. Significant associations were found between (a) amplitude asymmetry and state of arousal (p<0.001) as well as seizure-free duration (p 0.013); (b) atypical morphology and state of arousal (p<0.001).
  
  
  CONCLUSIONS
  In GGE, there are both common and rare atypical epileptiform EEG abnormalities that may vary according to the state of arousal and seizure-free duration.
  
  
  CONCLUSIONS
  Awareness of these variations is important to avoid misdiagnosis.
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: Statistical Consulting Centre, The University of Melbourne, Melbourne, Australia. Electronic address: hepworth@unimelb.edu.au.
authors.forename: Graham
authors.initials: G
authors.lastname: Hepworth
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: D000293:Adolescent; D000328:Adult; D002540:Cerebral Cortex / Q000503:physiopathology*; D004569:Electroencephalography / Q000379:methods*; D004829:Epilepsy, Generalized / Q000175:diagnosis / Q000235:genetics* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D055815:Young Adult
keywords: Atypical; Generalized epilepsy; Morphology; Paroxysmal fast; Seizure; Spike-wave; Topography