title: Spike orientation may predict epileptogenic side across cerebral sulci containing the estimated equivalent dipole.
abstract: OBJECTIVE
  To evaluate whether the orientation of interictal spikes, localized in major sulci by magnetoencephalography (MEG), predicts the epileptogenic side of the sulcal wall.
  
  
  METHODS
  Sixteen epilepsy patients were analyzed in whom equivalent current dipoles (ECDs) of MEG spikes were localized on the central (four patients), interhemispheric (4), or sylvian fissure (8); and the epileptogenic side across the sulci had been confirmed by seizure semiology, structural lesions, or intracranial electroencephalography (EEG). ECD was classified as epileptogenic side or normal side oriented and correlated to the scalp EEG map.
  
  
  RESULTS
  All central (n=50) and interhemispheric (n=83) spike ECDs were oriented toward the epileptogenic side at peak latency. In scalp EEG, 91% of the spikes showed radial pattern of broad negativity above the sulcus whereas 9% showed tangential pattern with positive maximum above the epileptogenic side. Sylvian spikes were only found in patients with temporal lobe epilepsy (TLE). In sylvian spikes (n=220), 73% of ECDs were oriented toward the epileptogenic side, whereas 27% were oriented toward the normal side.
  
  
  CONCLUSIONS
  In central and interhemispheric spikes, epileptogenic side cortex may be gross surface negative through the sulcal wall to the adjacent gyrus. Inconsistent orientation of the sylvian spikes suggests a complex pattern of spike propagation in TLE.
  
  
  CONCLUSIONS
  ECD orientation of central and interhemispheric spikes in MEG may predict the epileptogenic side.
authors.affiliation: Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Kamran Ali
authors.initials: KA
authors.lastname: Salayev
authors.forename: Nobukazu
authors.initials: N
authors.lastname: Nakasato
authors.forename: Mamiko
authors.initials: M
authors.lastname: Ishitobi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shamoto
authors.forename: Akitake
authors.initials: A
authors.lastname: Kanno
authors.forename: Kazuie
authors.initials: K
authors.lastname: Iinuma
mesh_terms: D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D004569:Electroencephalography; D004827:Epilepsy / Q000503:physiopathology*; D007839:Functional Laterality; D006801:Humans; D015225:Magnetoencephalography