Transitional sharp waves at ictal onset--a neocortical ictal pattern

Clin Neurophysiol. 2009 Apr;120(4):665-72. doi: 10.1016/j.clinph.2009.01.010. Epub 2009 Mar 4.


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.

Conclusion: 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.

Significance: TShW at seizure onset should suggest a neocortical rather than hippocampal seizure onset.

MeSH terms

  • Adolescent
  • Adult
  • Brain Mapping
  • Electroencephalography / methods
  • Epilepsies, Partial / diagnostic imaging
  • Epilepsies, Partial / physiopathology*
  • Epilepsies, Partial / surgery
  • Female
  • Humans
  • Magnetic Resonance Imaging / methods
  • Male
  • Middle Aged
  • Neocortex / diagnostic imaging
  • Neocortex / physiopathology*
  • Neocortex / surgery
  • Retrospective Studies
  • Signal Processing, Computer-Assisted*
  • Tomography, Emission-Computed, Single-Photon / methods
  • Young Adult