title: The applications of time-frequency analyses to ictal magnetoencephalography in neocortical epilepsy.
abstract: OBJECTIVE
  Ictal magenetoencephalographic (MEG) discharges convey significant information about ictal onset and propagation, but there is no established method for analyzing ictal MEG. This study sought to clarify the usefulness of time-frequency analyses using short-time Fourier transform (STFT) for ictal onset and propagation of ictal MEG activity in patients with neocortical epilepsy.
  
  
  METHODS
  Four ictal MEG discharges in two patients with perirolandic epilepsy and one with frontal lobe epilepsy (FLE) were evaluated by time-frequency analyses using STFT. Prominent oscillation bands were collected manually and the magnitudes of those specific bands were superimposed on individual 3D-magnetic resonance images.
  
  
  RESULTS
  STFT showed specific rhythmic activities from alpha to beta bands at the magnetological onset in all four ictal MEG records. Those activities were located at the vicinity of interictal spike sources, as estimated by the single dipole method (SDM), and two of the four ictal rhythmic activities promptly propagated to ipsilateral or bilateral cerebral cortices. The patients with FLE and perirolandic epilepsy underwent frontal lobectomy and resection of primary motor area, respectively including the origin of high-magnitude areas of a specific band indicated by STFT, and have been seizure free after the surgery.
  
  
  CONCLUSIONS
  STFT for ictal MEG discharges readily demonstrated the ictal onset and propagation. These data were important for decisions on surgical procedure and extent of resection. Ictal MEG analyses using STFT could provide a powerful tool for noninvasive evaluation of ictal onset zone.
authors.affiliation: Department of Pediatrics, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan. kazuyori@med.hokudai.ac.jp
authors.forename: Kazuyori
authors.initials: K
authors.lastname: Yagyu
authors.forename: Fumiya
authors.initials: F
authors.lastname: Takeuchi
authors.forename: Hideaki
authors.initials: H
authors.lastname: Shiraishi
authors.forename: Shingo
authors.initials: S
authors.lastname: Nakane
authors.forename: Keitaro
authors.initials: K
authors.lastname: Sueda
authors.forename: Naoko
authors.initials: N
authors.lastname: Asahina
authors.forename: Shinobu
authors.initials: S
authors.lastname: Kohsaka
authors.forename: Shuichi
authors.initials: S
authors.lastname: Umeoka
authors.forename: Naotaka
authors.initials: N
authors.lastname: Usui
authors.forename: Koichi
authors.initials: K
authors.lastname: Baba
authors.forename: Shinji
authors.initials: S
authors.lastname: Saitoh
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D002648:Child; D004569:Electroencephalography; D004827:Epilepsy / Q000503:physiopathology*; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D019579:Neocortex / Q000503:physiopathology*; D012640:Seizures / Q000503:physiopathology*; D012815:Signal Processing, Computer-Assisted