title: Very high frequency oscillations (over 1000 Hz) in human epilepsy.
abstract: OBJECTIVE
  High frequency oscillations (HFO) of 100-500Hz have been reported in epileptic human brain. However, the questions of how fast these oscillations can reach, and which frequency range is clinically important remain unanswered. We recorded interictal and ictal very high frequency oscillations (VHFO) of 1000-2500Hz by subdural electrodes using 10kHz sampling rate. We describe the characteristics of VHFO, and discuss their underlying mechanism and clinical significance.
  
  
  METHODS
  Five patients with neocortical epilepsy were studied. All patients underwent intracranial EEG monitoring with subdural electrodes. EEG recording with sampling rate of 10kHz was conducted. Histopathology revealed malformation of cortical development in all cases.
  
  
  RESULTS
  In four of five patients, very high frequency activities of 1000-2500Hz were detected in highly localized cortical regions (one to four electrodes in individual patient). We named these activities "very high frequency oscillations (VHFO)". Interictally, VHFO appeared intermittently, and were interrupted by spikes. Sustained VHFO without spikes appeared around the start of seizures.
  
  
  CONCLUSIONS
  Both interictal and ictal VHFO can be recorded by subdural electrodes. Compared to HFO previously reported, VHFO have much higher frequency, more restricted distribution, smaller amplitude, and different timing of onset.
  
  
  CONCLUSIONS
  Recording of VHFO may be useful for identifying the epileptogenic zone.
authors.affiliation: National Epilepsy Center, Shizuoka Institute of Epilepsy and Neurological Disorders, Shizuoka, Japan. n-usui@szec.hosp.go.jp
authors.forename: Naotaka
authors.initials: N
authors.lastname: Usui
authors.forename: Kiyohito
authors.initials: K
authors.lastname: Terada
authors.forename: Koichi
authors.initials: K
authors.lastname: Baba
authors.forename: Kazumi
authors.initials: K
authors.lastname: Matsuda
authors.forename: Fumihiro
authors.initials: F
authors.lastname: Nakamura
authors.forename: Keiko
authors.initials: K
authors.lastname: Usui
authors.forename: Takayasu
authors.initials: T
authors.lastname: Tottori
authors.forename: Shuichi
authors.initials: S
authors.lastname: Umeoka
authors.forename: Shigeru
authors.initials: S
authors.lastname: Fujitani
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Mihara
authors.forename: Yushi
authors.initials: Y
authors.lastname: Inoue
mesh_terms: D000293:Adolescent; D000328:Adult; D001683:Biological Clocks / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods*; D004827:Epilepsy / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D013355:Subdural Space / Q000502:physiology; D055815:Young Adult