High frequency oscillations in intra-operative electrocorticography before and after epilepsy surgery.
OBJECTIVE
Removal of brain tissue showing high frequency oscillations (HFOs; ripples: 80-250Hz and fast ripples: 250-500Hz) 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 2048Hz 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.


CONCLUSIONS
Fast ripples in intra-operative ECoG can help identify the epileptogenic zone, while ripples might also be physiological.
Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, The Netherlands; MIRA, Institute for Technical Medicine, University of Twente, The Netherlands. Electronic address: n.vanklink-2@umcutrecht.nl.
N E C
NEC
van Klink
Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, The Netherlands.
M A
MA
Van't Klooster
Montreal Neurological Institute, McGill University, Canada.
R
R
Zelmann
Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, The Netherlands.
F S S
FSS
Leijten
Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, The Netherlands.
C H
CH
Ferrier
Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, The Netherlands.
K P J
KPJ
Braun
Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, The Netherlands.
P C
PC
van Rijen
MIRA, Institute for Technical Medicine, University of Twente, The Netherlands.
M J A M
MJAM
van Putten
Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, The Netherlands.
G J M
GJM
Huiskamp
Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, The Netherlands; Epilepsy Institutes in the Netherlands, SEIN, Heemstede, The Netherlands.
M
M
Zijlmans
D000293:Adolescent; D000328:Adult; D001921:Brain / Q000503:physiopathology* / Q000601:surgery; D001931:Brain Mapping; D058256:Brain Waves / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography; D004827:Epilepsy / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome; D055815:Young Adult
Electrocorticography; Epilepsy surgery; Focal epilepsy; High frequency oscillations