title: The additional lateralizing and localizing value of the postictal EEG in frontal lobe epilepsy.
abstract: OBJECTIVE
  The aim of this study was to describe the additional lateralizing and localizing value of the postictal EEG in frontal lobe epilepsy (FLE). The ictal EEG in FLE is frequently challenging to localize.
  
  
  METHODS
  We identified patients investigated for epilepsy surgery with unilateral FLE based on consistent semiology, a clear lesion and/or with frontal onset on intracranial EEG. A one hour section of postictal EEG was analyzed by two raters for new or activated EEG features and it was assessed whether these features offered additional information when compared to the ictal EEG. Postictal features assessed included asymmetrical return of the posterior dominant rhythm and potentiated lateralized or regional frontal slowing, spikes or sharp waves.
  
  
  RESULTS
  Thirty-eight patients were included who had a combined total of ninety-six seizures. 47/96 (49%) postictal periods contained correctly lateralizing or localizing information. The sensitivity for asymmetrical return of the posterior dominant rhythm was 24%. The sensitivity for regional frontal slow and frontal spikes was 23% and 20% respectively. Further analysis showed that in 14/38 (39%) patients, at least one seizure with an unhelpful ictal EEG was followed by postictal EEG features that added new localizing or lateralizing information. A subgroup of 11 patients who were ⩾1 year seizure-free (ILAE class 1) and thus classified as having a 'gold-standard' FLE diagnosis were analyzed separately and it was found that 14/30 of their seizures (47%) had extra postictal information.
  
  
  CONCLUSIONS
  The new postictal information was always concordant with the ultimate diagnosis, except for asymmetric postictal return of background activity ipsilateral to the epileptogenic zone in three patients.
  
  
  CONCLUSIONS
  This study shows that a close examination of the postictal EEG can offer additional information which can contribute to the identification of a potentially resectable epileptogenic zone.
authors.affiliation: Sir Jules Thorn Telemetry Unit, National Hospital for Neurology and Neurosurgery, London, UK. Electronic address: k.whitehead@ucl.ac.uk.
authors.forename: Kimberley
authors.initials: K
authors.lastname: Whitehead
authors.affiliation: UCL Institute of Neurology, Department of Clinical and Experimental Epilepsy, London, UK.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Gollwitzer
authors.affiliation: Sir Jules Thorn Telemetry Unit, National Hospital for Neurology and Neurosurgery, London, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Millward
authors.affiliation: Sir Jules Thorn Telemetry Unit, National Hospital for Neurology and Neurosurgery, London, UK; UCL Institute of Neurology, Department of Clinical and Experimental Epilepsy, London, UK.
authors.forename: Tim
authors.initials: T
authors.lastname: Wehner
authors.affiliation: Sir Jules Thorn Telemetry Unit, National Hospital for Neurology and Neurosurgery, London, UK.
authors.forename: Catherine
authors.initials: C
authors.lastname: Scott
authors.affiliation: Sir Jules Thorn Telemetry Unit, National Hospital for Neurology and Neurosurgery, London, UK; UCL Institute of Neurology, Department of Clinical and Experimental Epilepsy, London, UK.
authors.forename: Beate
authors.initials: B
authors.lastname: Diehl
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000503:physiopathology; D001931:Brain Mapping / Q000379:methods*; D004569:Electroencephalography / Q000379:methods*; D017034:Epilepsy, Frontal Lobe / Q000175:diagnosis* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D055815:Young Adult
keywords: Epilepsy surgery; Epileptogenic zone; Frontal lobe epilepsy; Postictal