High frequency oscillations in intra-operative electrocorticography before and after epilepsy surgery

N.E.C. van Klink, M.A. van 't Klooster, R. Zelmann, F.S.S. Leijten, C.H. Ferrier, K.P.J. Braun, P.C. van Rijen, Michel Johannes Antonius Maria van Putten, G.J.M. Huiskamp, M. Zijlmans

Research output: Contribution to journalArticleAcademicpeer-review

68 Citations (Scopus)
6 Downloads (Pure)


Objective Removal of brain tissue showing high frequency oscillations (HFOs; ripples: 80–250 Hz and fast ripples: 250–500 Hz) in preresection electrocorticography (preECoG) in epilepsy patients seems a predictor of good surgical outcome. We analyzed occurrence and localization of HFOs in intra-operative preECoG and postresection electrocorticography (postECoG). Methods HFOs were automatically detected in one-minute epochs of intra-operative ECoG sampled at 2048 Hz of fourteen patients. Ripple, fast ripple, spike, ripples on a spike (RoS) and not on a spike (RnoS) rates were analyzed in pre- and postECoG for resected and nonresected electrodes. Results Ripple, spike and fast ripple rates decreased after resection. RnoS decreased less than RoS (74% vs. 83%; p = 0.01). Most fast ripples in preECoG were located in resected tissue. PostECoG fast ripples occurred in one patient with poor outcome. Patients with good outcome had relatively high postECoG RnoS rates, specifically in the sensorimotor cortex. Conclusions Our observations show that fast ripples in intra-operative ECoG, compared to ripples, may be a better biomarker for epileptogenicity. Further studies have to determine the relation between resection of epileptogenic tissue and physiological ripples generated by the sensorimotor cortex. Significance Fast ripples in intra-operative ECoG can help identify the epileptogenic zone, while ripples might also be physiological.
Original languageEnglish
Pages (from-to)2212-2219
JournalClinical neurophysiology
Issue number11
Publication statusPublished - 2014


  • METIS-311039
  • IR-96637


Dive into the research topics of 'High frequency oscillations in intra-operative electrocorticography before and after epilepsy surgery'. Together they form a unique fingerprint.

Cite this