Ictal and interictal high frequency oscillations in patients with focal epilepsy

Maeike Zijlmans*, Julia Jacobs, Yusuf U. Kahn, Rina Zelmann, Francois Dubeau, Jean Gotman

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Objective: High frequency oscillations (HFOs) can be recorded with depth electrodes in focal epilepsy patients. They occur during seizures and interictally and seem important in seizure genesis. We investigated whether interictal and ictal HFOs occur in the same regions and how they relate to epileptiform spikes.

Methods: In 25 patients, spikes, ripples (80-250 Hz) and fast ripples (FR: 250-500 Hz) and their co-occurrences were marked during interictal slow wave sleep (5-10 min), during 10 pre-ictal seconds and 5 s following seizure onset. We compared occurrence and spatial distribution between these periods.

Results: HFOs and spikes increased from interictal to ictal periods: the percentage of time occupied by ripples increased from 2.3% to 6.5%, FR from 0.2% to 0.8%, spikes from 1.1% to 4.8%. HFOs increased from interictal to pre-ictal periods in contrast to spikes. Spikes were in different channels in the interictal, pre-ictal and ictal periods whereas HFOs largely remained in the same channels.

Conclusions: HFOs remain confined to the same, possibly epileptogenic, area, during interictal and ictal periods, while spikes are more widespread during seizures than interictally.

Significance: Ictal and interictal HFOs represent the same (epileptogenic) area and are probably similar phenomena. (C) 2010 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)664-671
Number of pages8
JournalClinical Neurophysiology
Volume122
Issue number4
DOIs
Publication statusPublished - Apr 2011

Keywords

  • High frequency oscillations
  • Focal epilepsy
  • Epilepsy surgery
  • Depth EEG
  • Ictogenesis
  • TEMPORAL-LOBE EPILEPSY
  • ENTORHINAL CORTEX
  • 100-500 HZ
  • STATUS EPILEPTICUS
  • INTRACEREBRAL EEG
  • INTRACRANIAL EEG
  • FAST RIPPLES
  • SEIZURES
  • BRAIN
  • HIPPOCAMPUS

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