title: Transitional sharp waves at ictal onset--a neocortical ictal pattern.
abstract: OBJECTIVE
  Some seizures are characterized by a transitional sharp wave (TShW) at ictal onset. We evaluated the clinical significance and localizing value of TShW in partial-onset seizures.
  
  
  METHODS
  We identified and analyzed all scalp ictal recordings with a TShW at ictal onset in the Vanderbilt Epilepsy Monitoring Unit over a period of 12 months.
  
  
  RESULTS
  A total of 52 ictal discharges in 13 patients started with a TShW. The center of TShW field was concordant with the final localization/lateralization, while that of the subsequent ictal discharge was concordant in only 6 patients. The subsequent rhythmic ictal discharge was non-localizing in 4 patients and misleading in the remaining 3 patients. The final localization was neocortical temporal or frontal in 11 patients, occipito-parietal in one, and undetermined in 1 patient. None of 61 ictal discharges in 15 patients with mesial temporal lobe epilepsy studied in the same time period started with a TShW.
  
  
  CONCLUSIONS
  In this patient series, the TShW was a marker of neocortical seizure onset. The TShW field provided more accurate localization or lateralization of the ictal focus than the following rhythmic ictal discharge.
  
  
  CONCLUSIONS
  TShW at seizure onset should suggest a neocortical rather than hippocampal seizure onset.
authors.affiliation: Neurology Department, Vanderbilt University Medical Center, A-0118 MCN 2551, Nashville, TN 37232-2551, USA.
authors.forename: Nabil J
authors.initials: NJ
authors.lastname: Azar
authors.forename: Andre H
authors.initials: AH
authors.lastname: Lagrange
authors.forename: Bassel W
authors.initials: BW
authors.lastname: Abou-Khalil
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D004569:Electroencephalography / Q000379:methods; D004828:Epilepsies, Partial / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D019579:Neocortex / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D012189:Retrospective Studies; D012815:Signal Processing, Computer-Assisted; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods; D055815:Young Adult