Dynamic changes of ictal high-frequency oscillations in neocortical epilepsy: using multiple band frequency analysis.
OBJECTIVE
To characterize the spatial and temporal course of ictal high-frequency oscillations (HFOs) recorded by subdural EEG in children with intractable neocortical epilepsy.


METHODS
We retrospectively studied nine children (four girls, five boys; 4-17 yr) who presented with intractable extrahippocampal localization-related epilepsy and who underwent extraoperative video subdural EEG (1000 Hz sampling rate) and cortical resection. We performed multiple band frequency analysis (MBFA) to evaluate the frequency, time course, and distribution of ictal HFOs. We compared ictal HFO changes before and after clinical onset and postsurgical seizure outcomes.


RESULTS
Seventy-eight of 79 seizures showed HFOs. We observed wide-band HFOs ( approximately 250 Hz, approximately 120 electrodes) in six patients either with partial seizures alone (three patients) or with epileptic spasms (three patients). Three patients with partial seizures that secondarily generalized had wide-band HFOs ( approximately 170 Hz) before clinical onset and sustained narrow-band HFOs (60-164 Hz) with electrodecremental events after clinical onset ( approximately 28 electrodes). In four postoperatively seizure-free patients, more electrodes recorded higher-frequency HFOs inside the resection area than outside before and after clinical seizure onset. In five patients with residual seizures, electrodes recorded more HFOs that were of higher or equal frequency outside the surgical area than inside after clinical onset.


CONCLUSIONS
For partial seizures alone and epileptic spasms, more electrodes recorded only wide-band HFOs; for partial seizures that secondarily generalized, fewer electrodes recorded wide-band HFOs, but in these seizures electrodes also recorded subsequent sustained narrow-band ictal HFOs. Resection of those brain regions having electrodes with ictal, higher HFOs resulted in postsurgical seizure-free outcomes.
Ochi
Ayako
A
The Divisions of Neurology, The Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada. ayako.ochi@sickkids.ca
Otsubo
Hiroshi
H
Donner
Elizabeth J
EJ
Elliott
Irene
I
Iwata
Ryoichi
R
Funaki
Takanori
T
Akizuki
Yoko
Y
Akiyama
Tomoyuki
T
Imai
Katsumi
K
Rutka
James T
JT
Snead
O Carter
OC
D000293:Adolescent; D001931:Brain Mapping; D002648:Child; D002675:Child, Preschool; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000706:statistics & numerical data*; D004828:Epilepsies, Partial / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery; D004827:Epilepsy / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D005260:Female; D006612:High-Frequency Ventilation / Q000706:statistics & numerical data*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D019579:Neocortex / Q000503:physiopathology* / Q000601:surgery; D011300:Preoperative Care; D012189:Retrospective Studies; D012640:Seizures / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery; D012815:Signal Processing, Computer-Assisted; D013355:Subdural Space; D016896:Treatment Outcome; D014743:Videotape Recording